Isar

The Isar is a river in Tyrol, Austria and Bavaria, Germany, which is not navigable for watercraft above raft size. Its source is in the Karwendel range of the Alps in Tyrol; it enters Germany near Mittenwald and flows through Bad Tölz, Munich, and Landshut before reaching the Danube near Deggendorf. At in length, it is the fourth largest river in Bavaria, after the Danube, Inn, and Main. It is Germany's second most important tributary of the Danube after the Inn.
Etymology.
One theory is that the name "Isar" comes from the hypothetical Indo-European root "*es" or "*is", which generally meant "flowing water" and later turned into a word with a meaning narrowed to frozen water (hence English "ice", ) in Proto-Germanic. An older theory is that it comes from Celtic words and the name "Isar" is a construction of the Celtic stems "ys" "fast, torrential" and "ura" "water, river". According to another interpretation "ys" may mean "high" as well as "low", referring to the rapidly changing water level in the river Isar. In the ancient settlement area of the Celts several related river names can be found:
It may be possible that the ancient name of the lower part of the river Danube, Ister, has the same source. Newer interpretations relate it to the Proto-Basque particle "*(w)its-", "water", also seen in similar but otherwise unexplained river names, such as Vézère, Vizela, Weser and Vistula.
Geography.
The Isar drains a substantial part of the Alps and parts of the Karwendel mountains northeast towards the Danube river and thus finally towards the Black Sea. Apart from the larger tributaries Amper and Loisach many smaller rivers empty into the Isar, such as the Leutasch, the Jachen, the Dürrach, the Dorfen, the Sempt, the Pfettrach and the Gleirschbach. The drainage basin contains some 9,000 square kilometers (3,500 square miles). During the winter most of the precipitation in the Alps falls as snow. This results in an increased water flow during the spring meltdown. It has an average discharge of 175 cubic meters (6,200 cubic feet) per second. This makes it comparable to other medium-sized rivers in Germany, like the Moselle, Lech or Main.
The official head of the Isar is located in the Hinterau valley east of the village Scharnitz in the Karwendel mountains in Tyrol at a height above sea level of . In 2003 the Isar spring was “developed”, however, this move has been discussed due to environmental reasons. The Lavatschbach, which is the Isar’s longest headstream, has its source farther to the southeast near a mountain cabin named Hallangerhaus. It is also sometimes called the Isar’s head. Further on the young Isar is supplied water by the Birkkarbach, which has its source at the foot of the highest mountain of the Karwendel, the Birkkarspitze and the Moserkarbach.
Having entered Upper Bavaria after ca. just north of Scharnitz, the Isar is dammed for the first time between Mittenwald and Krün. Some of its waters are led via the Rißbach, whose flowing direction was reversed for this purpose, into the Walchensee. Here it is fed into the giant downpipes of the Walchensee power plant. 200 metres lower the plant releases this part of the water into the Kochelsee. From here it flows into the river Loisach, Isar's second most important tributary. Not far down the river a large reservoir called Sylvensteinsee was created between 1954 and 1959 to make more energy generation possible and also to avoid flooding. It is located some south of Lenggries. It has prevented some bad floods in Munich, for example in 1979, 1999 and most important, in 2005. In that year for the first time ever water had to be released from the lake because its capacity was exhausted. Flooding was barely avoided in Munich, literally 'by the width of one hand'. At Bad Tölz the Isar leaves the Bavarian Alps. This town marks the river's transit from its upper to its middle course.
It now flows through a sub-alpine, glacial morainic landscape towards Wolfratshausen. Just north of the town it absorbs the Loisach, including the water previously drained off for the power plant. The Isar continues on to and through the Munich gravel plain, into which it cuts a narrow, steeply sloped valley. The latter finally opens up and ends within the city limits of Munich. Further downstream the river passes Freising and then absorbs the waters of the Amper, its most important tributary, at Moosburg. This is where its lower course begins.
Passing Landshut, the river makes its way through the Tertiary Hills of Lower Bavaria all the way into the Danube valley. Its mouth at the Danube some five kilometres away from Deggendorf is at above sea level. Thus the Isar descends some from its head to its mouth.
Islands.
Most of the small islands and gravel banks keep changing shape and size due to the annual floods. Some of the islands within the bigger cities were built up during the 19th century and thus protected against the abrasive powers of the water. Among those are the Museumsinsel (on which the Deutsches Museum is located); formerly this island was called Kohleninsel (coal island), the Praterinsel (both located in Munich) and the Mühleninsel in Landshut.
History.
It is quite likely that the Isar was used as a trade route, even in prehistoric times, to transport wares from the Alps and even Italy towards the Danube with rafts. An existing trade road from the Inn valley across Seefelder Pass into the northern foothills of the alps was built up and called Via Raetia by the Romans. The town of Mittenwald thus became an important trade post in the Werdenfelser Land.
At a few places the Romans built wooden bridges across the "Isara" so they could cross the river with its strong currents more easily. One of these could have been along the Roman road from Salzburg to Augsburg south of contemporary Munich. Thus trade traffic could easily be controlled and income from tolls was frequent and regular. The medieval foundation of the cities of Munich and Landshut are directly connected with the building of bridges and the resulting conflicts concerning power and influence on the economy. Due to the continuing growth of the cities there was a constant demand for timber and lime, which resulted in an increase of commercial rafting. Beginning in the 17th century wares like Mediterranean fruit, spices, cotton and silk from the "Venetian Market" in Mittenwald were transported down the Isar and Danube all the way to Vienna and Budapest. During the 19th century when commercial rafting was at its peak, some 8,000 rafts arrived in Munich each year.
Since the Middle Ages water mills were working at the banks of the Isar by hydro mechanical power. To ensure a more constant flow for the mills the water in Munich was led into small canals. The canals were also used to provide freshwater to the population of the city and also the numerous tanneries of the city and to fill the protecting ditches located outside the medieval town wall. During the annual floodings cities along the Isar were flooded again and again, causing severe damage and even killing people. In 1813 a bridge in Munich collapsed during a flood, killing more than 100 people who were watching the flooding from the bridge. From 1806 on, the banks of the river were fixed and the river was canalized. This led to its deeper digging into the river bed due to its flowing faster. Further extensive measures have been taken since the 1920s to install hydroelectric power plants. From 1954 to 1959 the then much-disputed Sylvensteinspeicher was built for the generation of electricity and for protection against floodings. The village of Fall was drowned in the reservoir. When the water level in the reservoir is very low the church tower can still be seen sticking out of the water. Only over the last few years the Isar was partly turned back from a canal into a more natural river.
At the lower Isar between Moosburg and Plattling gold was washed from the river’s sediments during the 16th and 17th century. However, there was no big economic revenue in this due to the minor amounts of the metal found in the river.
Following their executions on October 16, 1946, the ashes of the convicted Nazi war criminals Joachim von Ribbentrop, Hans Frank, Wilhelm Keitel, Alfred Jodl, Alfred Rosenberg, Ernst Kaltenbrunner, Wilhelm Frick, Arthur Seyss-Inquart, Fritz Sauckel and Julius Streicher were scattered in the Isar, as were those of Hermann Göring who had committed suicide the previous night in defiance of his scheduled execution.
Environmental issues.
Since the 1920s the water of the Isar has been used for the generation of electricity. This has had far-reaching consequences not only for the local fauna and flora but also for people. To provide the 28 hydroelectric power plants with enough water power the river’s water is diverted several times and almost the whole river was canalized. For example, just north of Mittenwald all the river’s water was diverted to the lake Walchensee in 1923 for the Walchensee hydroelectric plant. Since 1990 a small portion of the water, 4 cubic meters per second (1100 U.S. gallons per second) is allowed to remain in the river to keep the area from being dry. The construction of the Sylvenstein Dam and numerous regulations relating to the river (pushed through in the early 19th century) have strongly enhanced its character. The construction of the Sylvenstein dam has prevented the river from overflowing its banks.
Lately, there have been attempts to bring the Isar closer back to a natural character. For example, since May, 2000, the river is being re-naturalized in the southern part of the river’s passage through the city of Munich, between Großhesseloher Brücke and Reichenbachbrücke. To achieve this the riverbed is being widened, the banks are flattened and small gravel islands are built along with near-natural ramps to slow the waterflow. Also, the dams are enlarged in width and height.
Besides an improved protection against flooding the river was, thus, brought into an almost natural state and this resulted in an improved quality of the recreational area within the city of Munich. The quality of the water has also improved due to the upgrading of the sewage plants along the river. The number of germs, however, is still relatively high. Together with other cities and communities along the Isar, Munich has set a goal to reduce the number of germs until the water quality is good enough to allow bathing in the river. If this is achieved, Munich would be one of the few big cities in Europe with a river with water of good enough quality to allow swimming in it. The sewer plants on the upper river are now treating the sewage with ultraviolet light, which greatly reduces the number of germs, but still the Isar cannot be guaranteed safe to bathe in because of the entrance of polluted rainwater into the river, especially during strong precipitation.
There are a number of natural reservations along the Isar, including special protection areas for birds, for example the natural reserve "Vogelfreistätte Mittlere Isarstauseen" northeast of Moosburg. This area is an important resting place for migrating water birds. There has been evidence for more than 260 different species of birds, among them rare species like the common tern and the bluethroat.
To preserve the beauty of the Isar valley Gabriel von Seidl founded the "Isartalverein" in 1902. This first civil initiative from Munich purchased of land, and today maintains more than of hiking trails.
Recreation.
There are several areas along the river Isar that have been designated since the 1960s as nudist resorts. However, along much of its banks, even within the city of Munich, people can be seen skinny-dipping wherever they please.


Ziller

The Ziller () is a right tributary to the Inn, in the Zillertal in Tyrol, Austria. It is long, and its basin area is . It springs from the ridge of the Zillertal Alps, and feeds the Zillergründl Dam. In Mayrhofen it receives the Zemmbach (that in turn receives the Tuxbach. By Zell am Ziller it receives the Gerlosbach, before it flows into the Inn by Strass im Zillertal.
For historical reasons, the Ziller—first mentioned in 927 as "Zilare"—for most of its course makes up the border between the Diocese of Innsbruck on the west and the Archdiocese of Salzburg on the east. The Ziller today shows a good presence of brown trout and rainbow trout, as well as grayling. It is up to wide and deep, and it has an average discharge of .


Kildare Capes Formation

The Kildare Capes Formation is a geologic formation in Prince Edward Island. It preserves fossils dating back to the Permian period.


Boca de Serpiente Formation

The Boca de Serpiente Formation is a geologic formation in Trinidad and Tobago. The limestones stained red with hematite, preserve fossils dating back to the Priabonian period.


Bardahessiagh Formation

The Bardahessiagh Formation is a geologic formation in Northern Ireland. It has been described from a locality lying about 3 km NNE of Pomeroy, south of Craigbardahessiagh. It is now known as comprising the former ‘Bardahessiagh Formation’, or Bardahessiagh Beds and the ‘Junction Beds’ that is underlain by a stratigraphical unit not recognised, until fieldwork by the Ulster Museum staff in 1992. The Bardahessiagh Formation is divided into three units, but the summit of the formation is not known. Field evidence indicates that the local top of the formation is characterised by a thrust contact with the Killey Bridge and Tirnaskea Formation (upper Katian and Hirnantian, respectively), exposed south of the Well Field, which lies 650 metres SSW of Craigbardahessiagh.
Constraints on the age of the formation is based on the brachiopod faunas and an upper Sandbian to lower Katian age has been proposed.
The Bardahessiagh Formation preserves a diverse and well-preserved assemblage of fossils. Only the brachiopods, cephalopods, bivalves and kilbuchophyllid corals have been systematically described.
Based on the brachiopod faunas, the Bardahessiagh Formation has been interpreted as deposited in a transgressive regime, below storm-wave base environments, peaking in the second unit, with the presence of typical Sericoidea association (Candela 2001, 2006).
The integrity of the formation is currently endangered by excavation by locals using trenchers to dig irrigation ditches.


Alluvium

Alluvium (from the Latin "alluvius", from "alluere", "to wash against") is loose, unconsolidated (not cemented together into a solid rock) soil or sediment that has been eroded, reshaped by water in some form, and redeposited in a non-marine setting. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. When this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it is called an alluvial deposit.
Definitions.
The term "alluvium" is not typically used in situations where the formation of the sediment can clearly be attributed to another geologic process that is well described. This includes (but is not limited to): lake sediments (lacustrine), river sediments (fluvial), or glacially-derived sediments (glacial till). Sediments that are formed or deposited in a perennial stream or river are typically not referred to as alluvial.
Age.
Most alluvium is geologically Quaternary in age and is often referred to as "cover" because these sediments obscure the underlying bedrock. Most sedimentary material that fills a basin ("basin fill") that is not lithified is typically lumped together as "alluvial". On basis of their ages it is divided into two types:
Alluvium of Pliocene age occurs, for example, in parts of Idaho. Alluvium of late Miocene age occurs, for example, in the valley of the San Joaquin River, California.


Yarlung Tsangpo

The Yarlung Tsangpo, also called Yarlung Zangbo () or Yalu Zangbu () is the upper stream of the Brahmaputra River located in the Tibet Autonomous Region, China. It is the longest river of Tibet.
Originating at Angsi Glacier in western Tibet, southeast of Mount Kailash and Lake Manasarovar, it later forms the South Tibet Valley and Yarlung Tsangpo Grand Canyon before passing into the state of Arunachal Pradesh, India. Downstream from Arunachal Pradesh the river becomes far wider and is called the Siang. After reaching Assam, the river is known as Brahmaputra. From Assam, the river enters Bangladesh at Ramnabazar. From there until about 200 years ago it used to flow eastward and joined the Meghna River near Bhairab Upazila. This old channel has been gradually dying. At present the main channel of the river is called Jamuna River, which flows southward to meet Ganges, which in Bangladesh is called the Padma.
When leaving the Tibetan Plateau, the River forms the world's largest and deepest canyon, Yarlung Tsangpo Grand Canyon.
Description.
The Yarlung Tsangpo River is the highest major river in the world. Its longest tributary is the Nyang River. Major tributaries of Yarlung Tsangpo include Nyangchu River, Lhasa River, Nyang River, and Parlung Tsangpo.
In Tibet the river flows through the South Tibet Valley, which is approximately long and wide. The valley descends from above sea level to . As it descends, the surrounding vegetation changes from cold desert to arid steppe to deciduous scrub vegetation. It ultimately changes into a conifer and rhododendron forest. The tree line is approximately . Sedimentary sandstone rocks found near the Tibetan capital of Lhasa contain grains of magnetic minerals that record the Earth's alternating magnetic field current.
The basin of the Yarlung River, bounded by the Himalayas in the south and Kang Rinpoche and Nyenchen Tanglha Mountains in the north, has less severe climate than the more northern (and higher-altitude) parts of Tibet, and is home to most of the population of the Tibetan Autonomous Region.
The Yarlung Tsangpo Grand Canyon, formed by a horse-shoe bend in the river where it leaves the Tibetan Plateau and flows around Namcha Barwa, is the deepest, and possibly longest canyon in the world.
The Yarlung Tsangpo River has three major waterfalls in its entire course. The largest waterfall of the river, the "Hidden Falls", was not publicized in the West until 1998, when its sighting by Westerners was briefly hailed as a "discovery." They were even portrayed as the discovery of the great falls which had been the topic of stories told to early Westerners by Tibetan hunters and Buddhist monks, but which had never been found by Western explorers at the time. The Chinese authorities protested, however, saying that Chinese geographers, who had explored the gorge since 1973, had already taken pictures of the falls in 1987 from a helicopter.
Kayak exploration.
Since the 1990s the Yarlung Tsangpo River has been the destination of a number of teams that engage in exploration and whitewater kayaking. The river has been called the "Everest of Rivers" because of the extreme conditions of the river. The first attempt to run was made in 1993 by a Japanese group who lost one member on the river.
In October 1998, a kayaking expedition sponsored by the National Geographic Society attempted to navigate the Yarlung Tsangpo Grand Canyon. Troubled by unanticipated high water levels, the expedition ended in tragedy with the death of expert kayaker Doug Gordon.
In January–February, 2002, an international group consisting of Scott Lindgren, Steve Fisher, Mike Abbott, Allan Ellard, Dustin Knapp, and Johnnie and Willie Kern, completed the first descent of the upper Tsangpo gorge section.
Dams and hydropower projects.
In November 2020, the chairman of PowerChina announced the construction of a "super" dam on the Yarlung Zangbo which would be the world's largest hydroelectric project.


Nevremont Formation

The Nevremont Formation is a geologic formation in France. It preserves fossils dating back to the Devonian period.


Grevenstein Formation

The Grevenstein Formation is a geologic formation in Germany. It preserves fossils dating back to the Devonian period.


Devils Gate Limestone

The Devils Gate Limestone is a limestone geologic formation in Nevada.
It preserves fossils dating back to the Devonian period.


Ignotornis

Ignotornis was a bird ichnogenus dating back to the Barremian-Cenomanian of Colorado, Canada and South Korea.


Chambers Tuff

The Chambers Tuff is a geologic group in Texas. It preserves fossils dating back to the Paleogene period.


Macula (planetary geology)

Macula (pl. maculae ) is the Latin word for 'spot'. It is used in planetary nomenclature to refer to unusually dark areas on the surface of a planet or moon. They are seen on the icy surfaces of Pluto, Jupiter's moon Europa, Saturn's moon Titan, Neptune's moon Triton, and Pluto's moon Charon. The term was adopted for planetary nomenclature when high resolution pictures of Europa revealed unusual new surface features.


Steganoposaurus

Steganoposaurus is an ichnogenus of fossil reptile footprints. The ichnospecies "Steganoposaurus belli", was erected for footprints discovered in Wyoming's Tensleep Sandstone. The find was first reported to the scientific literature by Edward Branson and Maurice Mehl in 1932. This creature was originally presumed to be an amphibian, but the toe prints it left behind were pointed like a reptile's rather than round like an amphibians. The actual trackmaker may have been similar to the genus "Hylonomus". The ichnogenus "Tridentichnus" are similar footprints preserved in the Supai Formation of Arizona.


Joins Formation

The Joins Formation is a geologic formation in Oklahoma. It preserves fossils dating back to the Ordovician period.


Winifred Goldring

Winifred Goldring (February 1, 1888 – January 30, 1971), was an American paleontologist whose work included a description of stromatolites, as well as the study of Devonian crinoids. She was the first woman in the nation to be appointed as a State Paleontologist.
Early life and education.
Goldring was born in Kenwood, [[New York (state)|New York, to Frederick Goldring, an orchid specialist at the Erastus Corning estate, and Mary Grey, a local school teacher whose father was the head of the orchid that Frederick was employed. Shortly after, in 1890, Goldring, her parents and her seven sisters and one brother moved to Slingerlands, New York, so her family could operate a greenhouse business. Goldring lived here, in her childhood home, for the majority of her life (81 years). Goldring spent her live devout to her education and professional career, and as a result, she never married. She did, however, spend time learning the violin purely for her love of music.
Her journey into education began at Slingerland District school, and then after spending nine years there, she went on to [[The Milne School]] in Albany, NY in which she graduated as valedictorian in 1905. Between classes, she spent much of her free time exploring the outdoors, where she developed a love and curiosity for Lower Devonian rocks. Following this, she enrolled in [[Wellesley College]], a school for women, with an intended major in classical languages before developing a love for science. She attained her Bachelors in 1909 and her Masters in 1912, while also obtaining graduate work at [[Harvard University]]. She finished her education at [[Johns Hopkins University]], her school in 1921.
Professional career.
Goldring first began her career as a geology professor at her alma mater Wellesley College, and as well obtained a position at Boston's Teacher's School of Science. In 1912, Goldring went on to work for the New York state Museum as a Scientific Expert in Paleontology. At the New York State Museum, she was hired to work as a scientific expert where she specialized in invertebrate paleontological exhibits and dioramas. From here, she successfully collected and organized data from an unfinished collaborative study on Devonian Crinoids. In 1916, her boss at the New York State Museum requested her to continue work on a crinoid fossil study, which had been started but not completed by several other palaeontologists before her. She was required to finish identifying the different taxonomies of crinoid fossils. Not only was she able to complete this study in seven years, but out of the 25 families, 60 genera, and 155 species she recorded, she identified 2 new families, 18 new genera and 58 new species. Based on this evidence Goldring concluded the stumps were a new genus she chose to name Eospermatoperis. Goldring published her findings in a monograph in 1923. This was so successful that other scientists and palaeontologists sent her their own fossil samples for her to identify.
On top of the Devonian Crinoids, Goldring also contributed many other dioramas to the New York State Museum. The [[Petrified Sea Gardens]], the stromatolite site that she studied, is a [[National Natural Landmark]] and a [[National Historic Landmark]] of the United States. Her most famous diorama recreated the living fossil seed fern forest from the Devonian period in what is now [[Gilboa, New York]]. This model truly solidified her reputation as an excellent paleontologist. This was possibly the first-ever diorama about early life anyone had created. This acclaimed diorama was named the Gilboa Fossil Forest after where it was located, as well as what Goldring used to piece together the layout of this diorama. In 1850 and 1920 in Gilboa, New York, petrified wood and fossilized rocks, respectively, were found and in 1920, Goldring studied them and eventually identified them to be the fossils of seed ferns.
Goldring was an educator as well as a researcher, so while she devoted most of her life to the museum, she extensively utilized her knowledge to make the contents go beyond simply filling the museum by exploring ways to teach paleontology to the visitors. For example, Goldring's success with geological models and teaching displays progressed into her publishing many books on geology, some of these publications were even used for post secondary education purposes. She created two geological models that were made to teach geological basics. They were titled “What is a Fossil” and “What is a Geological Formation”.
She rarely conducted research abroad or traveled out of the state of New York, however, the one trip she had made was of great importance. In order to help Dr. John M. Clarke write his memoir on the areas of Gaspé and Nova Scotia, Goldring travelled there to collect Devonian fossils. Over the first 10 years of her career, she quickly proved her skills, earning different promotions including first Assistant Paleontologist, the Associate Paleontologist, Paleobotanist, and Assistant State Paleontologist. Goldring eventually became the fourth State [[Paleontologist]] of [[New York (state)|New York]], and the first woman to hold that position. In 1949 she was elected president of the [[Paleontological Society]] (the largest association of paleontologists in the world), the first woman to hold that office and one of only three women to attain that position to this day. Because these were (and still are) male-dominated geological societies, large numbers of men would not have supported her candidacy, underscoring her prominence as a nationally-known geologist respected for the quality of her research, despite prevalent gender prejudices in academia. Winfred faced many equality issues such as unfair compensation and rare opportunities for advancement and in 1918 she briefly resigned over issues of inadequate salary combined with great pressures.
After forty years of commitment to the field, Goldring retired in 1954 and spent the next sixteen years at her family home in Slingerlands.
References.
[[Category:American paleontologists]]
[[Category:1888 births]]
[[Category:1971 deaths]]
[[Category:Women paleontologists]]
[[Category:20th-century American geologists]]
[[Category:20th-century American women scientists]]
[[Category:20th-century American biologists]]
[[Category:People from Bethlehem, New York]]
[[Category:Wellesley College alumni]]
[[Category:Wellesley College faculty]]
[[Category:Harvard University alumni]]
[[Category:Johns Hopkins University alumni]]
[[Category:Scientists from New York (state)]]
[[Category:American women academics]]


Cheney Longville Formation

The Cheney Longville Formation is a geologic formation in England. It preserves fossils dating back to the Ordovician period.


Poudingue de Vihiers

The Poudingue de Vihiers is a geologic formation in France. It preserves fossils dating back to the Cambrian period.


Cherryvale Formation

The Cherryvale Formation is a geologic formation in Oklahoma. It preserves fossils dating back to the Carboniferous period.


William D. Turnbull

William D. Turnbull (1922-2011) was an American paleontologist associated with the Chicago Field Museum. He published over 100 papers on mammals, continuing after his retirement as the museum's curator of mammals. He searched in Australia for evidence of recently extinct species, and made frequent expeditions to sites at the Washakie Formation in southwest Wyoming. His studies are considered significant contributions to the paleontology and biogeography of dinosaurs and Eocene mammals.
A species of marsupial in the Thylacinidae family, an ancestor of the Tasmanian tiger "Thylacinus cynocephalus", was named "Badjcinus turnbulli" in honour of Turnbull's contributions to Australian palaeontology.


Faceting machine

A faceting machine is broadly defined as any device that allows the user to place and polish facets onto a mineral specimen. Machines can range in sophistication from primitive jamb-peg machines to highly refined, and highly expensive, commercially available machines. A major division among machines is found between those that facet diamonds and those that do not. Specialized equipment is required for diamond faceting, and faceting as an occupation rarely bridges the gap between diamond and non-diamond workmanship. A second division can be made between industrial faceting and custom/hobby faceting. The vast majority of jewelry-store gemstones are faceted either abroad in factories or entirely by machines. (Diamonds are the exception, owing to the training and specialized equipment required to facet them.) Custom jewelry is still commonly made of custom metalwork and mass-produced gemstones, but unusual cuts or particularly valuable gemstone material will likely be faceted on a personal faceting machine.
Home and custom faceting machines.
A number of manufacturers sell non-commercial faceting machines. Among the more common names are Ultra-Tec, Facetron, Graves and Poly-Metric, although there are many competing brands. They range in price from just over $1,000 to upwards of $4,000.
The essentials of how a faceting machine works will be explored through this type of machine. There are two major components of a faceting machine: The mast/head assembly, and the grinding wheel, or lap. A rough piece of mineral is attached to the head, and through angle, rotation, and height adjustments of the head, the mineral is lowered into contact with the grinding wheel until a facet has been ground.
Major components.
The mast assembly is the heart of the faceting machine. The rest of the machine is simple in construction, including the arbor for the grinding wheel, the motor that runs the arbor, a drip tank, and the controlling switches. These are described below:
Arbor: Similar to the prong in the middle of a record player, onto which the record is placed. The lap, or grinding wheel, is placed onto it rather than a record, and the arbor is machined to run perfectly flat when turning.
Arbor Nut: The screw that fits through the top of the lap and secures it to the arbor.
Motor: Typically the motor is housed beneath the machine and is attached by one of several means to the arbor. Motors are always velocity-variable and some can be reversed, i.e. clockwise as well as counterclockwise.
Drip Tank: The drip tank serves two purposes. 1) The friction produced from contact between the rough and the lap creates heat, which can damage the lap and create stress fractures in the stone. The drip tank allows the user to choose a drip rate via spigot and to position the spigot over the lap, nearer or farther from the arbor. 2) The dust produced from grinding minerals can cause pulmonary disease if inhaled. The flow of water captures the particles in a slurry, which drains into a rubber container around and below the lap. This container has an exit tube that drains into a second receptacle.
Controls: The controls are generally simple and control the rotational velocity of the lap—the key control—and sometimes the direction of spin, i.e. clockwise or counterclockwise.
Mast assembly.
As stated above, the mast assembly is what makes a faceting machine a faceting machine. Its components are as follows:
Mast: A vertical pole mounted into the base of the machine on which the assembly is positioned. The pole must be machined with extreme care to ensure its perpendicularity to the lap. This is so that, when the angles for facets are chosen, they are placed at the correct angle. Facets at incorrect angles can mean a gemstone that is lifeless or transparent rather than sparkly.
Dop: The piece of rough gemstone is glued or attached with hot wax to the end of a brass or steel rod, known as a dop or dop stick. The other end of the dop is placed into the quill of the faceting head. The exposed piece of rough usually becomes the bottom of the stone, known as the pavilion. Once the pavilion is faceted and polished, a jig is used to attach the pavilion to another dop, and the rough side of the stone is freed from its dop. This rough side will now become the top of the stone, or the crown.
Quill: The dop is inserted into the quill, which is lowered toward the lap to place a facet. The quill is the part of the machine that is held in the hand during faceting. The other end of the quill is attached to the main head of the assembly.
Index Wheel: If you view a gemstone from the top, you will see it has some type of symmetry. Most
round brilliant diamonds will have eightfold symmetry; emerald cuts have two or fourfold. In order to cut facets around a stone, the quill must be rotated around its long axis. The index wheel is what allows this to be done in a repeatable, accurate manner. For example, the index wheel may have 64 teeth. If a round stone with eightfold symmetry is being cut, the index will be set at 0, 8, 16, 24, 32, 40, 48 and 56 for each of the main facets around the stone. If a square stone is being cut, only 0, 16, 32 and 48 would be used.
Angle Adjustment/Goniometer: Faceting machines differ greatly in the mechanism for setting the angle of the facet. Essentially, the angle is set and the quill will then lower to exactly that angle before physically being stopped or otherwise indicating arrival at the desired angle.
Height Adjustment: The depth of a facet is determined by how high or low the head assembly is relative to the lap. The way this is determined is by choosing an angle, lowering the quill, with dop inserted, to that angle, and then observing whether and how deeply the piece of rough is contacting the lap. Generally the first adjustment will set the rough just touching the lap, so that a very shallow facet will be placed. The head can then be lowered by a micro-adjustment and the facet can be cut and re-cut until it is of a desired depth. Many machines allow the head to be untightened from the mast and slid up and down for gross adjustments, and then have a separate mechanism for making fine adjustments up and down.
Overall procedure.
First the rough stone is glued to the end of the dop. Once the glue or wax has set, the other end of the dop is inserted into the quill. The index is set to 64, which is the same as 0. The mineral in this example is quartz, so the first angle will be 45 degrees. This is set, and the quill is lowered to make sure it will stop at roughly 45 degrees. The head is then grossly adjusted for height so that the rough is just touching the lap when it is lowered into position. The machine is turned on so the lap begins to spin. The drip tank spigot is opened and adjusted so that about one drip falls per second onto the lap, and the drip is made to fall near the center of the lap so the water will be carried outward by centrifugal force and cover the whole lap. The quill is carefully lowered to the lap and contact is made. This is a grinding lap, so it is very coarse, and the sound is something like a running faucet. Gentle pressure is applied and the mineral is ground away until the quill reaches the desired angle. The quill is lifted and the facet is inspected.
If it is of adequate depth, which generally means the inner side of the facet has reached the midline of the stone, the index is turned to number 8. The quill is again lowered and a second facet is ground to 45 degrees. The height of the mast no longer needs to be set, because it is standard to have every facet be the same depth when faceting a round stone. Six more facets are placed as the index is turned, resulting in an eight-sided pyramidal shape.
If this were a rectangular stone, two facets would be ground at 0 and 32 on the index, and then the head would be raised or lowered and two facets would be placed at a shallower or deeper level at 16 and 48.
The basic shape of the pavilion has now been created. More facets at different angles can be placed. Once the basic shape is established, a series of different laps can be used that are of increasingly fine grit. Once the facets are prepolished, a final polish can be performed with a gritless lap treated with polishing compound.
Diamond faceting.
Diamond is the hardest known substance on earth, so finding a material that can be used to cut it presents a problem. Luckily, diamond's hardness is slightly different along different crystal axes. The particles of diamond on the grinding wheel are randomly oriented, so some of them will be aligned with the harder axes toward the rough diamond to be cut. The rough, therefore, needs to be extensively studied so it can be positioned for optimal cutting on the machine. The machines must be more durable and have different features than cutting machines for other gemstones. The process is far more involved and, of course, more expensive, so diamond cutting hobbyists are far rarer than cutters of other gemstones. A gemcutter who can cut professional-quality diamonds is called a diamantaire.


Dynamic tidal power

Dynamic tidal power or DTP is an untried but promising technology for tidal power generation. It would involve creating a long dam-like structure perpendicular to the coast, with the option for a coast-parallel barrier at the far end, forming a large 'T' shape. This long T-dam would interfere with coast-parallel tidal wave hydrodynamics, creating water level differences on opposite sides of the barrier which drive a series of bi-directional turbines installed in the dam. Oscillating tidal waves which run along the coasts of continental shelves, containing powerful hydraulic currents, are common in "e.g." China, Korea, and the UK.
The concept was invented and patented in 1997 by Dutch coastal engineers Kees Hulsbergen and Rob Steijn.
A short video explaining the concept was completed in October 2013 and made available in English on YouTube and in Chinese on Youku.
Description.
A DTP dam is a long barrier of 30 km or more which is built perpendicular to the coast, running straight out into the sea, without enclosing an area. Along many coasts of the world, the main tidal movement runs parallel to the coastline: the entire mass of the ocean water accelerates in one direction, and later in the day back the other way. A DTP dam is long enough to exert an influence on the horizontal tidal movement, which generates a water level differential (head) over both sides of the dam. The head can be converted into power, using a long series of conventional low-head turbines installed in the dam.
Maximum head difference.
Estimates of the maximum head difference that can be obtained from a variety of dam configurations are based on numerical and analytical models. Field information from measured water level differences across natural barriers confirms the creation of significant head. The (maximum) head difference is more than what would be expected in stationary flow situations (such as rivers). The maximum head difference reaches values up to a few m, which can be attributed to the non-permanent character of the tidal flow (acceleration).
Benefits.
High power output.
It is estimated that some of the largest dams could accommodate over 15 GW (15000 MW) of installed capacity.
A DTP dam with 8 GW installed capacity and a capacity factor of about 30%, could generate about 21 TWh annually. To put this number in perspective, an average European person consumes about 6800 kWh per year, so one DTP dam could supply energy for about 3 million Europeans.
Stable power.
The generation of tidal power is highly predictable due to the deterministic nature of tides, and independent of weather conditions or climate change. Power output varies with the tidal phase (ebb & flow, neap & spring) but the shorter terms effects can be avoided by combining two dams, placed at certain distance from each other (in the order of 150–250 km), each generating maximum electricity output when the other is generating minimal output. This provides a predictable and fairly stable base generation to the energy grid.
High availability.
Dynamic tidal power doesn't require a very high natural tidal range, but instead an open coast where the tidal propagation is alongshore. Such tidal conditions can be found in many places around the world, which means that the theoretical potential of DTP is very high. Along the Chinese coast for example, the total amount of available power is estimated at 80 - 150 GW.
Potential for combined functions.
The long dam can be combined with various other functions, such as coastal protection, deep sea – and LNG ports, aquaculture facilities, controlled land reclamation and connections between islands and the mainland. These additional functions can share the investment costs, thus helping to lower the price per kWh.
Challenges.
A major challenge is that the proof of DTP functioning can only be demonstrated by putting it in practice. Testing the concept of DTP at a small scale within a demonstration project, would not be effective, since almost no power would be yielded. Not even at a dam length of 1 km or so, because the DTP principle is such that the power generation capacity increases as the square of the dam length increases (both head and volume increase in a more or less linear manner for increased dam length, resulting in a quadratic increase in power generation). Economic viability is estimated to be reached for dam lengths of about 30 km.
Demonstration project.
A demonstration project under consideration in China would not involve construction of a dam, but instead feature a newly cut channel through a long peninsula with a narrow isthmus (neck). The channel would feature a head of about , and be fitted with low-head bi-directional turbines, similar to the type which would be used for full-scale DTP.
Status of technological development.
No DTP dam has ever been built, although all of the technologies required to build a DTP dam are available. Various mathematical and physical models have been conducted to model and predict the 'head' or water level differential over a dynamic tidal power dam. The interaction between tides and long dams has been observed and recorded in large engineering projects, such as the Delta Works and the Afsluitdijk in the Netherlands. The interaction of tidal currents with natural peninsulas is also well-known, and such data is used to calibrate numerical models of tides. Formulas for the calculation of added mass were applied to develop an analytical model of DTP. Observed water level differentials closely match current analytical and numerical models. Water level differential generated over a DTP dam can now be predicted with a useful degree of accuracy.
Some of the key elements required include:
Recent progress.
In December 2011 the Dutch Ministry of Economy, Agriculture and Innovation (EL&I) awarded a grant funding subsidy to the POWER consortium, led by Strukton and managed by ARCADIS. The maximum grant is about 930.000 euro, which is matched by a similar amount of co-financing from the consortium partners. The POWER group conducts a detailed feasibility study on the development of Dynamic Tidal Power (DTP) in China in a 3-year programme jointly conducted with Chinese government institutes.
The commitments of the programme to achieve by 2015, registered under the UN Sustainable Energy for All initiative include:
In August 2012, China's National Energy Administration formed a consortium of companies and research institutes, led by the Hydropower and Water Resources Planning and Design General Institute (also known as China Renewable Energy Engineering Institute), to investigate DTP. A bilateral agreement on DTP cooperation was signed between China and the Netherlands on September 27, 2012. Following technical exchange to verify the principles, a modelling study was conducted to select sites. In October 2013, a more in-depth economic analysis study was started to better understand the economic costs and benefits of DTP.
A short video explaining the concept was completed in October 2013 and made available in English on YouTube and in Chinese on Youku.


Nosoni Formation

The Nosoni Formation is a geologic formation in California. It preserves fossils dating back to the Permian period.


Swasey Formation

The Swasey Formation is a geologic formation in Utah. It preserves fossils dating back to the Cambrian period.


Sonia Kreidenweis

Sonia Maria Kreidenweis is an American Professor of Atmospheric Sciences at Colorado State University. Her research considers aerosols and their impact on weather and the climate. She has previously served as President of the American Association for Aerosol Research and was a board member of the American Meteorological Society. She was elected a Fellow of the American Geophysical Union in 2019.
Early life and education.
Kreidenweis grew up in New York City. As a child she was aware of air pollution, and became interested in investigating smog. She studied chemical engineering at Manhattan College in 1983. She was the first in her family to complete a Bachelor's degree. During her undergraduate degree she decided she would pursue studying, and chose to for academics who were becoming increasingly interested in air quality and environmental issues. She moved to California Institute of Technology for her graduate studies, earning a Master's degree in 1985 and a doctorate in 1989. She was supervised by John H. Seinfeld and worked on binary nucleation.
Research and career.
After earning her PhD, Kreidenweis was appointed to San Jose State University as an Assistant Professor. She worked simultaneously as a consultant for Lawrence Livermore National Laboratory, where she advised on chemical interactions in the atmosphere. Kreidenweis joined the faculty at Colorado State University in 1991. She spent 1999 as a Visiting Fellow at the Goddard Space Flight Center and remains affiliated with the Airborne Science Program. Her research considers the physical, chemical and optical properties of atmospheric particles. She has investigated the interactions of atmospheric aerosol on climate and visibility, as well as how aerosols interact with water vapour. She has developed several new scientific approaches to study aerosols and atmospheric particulates. She has created the methodologies to evaluate the consequences of pollution on precipitation, leading to a better understanding of the impact of aerosols on cloud formation and evolution. Her work has focussed on air pollution in US National Parks.
In 2015 Kreidenweis was awarded a $7.5 million United States Naval Research Laboratory grant to characterise aerosol particles in coastal regions. She has investigated cloud condensation nuclei and their representation in climate models. In this capacity, she is a member of the National Science Foundation program "Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen" (WE-CAN). The program looks to understand the chemistry in western wildfire smoke, which has significant impacts on air quality, climate, weather and nutrient cycles. Kreidenweis leads the cloud condensation nuclei counter.
Kreidenweis is interested in the characteristics of atmospheric particles that are responsible for compromised visibility, and has extensively studied the impacts of wildfires. She has investigated how breathable particles grow and form new particles during wild fires, performing open burns of biomass at the Missoula Fire Sciences Lab.
She was made a University Distinguished Professor in 2014. In 2015 she served as Dean for Research at the Colorado State University College of Engineering. She serves on the Membership Committee of the American Meteorological Society.
Awards and honours.
Her awards and honours include;
Selected publications.
Her publications include;
Kreidenweis is Associate Editor of the Journal of Advances in Modeling Earth Systems.


Spence Shale

The Spence Shale is the middle member of the Langston Formation in southeastern Idaho and northeastern Utah. It is exposed in the Bear River Range, the Wasatch Range and the Wellsville Mountains. It is known for its abundant Cambrian trilobites and the preservation of Burgess Shale-type fossils.
The type locality is Spence Gulch in southeastern Idaho, near the town of Liberty. It was first described by Charles Doolittle Walcott in 1908.
Stratigraphy.
The Spence Shale spans the "Albertella" and "Glossopleura" biozones.
Fauna.
Generic list of the fauna of the Spence Shale:


Saelabonn Formation

The Saelabonn Formation is a geologic formation in Norway. It preserves fossils dating back to the Silurian period.


Cabaniss Formation

The Cabaniss Formation is a geologic formation in Missouri. It preserves fossils dating back to the Carboniferous period.


Chondrite

A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primitive asteroids. Some such bodies that are captured in the planet’s gravity well become the most common type of meteorite by (whether quickly, or after many orbits) arriving on a trajectory toward the Earth’s surface. Estimates for their contribution to the total meteorite population vary between 85.7% and 86.2%.
Their study provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the origin of life and the presence of water on Earth. One of their characteristics is the presence of chondrules, which are round grains formed by distinct minerals, that normally constitute between 20% and 80% of a chondrite by volume.
Chondrites can be differentiated from iron meteorites due to their low iron and nickel content. Other non-metallic meteorites, achondrites, which lack chondrules, were formed more recently.
There are currently over 27,000 chondrites in the world's collections. The largest individual stone ever recovered, weighing 1770 kg, was part of the Jilin meteorite shower of 1976. Chondrite falls range from single stones to extraordinary showers consisting of thousands of individual stones. An instance of the latter occurred in the Holbrook fall of 1912, in which an estimated 14,000 stones grounded in northern Arizona.
Origin and history.
Chondrites were formed by the accretion of particles of dust and grit present in the primitive Solar System which gave rise to asteroids over 4.54 billion years ago. These asteroid parent bodies of chondrites are (or were) small to medium-sized asteroids that were never part of any body large enough to undergo melting and planetary differentiation. Dating using 206Pb/204Pb gives an estimated age of 4,566.6 ± 1.0 Ma, matching ages for other chronometers. Another indication of their age is the fact that the abundance of non-volatile elements in chondrites is similar to that found in the atmosphere of the Sun and other stars in our galaxy.
Although chondritic asteroids never became hot enough to melt based upon internal temperatures, many of them reached high enough temperatures that they experienced significant thermal metamorphism in their interiors. The source of the heat was most likely energy coming from the decay of short-lived radioisotopes (half-lives less than a few million years) that were present in the newly formed solar system, especially 26Al and 60Fe, although heating may have been caused by impacts onto the asteroids as well. Many chondritic asteroids also contained significant amounts of water, possibly due to the accretion of ice along with rocky material.
As a result, many chondrites contain hydrous minerals, such as clays, that formed when the water interacted with the rock on the asteroid in a process known as aqueous alteration. In addition, all chondritic asteroids were affected by impact and shock processes due to collisions with other asteroids. These events caused a variety of effects, ranging from simple compaction to brecciation, veining, localized melting, and formation of high-pressure minerals. The net result of these secondary thermal, aqueous, and shock processes is that only a few known chondrites preserve in pristine form the original dust, chondrules, and inclusions from which they formed.
Characteristics.
Prominent among the components present in chondrites are the enigmatic chondrules, millimetre-sized spherical objects that originated as freely floating, molten or partially molten droplets in space; most chondrules are rich in the silicate minerals olivine and pyroxene.
Chondrites also contain refractory inclusions (including Ca–Al Inclusions), which are among the oldest objects to form in the solar system, particles rich in metallic Fe-Ni and sulfides, and isolated grains of silicate minerals. The remainder of chondrites consists of fine-grained (micrometre-sized or smaller) dust, which may either be present as the matrix of the rock or may form rims or mantles around individual chondrules and refractory inclusions. Embedded in this dust are presolar grains, which predate the formation of our solar system and originated elsewhere in the galaxy. The chondrules have distinct texture, composition and mineralogy, and their origin continues to be the object of some debate. The scientific community generally accepts that these spheres were formed by the action of a shock wave that passed through the Solar System, although there is little agreement as to the cause of this shock wave.
An article published in 2005 proposed that the gravitational instability of the gaseous disk that formed Jupiter generated a shock wave with a velocity of more than 10 km/s, which resulted in the formation of the chondrules.
Chondrite classification.
Chondrites are divided into about 15 distinct groups "(see Meteorites classification)" on the basis of their mineralogy, bulk chemical composition, and oxygen isotope compositions "(see below)". The various chondrite groups likely originated on separate asteroids or groups of related asteroids. Each chondrite group has a distinctive mixture of chondrules, refractory inclusions, matrix (dust), and other components and a characteristic grain size. Other ways of classifying chondrites include weathering and shock.
Chondrites can also be categorized according to their petrologic type, which is the degree to which they were thermally metamorphosed or aqueously altered (they are assigned a number between 1 and 7). The chondrules in a chondrite that is assigned a "3" have not been altered. Larger numbers indicate an increase in thermal metamorphosis up to a maximum of 7, where the chondrules have been destroyed. Numbers lower than 3 are given to chondrites whose chondrules have been changed by the presence of water, down to 1, where the chondrules have been obliterated by this alteration.
A synthesis of the various classification schemes is provided in the table below.
Enstatite chondrites.
Enstatite chondrites (also known as E-type chondrites) are a rare form of meteorite thought to comprise only about 2% of the chondrites that fall to Earth. Only about 200 E-Type chondrites are currently known. The majority of enstatite chondrites have either been recovered in Antarctica or have been collected by the American National Weather Association. They tend to be high in the mineral enstatite (MgSiO3), from which they derive their name.
E-type chondrites are among the most chemically reduced rocks known, with most of their iron taking the form of metal or sulfide rather than as an oxide. This suggests that they were formed in an area that lacked oxygen, probably within the orbit of Mercury.
Ordinary chondrites.
Ordinary chondrites are by far the most common type of meteorite to fall to Earth: about 80% of all meteorites and over 90% of chondrites are ordinary chondrites. They contain abundant chondrules, sparse matrix (10–15% of the rock), few refractory inclusions, and variable amounts of Fe-Ni metal and troilite (FeS). Their chondrules are generally in the range of 0.5 to 1 mm in diameter. Ordinary chondrites are distinguished chemically by their depletions in refractory lithophile elements, such as Ca, Al, Ti, and rare earths, relative to Si, and isotopically by their unusually high 17O/16O ratios relative to 18O/16O compared to Earth rocks.
Most, but not all, ordinary chondrites have experienced significant degrees of metamorphism, having reached temperatures well above 500 °C on the parent asteroids. They are divided into three groups, which have different amounts of metal and different amounts of total iron:
An example of this group is the NWA 869 meteorite.
Carbonaceous chondrites.
Carbonaceous chondrites (also known as C-type chondrites) make up less than 5% of the chondrites that fall on Earth. They are characterized by the presence of carbon compounds, including amino acids. They are thought to have been formed the farthest from the sun of any of the chondrites as they have the highest proportion of volatile compounds. Another of their main characteristics is the presence of water or of minerals that have been altered by the presence of water.
There are many groups of carbonaceous chondrites, but most of them are distinguished chemically by enrichments in refractory lithophile elements relative to Si and isotopically by unusually low 17O/16O ratios relative to 18O/16O compared to Earth rocks. All groups of carbonaceous chondrites except the CH group are named for a characteristic type specimen:
Kakangari chondrites.
Three chondrites form what is known as the K (Kakangari type) grouplet: Kakangari, LEW 87232, and Lea Co. 002. They are characterized by large amounts of dusty matrix and oxygen isotope compositions similar to carbonaceous chondrites, highly reduced mineral compositions and high metal abundances (6% to 10% by volume) that are most like enstatite chondrites, and concentrations of refractory lithophile elements that are most like ordinary chondrites.
Many of their other characteristics are similar to the O, E and C chondrites.
Rumuruti chondrites.
R (Rumuruti type) chondrites are a very rare group, with only one documented fall out of almost 900 documented chondrite falls. They have a number of properties in common with ordinary chondrites, including similar types of chondrules, few refractory inclusions, similar chemical composition for most elements, and the fact that 17O/16O ratios are anomalously high compared to Earth rocks. However, there are significant differences between R chondrites and ordinary chondrites: R chondrites have much more dusty matrix material (about 50% of the rock); they are much more oxidized, containing little metallic Fe-Ni; and their enrichments in 17O are higher than those of ordinary chondrites. Nearly all the metal they contain is oxidized or in the form of sulfides. They contain fewer chondrules than the E chondrites and appear to come from an asteroid's regolith.
Composition.
Because chondrites accumulated from material that formed very early in the history of the solar system, and because chondritic asteroids did not melt, they have very primitive compositions. "Primitive," in this sense, means that the abundances of most chemical elements do not differ greatly from those that are measured by spectroscopic methods in the photosphere of the sun, which in turn should be well-representative of the entire solar system (note: to make such a comparison between a gaseous object like the sun and a rock like a chondrite, scientists choose one rock-forming element, such as silicon, to use as a reference point, and then compare ratios. Thus, the atomic ratio of Mg/Si measured in the sun (1.07) is identical to that measured in CI chondrites).
Although all chondrite compositions can be considered primitive, there is variation among the different groups, as discussed above. CI chondrites seem to be nearly identical in composition to the sun for all but the gas-forming elements (e.g., hydrogen, carbon, nitrogen, and noble gases). Other chondrite groups deviate from the solar composition (i.e., they are "fractionated") in highly systematic ways:
Petrologic types.
A chondrite's group is determined by its "primary" chemical, mineralogical, and isotopic characteristics (above). The degree to which it has been affected by the "secondary" processes of thermal metamorphism and aqueous alteration on the parent asteroid is indicated by its petrologic type, which appears as a number following the group name (e.g., an LL5 chondrite belongs to the LL group and has a petrologic type of 5). The current scheme for describing petrologic types was devised by Van Schmus and Wood in 1967.
The petrologic-type scheme originated by Van Schmus and Wood is really two separate schemes, one describing aqueous alteration (types 1–2) and one describing thermal metamorphism (types 3–6). The aqueous alteration part of the system works as follows:
The thermal metamorphism part of the scheme describes a continuous sequence of changes to mineralogy and texture that accompany increasing metamorphic temperatures. These chondrites show little evidence of the effects of aqueous alteration:
Some workers have extended the Van Schmus and Wood metamorphic scheme to include a type 7, although there is not consensus on whether this is necessary. Type 7 chondrites have experienced the highest temperatures possible, short of that required to produce melting. Should the onset of melting occur the meteorite would probably be classified as a primitive achondrite instead of a chondrite.
All groups of ordinary and enstatite chondrites, as well as R and CK chondrites, show the complete metamorphic range from type 3 to 6. CO chondrites comprise only type 3 members, although these span a range of petrologic types from 3.0 to 3.8.
Presence of water.
These meteorites either contain a proportion of water or minerals that have been altered by water. This suggests that the asteroid from which these meteorites originate must have contained water. At the beginning of the Solar System this would have been present as ice and a few million years after the asteroid formed the ice would have melted allowing the liquid water to react with and alter the olivines and pyroxenes. The formation of rivers and lakes on the asteroid is thought to have been unlikely if it was sufficiently porous to allow the water to percolated towards its interior, as occurs in terrestrial aquifers.
It is thought possible that a proportion of the water present on the Earth comes from the impact of comets and carbonaceous chondrites with the Earth's surface.
Origin of life.
Carbonaceous chondrites contain more than 600 organic compounds that were synthesized in distinct places and at distinct times. These organic compounds include: hydrocarbons, carboxylic acids, alcohols, ketones, aldehydes, amines, amides, sulfonic acids, phosphonic acids, amino acids, nitrogenous bases, etc. These compounds can be divided into three main groups: a fraction that is not soluble in chloroform or methanol, chloroform soluble hydrocarbons and a fraction that is soluble in methanol (which includes the amino acids).
The first fraction appears to originate from interstellar space and the compounds belonging to the other fractions derive from a planetoid. It has been proposed that the amino acids were synthesized close to the surface of a planetoid by the radiolysis (dissociation of molecules caused by radiation) of hydrocarbons and ammonium carbonate in the presence of liquid water. In addition, the hydrocarbons could have formed deep within a planetoid by a process similar to the Fischer-Tropsch process. These conditions could be analogous to the events that caused the origin of life on Earth.
The Murchison meteorite has been thoroughly studied; it fell in Australia close to the town that bears its name on 28 September 1969. It is a CM2 and it contains common amino acids such as glycine, alanine and glutamic acid as well as other less common ones such as isovaline and pseudo-leucine.
Two meteorites that were collected in Antarctica in 1992 and 1995 were found to be abundant in amino acids, which are present at concentrations of 180 and 249 ppm (carbonaceous chondrites normally contain concentrations of 15 ppm or less). This could indicate that organic material is more abundant in the Solar System than was previously believed, and it reinforces the idea that the organic compounds present in the primordial soup could have had an extraterrestrial origin.


Principia (alga)

Principia is a genus of alga that has been placed in the coralline stem group on the basis of its slightly differentiated thallus; it forms an "intermediate" between "Hortonella", "Neoprincipia" and "Archaeolithophyllum".


Limestone Point Formation

The Limestone Point Formation is a geologic formation in New Brunswick. It preserves fossils dating back to the Silurian period.


Systems geology

Systems geology emphasizes the nature of geology as a system – that is, as a set of interacting parts that function as a whole. The systems approach involves study of the linkages or interfaces between the component objects and processes at all levels of detail in order to gain a more comprehensive understanding of the solid Earth. A long-term objective is to provide computational support throughout the cycles of investigation, integrating observation and experiment with modeling and theory, each reinforcing the other. The overall complexity suggests that systems geology must be based on the wider emerging cyberinfrastructure, and should aim to harmonize geological information with Earth system science within the context of the e-science vision of a comprehensive global knowledge system (see Linked Data, Semantic Web).
Background.
Systems geology can be seen as an integral part of the science of earth systems, "encompassing all components of the Earth system – air, life, rock and water – to gain a new and more comprehensive understanding of the world as we know it". Much of the background was set out in "Solid-Earth Science and Society" in 1993. Since then, considerable progress has resulted from large investments in geoinformatics by the US National Science Foundation and the European Commission, much of it implemented on their high-level computing networks. The concepts of Earth Systems are reflected in the teaching of geology. Nevertheless, geology has unique aspects that justify consideration of systems geology as a distinct subsystem. These include the availability of detailed world-wide geological mapping and stratigraphical classification, and the rapidly growing understanding of Earth history in terms of past configurations of geological objects and processes.
Related initiatives.
Cornell University's Geoscience Information System Project started in 1995. ‘Building the Digital Earth’ aims to develop a comprehensive geoscience information system, which they see as one of the most important steps that geoscientists could undertake in response to new technological advancements. Their ambition is to place all information and knowledge, along with access, modeling, and visualization tools, ‘under the finger tips of a user’. This objective is echoed in Keller and Baru (2011) where the Earth is considered as a single system (pages 3, 12, 15, 37), and progress is recorded in moving towards the geoinformatics vision set out in 2007: to facilitate ‘a future in which someone can sit at a terminal and have easy access to vast stores of data of almost any kind, with the easy ability to visualize, analyze and model those data.’ (p15). Because the treatment of earth systems and geology has repercussions in other fields, there is a need for them to share a wider-ranging cyberinfrastructure (p3, chapters 3, 4).
Wider context.
The systems approach is being actively developed in many other areas, such as biology and medicine (EuroPhysiome) opening the prospect of widely shared concepts, structures and implementations. Geospatial cyberinfrastructure applications, which seem particularly relevant to communicating information from geologists to end-users, are discussed by Yang et al., 2010.
Conclusions.
The systems approach may be particularly relevant to geological surveys, which are typically state, national or federal institutions that maintain and advance knowledge of geosciences. Traditionally, they have focused on the systematic production of geological maps, reports and archives of records and specimens. In the long run, geoinformatics could support integration at a systems level of geological surveys activities world-wide, all contributing to, using, testing and extending a shared cloud-based model. The British Geological Survey website tentatively suggests some possible developments in systems geology and the consequences for future geological mapping. It makes available "A Scenario for Systems Geology" which brings together relevant material from many sources to suggest how a comprehensive approach to systems geology might evolve. The scenario is not a statement of intent or a proposal for implementation, but an account of some possibilities that can be considered, discussed, criticized and improved. The ideas of systems geology will contribute to the future framework for studying geology in its wider context, but exploration of its full potential is still at an early stage.


Buckskin Mountain Formation

The Buckskin Mountain Formation is a geologic formation in Nevada. It preserves fossils dating back to the Permian period.


Paleozoic Museum

Following the success of Benjamin Waterhouse Hawkins' life-sized concrete dinosaur models created for England's Crystal Palace for the Great Exhibition of 1851, in 1868 the Commissioners of Manhattan's newly created Central Park recruited the sculptor to create replicas of America's antediluvian giants for a proposed museum in Central Park. The museum was to have been known as the Paleozoic Museum (or Palaeozoic Museum), and foundations for the structure were laid by architect Frederick Law Olmsted at Central Park West and 63rd Street. Like Hyde Park's Crystal Palace, Hawkins' display was to be housed within a great iron frame and an arched glass roof. Surviving sketches and photographs show that Hawkins had planned an elaborate, if anachronistic, menagerie, mixing Mesozoic dinosaurs, plesiosaurs, and mosasaurs with extinct Cenozoic mammals.
However, unfortunately for Hawkins and future generations, the planned museum ran afoul of 19th Century New York's corrupt politics. After Hawkins spoke out publicly against "Boss" William Magear Tweed, vandals in the employ of Tweed broke into Hawkins' workshop on a spring day in 1871 and used sledge-hammers to reduce the seven finished models and their molds, as well as other materials, to rubble. The ruined sculptures were then buried somewhere near the southwestern corner of the park.
Afterwards, Hawkins went to Princeton University where he painted a number of restorations of America's Late Cretaceous environments (these have survived). He also managed to build one last dinosaur, a hadrosaur ("Hadrosaurus foulkii"). It was exhibited in Philadelphia and Washington D.C. as part of commemorations of the centenary of the Declaration of Independence in 1876. Though the hadrosaur sculpture was allowed to decay and crumble, some fragments have recently been located, all that now survives of Hawkins' ill-fated American dinosaur models.
Extant drawings by Hawkins, along with other records, indicate that the Paleozoic Museum would have included life-sized restorations of the theropod "Laelaps" (="Dryptosaurus"), the hadrosaurid "Hadrosaurus", the plesiosaur "Elasmosaurus", and the mosasaur "Mosasaurus" (all from the Upper Cretaceous marls of New Jersey), along with glyptodont models, a pair of giant ground sloth, giant Pleistocene elk, mammoths, and extinct mammalian carnivores. Hawkins models from the Crystal Palace exhibition have survived and can be seen today in Sydenham Park.


Elizabeth Philpot

Elizabeth Philpot (1780–1857) was an early 19th-century British fossil collector, amateur palaeontologist and artist who collected fossils from the cliffs around Lyme Regis in Dorset on the southern coast of England. She is best known today for her collaboration and friendship with the well known fossil hunter Mary Anning. She was well known in geological circles for her knowledge of fossil fish as well as her extensive collection of specimens and was consulted by leading geologists and palaeontologists of the time including William Buckland, and Louis Agassiz. When Mary Anning discovered that belemnite fossils contained ink sacks, it was Philpot who discovered that the fossilised ink could be revivified with water and used for illustrations, which became a common practice for local artists.
Life and friendship with Anning.
Born in 1780, Elizabeth Philpot and her sisters Mary and Margaret moved to Lyme from London in 1805. They shared a house purchased for them by their brother, a London lawyer. They lived in Lyme for the rest of their lives. The Philpots became well known locally for their fossil collecting, as well as for a home made medication, a soothing salve, that they made and distributed. Elizabeth Philpot befriended Mary Anning when Anning was still a child; despite the almost 20-year age difference and the fact that the working class Anning was from a much poorer background, the two became close and were frequently seen collecting fossils together. Philpot encouraged the young Anning to read about geology and understand the science behind the fossils she collected and sold.
Fossils.
The Philpot sisters' extensive and meticulously labelled fossil collection was used for research by many geologists. All three sisters contributed to the collection, but it was Elizabeth Philpot who corresponded with leading geologists like William Buckland, William Conybeare, and Henry De la Beche about the collection. The collection was well known for its fossil fish. It also contained the fossil teeth that William Buckland combined with a famous partial skeleton discovered by Mary Anning when he described the pterosaur "Pterodactylus macronyx" (later renamed by Richard Owen to "Dimorphodon macronyx"), in 1829. In his famous 1824 paper that described the almost complete plesiosaur skeleton discovered by Anning in 1823 Conybeare mentioned examining a plesiosaur skull in the possession of "Miss Philpot".
In 1834 Buckland arranged for the Swiss palaeontologist Louis Agassiz to visit Lyme to work with Elizabeth Philpot and Anning to obtain and study fish fossils found in the region. They were able to show him fossils of 34 different species, and he was so impressed by the knowledge of Philpot and Anning that he wrote in his journal: "Miss Philpot and Mary Anning have been able to show me with utter certainty which are the ichthyodorulites dorsal fins of sharks that correspond to different types." He thanked both women for their help in his monumental book, "Studies of Fossil Fish", and he named a fossil fish species, "Eugnathus philpotae", after Philpot and another two species after Anning.
Fossil ink.
In 1826 Mary Anning discovered what appeared to be a chamber containing dried ink inside a belemnite fossil. She showed it to her friend Elizabeth Philpot. Philpot was able to revivify the ink by mixing it with water and used it to illustrate some of her own ichthyosaur fossils, and other local artists were soon doing the same as more such fossilised ink chambers were discovered.
Legacy.
The Philpot sisters' important fossil collection ended up at the Oxford University Museum of Natural History. The Philpot Museum (now known as the Lyme Regis Museum) was built in Lyme Regis in honour of the sisters by their nephew Thomas Philpot. In 2009 Tracy Chevalier wrote a historical novel entitled "Remarkable Creatures" about Elizabeth Philpot and Mary Anning, and in March 2010 an Australian production company acquired the rights to produce a feature film from the book. Elizabeth is portrayed by actress Fiona Shaw in the romantic drama film "Ammonite" (2020).


Lynton Slates

The Lynton Slates is a geologic formation in England. It preserves fossils dating back to the Devonian period.


Aller Formation

The Aller Formation is a geologic formation in Germany. It preserves fossils dating back to the Permian period.


Compton Limestone

The Compton Limestone is a geologic formation in southwest Missouri. It preserves brachiopod and echinoderm fossils of the Mississippian subperiod. The Compton rests unconformably on the Cotter Dolomite of Ordovician age. The Compton was named for the community of Compton, Missouri as the type sections were described for outcrops along the James River and its tributary the Compton Branch.


Gemmological Association of Great Britain

The Gemmological Association of Great Britain (Gem-A) is an international gemmology education and qualifications body based in the United Kingdom.
History.
Gem-A dates back to 1908 when a gemmological committee was established by "The National Association of Goldsmiths". The aim of the committee was how to best provide the United Kingdom jewellery trade with recognised gemmology qualifications.
The recent development of synthetic rubies, synthetic sapphires and cultured pearls had made formal education essential. This committee matured into the Gemmological Association of Great Britain, a Branch of the NAG, and eventually became a wholly independent organisation. Now Gem-A is a registered United Kingdom-based charity and its gemmology and diamond courses are taught in some 25 countries worldwide.
Coat of Arms.
One of the most common symbols used to denote the Association, the Coat of Arms is based upon a design submitted by H. Ellis Tomlinson on behalf of the Association in 1966. Mr Tomlinson, who was also responsible for the design of the Arms of the National Association of Goldsmiths a few years prior, combined mediaeval heraldry with colours, language and ornament to create what is now a well-known symbol denoting the Association. It was not until 1967, when the Association received the official grant of arms from the King of Arms under royal authority, that it became the logos prentice of the Association and all its related activities.
The Gem-A Coat of Arms itself is composed of a Shield, Crest and Motto.
The Shield.
The Shield is the focal part of the Coat of Arms. In its centre is a gold jewelled book representing the study of gemmology. Above this is a rose-cut diamond within a circle, suggesting the examination of gems under magnification. To each side are octahedral diamond crystals, indicating gems as found, and below is a pearl-set ring representing gem-set jewellery.
The Crest.
The Crest is in the form of a lynx. This species of wildcat is traditionally renowned for its keenness of sight and, with perhaps just a touch of humour, was employed here as a perfect symbol for gemmologists and gemmology students. In its paws it holds one of the oldest heraldic emblems, an ‘escarbuncle’. This is a symbol of supremacy, but also represents a brilliant jewel with light radiating from it. Its tips are jewels of many different colours. Gem-A is often referred to as the central jewel, with gem education and knowledge radiating from it with the jewelled tips being the graduates and members of the Association.
Courses.
Gem-A provides courses in gemmology and diamond as well as offering a wide range of short courses, lab classes and one-day workshops, catering for both beginners and experts in the field.
Gem-A certificated courses include :
Foundation in Gemmology course (leading to Cert. GA status)
Diploma in Gemmology course (leading to possible FGA membership )
Diamond Diploma (leading to possible DGA membership)
Graduates of the Diploma in Gemmology are eligible for election to Fellowship of the Gemmological Association and may use the letters FGA after their name for as long as they remain paid-up members of the Association. Graduates of the Diamond Diploma may use the letters DGA after their name for as long as they remain paid-up members of the Association.
Certificated courses can be studied in-house at the Gem-A London headquarters through daytime or evening classes, at one of Gem-A's international Accredited Teaching Centres or by Open Distance Learning (ODL) online classes.
Gem-A holds an annual conference, bringing together international speakers and delegates to meet and discuss important changes within the gem industry. It publishes the Gems & Jewellery magazine seven times a year as well as NAG’s The Jeweller.
Charitable status.
As an education Charity (UK Registered Charity No. 11099555) Gem-A has a responsibility to provide gem information and education to the widest possible audience. To this end Gem-A has worked with developing countries including Madagascar, Pakistan and Afghanistan, and it also plays an active part in promoting high ethical and environmental standards in the gem industry.
Publications.
"Gems and Jewellery", a magazine published seven times a year, dealing with all aspects of gems and jewellery as well as NAG’s the Jeweller.
"The Journal of Gemmology", a quarterly academic peer-reviewed journal, published in collaboration with the Swiss Gemmological Institute SSEF and supported by the American Gemological Laboratories (AGL) and the Gem and Jewelry Institute of Thailand (GIT).”


Lewis Hunton

Lewis Hunton (August 1814 – 17 February 1838) was a geologist who made important early contributions to the development of the idea that the geological succession could be sub-divided through analysis of its fossil content, at a time when such ideas were yet to be widely accepted. This principle, later dubbed biostratigraphy, became a fundamental aspect of the modern science of geology. Little detail of his life exists and, as far as the author can ascertain, there are no surviving images of Lewis.
Early Life & Influences.
Born at Hummersea House near Loftus, and raised on the rugged Cleveland coast notable for its fine exposures of Lower and Middle Jurassic strata, Hunton was christened at St. Leonard's Church, Loftus on 6 August 1814. His father William (1789-1863) and grandfather, also William (1761-1809), acted as Alum Agent and Alum Maker respectively at Loftus Alum Works using shale from adjoining quarries on some of Britain's highest sea cliffs. The Hunton family's close associations with the Yorkshire alum trade, which flourished in north east Yorkshire (Cleveland) between "ca".1604 and 1871, played an important role in influencing Lewis Hunton's later work in both geology and chemistry.
Education and Work.
Following early education, at a school for children of the local alum workers at Loftus, between 1833 and 1836 Hunton attended King's and University Colleges, London studying comparative anatomy, fossil zoology and natural philosophy. Lecturers at the time included the eminent Sir Charles Lyell (1797-1875). In 1836 Hunton also published his first scientific paper entitled: "Remarks on a section of the Upper Lias and Marlstone of Yorkshire, showing the limited vertical range of the species of Ammonites, and other Testacea, with their value as geological tests" read at the Geological Society of London on 25 May of the same year.
Fieldwork for this paper was carried out across north east Yorkshire including at many of the district's alum works. The vertical section eventually published was surveyed at Easington Heights, near Loftus and Boulby Alum Quarries, now a joint SSSI. From this fieldwork Hunton gained evidence for the notion that certain fossil species (particularly ammonites which are abundant in the district's Lower Jurassic rocks) could be found occupying very limited vertical horizons sometimes only a few centimetres thick. Hunton writes: "Ammonites afford the most beautiful illustration of the subdivision of strata, for they appear to have been the least able, of all the Lias genera, to conform to a change of external consequences".
This variation in fossil species was used to sub-divide the vertical succession locally, and to correlate beds of the same relative age across wider areas. He further proposed formal rules for performing such surveys to ensure that the information recorded was accurate. In conclusion Hunton says: "Ammonites from unequal geographical distribution may be more abundant in one place than another ... yet they constantly maintain an invariable relative position.".
"... one great source of error has hitherto been the collecting of specimens from the debris of the whole formation accumulated at the foot of the cliffs ... and the inferring of their position from the nature of the matrix."
Later in 1836 Hunton continued his work in Loftus Quarry excavating the remains of a 5-metre (16 feet) long ichthyosaur, or fish lizard, named "Temnodontosaurus platyodon" (formerly "Ichthyosaurus platyodon"). In 1869 this leviathan was donated by the Hunton family to Pannett Park Museum, Whitby where it remains on display (Specimen no. 5) along with many other fossils from the local area.
Hunton only produced one other published scientific work appearing in the "London and Edinburgh Philosophical Magazine" in 1837. The paper, on his other interest, chemistry, discusses combining sugar with alkalis and metallic oxides - reactions that would have been of interest to alum makers.
Early Demise.
In later life Hunton chose to alter the spelling of his forename to the French ’Louis’, it is thought because of his love of France in general and admiration of scientist Antoine-Laurent de Lavoisier (1743-1794) in particular.
Aged only 23, and suffering ill health, the promising young scientist departed for the continent only to pass away, near Nîmes, of tuberculosis on 17 February 1838 whilst staying with pharmacist Alix Pleindoux. A memorial stone in Loftus churchyard where many of the Hunton family are laid to rest reads: "Sacred to the memory of Lewis son of William and Jane Hunton who died at A------ in the south of France, 17 Feb 1838"
It appears likely that Lewis does not lie alongside the rest of his family at Loftus but was buried in France. He is posthumously remembered by an ammonite ("Tragophylloceras huntoni") named after him by Martin Simpson, curator at Whitby Museum, in 1843.
A special Service of Thanksgiving at St Leonard's Parish Church, Loftus-in-Cleveland on Sunday 14 September 2014 celebrated the 200th Anniversary of the birth of Lewis Hunton 1814 – 1838.


Bod Deiniol Formation

The Bod Deiniol Formation is a geologic formation in Wales. It preserves fossils dating back to the Ordovician period.


Spirorhaphe

Spirorhaphe (sometimes misspelt Spiroraphe) is an ichnogenus of spiraling burrows. It is associated with the "Nereites" ichnofacies, which is interpreted as an indicator of deep-sea, pelagic, turbidity current-dominated systems. It is one of the most common graphoglyptid traces found in modern ocean beds.


Igneous textures

Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.
"Aphanitic" ("a" = not, "phaner" = visible) rocks, in contrast to phaneritic rocks, typically form from lava which crystallize rapidly on or near Earth's surface. When extrusive rocks make contact with the atmosphere they cool quickly, so the minerals do not have time to form large crystals. The individual crystals in an aphanitic igneous rock are not distinguishable to the naked eye. Examples of aphanitic igneous rock include basalt, andesite and rhyolite.
"Glassy" or "vitreous" textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass with few or no crystals. Examples include obsidian.
"Pegmatitic" texture occurs during magma cooling when some minerals may grow so large that they become massive (the size ranges from a few centimetres to several metres). This is typical of pegmatites.
"Phaneritic" ("phaner" = visible) textures are typical of intrusive igneous rocks, these rocks crystallized slowly below Earth's surface. As magma cools slowly the minerals have time to grow and form large crystals. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye. Examples of phaneritic igneous rocks are gabbro, diorite and granite.
"Porphyritic" textures develop when conditions during cooling of a magma change relatively quickly. The earlier formed minerals will have formed slowly and remain as large crystals, whereas, sudden cooling causes the rapid crystallization of the remainder of the melt into a fine grained (aphanitic) matrix. The result is an aphanitic rock with some larger crystals (phenocrysts) imbedded within its matrix. Porphyritic texture also occurs when magma crystallizes below a volcano but is erupted before completing crystallization thus forcing the remaining lava to crystallize more rapidly with much smaller crystals.
"Pyroclastic" ("pyro" = igneous, "clastic" = fragment) textures occur when explosive eruptions blast the lava into the air resulting in fragmental, typically glassy material which fall as volcanic ash, lapilli and volcanic bombs.


Calcite rafts

Calcite crystals form on the surface of quiescent bodies of water, even when the bulk water is not supersaturated with respect to calcium carbonate. The crystals grow, attach to one other and appear to be floating rafts of a white, opaque material. The floating materials have been referred to as calcite rafts or "leopard spots".
Chemistry.
Calcium carbonate is known to precipitate as calcite crystals in water supersaturated with calcium and carbonate ions. Under quiescent conditions, calcite crystals can form on a water surface when calcium carbonate supersaturation conditions do not exist in the bulk water. Water evaporates from the surface and carbon dioxide degasses from the surface layer to create a thin layer of water with high pH and concentrations of calcium and carbonate ions far above the saturation concentration for calcium carbonate. Calcite crystals precipitate in this highly localized environment and attach to one another to form what appear to be rafts of a white material.
Scanning electron micrographs of calcite rafts show interconnected calcite crystals formed around holes on the raft surface. The holes may be caused by air bubbles or other foreign matter on the water surface. Micrographs of calcite rafts show lace-like structure. The surface tension of the water keeps the interconnected calcite crystals, which individually have a specific gravity of 2.7, floating on the water surface.
Cave and river system formation.
Calcite rafts are most commonly formed in limestone cave systems. Limestone caves provide a favorable environment due to little air movement and water containing significant concentrations of calcium and carbonate ions. Evidence of calcite rafts has been found in limestone caves all over the world.
One example of calcite raft formation in a spring-fed river system has been reported.
Drinking water reservoir.
In 2005, the Carpinteria Valley Water District in Carpinteria, California, raised water quality concerns when "leopard spots" approximately 5 to 10 cm. in diameter appeared on the water surface under a newly constructed aluminum reservoir cover. The floating material had not been observed when the reservoir (13 million gallons) was open to the atmosphere. The concern raised was that a potentially toxic metallic precipitate was forming on the water surface from condensate dripping from the metal cover.
Water analyses found that the water in the reservoir was saturated with respect to calcium carbonate but no calcite crystals were formed in the bulk solution. X-ray diffraction analysis showed that the floating solid material was greater than 97 percent calcite. Scanning electron micrographs confirmed that the shape of the crystalline material was rhombohedral, which is consistent with calcite crystal formation.
While the floating material was not toxic, it was recommended that movement of the water surface be induced so that quiescent conditions would be avoided which would eliminate the primary condition for calcite raft formation.
Concrete leachate drops.
Micro calcite rafts have been observed on (soda) straw stalactites solution drops suspended beneath concrete structures. These secondary deposits which form outside the cave environment, are known as calthemites. They are derived from concrete, lime or mortar, and mimic the shapes and forms of speleothems created in caves.
The micro rafts which form on the surface of hyperalkaline leachate solution drips are typically about 0.5 mm in size when visible to the naked eye, and appear on the drip's surface after it has been suspended for greater than ≈5 minutes. The chemical reaction which creates the rafts, involves carbon dioxide (CO2) being absorbed (diffusing) into solution from the atmosphere and calcium carbonate (CaCO3) precipitates as rafts or deposited as a stalagmite, stalactite or flowstone. This chemistry is very different to that which creates speleothems in caves.
Internal water pulses from the straw (into the drop) and air movement around the suspended solution drop, can cause the rafts to spin swiftly around the drop surface. If there is almost no air movement around the suspended drop, then after approximately 12 minutes or more, the micro rafts may join up and form a latticework, which covers the entire drop surface. If the solution drop hangs too long on the straw (≈ >30 minutes), it may completely calcify over and block the calthemite straw tip.


Meudon Formation

The Meudon Formation is a geologic formation in France. It preserves fossils dating back to the Paleogene period.