Barn Bluff

Barn Bluff is a mountain located in the Central Highlands region of Tasmania, Australia. The mountain is situated in the Cradle Mountain-Lake St Clair National Park at the junction of the easternmost points of the Murchison and Mackintosh river catchments.
At above sea level it is the fourth highest mountain in Tasmania, exceeding the height of the more famous Cradle Mountain by .
The Barn Bluff is frequently snow-covered, sometimes even in summer. This mountain is perhaps the most prominent peak of the Cradle Mountain-Lake St Clair National Park and is visible from most areas and stands on its own, well away from other peaks. It is a popular venue for bushwalkers and mountain climbers, accessible via a side trip from the Overland Track. The path is moderate to difficult and has very steep sections, with boulder scrambling toward summit. The route is marked by cairns.
The mountain was formed by glacial action and erosion and is characterised, for the most part, by the dolerite slabs and boulders typical of the alpine regions of the state. Many of the summits in Tasmania are rather obscure tors perched only slightly higher than the alpine plateau on which they sit. Barn Bluff, like Cradle Mountain, presents a classic summit. The mountain's nearest neighbours are quite distant and, therefore, the 360-degree panorama from the summit is uninterrupted and spectacular.


Kirsty McCabe

Kirsty McCabe (born 10 July 1975) is a Scottish weather forecaster and presenter at Sky News, and was formerly the senior meteorologist at The Weather Channel, based at the UK office in London.
Early life.
Kirsty attended Annanhill Primary School and Grange Academy, while at high school McCabe was an early member of the Palace Youth Theatre which was a joint venture between Kilmarnock and Loudoun District Council and Borderline Theatre Company. During this time she played roles in many stage productions including Alice in "Alice in Wonderland" and performed as a solo singer on many occasions, notably performing John Lennon's "Imagine" in the 1993 production of "Summertime Blues".
McCabe studied Geophysics at the University of Edinburgh, graduating with a first class honours degree before going on to spend three months as an intern at NASA's Goddard Space Flight Center in Maryland, where she used satellite magnetic data to interpret the underlying crustal structure of parts of Australasia. Further study at the University of Oxford saw her involved in a project to look for evidence of climate change in old volcanic soils on the Greek island of Santorini (Thera). While at Oxford she was elected President of the Jesus College Graduate Common Room. During her time at Oxford, she was offered a three-month internship at "New Scientist" magazine where she went on to work as a sub-editor for four years.
Career.
McCabe joined the BBC Weather team in September 2003 and started her training on new media forecasts working on the BBC Digital's interactive service and online. She completed the first part of her forecaster training at the Met Office college in 2004 and her advanced forecaster exams in 2005. She then presented forecasts across a number of BBC outlets, including BBC News, Radio 4, BBC World News and BBC One. McCabe was a main weather presenter for "BBC News at One" and occasionally presented the weather on "BBC Breakfast".
In January 2009, she replaced Andrea McLean as GMTV's weather forecaster. In September 2010, McCabe joined GMTV replacement programme "Daybreak" on ITV Breakfast as a weather presenter and environment correspondent alongside Lucy Verasamy. On 7 February 2012, it was announced McCabe had left "Daybreak".
In June 2012, she joined "South Today" on BBC South as a weather forecaster for a six-month stint. In January 2013, she moved to "Reporting Scotland" on BBC Scotland.
From July 2013 to October 2016, she also presented weather forecasts for "5 News" on Channel 5, providing cover for Sian Welby.
Since January 2015, she has presented weather forecasts for "Sunrise" on Sky News as well as working as a weather producer for Sky News.
McCabe was the senior meteorologist for The Weather Channel UK's office from January 2015 to May 2016, broadcasting via weather.com and the Weather Channel app.
In June 2017, she became the first meteorologist in residence for the London Marriott Hotel County Hall providing bespoke weather forecasts.
Personal life.
McCabe married South African architect Renato Marchio in July 2008.
She gave birth to son Ethan on Christmas Day 2010, and to a second son Logan on 7 May 2013. Her third child Ava was born on Valentine's Day 2018.


McKelligon Canyon Formation

The McKelligon Canyon Formation is a geologic formation in Texas. It preserves fossils dating back to the Ordovician period.


Churchill River Group

The Churchill River Group is a geologic group in Manitoba. It preserves fossils dating back to the Ordovician period.


Canso Formation

The Canso Formation is a geologic formation in New Brunswick. It preserves fossils dating back to the Carboniferous period.


Sulcus (geology)

Sulcus (plural: sulci ) is, in astrogeology, an area of complex parallel or subparallel ridges and furrows on a planet or moon.
For example, Uruk Sulcus is a bright region of grooved terrain adjacent to Galileo Regio on Jupiter's moon Ganymede.


Julie Libarkin

Julie Carol Libarkin is a professor of Earth Sciences and Director of the Geocognition Laboratory at Michigan State University. Her research considers how people understand and make decision about the planet. She is a Fellow of the Geological Society of America. She also researches and addresses inequality in academia, and tracks academic sexual misconduct cases.
Early life and education.
Libarkin studied physics and geology at the College of William & Mary and graduated in 1994. She moved to the University of Arizona for her graduate studies, where she studied palaeomagnetism and cosmogenic isotopes. Upon graduation, Libarkin switched her focus to tectonic and geocognition.
Research and career.
Libarkin was appointed a National Science Foundation Postdoctoral Fellow in the Harvard–Smithsonian Center for Astrophysics. She was made a Research Associate in 2002. In 2003 Libarkin was appointed Assistant Professor at Ohio University. She moved to Michigan State University in 2006, where she was made Director of Educational Research in 2011. She was promoted to Professor in 2016, where she Directs the Georecognition Research Laboratory. She investigates how people see and understand the Earth, and how this impacts the decisions they make.
Academic service.
Libarkin is involved with research and mentoring to tackle inequality in academia. She has created a database of reported sexual misconduct cases. As of 2020, the database includes over 1,000 cases – all of which included substantiated reports, institutional findings and legal outcomes. Libarkin has investigated sexual harassment in the physics undergraduate community. She serves on the National Academies of Sciences, Engineering, and Medicine Action Collaborative on Preventing Sexual Harassment in Higher Education. She has called for job applicants to be required to disclose whether they have had formal or informal findings of misconduct against them.
Libarkin has been involved with the transformation of science education, including creating a mechanism to better understand the interactions of science and policy. She serves as a member of the Create for STEM initiative.
Selected publications.
Libarkin has served as Editor-in-Chief of the "Journal of Geoscience Education".


Timeline of Silurian research

This timeline of Silurian research is a chronological listing of events in the history of geology and paleontology focused on the study of Earth during the span of time lasting from 443.4–419.2 million years ago; the Silurian, and the legacies of this period in the rock and fossil records.
19th century.
1825
1835
1844
1859
20th century.
1937
1972
21st century.
2010


Copper Canyon Formation

The Copper Canyon Formation is a geologic formation in California. It preserves fossils dating back to the Neogene period.


Ardwell Group

The Ardwell Group is a geologic group in Scotland. It preserves fossils dating back to the Ordovician period.


Petrological Database of the Ocean Floor

The Petrological Database of the Ocean Floor (PetDB) is a relational database and repository for global geochemical data on igneous and metamorphic rocks generated at mid-ocean ridges including back-arc basins, young seamounts, and old oceanic crust, as well as ophiolites and terrestrial xenoliths from the mantle and lower crust and diamond geochemistry. These data are obtained by analyses of whole rock powders, volcanic glasses, and minerals by a wide range of techniques including mass spectrometry, atomic emission spectrometry, x-ray fluorescence spectrometry, and wet chemical analyses. Data are compiled from the scientific literature by PetDB data managers, as well as being provided by members of the scientific community. PetDB is administered by the EarthChem group under the IEDA facility at LDEO headed by K. Lehnert.PetDB is supported by the U.S. National Science Foundation.
History.
Development of PetDB began in 1995 when scientists from the Lamont-Doherty Earth Observatory (LDEO) C. Langmuir (now at Harvard University), W. Ryan, and A. Boulanger saw the potential impact of new information technologies such as the World Wide Web and relational databases on the use of scientific data in research and in the classroom.
The initial funding phase of PetDB (1996–2001) supported the development of the database structure and population with data values. Renewed funding (2002–2007) permitted the migration of the database into an ORACLE-based environment administered by the Center for International Earth Science Information Network (CIESIN) of Columbia University, continued data entry, and enhancement of the web-interface with a more user-friendly design.
PetDB is now maintained by EarthChem and funded by the US National Science Foundation as part of the Interdisciplinary Earth Data Alliance facility. IEDA is an umbrella data facility that joins EarthChem and the Marine Geoscience Data System. This joint facility is funded by the U.S. National Science Foundation as a cooperative agreement.
The relational database structure of PetDB is a sample-based implementation and designed to accommodate chemical and petrological data for any type of rock sample, along with essential metadata that provide information about the sample (e.g. location and time of collection, taxonomy, petrographic description) and the data quality (e.g. analytical procedure, reference standard measurements) (Lehnert et al. 2000). Initially developed for PetDB and its subareal counterpart GEOROC, this relational data model has demonstrated utility and flexibility by its application in subsequent geochemical database projects including NAVDAT, MetPetDB, and SedDB
Since its inception, PetDB has supported a wide array of scientific endeavors, providing easy access to a comprehensive global dataset of geochemical data for mid-ocean ridge basalts, abyssal peridotites and also xenolith samples from the Earth's mantle and lower crust. PetDB has been cited in more than 800 peer-reviewed scientific articles as the source of data used to develop and test new hypotheses which range from the chemical and mineralogical composition of Earth's mantle (e.g. Salters & Stracke 2004, Thirlwall et al. 2004), to the generation and evolution of continental and oceanic crust (e.g. Weyer et al. 2003, Cipriani et al. 2004), melt transport phenomena (Braun & Kelemen 2002, Spiegelman & Kelemen 2003), to global geochemical seawater budgets (e.g. van der Flierdt et al. 2004).
Contents.
In its current application, PetDB contains and provides on-line access to a complete set of chemical parameters (currently over 250 elements, oxides, isotopes and isotope ratios), as well as petrographic (mode) data through a sophisticated query interface. New data are continuously being added to the database as it is published and submitted to PetDB by authors. Data for a specific sample that is generated by different laboratories or published by various authors are linked and integrated through the use of a unique sample identifier generated by the database application.
Statistics.
As of May 12, 2021, PetDB holdings consist of:
Up-to-date current holdings can be viewed on the PetDB homepage.
Data output.
Data from PetDB can be viewed in HTML tables and downloaded in spreadsheets in XLS format. During selection of chemical parameters a user can choose to retrieve data as individual values (each row in the data table contains values measured on the same sample with the same method and linked to the same reference) or in precompiled format. The precompiled format arranges all data associated with a sample in a single row, even when data is sourced from multiple publications. In cases where there is more than one data value for a particular chemical item, the precompilation algorithm selects the most recent analysis and the most precise method available. Links in the HTML table permit the user to access more detailed information about the sample, reference or data value (analytical procedure). The final spreadsheet output contains two worksheets. The first contains queried chemical data, geospatial coordinates, and abridged methods and references, while the second contains metadata on analytical methods and publication information.


Sole markings

Sole marks are sedimentary structures found on the bases of certain strata, that indicate small-scale (usually on the order of centimetres) grooves or irregularities. This usually occurs at the interface of two differing lithologies and/or grain sizes. They are commonly preserved as casts of these indents on the bottom of the overlying bed (like flute casts). This is similar to casts and molds in fossil preservation. Occurring as they do only at the bottom of beds, and their distinctive shapes, they can make useful way up structures and paleocurrent indicators.
Sole markings are found most commonly in turbidite deposits, but are also often seen in modern river beds and tidal channels.
History.
Sole markings were first recognized in the Devonian rocks of New York State by James Hall in 1843. Originally, the features found on the undersides of beds were called "hieroglyphs", "fucoids", and "bio hieroglyphs", because of their structure and how they were thought to be created; however, the term "sole mark" is used by geologists at present.
Scour marks and flute casts.
Scour marks and flute casts are scours dug into soft, fine sediment which typically get filled by an overlying bed (hence the name cast). Measuring the long axis of the flute cast gives the direction of flow, with the tapered end pointing toward the flow and the steep end up current. The concavity of the flute cast also points stratigraphically up. Flute casts can be characterized into four types, parabolic, spindle-shaped, comet-shaped, and asymmetrical.
Tool marks.
Tool marks are a type of sole marking formed by grooves left in a bed by things like sticks being dragged along by a current. The average direction of these can be assumed to be the flow direction, though it is bidirectional, so it could be either way along the mark. Tool marks also have a more specific breakdown. There are grooves and striations, skip or prod marks, and roll marks. Groove or striation marks result from the continuous contact with the muddy bed. Skip or prod marks come from objects that bounce along the surface of the muddy bed. And roll marks result from objects rolling along the muddy bed.
Groove casts.
Groove casts are straight parallel ridges that are raised a few millimeters from the bedding surface. These structures were named and defined by Shrock in 1948 because of their long and narrow appearance, and they were formed from the filling in of grooves. Even though they may seem similar to flute casts, they each have many distinguishing characteristics, and the two are generally not found in the same vicinity. Groove casts are closely spaced, but not on top of each other, and exist in pairs, triples, and even larger groups. Groove casts form when high velocity flows (e.g. turbidite) create a pattern on an underlying bed. In 1957, Kuenen published that "groove cast" was a general term encompassing both drag marks and slide marks.
Load casts.
Load casts are secondary structures that are preserved as bulbous depressions on the base of a bed. They form as dense, overlying sediment (usually sand) settles into less dense, water-saturated sediment (usually mud) below.


Volcanological Survey of Indonesia

Volcanological Survey of Indonesia is the official Indonesian government agency under Ministry of Energy and Mineral Resources which are responsible for investigating, recording, and warning about volcanoes within the Indonesian region of responsibility and geological hazard mitigation.
The full official Indonesian name is the "Pusat Vulkanologi dan Mitigasi Bencana Geologi" (English: "Centre of Vulcanology and Geological Hazard Mitigation"), often abbreviated to PVMBG. The Centre is based in Bandung in West Java.
It was preceded by the "Netherlands East Indies Volcanological Survey". It has also been known as the "Direktorat Vulcanologi". Its main publication has been known as "Berita Berkala vulkanologi".


Imbrication (sedimentology)

In sedimentology imbrication refers to a primary depositional fabric consisting of a preferred orientation of clasts such that they overlap one another in a consistent fashion, rather like a run of toppled dominoes. Imbrication is observed in conglomerates and some volcaniclastic deposits.
Types.
Relation to paleocurrent.
The type of imbrication is generally related to paleoflow direction. Wadell found the long axis aligned with paleocurrent, and dipping basinward in glacial sediments, whereas deltaic gravels may be oppositely inclined.


Anticosti Group

The Anticosti Group is a geologic group in Quebec. It preserves fossils dating back to the Silurian period.


Ballysteen Limestone

The Ballysteen Limestone is a geologic formation in Ireland. It preserves fossils dating back to the Carboniferous period.


Emmanuil B. Chekaliuk

Emmanuïl Bogdanovych Chekaliuk ( Gnizdychev, Zhydachiv District, Lviv Oblast, May 6, 1909 – Lviv, January 5, 1990) was a Ukrainian petroleum engineer and statistical thermodynamicist. He first produced rigorous physical and mathematical evidences of petroleum thermodynamic stability at mantlean conditions. Since the 1990s the heavy hydrocarbons mixture enriched with organometallic compounds is widely known as "Chekaliuk’s petroleum".
Born in the family of a parson he graduated from Electromechanics Faculty at Lviv Polytech Institute in 1933 and then worked as an electrician at Kalush potash plant and later received the job of an engineer at the factory for domestic electric appliances in Warsaw. His first research paper on electrophysics was published in "Przeglad electrotechniczny Jour". in 1938. After WW II he come back to Ukraine and linked his career with petroleum industry and passed through all positions from a field engineer to a director of large production enterprise. In 1951 Chekaliuk started to work at Central Research Lab of Ukrnafta Co. in Boryslav, and in 1955 he joined Ukrainian Research Geoexploration Institute (UkrDGRI). Defended his PhD thesis entitled "Non-stationary phenomena of homogeneous liquid inflow from porous medium" at Lviv Polytech Inst. in 1957. A Dr.Sc. dissertation in Engineering "Some thermodynamic phenomena in porous medium and the ways of their application to petroleum industry" was defended in Moscow at All-Union Research Institute for Petroleum (VNIGNI) in 1962. He studied different aspects of reservoir properties, filtration of liquids and gases, physical parameters of deep oils, pay zone testing, production well-logging, oil field development, enhanced oil recovery, thermodynamics of hydrocarbon deposits, liquidation of accidental gas gushers.
Since 1964 he worked for Inst. of Geology and Geochemistry of Combustible Minerals, Nat’l Ac. Sci. Ukraine, in Lviv where he headed the Abyssal Hydrocarbons Dept. and coined new scientific trend of petroleum geology, geo-thermodynamics. With his colleagues he developed a principally new technology of enhanced oil recovery from the deep pools (to 3000 m depth) using the water with higher thermodynamic parameters. He has determined the optimal depth to preserve mantlean hydrocarbons and calculated their chemical composition and with his teammates conducted first experiments on high temperature synthesis of hydrocarbon systems in hydrocarbonate medium. Also he studied the problem of hydrocarbon systems kinetic transformation at sedimentary cover conditions. Besides, he interested in theoretical physics and published a fundamental monograph "Gnoseological potential of classical mechanics (to 300th anniversary of Isaac Newton research career)" and several articles on the topic.
He generated more than 170 research publications, including 9 monographs and received 14 inventor's certificates related to hydrocarbon fields development and enhanced oil recovery. His technology applying the special water solution for oil recovery was patented in the UK, Canada, and Mexico.
Soviet authorities did not value Chekaliuk's work because his own brother was a soldier of Ukrainian Insurgent Army (UPA) and sentenced to 25 years of imprisonment. Therefore, Chekaliuk had no chance to become a Member of UkrSSR Academy of Sciences, to head the institute or even to travel abroad.


Boudinage

Boudinage is a geological term for structures formed by extension, where a rigid tabular body such as hornfels, is stretched and deformed amidst less competent surroundings. The competent bed begins to break up, forming sausage-shaped boudins. Boudinage is common and can occur at any scale, from microscopic to lithospheric, and can be found in all terranes. In lithospheric-scale tectonics, boudinage of strong layers can signify large-scale creep transfer of rock matter. The study of boudinage can, also, help provide insight to the forces involved in tectonic deformation of rocks and their strength.
Boudinage can develop in two ways: planar fracturing into rectangular fragments or by necking or tapering into elongate depressions and swells. Boudins are typical features of sheared veins and shear zones where, due to stretching along the shear foliation and shortening perpendicular to this, rigid bodies break up. This causes the resulting boudin to take a characteristic sausage or barrel shape. They can also form rectangular structures. Ductile deformation conditions also encourage boudinage rather than imbricate fracturing. Boudins can become separated by fractures or vein material, this zone of separation is known as boudin necks.
In three dimensions, the boudinage may take the form of ribbon-like boudins or chocolate-tablet boudins, depending on the axis and isotropy of extension. They range in size from about 20 m thick to about 1 cm.
Types.
There are three different types of boudinage. These include no-slip boudinage, s-slip boudinage, and a-slip boudinage. No-slip boudinage occurs when there is no slip, resulting in a symmetrical structure. S-slip boudinage occurs when the boudin moves in opposition to the shear movement, where A-slip occurs when it moves with the direction of the shear. These types can be further classified into 5 different groups with relation to their general shape. These groups are drawn, torn, domino, gash and shearband boudins. In general, drawn and torn shapes form where there is a no-slip boudinage, domino and gash boudins by A-slip and shearband boudins by S-slip boudinage.
Etymology.
Lohest (1909) coined the term boudinage which is derived from the French word "boudin", meaning blood sausage. Boudins were first observed and described by Belgian geologists in the Collignon quarry near Bastogne in the Ardennes (Belgium).
References.
Urai, J. L., Spaeth, G., van der Zee, W. & Hilgers, C. 2001. "Evolution of Mullion (Boudin) structures in the Variscan of the Ardennes and Eifel." In: Jessell, M. J. 2001. General Contributions: 2001. Journal of the Virtual Explorer, 3, 1-16 https://web.archive.org/web/20070908134406/http://www.virtualexplorer.com.au/journal/2001/03/urai/


Mineola Limestone

The Mineola Limestone is a geologic formation in Missouri. It preserves fossils dating back to the Devonian period.


Stalagmite

A stalagmite ( or ; from the Greek , from , "dropping, trickling")
is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist of lava, mud, peat, pitch, sand, sinter and amberat (crystallized urine of pack rats).
The corresponding formation hanging down from the ceiling of a cave is a stalactite.
Formation and type.
Limestone stalagmites.
The most common stalagmites are speleothems, which usually form in limestone caves. Stalagmite formation occurs only under certain pH conditions within the cavern. They form through deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is the chief form of calcium carbonate rock, which is dissolved by water that contains carbon dioxide, forming a calcium bicarbonate solution in caverns. The partial pressure of carbon dioxide in the water must be greater than the partial pressure of carbon dioxide in the cave chamber for conventional stalagmite growth.
If stalactites – the ceiling formations – grow long enough to connect with stalagmites on the floor, they form a column.
Stalagmites should normally not be touched, since the rock buildup is formed by minerals precipitating out of the water solution onto the existing surface; skin oils can alter the surface tension where the mineral water clings or flows, thus affecting the growth of the formation. Oils and dirt from human contact can also stain the formation and change its color permanently.
Lava stalagmites.
Another type of stalagmite is formed in lava tubes while lava is still active inside. The mechanism of formation is similar to that of limestone stalagmites. Essentially, it is still the deposition of material on the floors of caves; however with lava stalagmites, formation happens very quickly in only a matter of hours, days, or weeks, whereas limestone stalagmites may take up to thousands of years. A key difference with lava stalagmites is that once the lava has ceased flowing, so too will the stalagmites cease to grow. This means if the stalagmite were to be broken it would never grow back. Stalagmites in lava tubes are rarer than their stalactite counterparts because during formation the dripping material falls onto still-moving lava floors that absorb or carry the material away.
The generic term "lavacicle" has been applied to lava stalactites and stalagmites indiscriminately, and evolved from the word "icicle".
Ice stalagmites.
A common stalagmite found seasonally or year round in many caves is the ice stalagmite, commonly referred to as icicles, especially in above-ground contexts. Water seepage from the surface will penetrate into a cave and if temperatures are below freezing temperature, the water will collect on the floor into stalagmites. Deposition may also occur directly from the freezing of water vapor. Similar to lava stalagmites, ice stalagmites form very quickly within hours or days. Unlike lava stalagmites however, they may grow back as long as water and temperatures are suitable. Ice stalagmites are more common than their stalactite counterparts because warmer air rises to the ceilings of caves and may raise temperatures to above freezing.
Ice stalactites may also form corresponding stalagmites below them, and given time, may grow together to form an ice column.
Concrete derived stalagmites.
Stalactites and stalagmites can also form on concrete ceilings and floors, although they form much more rapidly there than in the natural cave environment.
The secondary deposits derived from concrete are the result of concrete degradation, where calcium ions are leached out of the concrete in solution and redeposited on the underside of a concrete structure to form stalactites and stalagmites. Calcium carbonate deposition as a stalagmite occurs when the solution carries the calcium laden leachate solution to the ground under the concrete structure. Carbon dioxide is absorbed into the alkaline leachate solution, which facilitates the chemical reactions to deposit calcium carbonate as a stalagmite. These stalagmites rarely grow taller than a few centimetres.
Secondary deposits, which create stalagmites, stalactites, flowstone etc., outside the natural cave environment, are referred to as "calthemites". These concrete derived secondary deposits cannot be referred to as "speleothems" due to the definition of the word.
Records.
The largest known stalagmite in the world exceeds in height and is in Sơn Đoòng Cave, Vietnam.
In the Zagros Mountains of south Iran, approximately from the ancient city of Bishapur, in the Shapur cave on the fourth of five terraces stands the 3rd-century colossal statue of Shapur I, second ruler of the Sassanid Empire. The statue, carved from one stalagmite, is nearly high.


Timeline of paleontology in West Virginia

This timeline of paleontology in West Virginia is a chronologically ordered list events in the history of paleontological research occurring within or conducted by people from the U.S. state of West Virginia.
18th century.
1790s.
1796
20th century.
1990
1993
1995
21st century.
2008


Great Unconformity

Of the many unconformities (gaps) observed in geological strata, the term Great Unconformity is frequently applied to either the unconformity observed by James Hutton in 1787 at Siccar Point in Scotland, or that observed by John Wesley Powell in the Grand Canyon in 1869. Both instances are exceptional examples of where the contacts between sedimentary strata and either sedimentary or crystalline strata of greatly different ages, origins, and structure represent periods of geologic time sufficiently long to raise great mountains and then erode them away.
Background.
Unconformities tend to reflect long-term changes in the pattern of the accumulation of sedimentary or igneous strata in low-lying areas (often ocean basins, such as the Gulf of Mexico or the North Sea, but also Bangladesh and much of Brazil), then being uplifted and eroded (such as the ongoing Himalayan orogeny, the older Laramide orogeny of the Rocky Mountains, or much older Appalachian (Alleghanian) and Ouachita orogenies), then subsequently subsiding, eventually to be buried under younger sediments. The intervening periods of tectonic uplift are generally periods of mountain building, often due to the collision of tectonic plates. The "great" unconformities of regional or continental scale (in both geography and chronology) are associated with either global changes in eustatic sea level or the supercontinent cycle, the periodic merger of all the continents into one approximately every 500 million years.
Hutton's Unconformity.
Hutton's Unconformity at Siccar Point, in county of Berwickshire on the east coast of Scotland, is an angular unconformity that consists of gently dipping, reddish, Upper Devonian and Lower Carboniferous breccias, sandstones, and conglomerates of the Old Red Sandstone overlying deeply eroded, near-vertical, greyish, Silurian (Llandovery) greywackes and shales. The Llandovery greywackes and graptolite-bearing shales of the Gala Group were deposited by turbidity currents in a deep sea environment about 425 million years ago. The overlying Devonian strata were deposited by rivers and streams about 345 million years ago. Thus, this unconformity reflects a gap of about 80 million years during which deep sea sediments were lithified, folded, and uplifted; later deeply eroded and weathered subaerially; and finally buried by river and stream sediments.
Exposures of the unconformity at Siccar Point, provided James Hutton, accompanied by John Playfair and Sir James Hall, the clearest example of an unconformable relationship between two sets of sedimentary strata that involved a complex geological history. The clear truncation of near-vertical Silurian sedimentary strata by well-bedded conglomerates and sandstones belonging to the Upper Old Red Sandstone allowed Hutton to demonstrate the existence of significant breaks in the geological record, in this case a break separating strata that were then called "alpine schistus" and "secondary strata." This and other unconformities provided evidence for Hutton's ideas about the "recycling" of geological materials and for unconformities representing very large time periods He argued that these concepts pointed to the great antiquity of the Earth and the vastness of the geological time-scale.
Powell’s Unconformity, Grand Canyon.
The Great Unconformity of Powell in the Grand Canyon is a regional unconformity that separates the Tonto Group from the underlying, faulted and tilted sedimentary rocks of the Grand Canyon Supergroup and vertically foliated metamorphic and igneous rocks of the Vishnu Basement Rocks. The unconformity between the Tonto Group and the Vishnu Basement Rocks is a nonconformity. The break between the Tonto Group and the Grand Canyon Supergroup is an angular unconformity.
Powell's Great Unconformity is part of a continent-wide unconformity that extends across Laurentia, the ancient core of North America. It was first recognized twelve years before Powell's expedition by John Newberry in New Mexico, during the Ives expedition of 1857-1858. However, the disruption of the American Civil War kept Newberry's work from becoming widely known. This Great Unconformity marks the progressive submergence of this landmass by a shallow cratonic sea and its burial by shallow marine sediments of the Cambrian-Early Ordovician Sauk sequence. The submergence of Laurentia ended a lengthy period of widespread continental denudation that exhumed and deeply eroded Precambrian rocks and exposed them to extensive physical and chemical weathering at the Earth's surface. As a result, Powell's Great Unconformity is unusual in its geographic extent and its stratigraphic significance.
The length of time represented by Powell's Great Unconformity varies along its length. Within the Grand Canyon, the Great Unconformity represents a period of about 175 million years between the Tonto Group and the youngest subdivision, the Sixtymile Formation, of the Grand Canyon Supergroup. At the base of the Grand Canyon Supergroup, where it truncates the Bass Formation, the period of time represented by this angular unconformity increases to about 725 million years. Where the Tonto Group overlies the Vishnu Basement Rocks, the Great Unconformity represents a period as much as 1.2 to 1.6 billion years. (See also geological timescale.)
Frenchman Mountain, Nevada.
A prominent exposure of Powell's Great Unconformity occurs in Frenchman Mountain in Nevada. Frenchman Mountain exposes a sequence of Phanerozoic strata equivalent to those found in the Grand Canyon. At the base of this sequence, the Great Unconformity, with the Tapeats Sandstone of the Tonto Group overlying the Vishnu Basement Rocks, is well exposed in a manner that is atypical and scientifically significant in its combination of extent and accessibility. This exposure is frequently illustrated in popular and educational publications, and is often part of geological fieldtrips. There is a gap of about 1.2 billion years where 550 million year old strata of the Tapeats Sandstone rests on 1.7 billion (1700 million) year old Vishnu Basement Rocks.
As a widespread phenomenon.
The term "Great Unconformity" has also been used to refer to the anomalous concentration of unconformities, including basement nonconformities, below the base of the Cambrian. Charles Walcott was among the first to note this phenomenon, remarking in 1910:
A potential link has been proposed between such sub-Cambrian unconformities and glacial erosion during the Neoproterozoic Snowball Earth glaciations. Alternatively, it has been proposed that multiple smaller events, such as the formation and breakup of Rodinia, created many unconformities worldwide. Evidence indicates that the Pikes Peak unconformity was formed before the Snowball Earth glaciations.
Possible causes of the Great Unconformity.
There is currently no widely accepted explanation for the Great Unconformity among geoscientists. There are theories that have been proposed; it is widely accepted that there was a combination of more than one event which may have caused such an extensive phenomenon. One example is a large glaciation event which took place during the Neoproterozoic, starting around 1 billion years ago. This is also when a significant glaciation event known as ‘Snowball Earth’ occurred. Snowball Earth covered almost the entire planet with ice. The areas that underwent glaciation were approximately those where the Great Unconformity is located today. When glaciers move, they drag and erode sediment away from the underlying rock. This would explain how a large section of rock was taken away from widespread areas around the same time.


Bear Bluff Formation

The Bear Bluff Formation is a geologic formation in North Carolina. It preserves fossils dating back to the Neogene period.


Earnley Formation

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


Red Eagle Formation

The Red Eagle Formation (or Red Eagle Limestone) is a geologic formation ranging from Oklahoma, through Kansas, into southeast Nebraska of the United States. Its members define the Carboniferous-Permian boundary in Kansas.
Lithology.
In the Oklahoma type location, the Red Eagle is a single limestone unit, not further defined into members. However, from the far southeast Nebraska type section into northern Kansas, the Red Eagle Formation consists of three members, each with distinctive lithologies. In Nebraska and northern Kansas in particular, the formation stands out on riverside bluffs and road cuts as two blocky, light-colored limestones sandwiching a dark layer of shale.
Howe Limestone.
Named from exposures south of Howe, Nebraska, the Howe Limestone member is a grey limestone, 4-5 feet thick, that weathers to buff or slightly yellow. The limestone exhibits brachiopods, baculites, and larger bivalve mollusks. The environment was an open, but very shallow sea with very little in the way of terrogenous sediments. As such, the topmost bed is particularly notable for algae beds and melon-sized stromatolites.
Bennett Shale.
Named from exposures along the Little Nemaha River and its branches south of Bennet, Nebraska, the Bennett Shale member is a dark, carbonaceous shale, 2.5 to 15 feet thick. This very dark shale shows contrasting light-colored, circular, thin-shelled Orbiculoidea, roughly 1cm (1/3") in diameter. However, south of Interstate 70 in Kansas, the member becomes increasing limestone to the point that within Oklahoma, the bed is completely limestone and the Red Eagle unit undivided by any significant shale bed.
The Bennett is the youngest Permian rock unit in Kansas.
Glenrock Limestone.
Named from exposures high in valley sides just northwest of Glenrock, Nebraska, the Glenrock Limestone member is lighter grey. It is a hard limestone; fresh fractures sparkle in full sunlight from tiny calcite crystals.
The Glenrock is the oldest Carboniferous rock unit in Kansas.


Clarendon Beds

The Clarendon Beds is a geologic formation in Texas. It preserves fossils dating back to the Neogene period.


Clapassous Formation

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


Big Sandy Formation

The Big Sandy Formation is a geologic formation in Arizona. It preserves fossils dating back to the Neogene period.


Kangaroo Ranch Formation

The Kangaroo Ranch Formation is a geologic formation in California. It preserves fossils dating back to the Ordovician period.


Platysolenites

Platysolenites is a genus of agglutinated foraminifera known from Ediacaran and lower Cambrian assemblages.


Robert R. Coats

Robert Roy Coats (1910–1995) was an American geologist known for his studies of the Aleutian Islands and his exhaustive report of Elko County, Nevada. He was born in Toronto, Canada, and grew up in Marshalltown, Iowa and Seattle, Washington. He graduated valedictorian of his high school class in Seattle at the age of 16, and attended the University of Washington, where he received both a B.S. and M.S. degree in Geology and Mining (1931 and 1932). He continued graduate work at the University of California, Berkeley, receiving his doctorate in 1938, with a thesis on the ore bodies of the Virginia City mining district in Nevada. He was known as an eccentric and brilliant student.
In 1937, Coats took a teaching job at the University of Alaska Fairbanks. He left that job for a post with the U.S. Geological Survey in 1939, in Washington, D.C.. As part of the Alaska Branch of the USGS, he continued working in Alaska, mapping in the Chichagof, Anikovik, Nome, Solomon, Kigluaik and Kobuk River areas, among others. During World War II, he spent time in the Aleutian Islands, returning in 1946 as part of the Survey’s Volcano Project. His field work in the Aleutians led to his 1962 paper (see references) on the origin of the Aleutian island arc. That prescient synthesis of tectonics and magmatism of the Aleutian arc contained several of the essential ideas of the subsequent paradigm of plate tectonics. He correctly interpreted:
Coats’s colleagues from the Alaska Branch of the USGS have commented on his extraordinary ability to comprehend the detailed geologic history of an area with only the most cursory examination. Visiting the Aleutian islands of Buldir, Adak, Kanaga, Semisophochnoi, Gareloi, Kiska and Amchitka (among others), typically for 1–2 days in notoriously bad weather, he produced geologic reports of such detail, insight and quality that they remain today, even in the face of much additional work, the prime source for understanding Aleutian geology.
From 1951 to 1954, Coats was engaged in the search for radioactive granitic rocks, and in field studies of rhyolitic extrusive rocks. His field work took him to New England, and to all of the western states. In 1954, he began a long and productive period of work in Elko County, Nevada, where he studied rhyolites, stratigraphy and structure, and mapped the geology of the Jarbidge, Owyhee, Mountain City and Tuscarora 15’ quadrangles. He relocated to Menlo Park, California in 1956, but spent most summers with his family in a field camp in Nevada. Many of his 70 publications were based on his work in this period, which culminated in his 1987 synthesis report on the Geology of Elko County, a complex area the size of Connecticut and Massachusetts together. The 1:250,000 scale map for the report has a total of 109 mapping units, with areas mapped as small as 10 ha.
Although most of his professional career was spent outside of academia, Coats enjoyed mentoring and teaching one-on-one. Many of his former field assistants and protégés have gone on to illustrious careers in universities and government service.
Coats was married for 58 years to Elizabeth Robinson Coats. He died peacefully at his home in Aptos, California, on January 12, 1995. He was survived by two sons (David of Minneapolis and Robert of Berkeley) and a daughter (Katherine Mrache, of Aptos), and seven grandchildren.


Ballyadams Formation

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


Rocknest 3

Rocknest 3 is a rock on the surface of Aeolis Palus, between Peace Vallis and Aeolis Mons (Mount Sharp), in Gale crater on the planet Mars. The approximate site coordinates are: .
The rock was encountered at Rocknest by the "Curiosity" rover on its way from Bradbury Landing to the Point Lake overlook while traveling toward Glenelg Intrigue in October 2012. The rock measures about high and wide and was a target of the ChemCam and APXS instruments on the "Curiosity" rover.


Rollover anticlines

Rollover anticlines are anticlines related to extensional normal faults. They must be differentiated from fault-propagation folds, which are associated with reverse faults.
A rollover anticline is a syn-depositional structure developed within the downthrown block (hanging wall) of large listric normal faults. Such faults are typically regional in nature and develop as a response to extensional collapse of a passive continental margin (i.e. Niger Delta, Mississippi Delta). Their main feature is that they flatten (sole out) with depth. The scale and shape of the anticline is controlled by the geometry of the listric fault plane and the amount of slip that has taken place along it. The actual fold develops as the hanging wall is pulled away from the footwall, the hanging wall bends to fill the void that is being formed between the two blocks. The result is an anticline feature in a completely extensional setting.
As rollover anticlines develop during sedimentation, each layer typically shows thickening toward the controlling fault. As the underlying layers bend, they create more accommodation space along the controlling fault versus the crest of the anticline. In the opposite direction, the layers exhibit thinning toward the crest of the rollover anticline.
The crest of a rollover anticline is generally an area of active faulting. The hanging wall experiences flexural bending, which creates extension, which in turn creates normal faults. Two families of hanging-wall faults develop in accordance with Coulomb's Law: synthetic (same sense of dip as the controlling fault) and antithetic (opposite sense). They intersect, often creating very complex fault patterns. These tend to be the most complex near the crest of the anticline. Often a collapse graben develops, controlled by localized extension over the outer arc of the culmination.
Rollover structures are often associated by large river deltas, and are favorable traps for hydrocarbons. Trapping is dependent on top seal integrity, and favorable juxtaposition of sandstone reservoirs against impermeable shale across the normal faults that develop within the hanging wall.


Albany Group

The Albany Group is a geologic group in Texas. It preserves fossils dating back to the Permian period.


Bochum Formation

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


Tasman River

The Tasman River is an alpine braided river flowing through Canterbury, in New Zealand's South Island.
The river's headwaters are in Aoraki / Mount Cook National Park, where it is the outflow of the proglacial Tasman Lake. It is also fed by the glacial waters of the tributary Murchison River, from Murchison Glacier, and the short Hooker River, an outflow of the proglacial lakes of the Hooker and Mueller glaciers.
The Tasman River flows south for through the wide flat-bottomed Tasman Valley in the Southern Alps and into the northern end of the glacial lake Pukaki, this forming part of the ultimate headwaters of the Waitaki hydroelectric scheme.


Ganis Chasma

Ganis Chasma is a group of rift zones on the surface of the planet Venus. Bright spots detected by the Venus Monitoring Camera on the European Space Agency's "Venus Express" in the area suggest that there may be active volcanism on Venus.
Introduction.
Ganis Chasma consists of a group of rift zones located in the Ganiki Planitia Quadrangle on Venus. A chasma is defined as a long, narrow, steep sided depression on a planet. These depressions, or canyons, formed as a result of extensional tectonics due to volcanism. Ganis Chasma is associated with volcanism of Sapas Mons, a coronae feature located in the Alta Regio region of Venus. The rifts that make up Ganis Chasma formed in the shape of an arc along the edge of Sapas Mons, orientated in a north–south direction.
Little is known about ongoing volcanic activity on Venus. So far, no volcanic activity has been determined to have occurred in the last two million years. In 2008 and 2009 images taken by the Venus Monitoring Camera on the European Space Agency's (ESA) "Venus Express" (VEx) in eight observational sessions detected four bright transient spots along the edges of Ganis Chasma. In 2014, this was interpreted by Eugene Shalygin and his colleagues as active hotspot volcanism. The team suggests that transient bright spots observed in several consequent images of Ganis Chasma is the first direct evidence of current volcanic activity on Venus.
Ganiki Planitia Quadrangle.
Ganis Chasma is located in the Ganiki Planitia Quadrangle. This quadrangle is positioned between two volcanic regions on Venus. To the north lies the Atlanta Planitia lowland which was formed as the result of mantle upwelling and downwelling. To the south lies Alta Regio. This region is a major volcanic rise and was formed as the result of mantle upwelling. The Ganiki Planitia Quadrangle was strongly influenced by mantle flow tectonics derived from these two regions. The area contains many volcanic, tectonic, and impact features. Ganis Chasma is one of the extensional features located in the region. Other features include grabens, troughs and lineaments. Chains of pit craters located throughout the Ganiki Planitia Quadrangle have been found to influence the formation and deformation of these extensional features.
Tectonics.
Ganis Chasma was formed due to extension associated with volcanism in Alta Regio. It formed in the shape of an arc around the Sapas Mons, a corona feature associated with Alta Regio.
There are two types of rift structures on Venus, rifts (or chasmata), and fracture belts. Ganis Chasma is younger than other chasmata on Venus, as evidenced by the lack of associated wrinkle ridges. Ganis Chasma has undergone additional deformation due to pit crater chains that induced fracturing along the rift zone.
Possible volcanic activity.
Previous studies have been conducted in search of current volcanic activity on Venus. These include observing increases in the amount of sulfur dioxide, a gas emitted by volcanoes, in Venus's upper atmosphere as well as observing possible lava flows emitting heat on Venus's surface. While these studies indicate presence of past volcanic activity, none could prove any volcanism occurring in the past 2 million years. In 2008 and 2009 images retrieved by the VEx Venus Monitoring Camera using a near infrared one micron filter indicated several transient bright spots located in Ganis Chasma along the edges of the rift zone. In 2014, these transient bright spots were interpreted by Eugene Shalyin and his colleagues as possible active hotspot volcanism. Shalygin and his team created mosaics of the images of the study area and created maps of relative surface brightness. They interpreted these bright spots as hot matter at or just above the surface due to the result of a process that releases hot matter such as lava or gas (volcanism). If this claim can be substantiated, it would be the first direct evidence of current volcanic activity on Venus.


Pangaea Proxima

Pangaea Proxima (also called Pangaea Ultima, Neopangaea, and Pangaea II) (Russian; Пангея Проксима,""Pangeya Proxsima"") is a possible future supercontinent configuration. Consistent with the supercontinent cycle, Pangaea Proxima could occur within the next 300 million years. This potential configuration, hypothesized by Christopher Scotese in November 1982, earned its name from its similarity to the previous Pangaea supercontinent. Scotese later changed Pangaea Ultima (Last Pangaea) to Pangaea Proxima (Next Pangaea) to alleviate confusion about the name Pangaea Ultima which could imply that it would be the last supercontinent. The concept was based on examination of past cycles of formation and breakup of supercontinents, not on current understanding of the mechanisms of tectonic change, which are too imprecise to project that far into the future. "It's all pretty much fantasy to start with," Scotese has said. "But it's a fun exercise to think about what might happen. And you can only do it if you have a really clear idea of why things happen in the first place."
Supercontinents describe the merger of all, or nearly all, of Earth's landmass into a single contiguous continent. In the Pangaea Proxima scenario, subduction at the western Atlantic, east of the Americas, leads to the subduction of the Atlantic mid-ocean ridge followed by subduction destroying the Atlantic and Indian basin, causing the Atlantic and Indian Oceans to close, bringing the Americas back together with Africa and Europe. As with most supercontinents, the interior of Pangaea Proxima would probably become a semi-arid desert prone to extreme temperatures.
Formation.
According to the Pangaea Proxima hypothesis, the Atlantic and Indian Oceans will continue to get wider until new subduction zones bring the continents back together, forming a future Pangaea. Most continents and microcontinents are predicted to collide with Eurasia, just as they did when most continents collided with Laurentia.
Around 50 million years from now, North America is predicted to shift west and Eurasia would shift to the east, and possibly even to the south, bringing Great Britain closer to the North Pole and Siberia southward towards warm, subtropical latitudes. Africa is predicted to collide with Europe and Arabia, closing the Mediterranean Sea (completely closing the Tethys Ocean (or Neotethys) and the Red Sea) and forming a supercontinent called Afro-Eurasia. A long mountain range (the Mediterranean Mountain Range) would then extend from Iberia, across Southern Europe and into Asia. Some are even predicted to have peaks higher than Mount Everest. Similarly, Australia is predicted to beach itself past the doorstep of Southeast Asia, causing the islands to be compressed inland, forming another potential mountain range, and forming a supercontinent, called Afro-Euraustralasia. Meanwhile, Southern and Baja California are predicted to have already collided with Alaska with new mountain ranges formed between them.
About 125 million years from now, the Atlantic Ocean is predicted to stop widening and begin to shrink because some of the Mid-Atlantic Ridge will have been subducted. In this scenario, a mid-ocean ridge between South America and Africa will probably be subducted first; the Atlantic Ocean is predicted to have narrowed as a result of subduction beneath the Americas. The Indian Ocean is also predicted to be smaller due to northward subduction of oceanic crust into the Central Indian trench. Antarctica is expected to split into two and shift northwards, colliding with Madagascar and Australia, enclosing a remnant of the Indian Ocean (called the Indo-Atlantic Ocean), and creating the supercontinent Terra Orientalis.
When the last of the Mid-Atlantic Ridge is subducted beneath the Americas, the Atlantic Ocean is predicted to close rapidly.
At 200 million years in the future, the Atlantic is predicted to have closed. North America is predicted to have already collided with Africa, but be in a more southerly position than where it drifted. South America is predicted to be wrapped around the southern tip of Africa, completely enclosing the Indo-Atlantic Ocean. The Pacific Ocean will have grown wider, encircling half the Earth.
Models.
There are two models for the formation of Pangaea Proxima - an early model and the current model. The two models differ in where they place Australia and Antarctica. The early model, shown on the Paleomap Project website, places Australia and Antarctica connected to each other as a separate landmass to Pangaea Proxima, close to the south pole. The current model, shown on Christopher Scotese's Youtube channel, has Australia attached to China, East Antarctica attached to South America, and West Antarctica attached to Australia.
Other suggested supercontinents.
Paleogeologist Ronald Blakey has described the next 15 to 85 million years of tectonic development as fairly settled and predictable, without supercontinent formation. Beyond that, he cautions that the geologic record is full of unexpected shifts in tectonic activity that make further projections "very, very speculative". In addition to Pangaea Proxima, two other hypothetical supercontinents—"Amasia" and "Novopangaea"—were illustrated in an October 2007 "New Scientist" article.


Assise de Lebach

The Assise de Lebach is a geologic formation in France. It preserves fossils dating back to the Permian period.


Tir Planitia

Tir Planitia is a large basin on the planet Mercury. The name Tir (تیر) is the Persian word for "Mercury".


Lake Mathews Formation

The Lake Mathews Formation is a geologic formation in Riverside County, California.
It is located in the Lake Mathews reservoir area, in the Temescal Mountains.
The sedimentary formation preserves fossils dating back to the Neogene period.


Gros Ventre Formation

The Gros Ventre Formation is a geologic formation in Wyoming, USA. It preserves fossils dating back to the Cambrian period. The Gros Ventre consists of three main members; the Wolsey Shale, the Death Canyon Limestone, and the Park Shale.


Sedimentary basin analysis

Sedimentary basin analysis is a geologic method by which the formation and evolution history of a sedimentary basin is revealed, by analyzing the sediment fill and subsidence. Subsidence of sedimentary basins generates the spatial distribution of accommodation infilling sediments. Aspects of the sediment, namely its composition, primary structures, and internal architecture, can be synthesized into a history of the basin fill. Such a synthesis can reveal how the basin formed, how the sediment fill was transported or precipitated, and reveal sources of the sediment fill. From such syntheses models can be developed to explain broad basin formation mechanisms. Examples of such basinal environments include backarc, forearc, passive margin, epicontinental, extensional, and pull-apart basin.
Sedimentary basin analysis is largely conducted by two types of geologists who have slightly different goals and approaches. The petroleum geologist, whose ultimate goal is to determine the possible presence and extent of hydrocarbons and hydrocarbon-bearing rocks in a basin, and the academic geologist, who may be concerned with any or all facets of a basin's evolution. Petroleum industry basin analysis is often conducted on subterranean basins through the use of reflection seismology and data from well logging. Academic geologists study subterranean basins as well as those basins which have been exhumed and dissected by subsequent tectonic events. Thus academics sometimes use petroleum industry techniques, but in many cases they are able to study rocks at the surface. Techniques used to study surficial sedimentary rocks include: measuring stratigraphic sections, identifying sedimentary depositional environments and constructing a geologic map.
An important tool in sedimentary basin analysis is sequence stratigraphy, in which various sedimentary sequences are related to pervasive changes in sea level and sediment supply.


Blackstokes Limestone

The Blackstokes Limestone is a geologic formation in Northern Ireland. It preserves fossils dating back to the Carboniferous period.


Louise H. Kellogg

Louise H. Kellogg (November 18, 1959 – April 15, 2019) was an American geophysicist with expertise in chemical geodynamics and computational geophysics and experience in leading multidisciplinary teams to advance geodynamics modeling and scientific visualization. Kellogg was a Distinguished Professor at the University of California, Davis and director of the Computational Infrastructure for Geodynamics. She was also a major contributor to the Deep Carbon Observatory project of the Sloan Foundation.
Career.
Kellogg received her B.S. in Engineering Physics and B.A. in Philosophy from Cornell University in 1982. She followed with her Masters in Engineering and Engineering Physics in 1985 and her PhD in Geological Sciences in 1988 both from Cornell University.
After receiving her Ph.D, she was named the Myron C. Bantrell Research Fellow in Geochemistry and Geophysics at the California Institute of Technology. She taught geology as an assistant and then associate professor at the University of California Davis from 1990 to 1998. Since 1998, she has been a professor in Earth and Planetary Sciences at UC Davis and served as the Department's Chair from 2000 to 2008. She also headed the Keck Center for Active Visualization in Earth Sciences (KeckCAVES), which provides expertise on scientific visualization of complex data and models. Kellogg was on the Executive Committee of the Deep Carbon Observatory and a member of its Synthesis Group 2019.
Research initiatives.
Kellogg's main research initiatives focused on understanding the flow in the Earth's mantle that drives plate tectonics, and observing and interpreting deformation in the Earth's crust. At U.C. Davis Kellogg used numerical methods to model aspects of mantle convection. Kellogg also studied Earthquake Physics and Crustal deformation in order to assess seismic hazard of faults. She also worked on the visualization of geosciences data in an immersive environment.
Awards.
From 1992 to 1996, Kellogg received a grant from the National Science Foundation as a Presidential Faculty Fellow. She was invited to present the Francis Birch lecture ("Structure and Dynamics: An Earth Odyssey") at the American Geophysical Union in 2001. She was elected fellow of the American Geophysical Union in 2010 and the American Association for the Advancement of Science in 2012. She was elected to the American Academy of Arts and Sciences in 2013.
Publications.
Kellogg has published 239 papers for a total of over 3000 citations and an h-index of 29. A selection follows.


Ames Limestone

The Ames Limestone is a geologic formation in West Virginia. It preserves fossils dating back to the Carboniferous period.


Onyx Marble

The Onyx Marble is a geologic formation in Arizona. It preserves fossils dating back to the Neogene period.


Helminthopsis

Helminthopsis is the ichnogenus of a type of trace fossil that is found preserved on the bedding planes of fine-grained sedimentary rocks. It is characterized by short, curvilinear, non-branching, parallel-sided, unlined traces on bedding surfaces. It is thought to represent the submarine feeding trails of an invertebrate organism that worked the surface of muddy substrates in search of food. Because "Helminthopsis" traces never cross over themselves, the ichnogenus is distinguished from similar traces assigned to the "Gordia" ichnogenus. The similar sounding, but now obsolete, ichnogenus "Helminthoida" refers to a somewhat similar trace characterized by regular, back-and-forth meanders, whereas "Helminthopsis" traces are irregular.


Colville Group

The Colville Group is a geologic group in Alaska. It preserves fossils dating back to the Paleogene period.


Natural gas field


Pressure-temperature-time path

The Pressure-Temperature-time path (P-T-t path) is a record of the pressure and temperature (P-T) conditions that a rock experienced in a metamorphic cycle from burial and heating to uplift and exhumation to the surface. Metamorphism is a dynamic process which involves the changes in minerals and textures of the pre-existing rocks (protoliths) under different P-T conditions in solid state. The changes in pressures and temperatures with time experienced by the metamorphic rocks are often investigated by petrological methods, radiometric dating techniques and thermodynamic modeling.
Metamorphic minerals are unstable upon changing P-T conditions. The original minerals are commonly destroyed during solid state metamorphism and react to grow into new minerals that are relatively stable. Water is generally involved in the reaction, either from the surroundings or generated by the reaction itself. Usually, a large amount of fluids (e.g. water vapor, gas etc.) escape under increasing P-T conditions e.g. burial. When the rock is later uplifted, due to the escape of fluids at an earlier stage, there is not enough fluids to permit all the new minerals to react back into the original minerals. Hence, the minerals are not fully in equilibrium when discovered on the surface. Therefore, the mineral assemblages in metamorphic rocks implicitly record the past P-T conditions that the rock has experienced, and investigating these minerals can supply information about the past metamorphic and tectonic history.
The P-T-t paths are generally classified into two types: "clockwise P-T-t paths", which are related to collision origin, and involve high pressures followed by high temperatures; and "anticlockwise P-T-t paths", which are usually of intrusion origin, and involve high temperatures before high pressures. (The "clockwise" and "anticlockwise" names refer to the apparent direction of the paths in the Cartesian space, where the x-axis is temperature, and the y-axis is pressure.)
Stages in P-T-t paths.
P-T-t paths often reflect various stages of the metamorphic cycle. A metamorphic cycle implies the series of processes that a rock experienced from burial, heating to uplift and erosion. The P-T conditions experienced by a rock throughout these processes can be classified into three main stages according to temperature changes:
However, retrograde metamorphism may not always be observed in metamorphic rocks. This is due to the loss of fluids (e.g. CO2, H2O) from prograde metamorphism, after which there is insufficient fluid to permit reverse reaction of the mineral assemblages. Another reason is that the rocks are of inappropriate composition to generate all the minerals that record their complete metamorphic events. On average, only one-in-twenty metamorphic rock samples display all the three stages of metamorphism.
P-T-t path trajectories.
P-T-t paths can generally be classified into two types: "clockwise P-T-t paths" and "anticlockwise P-T-t paths".
Clockwise P-T-t paths.
Metamorphic rocks with clockwise P-T-t paths are commonly associated with a near-isothermal decompressional P-T trajectory.
Clockwise P-T-t path normally consists of three parts:
One might expect that the rock reaches its peak metamorphism at the peak temperature and pressure at similar time, and near-isothermal decompression P-T-t path is observed at its stage 1 metamorphism. However, in reality, the rocks commonly experience the peak pressure prior to the peak temperature. This is due to the relative insensitivity of rocks to thermal events, i.e. poor conductivity of rock upon external thermal changes, whereas the rocks instantaneously experience pressure changes.
Examples of metamorphic rocks that consist of clockwise P-T-t paths can be found at:
Anticlockwise P-T-t paths.
Metamorphic rocks with anticlockwise P-T-t paths are commonly associated with a near-isobaric cooling P-T trajectory.
Anticlockwise P-T-t path normally consists of two parts:
It is commonly observed that the peak temperature is reached prior to the peak pressure in anticlockwise P-T-t paths, as the rocks usually experienced the heat from the heat source before being extensively pressurized.
Examples of metamorphic rocks that consist of anticlockwise P-T-t paths can be found at:
Reconstruction of P-T-t paths.
The reconstruction of P-T-t paths includes two types of approaches:
Backward approach (Petrological P-T-t reconstruction).
Petrological reconstruction is a backward approach which utilizes mineral compositions of rocks samples to deduce the possible P-T conditions. Common techniques include optical microscopy, geothermobarometry, pseudosections, and geochronology.
Optical microscopy.
In "qualitative" reconstruction of P-T conditions, geologists examine thin sections under polarized light microscope to determine the sequence of formation of the minerals. Due to incomplete replacement of the earlier formed minerals under changing P-T conditions, minerals formed at various P-T environments can be found in the same rock specimen. As different minerals have different optical characteristics and textures, determination of the mineral compositions in metamorphic rocks is made possible.
Common textures at different stages of metamorphism:
Not all rock samples exhibit all the P-T conditions they experienced throughout geological evolution. This is attributed to the complexity of the geological processes, which the samples may have undergone complicated thermodynamic histories, or of inappropriate mineral compositions to produce minerals that record their metamorphic events.
Geothermobarometry.
Geothermobarometry is a "quantitative" measurement of the P-T conditions, which is widely used in analyzing the P-T conditions of metamorphic and intrusive igneous rocks.
The underlying principle of geothermobarometry is by utilizing the equilibrium constants of mineral assemblages in a rock to infer the metamorphic P-T conditions. An electron microprobe is usually used in geothermobarometry to measure the distribution of components in the minerals and give precise determination of the chemical equilibrium within the specimen.
Geothermobarometry is a combination of:
Geothermometers are usually represented by exchange reactions, which are sensitive to temperature but with little effect under changing pressure, such as exchange of Fe2+ and Mg2+ between "garnet-biotite" reaction:
Geobarometers are typically occurred as net-transfer reactions, which are sensitive to pressure but have little change with temperature, such as "garnet-plagioclase-muscovite-biotite" reaction that involves a significant volume reduction upon high pressure:
Since mineral assemblages at equilibrium are dependent on pressures and temperatures, by measuring the composition of the coexisting minerals, together with using suitable activity models, the P-T conditions experienced by the rock can be determined.
After one equilibrium constant is found, a line would be plotted on the P-T diagram. As different equilibrium constants of mineral assemblages would occur as lines with different slopes in the P-T diagram, therefore, by finding the intersection of at least two lines in the P-T diagram, the P-T condition of the specimen can be obtained.
Despite the usefulness of geothermobarometry, special attention should be paid to whether the mineral assemblages represent an equilibrium, any occurrence of retrograde equilibrium in the rock, and appropriateness of calibration of the results.
Garnet growth zoning.
Garnet growth zoning is a special type of geothermobarometry that focuses on the composition variations in garnet.
Zoning is a texture in solid-solution minerals which the minerals form concentric rings from core to rim upon changing P-T conditions. In a changing environment, minerals would be unstable and alter itself to reduce its Gibbs free energy to achieve stable states. However, sometimes the mineral core has not reached equilibrium upon the environmental change and zoning occurs. Zoning is also found in other minerals such as plagioclase and fluorite.
In practice, garnet is commonly used in the study of metamorphic rocks due to its refractory nature. In past studies, garnet is found to be a mineral that is stable under a wide range of P-T conditions, meanwhile chemically displays responses (e.g. ions exchange) to the P-T variations throughout its metamorphic history without reaching complete equilibrium. The non-equilibriated garnet formed previously are often zoned by younger garnet. Therefore, many past P-T characteristics are preserved in the zoned areas. Electron microprobes are used to measure the composition of the garnet zones.
However, melting within garnet sometimes occurs or diffusion rate is too rapid at high temperature, some garnet zones are merged and cannot provide sufficient information about the complete metamorphic history of the rocks.
Gibbs method.
The Gibbs method formalism is a method used to analyze pressures and temperatures of zoned minerals and textural changes in metamorphic rocks by applying differential thermodynamic equations based on Duhem's Theorem. It attempts to simulate the garnet growth zoning numerically by solving a set of differential equations involving variables pressure (P), temperature (T), chemical potential (μ), mineral composition (X). Modal abundance of mineral phases (M) was later added as an extensive variable in the Gibbs method with mass balance added as a constraint. The aim of this analysis is to search for the absolute P-T condition during different zonal growth and matches the observed composition of zones in the sample. The computer program is commonly used for calculation of the equations.
Pseudosection.
Pseudosection is an equilibrium phase diagram which shows all the stable mineral assemblages of a rock at different P-T ranges for a single whole-rock chemical composition (bulk-rock composition). The stable mineral assemblages are marked as different areas in the P-T graph.
Unlike geothermobarometry, which focuses only on single chemical equilibrium equations, pseudosections make use of multiple equilibrium equations to search for the past P-T conditions. It is widely used in metamorphic rock analysis due to its consideration of multiple reactions which resemble metamorphic processes of multiple minerals in reality.
In the construction of pseudosections, the bulk-rock composition is firstly determined using geochemical techniques, then inserted into computer programs for calculations based on thermodynamics equations to generate pseudosection diagrams.
There are two geochemical methods in determining the bulk-rock composition:
Both methods have their advantages and limitations. The XRF method provides a non-biased estimation, but may neglect the proportion of existing minerals in the rock. Meanwhile, the point-counting method takes into account of mineral proportions, but is based on human judgement and may be biased.
Common computer programs for computing pseudosections:
The results from a single pseudosection is not completely reliable, since in reality the rock specimen is not always in equilibrium. However, analysis can be done on fractions of the P-T-t path e.g. at boundaries of mineral inclusions, or on local bulk composition analysis would improve precision and accuracy of the P-T-t path.
Geochronology.
To figure out the age of the metamorphic events, geochronological techniques are used. It utilizes the idea of radioactive decay of long-lived unstable isotopes in minerals to search for the "age" of events.
Monazite geochronology.
In the study of metamorphic petrology, U-Th-Pb dating (Uranium-Thorium-Lead dating) of monazite (monazite geochronology) is an effective method to determine the P-T history. Monazite is a phosphate mineral containing light rare-earth-elements (LREE) that occurs in a wide range of rock types. It usually incorporates radioactive thorium (Th) during its crystal formation, making age determination possible.
Monazite has characteristics of high closure temperature (>1000 °C), variable composition, and robustness under a large temperature range, which help in the record of geological history in metamorphic rocks. An electron microprobe is usually used for the measurement of monazite composition.
Monazite inclusions.
Monazite usually occurs as inclusions in the porphyroblasts in metamorphic rocks.
For instance, during the growth of garnet zones in metamorphic processes, monazite grains are included into the zones of garnets. Since garnets are quite stable upon changing temperature, the included monazite grains are well preserved and prevented from the re-setting of decay system and age. Therefore, the age of the metamorphic events in each zone can be estimated.
Monazite growth zoning.
Apart from occurring as inclusion in garnets, monazite also display zonal growth pattern itself upon changing P-T conditions.
Monazite tends to capture Th when it is formed. When monazite crystal is growing, the earlier formed monazites incorporate many Th, and leaving a Th-depleted surrounding environment. Hence, the older formed monazite has a higher concentration of Th than younger monazite. Therefore, dating zoned matrix monazites (i.e. monazites that do not form as inclusions in other minerals) of the metamorphic rock can obtain information about the age as well as their formation sequence. The dating method is usually done by using an electron microprobe to observe the compositional zones of monazite, then analyzing the U-Th-Pb age of each zone to reconstruct the time of the relevant P-T conditions. Data obtained from matrix monazites are often compared with those obtained from monazite inclusions for the metamorphic history interpretation.
Zircon geochronology.
Zircon is another suitable mineral for dating metamorphic rocks. It occurs as an accessory mineral in rocks and contains trace amount of uranium (U).
As zircon is resistant towards weathering and high temperature, it is a useful mineral in recording geological processes. Similar as monazite, zircon also displays zoned patterns upon varying P-T conditions, which each zone records information of the changing past environment. U-Pb dating is commonly used in dating zircon ages. Zircon geochronology gives good record of ages in cooling and exhumation processes. However it is less reactive than monazite under metamorphic events, and performs better in dating igneous rocks.
Forward approach (Thermal modeling).
Unlike using traditional petrological investigation methods (e.g. optical microscopy, geothermobarometry) to inversely infer the metamorphic events from rock samples, thermal modeling is a forward method that attempts to work on the geological evolution of rocks.
Thermal modeling applies numerical modeling techniques based on heat transfer equations, different tectonics models and reactions of metamorphic minerals in the simulation of the possible metamorphic events. It works on the temperature variation of the earth crust over time based on rate of heat transfer and diffusion along the disturbed geothermal gradient (normal heat distribution in the ground).
Thermal modeling does not give the actual geological time. However, it provides accurate estimation of the duration of the thermal events. An advantage of thermal modeling is that it provides a holistic estimation of the duration of different stages of metamorphism, which is somehow difficult to completely extract from geochronological methods.
The model simulation involves solving the continuous time-dependent differential heat transfer equation by its approximate discrete finite difference form using computer programs such as .
After the equations are set, a grid of nodes is generated for calculation of each point. Boundary conditions (normally temperature of the geothermal gradients) are input into the equations to calculate the temperature at boundaries. Results are compared with petrological experimental results for validation.
By combining petrological methods and thermal modeling techniques, the understanding of metamorphic processes due to tectonic events is facilitated. Petrological results provide realistic variables to be plugged into a model simulation, while numerical modeling techniques often place constraints on the possible tectonic environments. The two methods complement the limitations of each other, and formulate a comprehensive evolutionary history of the metamorphic and tectonic events.
Tectonic implications.
Collision setting.
Areas with collision-related tectonic events or under subduction zones commonly produce metamorphic rocks with "clockwise P-T-t paths" with near-isothermal decompressional P-T trajectories, and the reason is as follows:
In addition, recent studies based on mechanical analysis reveal that peak pressure recorded in clockwise P-T paths does not necessarily represent the maximum depth of burial, but can also represent a change in the tectonic pattern.
Intrusion.
Intrusions such as hotspots or rifts at mid-ocean ridges commonly produce metamorphic rocks displaying "anticlockwise P-T-t paths" patterns with near-isobaric cooling P-T trajectories, and the reason is as follow:
Paired metamorphic belts.
"Both clockwise and anticlockwise metamorphic P-T-t paths" are found in paired metamorphic belts at convergent plate boundaries. Paired metamorphic belts display two contrasting mineral assemblages sets:
The HPLT metamorphic belt is located along subduction zones, and commonly associated with a clockwise P-T-t path. The HPLT condition is resulted from crustal thickening due to convergence meanwhile without being heated by magma.
The LPHT metamorphic belt is observed at volcanic arcs or back-arc basins, which is attributed to magma intrusion derived from partial melting of the subducting slab, and the melt rises to the crust. This area is associated with an anticlockwise P-T-t path.
The P-T-t paths provide in-depth investigations and implications of the mechanisms in the lithosphere, and further support the plate tectonic theory and the formation of supercontinents.
Plume tectonics.
P-T-t paths play an important role in the development of plume tectonics, supported by "anticlockwise P-T paths."
Plume tectonics are considered to be the dominant process forming the Archean crust with evidence from the study of the Archean cratonic blocks in the North China Craton. Anticlockwise P-T paths with near-isobaric cooling after the peak are normally found in the Archean rocks, suggesting an intrusion origin.
The lack of a paired metamorphic belt as well as a paired clockwise P-T path in the Archean rocks eliminates the possibility of the volcanic arc formation. Evidenced together by a large doming structure, widespread of komatiites and bimodal volcanism, it is proposed that plume tectonics is the major crust-forming process in the Archean. This has led to further research on the beginning of plate tectonics and numerical modeling of the early Earth condition.
Structural deformation.
P-T-t paths can be used to estimate possible structures in the field as heat would transfer in small scale advective heat flow during thrusting and folding of metamorphic rocks.
For example, during the formation of fault-bend-fold, the rocks in the lower segment (footwall) are heated due to contact with the hotter upper thrust sheet (hanging wall), while the upper thrust sheet is cooling because of losing heat in a downward direction. Thus, the lower segment and the upper thrust sheet are undergoing prograde metamorphism and retrograde metamorphism respectively.
Nevertheless, special attention should be taken to the effect of multiple thrusting such as duplexes, where the initial lower plate in an earlier thrust would become the upper plate in a later thrusting event. Depending on the location of the rock, a variety of complex P-T trajectories can be found, which may make interpretation of a terrain challenging.
Historical development of P-T-t paths.
Metamorphic facies.
Metamorphic facies is a classification system first introduced by Pentti Eskola in 1920 to classify particular metamorphic mineral assemblages that are stable under a range of P-T conditions. Before the mid-1970s, geologists utilized the metamorphic facies classification to investigate metamorphic rocks and determined their P-T characteristics. However, little was known about the evolutionary processes of these P-T conditions and how metamorphic rocks reach the surface at that time.
Metamorphic path.
The relation between metamorphism and tectonic setting was not well investigated until 1974, which Oxburgh and Turcotte suggested that the origin of the metamorphic belt is a result of the thermal effects brought by continental collision. The idea was picked up by England and Richardson and further research was done in 1977, and the P-T-t path concept was fully developed by Richardson and Thompson in 1984.
Findings.
The thermal modeling from Richardson and Thompson (1984) reveals that in every case of thermal relaxation after the tectonic event, there is a large portion of heat equilibrium before being significantly influenced by erosion, i.e. the rate of metamorphism is found to be much slower than duration of the thermal event. This infers that the rock is a poor heat conductor, which the maximum temperature experienced by the rock as well as its temperature change are insensitive to erosion rate. Therefore, both the evidence of the maximum pressures and temperatures experienced by the buried layers can be imprinted in the underlying metamorphic rocks. Hence, the buried depth as well as plausible tectonic settings can be deduced. Altogether with dating techniques, geologists can even determine the time scale of the tectonic events in respect to the metamorphic events.
Future development.
Metamorphic P-T-t paths have been widely recognized as a useful tool in determining the metamorphic history and tectonic evolution of a region. Potential future research directions for P-T-t paths will be likely developed in the following areas:


Petit Jardin Formation

The Petit Jardin Formation is a geologic formation in Newfoundland and Labrador. It preserves fossils dating back to the Cambrian period.


Everton Formation

The Everton Formation is a geologic formation in northern Arkansas that dates to the middle Ordovician Period. Unconformities separate this formation from the underlying Powell Formation and the overlying St. Peter Sandstone Formation. Named for the town of Everton in Boone County, Arkansas in 1907, the Everton Formation is composed primarily of dolomite, limestone, and sandstone.
Stratigraphy.
Five named members of the Everton Formation are recognized (in stratigraphic order):


Kanayut Formation

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


Orinda Formation

The Orinda Formation is a Miocene epoch geologic formation in the Berkeley Hills of the East Bay region of the San Francisco Bay Area, California.
It is found within Alameda County and Contra Costa County.
Geology.
The Orinda Formation is a coarse alluvial conglomerates sedimentary formation. It underlies the volcanic Moraga Formation.
It preserves fossils dating back to the Miocene epoch of the Neogene period.
Geologic Hazards.
The Orinda Formation is prone to landsliding due to intrinsic properties such as its weak cohesive strength and low friction angle. Landslides less than or equal to 10 acres in size occur as slides, slumps, and earthflows on dip or parallel to dip slopes. In the formation, landslides greater than or equal to 10 acres in size are common to very common and occur as slumps and slides on anti-dip slopes.


Rockslide Formation

The Rockslide Formation is a geologic formation in Northwest Territories. It preserves fossils dating back to the Drumian (Plagiura-Pogiella to Bolaspidella Zone).
It was deposited in deep water on a reasonably distal slope; it contains carbonates, debris flows and siliciclastic siltstones, the latter being the fossil bearing horizons. It also contains deep-water microbial reefs.


Badger Flat Limestone

The Badger Flat Limestone is a limestone geologic formation in California.
It preserves fossils dating back to the Ordovician period.


Inn (river)

The Inn (; ) is a river in Switzerland, Austria and Bavaria. It is a right tributary of the Danube and is long. The highest point of its drainage basin is the summit of Piz Bernina, at . The Engadine, the valley of the En, is the only Swiss valley whose waters end up in the Black Sea (via the Danube).
Etymology.
The name Inn is derived from the old Celtic words "en" and "enios", meaning "water". In a document of 1338, the river was named "Wasser" (German for water). The first written mention from the years 105 to 109 (Publii Corneli Taciti historiarium liber tertius) reads: "... Sextilius Felix... ad occupandam ripam Aeni fluminis, quod Raetos Noricosque interfluit, missus..." ("... Sextilius Felix was sent to capture the banks of the Inn, which flows between the Rhaetian people and the Noric people.") The river is also mentioned by other authors of the Roman Empire as "Ainos" (Greek) or "Aenus" (Latin). In medieval Latin it was written as "Enus" or "Oenus". The change in the old Bavarian language from "e" to "i" turned Enus to "In". Until the 17th century, it was written like this or "Yn", but also "Ihn" or "Yhn". The double-n appeared only in the 16th century, for example in the Tyrolian Landreim of 1557, and since the 18th century this spelling and pronunciation with a short vowel has been customary.
The mentions in Roman times refer to the lower course. The Tyrolean section was first called Aenus by Venantius Fortunatus in the 6th century. The name Engadin and the Romansh name "En" indicate that the upper reaches of the river have always been called this way. Even though it was occasionally believed that the Inn originated near the Adige at the Reschen Pass, since the 16th century at the latest the origin has been seen uniformly in the area of the lakes at the Maloja Pass.
There may be a connection between the name Inn and the name of the French river Ain.
Geography.
The source is located in the Swiss Alps, west of St. Moritz in the Engadine region, which is named after the river (Romansh "Engiadina"; Latin "vallis Eniatina"). Shortly after it leaves its source, the Inn flows through the largest lakes on its course, Lake Sils and Lake Silvaplana. It runs north-eastwards, entering Austria, and from Landeck eastwards through the Austrian state of Tyrol and its capital, Innsbruck ("bridge over the Inn"), and crosses the border into Bavaria near Kufstein.
On Bavarian territory the river runs northwards and passes Rosenheim, Wasserburg am Inn, and Waldkraiburg; then it turns east, runs through Mühldorf and Neuötting and is enlarged by two major tributaries, the Alz and the Salzach. From here to the Danube, it forms the border between Germany (Bavaria) and Austria (Upper Austria). Towns on this last section of the river are Marktl am Inn, Simbach on Inn, Braunau am Inn and Schärding.
In Passau the Inn finally enters the Danube (as does the river Ilz there). Although the Inn has a greater average flow than the Danube when they converge in Passau, and its watershed contains the Piz Bernina, the highest point in the Danube watershed, the Inn is considered a tributary of the Danube, which has a greater length, drains a larger surface area, and has a more consistent flow.
The Inn is the only river originating in Switzerland that ends in the Black Sea (via the Danube).
Flow.
Average monthly flow (m³/s) of the Inn in Passau
Years 1921/2006
2013 flood.
On June 3, 2013, the discharge of the Inn in Passau reached and the water levels reached , the highest recorded historic flood level since 1501. The historic centre of Passau, where the Danube, Inn and Ilz converge, was flooded severely.
Hydroelectric power plants.
Currently, there are 24 hydroelectric power plants on the Inn. 17 of them are operated by Verbund AG. The power plants are listed beginning at the headwaters:


Flysch

Flysch () is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building episode. Examples are found near the North American Cordillera, the Alps, the Pyrenees and the Carpathians.
Sedimentological properties.
Flysch consists of repeated sedimentary cycles with upwards fining of the sediments. There are sometimes coarse conglomerates or breccias at the bottom of each cycle, which gradually evolve upwards into sandstone and shale/mudstone. Flysch typically consists of a sequence of shales rhythmically interbedded with thin, hard, graywacke-like sandstones. Typically the shales do not contain many fossils, while the coarser sandstones often have fractions of micas and glauconite.
Tectonics.
In a continental collision, a subducting tectonic plate pushes on the plate above it, making the rock fold, often to the point where thrust faults form, and a mountain chain rises. On the upper plate, the land between the mountains and the undeformed continent bends downward, forming a foreland basin. If the basin forms slowly, as in the northern Appalachians, it fills with shallow-water sediments. If it forms rapidly, as in the east side of the North American Cordillera, then sea water may rush in, and the first sedimentary deposits are deep water deposits. If the mountain slope is steep enough at the edge of the basin, it will shed material in rapidly moving sedimentary flows called turbidity currents, resulting in turbidite deposits. As the basin fills up, shallow-water sandstones and continental deposits form. Most of the resulting rocks have little deformation, but near the edge of the mountain chain they can be subject to folding and thrusting. After the basin fills up, continental sediments (molasse) are deposited on top of the flysch.
Name and use.
The name flysch was introduced in geologic literature by the Swiss geologist Bernhard Studer in 1827. Studer used the term for the typical alternations of sandstone and shale in the foreland of the Alps. The name comes from the German word "fliessen", which means "to flow", because Studer thought flysch was deposited by rivers. The insight that flysch is actually a deep marine sediment typical for a particular plate tectonic setting came only much later.
The name flysch is currently used in many mountain chains belonging to the Alpine belt. Well-known flysch deposits are found in the forelands of the Pyrenees and Carpathians and in tectonically similar regions in Italy, the Balkans and on Cyprus. In the northern Alps, the Flysch is also a lithostratigraphic unit.


Bighorn Dolomite

The Bighorn Dolomite is a geologic formation in Wyoming. It preserves fossils dating back to the Ordovician period.