Alaska Natives Russian colonial period When was the Russian colonial period? Arriving from Siberia by ship in the mid-eighteenth century, Russians began to trade with Alaska Natives. What did they trade? Rather than hunting the marine life, the Russians forced the Aleuts to do the work for them. What did  they hunt? I don't know. What else was significant during the Russian colonial period? Catherine the Great, who became Empress in 1763, proclaimed good will toward the Aleut How did they benefit? urged her subjects to treat them fairly. On some islands and parts of the Alaska Peninsula, groups of traders had been capable of relatively peaceful coexistence with the local inhabitants. When did this period end? I don't know. What else is notable about this time period? 80 percent of the Aleut population died from Eurasian infectious diseases.
What was the impact of this?
What was the impact of Eurasian infectious diseases on Aleut Population?
Arriving from Siberia by ship in the mid-eighteenth century, Russians began to trade with Alaska Natives. New settlements around trading posts were started by Russians, including Russian Orthodox missionaries. These were the first to translate Christian scripture into Native languages. British and American traders generally did not reach the area until the nineteenth century, and in some cases missionaries were not active until the twentieth century. In the 21st century, the numerous congregations of Russian Orthodox Christians in Alaska are generally composed mostly of Alaska Natives.  Rather than hunting the marine life, the Russians forced the Aleuts to do the work for them. As word spread of the riches in furs to be had, competition among Russian companies increased and they forced the Aleuts into slavery. Catherine the Great, who became Empress in 1763, proclaimed good will toward the Aleut and urged her subjects to treat them fairly. On some islands and parts of the Alaska Peninsula, groups of traders had been capable of relatively peaceful coexistence with the local inhabitants. Other groups could not manage the tensions. Russians took hostages, families were split up, and individuals were forced to leave their villages and settle elsewhere. The growing competition between the trading companies, merging into fewer, larger and more powerful corporations, created conflicts that aggravated the relations with the indigenous populations. Over the years, the situation became catastrophic for the natives.  As the animal populations declined, the Aleuts, already too dependent on the new barter economy created by the Russian fur trade, were increasingly coerced into taking greater risks in the dangerous waters of the North Pacific to hunt for more otter. As the Shelikhov-Golikov Company and later Russian-American Company developed as a monopoly, it used skirmishes and systematic violence as a tool of colonial exploitation of the indigenous people. When the Aleut revolted and won some victories, the Russians retaliated, killing many and destroying their boats and hunting gear, leaving them no means of survival.  The most devastating effects were from disease: during the first two generations (1741/1759-1781/1799 AD) of Russian contact, 80 percent of the Aleut population died from Eurasian infectious diseases. These were then endemic among the Europeans, but the Aleut had no immunity against the new diseases. CANNOTANSWER
These were then endemic among the Europeans, but the Aleut had no immunity against the new diseases.
Alaska Natives or Alaskan Natives are indigenous peoples of Alaska and include Iñupiat, Yupik, Aleut, Eyak, Tlingit, Haida, Tsimshian, and a number of Northern Athabaskan cultures. They are often defined by their language groups. Many Alaska Natives are enrolled in federally recognized Alaska Native tribal entities, who in turn belong to 13 Alaska Native Regional Corporations, who administer land and financial claims.

Ancestors of Alaska Natives migrated into the area thousands of years ago, in at least two different waves. Some are descendants of the third wave of migration, in which people settled across the northern part of North America. They never migrated to southern areas. For this reason, genetic studies show they are not closely related to native peoples in South America. Alaska Natives came from Asia. Anthropologists have stated that their journey from Asia to Alaska was made possible through the Bering land bridge or by traveling through the sea. Throughout the Arctic and the circumpolar north, the ancestors of Alaska Natives established varying indigenous, complex cultures that have succeeded each other over time. They developed sophisticated ways to deal with the challenging climate and environment. Historic groups have been defined by their languages, which belong to several major language families. Today, Alaska Natives constitute more than 15% of the population of Alaska.

List of peoples

Below is a full list of the different Alaska Native peoples, who are largely defined by their historic languages (within each culture are different tribes):
Ancient Beringian
Alaskan Athabaskans
Ahtna
Deg Hit'an
Dena'ina
Gwich'in
Hän
Holikachuk
Koyukon
Lower Tanana
Tanacross
Upper Tanana
Upper Kuskokwim (Kolchan)
Eyak
Tlingit
Haida
Tsimshian
 Eskimo
Iñupiat, an Inuit group
Yupik
Siberian Yupik
Yup'ik
Cup'ik
Nunivak Cup'ig
Sugpiaq ~ Alutiiq
Chugach Sugpiaq
Koniag Alutiiq
Aleut (Unangan)

Demographics 
The Alaska Natives Commission estimated there were about 86,000 Alaska Natives living in Alaska in 1990, with another 17,000 who lived outside Alaska. A 2013 study by the Alaska Department of Labor and Workforce Development documented more than 120,000 Alaska Native people in Alaska.  While the majority of Alaska Natives live in small villages or remote regional hubs such as Nome, Dillingham, and Bethel, the percentage who live in urban areas has been increasing. In 2010, 44% lived in urban areas, compared to 38% in the 2000 census. As of 2018, natives constitute 15.4% of the overall Alaskan population.

History
The modern history of Alaskan natives begins with the arrival of Europeans. Unusually for North America, Russians sailing from Siberia in the eighteenth century were the first to make contact. British and American traders, coming mostly from eastern settlements in North America, generally did not reach the area until the nineteenth century. In some cases, Christian missionaries were not active in Alaska until the twentieth century.

Russian colonial period
During an expedition, Vitus Bering spotted Alaska. Alaskan Natives first came into contact with Russians in the 18th century. Time of contact with Russians varied throughout each native group since the Alaskan natives groups were spread throughout Alaska. Arriving from Siberia by ship in the mid-eighteenth century, Russians began to trade with Alaska Natives in what became known as the Aleutian Islands. They started new settlements around trading posts, and Russian Orthodox missionaries were part of these. The Russian missionaries were the first persons to translate Christian scripture into Native languages, such as Tlingit. In the 21st century, the numerous congregations of Russian Orthodox Christians in Alaska reflect this early history, as they are generally composed mostly of Alaska Natives.

Rather than hunting and harvesting marine life, the Russians forced the Aleuts to do the work for them. As word spread of the riches in furs to be had, competition among Russian companies increased. They forced the Aleuts into slavery. Catherine the Great, who became Empress in 1763, proclaimed good will toward the Aleut and urged her subjects to treat them fairly. The growing competition between the trading companies, which merged into fewer, larger and more powerful corporations, created conflicts that aggravated the relations with the indigenous populations. Over the years, the situation became catastrophic for the natives.

As the animal populations declined, the Aleuts, already dependent on the new barter economy created by their fur trade with the Russians, were increasingly coerced into taking greater risks in the dangerous waters of the North Pacific to hunt for more otter. As the Shelikhov-Golikov Company and later Russian-American Company developed as a monopoly, it used skirmishes and systematic violence as a tool of colonial exploitation of the indigenous people. When the Aleut revolted and won some victories, the Russians retaliated, killing many. They also destroyed the peoples' boats and hunting gear, leaving them no means of survival.

The greatest mortality was caused by the Aleuts' encounters with new diseases: during the first two generations (1741/1759-1781/1799 AD) of Russian contact, 80 percent of the Aleut population died from Eurasian infectious diseases. These had been endemic among the Europeans for centuries, but the Aleut had no immunity against the new diseases.

Effects of Russian colonization 

The Russian Tsarist government expanded into Indigenous territory in present-day Alaska for its own geopolitical reasons. It consumed natural resources of the territory during the trading years, and Russian Orthodoxy was evangelized. Their movement into these populated areas of Indigenous communities altered the demographic and natural landscape.

Historians have suggested that the Russian-American Company exploited Indigenous peoples as a source of inexpensive labor. The Russian-American Company not only used Indigenous populations for labor during the fur trade, but also held some as hostages to acquire iasak. Iasak, a form of taxation imposed by the Russians, was a tribute in the form of otter pelts. It was a taxation method the Russians had previously found useful in their early encounter with Indigenous communities of Siberia during the Siberian fur trade. Beaver pelts were also customary to be given to fur traders upon first contact with various communities.

The Russian-American Company used military force on Indigenous families, taking them as hostage until  male community members produced furs for them. Otter furs on Kodiak Island and Aleutian Islands enticed the Russians to start these taxations. Robbery and maltreatment in the form of corporal punishment and the withholding of food was also present upon the arrival of fur traders. Catherine the Great dissolved the giving of tribute in 1799, but her government initiated mandatory conscription of Indigenous men between the ages of 18 to 50 to become seal hunters strictly for the Russian American Company. This mandatory labor gave the Russian American Company an edge in competition with American and British fur traders. But the conscription separated men from their families and villages, thus altering and breaking down communities. With able-bodied men away on the hunt, villages were left with little protection as only women, children, and the elderly remained behind.

In addition to changes that came with conscription, the spread of disease also altered the populations of Indigenous communities. Although records kept in the period were scarce, it has been said that 80% of the pre-contact population of the Aleut people were gone by 1800.

Relationships between Indigenous women and fur traders increased as Indigenous men were away from villages. This resulted in marriages and children that would come to be known as Creole peoples, children who were Indigenous and Russian. To reduce hostilities with Aleutian communities, it became policy for fur traders to enter into marriage with Indigenous women. The Creole   population increased in the territory controlled by the Russian American Company.

The growth of the Russian Orthodox Church was another important tactic in the colonization and conversion of Indigenous populations. Ioann Veniaminov, who later became Saint Innocent of Alaska, was an important missionary who carried out the Orthodox Church's agenda to Christianize Indigenous populations. The church encouraged Creole children to follow Russian Orthodox Christianity, while the Russian American Company provided them with an education. Creole people were believed to have high levels of loyalty toward the Russian crown and Russian American Company. After completing their education, children were often sent to Russia, where they would study skills such as mapmaking, theology, and military intelligence.  In the 1850's Russia lost much of its interest on Alaska.

American colonialism 

Alaska has many natural resources. Alaska's natural resources along with its gold caught the attention of the United States. In 1867, the United States purchased Alaska from Russia. It did not consider the wishes of Alaska Natives or view them as citizens. The land that belonged to Alaska Natives was considered to be "open land", which could be claimed by white settlers without redress to the Alaska Natives living there. The only schools for Alaska Natives were those founded by religious missionaries.  Most white settlers did not understand the sophisticated cultures the Alaska Natives had developed to live in that challenging place and considered them to be inferior to European Americans. The Americans imposed racial segregation and what were effectively Jim Crow laws applied against the Alaska Natives and treating them as second-class residents. Since Jim Crow law were imposed, it led to segregation amongst Alaskan Natives and Americans. Buildings would even have signs saying that no natives were allowed. There was also segregated schools. In 1880, there was a court case where a child was not allowed to attend a school with Americans because his step father was native. A child that was part native and part American would only be allowed to attend a school with American children if the family has abandoned their culture. This means that they could no longer speak their native language, wear traditional native clothing, be amongst other natives, eat native foods, or practice any native religion.

In 1912, the Alaska Native Brotherhood (ANB) was formed to help fight for citizenship rights. The Alaska Native Sisterhood (ANS) was created in 1915. Also in 1915, the Alaska Territorial legislature passed a law allowing Alaskan Natives the right to vote - but on the condition that they give up their cultural customs and traditions. The Indian Citizenship Act, passed in 1924, gave all Native Americans United States citizenship.

ANB began to hold a great deal of political power in the 1920s. They protested the segregation of Alaska Natives in public areas and institutions, and also staged boycotts. Alberta Schenck (Inupiaq) staged a well-publicized protest against segregation in a movie theater in 1944. With the help of Elizabeth Peratrovich (Tlingit), the Alaska Equal Rights Act of 1945 was passed, ending segregation in Alaska.

In 1942, during World War II, the United States forced evacuation of around nine hundred Aleuts from the Aleutian Islands. The idea was to remove the Aleuts from a potential combat zone during World War II for their own protection, but European Americans living in the same area were not forced to leave. The removal was handled so poorly that many Aleuts died after they were evacuated; the elderly and children had the highest mortality rates.  Survivors returned to the islands to find their homes and possessions destroyed or looted.

Alaska became part of the United States in 1959 upon President Dwight D. Eisenhower recognizing Alaska as the 49th state.

ANCSA and since (1971 to present)
 
In 1971, with the support of Alaska Native leaders such as Emil Notti, Willie Hensley, and Byron Mallot, the U.S. Congress passed the Alaska Native Claims Settlement Act (ANCSA), which settled land and financial claims for lands and resources which the Alaska Natives had lost to European-Americans. It provided for the establishment of thirteen Alaska Native Regional Corporations to administer those claims. Similar to the separately defined status of the Canadian Inuit and First Nations in Canada, which are recognized as distinct peoples, in the United States, Alaska Natives are in some respects treated separately by the government from other Native Americans in the United States. This is in part related to their interactions with the U.S. government which occurred in a different historic period than its interactions during the period of westward expansion during the 19th-century.

Europeans and Americans did not have sustained encounters with the Alaska Natives until the late nineteenth and early twentieth centuries when many were attracted to the region in gold rushes. The Alaska Natives were not allotted individual title in severalty to land under the Dawes Act of 1887 but were instead treated under the Alaska Native Allotment Act of 1906.

It was repealed in 1971, following ANSCA, at which time reservations were ended. Another characteristic difference is that Alaska Native tribal governments do not have the power to collect taxes for business transacted on tribal land, per the United States Supreme Court decision in Alaska v. Native Village of Venetie Tribal Government (1998). Except for the Tsimshian, Alaska Natives no longer hold reservations but do control some lands. Under the Marine Mammal Protection Act of 1972, Alaska Natives are reserved the right to harvest whales and other marine mammals.

Climate Change

Four indigenous tribes in Alaska, the Shishmaref, Kivalina, Shaktoolik and Newtok tribes, are being considered the first climate refugees for America, due to sea ice melting and increased wildfires in the regions (Bronen and Brubaker). The effects of climate change on the people of Alaska are extensive and include issues such as increased vulnerability to disease, mental health issues, injury, food insecurity, and water insecurity (Brubaker). According to the Environmental Protection Agency (EPA), the loss of sea ice will increase erosion area and further displace more native communities. The melting sea ice will also affect the migration of some animals that the tribes rely on and with the ice melting there will be no place to store the food that they do obtain (EPA). Due to the permafrost melting, the infrastructure that has been around in the past will become unstable and native villages will collapse (EPA). 
	
The Shishmaref, Kivalina, Shaktoolik and Newtok tribes are located on the west coast of Alaska and due to sea-level rise the villages are experiencing more severe storm surges that are eroding their coastlines (Bronen). There is no land for these tribes to move to that are already in the area they live in which forces these communities to migrate and change their whole way of living (Bronen). Governments are lacking in response to climate refugees, there are no policies in place to determine where these refugees should go or if they get aid to pay for the cost of traveling (Bronen). It is predicted that a climate event will submerge the tribes completely in less than fifteen years (Bronen).

Extreme weather conditions has increased the risk of injury, usually there are thick layers of ice all year long but due to increasing temperatures in the atmosphere and the sea the ice in becoming thinner and is increasing the number of people who fall through the ice, if a person survives falling through the ice they are faced with other health concerns (Brubaker). Increased water insecurity and failing infrastructure caused by climate change has created sanitation issues which has increased the amount of respiratory illnesses in many regions in Alaska, in 2005 pneumonia was the leading cause of hospitalizations (Brubaker). Many of the affected tribes are experiencing increased mental stress due to climate change and the problem of relocating but no policy or way to relocate (Brubaker). Stress has also increased on villages who face infrastructure damage due to melting permafrost, there are almost no regulations other than the Alaskan government recommended not building on permafrost or using extra layers of insulation that is used on foundation walls (EPA). Food insecurity has also created stress and health issues, families can not get enough food due to animals also relocating to get to a climate that is more suitable to them (Brubaker). Families also do not have a secure food system because their ways of storing food, underground ice cellar, are no longer frozen year long due to climate change, their cellars thaw in the summers leaving their food supply inedible (Brubaker).

Subsistence

Gathering of subsistence food continues to be an important economic and cultural activity for many Alaska Natives.  In Utqiaġvik, Alaska in 2005, more than 91 percent of the Iñupiat households which were interviewed still participated in the local subsistence economy, compared with the approximately 33 percent of non-Iñupiat households who used wild resources obtained from hunting, fishing, or gathering.

But, unlike many tribes in the contiguous United States, Alaska Natives do not have treaties with the United States that protect their subsistence rights, except for the right to harvest whales and other marine mammals. The Alaska Native Claims Settlement Act explicitly extinguished aboriginal hunting and fishing rights in the state of Alaska.

See also

 Ancient Beringian
 List of Alaska Native Tribal Entities, the list of Native Villages and other "tribal entities" recognized by the US Bureau of Indian Affairs.
 Prehistory of Alaska
 First Alaskans Institute
 Indigenous Amerindian genetics
 Circumpolar peoples
 Indigenous peoples of the Pacific Northwest Coast
 Indigenous peoples of the Subarctic
 Indigenous peoples of Siberia
 Alaska Native Storytelling
 Alaska Equal Rights Act of 1945
 Shamanism among Alaska Natives
Women's suffrage in Alaska

References

Sources

Further reading
 Chythlook-Sifsof, Callan J. "Native Alaska, Under Threat." (Op-Ed) The New York Times. June 27, 2013.

External links

Alaska Federation of Natives
Alaska Native Health Board
Alaska Native Heritage Center
Alaska Native Language Center
First Alaskans Institute
Tlingit National Anthem, Alaska Natives Online
Arctic Studies Center

 

American culture
The Chicxulub crater () is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore near the communities of Chicxulub Puerto and Chicxulub Pueblo, after which the crater is named. It was formed when a large asteroid, about  in diameter, struck the Earth. The crater is estimated to be  in diameter and  in depth. It is one of the largest confirmed impact structures on Earth, and the only one whose peak ring is intact and directly accessible for scientific research.

The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán Peninsula during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan R. Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas.

The date of the impact coincides with the Cretaceous–Paleogene boundary (commonly known as the K–Pg or K-T boundary), roughly 66 million years ago, and it is now widely accepted that the devastation and climate disruption from the impact was the cause of the Cretaceous–Paleogene extinction event, a mass extinction in which 75% of plant and animal species on Earth became extinct, including all non-avian dinosaurs.

Discovery

In the late 1970s, geologist Walter Alvarez and his father, Nobel Prize–winning scientist Luis Walter Alvarez, put forth their theory that the Cretaceous–Paleogene extinction was caused by an impact event. The main evidence of such an impact was contained in a thin layer of clay present in the K–Pg boundary in Gubbio, Italy. The Alvarezes and colleagues reported that it contained an abnormally high concentration of iridium, a chemical element rare on earth but common in asteroids. Iridium levels in this layer were as much as 160 times above the background level. It was hypothesized that the iridium was spread into the atmosphere when the impactor was vaporized and settled across the Earth's surface among other material thrown up by the impact, producing the layer of iridium-enriched clay. At the time, consensus was not settled on what caused the Cretaceous–Paleogene extinction and the boundary layer, with theories including a nearby supernova, climate change, or a geomagnetic reversal. The Alvarezes' impact hypothesis was rejected by many paleontologists, who believed that the lack of fossils found close to the K-Pg boundary—the "three-meter problem"—suggested a more gradual die-off of fossil species.

The Alvarezes, joined by nuclear chemist Frank Asaro and Berkeley paleontologist Helen Michel, published their paper on the iridium anomaly in Science in June 1980. Their paper was followed by other reports of similar iridium spikes at the K-Pg boundary across the globe, and sparked wide interest in the cause of the K-Pg extinction; over 2,000 papers were published in the 1980s on the topic. There were no known impact craters that were the right age and size, spurring a search for a suitable candidate. Recognizing the scope of the work, Lee Hunt and Lee Silver organized a cross-discipline meeting in Snowbird, Utah in 1981. Unbeknownst to those gathered, evidence of just the crater they were looking for was being presented the same week, and would be largely missed by the scientific community.

Years earlier in 1978, geophysicists Glen Penfield and Antonio Camargo were working for the Mexican state-owned oil company Petróleos Mexicanos (Pemex) as part of an airborne magnetic survey of the Gulf of Mexico north of the Yucatán Peninsula. Penfield's job was to use geophysical data to scout possible locations for oil drilling. In the offshore magnetic data, Penfield noted anomalies whose depth he estimated and mapped. He then obtained onshore gravity data from the 1940s. When the gravity maps and magnetic anomalies were compared, Penfield described a shallow, -diameter "bullseye" appearing on the otherwise non-magnetic and uniform surroundings—clear evidence to him of an impact feature. A decade earlier, the same map had suggested a crater to contractor Robert Baltosser, but he was forbidden to publicize his conclusion by Pemex corporate policy.

Penfield presented his findings to Pemex, who rejected the crater theory, instead deferring to findings that ascribed the feature to volcanic activity. Pemex disallowed release of specific data, but let Penfield and Camargo present the results at the 1981 Society of Exploration Geophysicists conference. That year's conference was under-attended and their report attracted scant attention, with many experts on impact craters and the K-Pg boundary attending the Snowbird conference instead. Carlos Byars, a Houston Chronicle journalist who was familiar with Penfield and had seen the gravitational and magnetic data himself, wrote a story on Penfield and Camargo's claim, but the news did not disseminate widely.

Although Penfield had plenty of geophysical data sets, he had no rock cores or other physical evidence of an impact. He knew Pemex had drilled exploratory wells in the region. In 1951, one bored into what was described as a thick layer of andesite about  down. This layer could have resulted from the intense heat and pressure of an Earth impact, but at the time of the borings it was dismissed as a lava dome—a feature uncharacteristic of the region's geology. Penfield was encouraged by William C. Phinney, curator of the lunar rocks at the Johnson Space Center, to find these samples to prove his theory. Penfield tried to secure site samples, but was told they had been lost or destroyed. When attempts at returning to the drill sites and looking for corroborating rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work. Seeing the 1980 Science paper, Penfield wrote to Walter Alvarez about the Yucatán structure, but received no response.

Alvarez and other scientists continued their search for the crater, although they were searching in oceans based on incorrect analysis of glassy spherules from the K-Pg boundary that suggested the impactor had landed in open water. Unaware of Penfield's discovery, University of Arizona graduate student Alan R. Hildebrand and faculty adviser William V. Boynton looked for a crater near the Brazos River in Texas. Their evidence included greenish-brown clay with surplus iridium, containing shocked quartz grains and small weathered glass beads that looked to be tektites. Thick, jumbled deposits of coarse rock fragments were also present, thought to have been scoured from one place and deposited elsewhere by an impact event. Such deposits occur in many locations but seemed concentrated in the Caribbean basin at the K–Pg boundary. When Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on Haiti, Hildebrand suggested it could be a telltale feature of a nearby impact. Tests on samples retrieved from the K–Pg boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield nuclear detonations.

In 1990, Carlos Byars told Hildebrand of Penfield's earlier discovery of a possible impact crater. Hildebrand contacted Penfield and the pair soon secured two drill samples from the Pemex wells, which had sat stored in New Orleans for decades. Hildebrand's team tested the samples, which clearly showed shock-metamorphic materials. A team of California researchers surveying satellite images found a cenote (sinkhole) ring centered on the town of Chicxulub Puerto that matched the one Penfield saw earlier; the cenotes were thought to be caused by subsidence of bolide-weakened lithostratigraphy around the impact crater wall. More recent evidence suggests the crater is  wide, and the  ring is an inner wall of it. Hildebrand, Penfield, Boynton, Camargo, and others published their paper identifying the crater in 1991. The crater was named for the nearby town of Chicxulub. Penfield also recalled that part of the motivation for the name was "to give the academics and NASA naysayers a challenging time pronouncing it" after years of dismissing its existence.

In March 2010, forty-one experts from many countries reviewed the available evidence: 20 years' worth of data spanning a variety of fields. They concluded that the impact at Chicxulub triggered the mass extinctions at the K–Pg boundary. Dissenters, notably Gerta Keller of Princeton University, have proposed an alternate culprit: the eruption of the Deccan Traps in what is now the Indian subcontinent. This period of intense volcanism occurred before and after the Chicxulub impact; dissenting studies argue that the worst of the volcanic activity occurred before the impact, and the role of the Deccan Traps was instead shaping the evolution of surviving species post-impact. A 2013 study compared isotopes in impact glass from the Chicxulub impact with isotopes in ash from the K-Pg boundary, concluding that the they were dated almost exactly the same within experimental error.

Impact specifics
A 2013 study in Science obtained a mean estimate for the age of the impact as 66,043,000 ± 11,000 years ago (± 43,000 years ago considering systematic error), based on multiple lines of evidence, including argon–argon dating of tektites from Haiti and bentonite horizons overlying the impact horizon in northeastern Montana, United States. This date was supported by a 2015 study based on argon–argon dating of tephra found in lignite beds in the Hell Creek and overlying Fort Union formations in northeastern Montana. A 2018 study based on argon–argon dating of spherules from Gorgonilla Island, Colombia obtained a slightly different result of 66,051,000 ± 31,000 years ago. The impact has been interpreted to have occurred in Northern Hemisphere Spring or late Northern Hemisphere Spring or Summer based on annual isotope curves in sturgeon and paddlefish bones found at the Tanis site in southwestern North Dakota, which is thought to have formed within hours of impact. A 2020 study concluded that the Chicxulub crater was formed by an inclined (45–60° to horizontal) impact from the northeast. The site of the crater at the time of impact was a marine carbonate platform. The water depth at the impact site varied from  on the western edge of the crater to over  on the northeastern edge. The seafloor rocks consisted of a  thick sequence of Jurassic-Cretaceous aged marine sediments, predominantly carbonate rock including dolomite (35-40% of total sequence) and limestone (25-30%) along with evaporites (anhydrite 25-30%), and minor amounts of shale and sandstone (3-4%) underlain by ~ of continental crust, composed of igneous crystalline basement including granite.

There is broad consensus that the Chicxulub impactor was an asteroid with a carbonaceous chondrite composition, rather than a comet. The impactor was around  in diameter—large enough that, if set at sea level, it would have reached taller than Mount Everest.

Effects

Hitting the earth at a speed of perhaps  a second, the kinetic energy of the impact was estimated in 1996 to be roughly 3×1023 joules, more than a billion times more energy than the atomic bomb dropped on Hiroshima, Japan. The impact created winds in excess of  near the blast's center, and created a transient cavity  wide and  deep that later collapsed. This formed a crater mainly under the sea and covered by  of sediment by the 21st century. The impact, expansion of water after filling the crater, and related seismic activity spawned megatsunamis over  tall, with one simulation suggesting the immediate waves from the impact may have reached up to 1.5 kilometers (~1 mi) high. The waves scoured the sea floor, leaving ripples underneath what is now Louisiana with average wavelengths of 600 meters and average wave heights of 16 meters, the largest ripples documented. Material shifted by subsequent earthquakes and the waves reached all the way to what are now Texas and Florida, and may have disturbed sediments as far as 6000 kilometers from the impact site. The impact triggered a seismic event with an estimated magnitude 9–11  at the impact site.

A cloud of hot dust, ash and steam would have spread from the crater, with as much as 25 trillion metric tons of excavated material being ejected into the atmosphere by the blast. Some of this material escaped orbit, dispersing through the solar system, while some of it fell back to earth, heated to incandescence upon re-entry. The rock broiled the Earth's surface and ignited wildfires, estimated to have enveloped nearly 70% of the planet's forests. The devastation to living creatures even hundreds of kilometers away was immense, and much of present-day Mexico and the United States would have been desolated. Fossil evidence for an instantaneous die-off of diverse animals was found in a soil layer only  thick in New Jersey,  away from the impact site, indicating that death and burial under debris occurred suddenly and quickly over wide distances on land. Field research from the Hell Creek Formation in North Dakota published in 2019 shows the simultaneous mass extinction of myriad species combined with geological and atmospheric features consistent with the impact event.

Vaporized rock, including sulphur-rich gypsum from the shallow coastal waters, was injected into the atmosphere. This global dispersal of dust and sulfates would have led to a sudden and catastrophic effect on the climate worldwide, large temperature drops, and devastated the food chain. The researchers stated that the impact generated an environmental calamity that extinguished life, but it also induced a vast subsurface hydrothermal system that became an oasis for the recovery of life. Researchers using seismic images of the crater in 2008 determined that the impactor landed in deeper water than previously assumed, which may have resulted in increased sulfate aerosols in the atmosphere. This could have made the impact even deadlier by cooling the climate and generating acid rain.

The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. Production of carbon dioxide caused by the destruction of carbonate rocks would have led to a sudden greenhouse effect. Over a decade or longer, sunlight would have been blocked from reaching the surface of the Earth by the dust particles in the atmosphere, cooling the surface dramatically. Photosynthesis by plants would also have been interrupted, affecting the entire food chain. A model of the event developed by Lomax et al. (2001) suggests that net primary productivity (NPP) rates may have increased to higher than pre-impact levels over the long term because of the high carbon dioxide concentrations.

A long-term local effect of the impact was the creation of the Yucatán sedimentary basin which "ultimately produced favorable conditions for human settlement in a region where surface water is scarce."

Geology and morphology

The rocks above the impact feature are layers of marl and limestone reaching to a depth of almost , dating back as far as the Paleocene (56 to 66 million years ago) and therefore after the impact. Below these layers lie more than  of andesitic glass and breccia. These andesitic igneous rocks are only found within the impact feature, as is shocked quartz. The K–Pg boundary inside the feature is depressed to  compared with the normal depth of about  measured  away from the impact feature.

Along the edge of the crater are clusters of cenotes, which suggest that there was a water basin inside the feature during the Neogene period, after the impact. The groundwater of such a basin would have dissolved the limestone and created the caves and cenotes beneath the surface.

Chicxulub is the only known Earth crater with a remaining impact peak ring, but it is under  of sediment. Analyses indicate that the impactor was large enough to create a  peak ring. A joint United Kingdom-United States team obtained the first offshore core samples from the peak ring in 2016, surrounding the central zone of the crater. Drilling reached  below the ocean. Sample preparation and analysis were performed in Bremen, Germany.

Pink granite, usually found deep in the Earth's crust, was found in drilling samples. It suggests the impact was so great it shocked and melted rocks found deep in the crust, causing them to shoot up before falling back down to produce the peak rings. The granite samples were also found to be lighter and weaker than normal granite, a result of the shock and extreme conditions of the impact. The post-impact tsunamis were sufficient to lay down the largest-known layered bed of sand, around  deep and separated by grain size, directly above the peak ring.

The peak ring drilling below the sea floor also discovered a massive hydrothermal system, which modified ~1.4 × 105 km3 of Earth's crust and lasted for hundreds of thousands of years; in addition, those hydrothermal systems might support the impact origin of life hypothesis for the Hadean, when the entire surface of Earth was affected by impactors much larger than the Chicxulub impactor.

Astronomical origin of impactor
In 1998 a 2.5 mm sized meteorite was described from the North Pacific from sediments spanning the Cretaceous-Paleogene boundary, that was suggested to represent a fragment of the Chicxulub impactor. Analysis suggested that it best fit the criteria of CV, CO and CR carbonaceous chondrites.

In September 2007, a report published in Nature proposed an origin for the asteroid that created the Chicxulub crater. The authors, William F. Bottke, David Vokrouhlický, and David Nesvorný, argued that a collision in the asteroid belt 160 million years ago resulted in the Baptistina family of asteroids, the largest surviving member of which is 298 Baptistina. They proposed that the "Chicxulub asteroid" was also a member of this group. The connection between Chicxulub and Baptistina is supported by the large amount of carbonaceous material present in microscopic fragments of the impactor, suggesting the impactor was a member of an uncommon class of asteroids called carbonaceous chondrites, like Baptistina. According to Bottke, the Chicxulub impactor was a fragment of a much larger parent body about  across, with the other impacting body being around  in diameter.

In 2011, data from the Wide-field Infrared Survey Explorer revised the date of the collision which created the Baptistina family to about 80 million years ago. This makes an asteroid from this family highly improbable to be the asteroid that created the Chicxulub crater, as typically the process of resonance and collision of an asteroid takes many tens of millions of years. In 2010, another hypothesis was offered which implicated the newly discovered asteroid 354P/LINEAR, a member of the Flora family of asteroids, as a possible remnant cohort of the K/Pg impactor.

Four independent laboratories showed elevated concentrations of iridium in the crater's peak ring, further corroborating the asteroid impact hypothesis. In the same month Avi Loeb and a colleague published a study in Scientific Reports suggesting the impactor was a fragment from a disrupted comet, rather than an asteroid which has long been the leading candidate among scientists. This was followed by a rebuttal published in Astronomy & Geophysics in June of the same year, which charged that the paper ignored the fact that the mass of iridium deposited across the globe by the impact (estimated to be approximately 2.0 - 2.8 × 1011 grams), was too large to be created by a comet impactor, and suggested based on geochemical evidence, including the excess of chromium isotope 54Cr and the ratios of platinum group metals found in marine impact layers, that the impactor was either a CM or CR carbonaceous chondrite C-type asteroid. In July 2021, a study reported that the impactor likely originated in the outer main part of the asteroid belt, based on numerical simulations.

See also 
 Barberton Greenstone Belt
 List of impact craters on Earth
 List of possible impact structures on Earth 
 Permian–Triassic extinction event
 Timeline of Cretaceous–Paleogene extinction event research

References

External links 

 Chicxulub Crater
 Chicxulub: Variations in the magnitude of the gravity field at sea level image (Lunar and Planetary Institute, USRA)
 "Doubts On Dinosaurs" – Scientific American
 Papers and presentations resulting from the 2016 Chicxulub drilling project

Impact craters of Mexico
Cretaceous impact craters
Oceans
 
Prehistoric dinosaurs
Extinction events
Mérida, Yucatán
Natural history of the Caribbean
Natural history of the Yucatán Peninsula Doug Oldham (November 30, 1930 – July 21, 2010) was an American Southern Gospel singer and a member of the Gospel Music Hall of Fame.

Early years
Oldham was the son of Dr. Dale Oldham, a minister in the Church of God. His grandfather was also a clergyman. He nearly died from pneumonia as a child.

Musical career
Oldham was a musical performer for more than 60 years, with 64 albums to his credit, often traveling and performing with his wife Laura Lee. The couple produced a CD and wrote three books together.

Early years
Oldham traveled with Fred Waring and Waring's Pennsylvanians in 1951 and sang as a member of that group's Glory Voices Quartet.

Radio
Beginning in 1950, Oldham was a soloist on the Christian Brotherhood Hour, after having served as soloist for several years on the broadcast of Cadle Tabernacle in Indianapolis, Indiana.

Television
Oldham was a regular performer on The Old Time Gospel Hour with Jerry Falwell, The PTL Club with Jim and Tammy Faye Bakker during the 1970s and 80s, and traveled with the Bill Gaither Trio and the Slaughters during the 1960s. In 1975, he sang with the Speer Family for Christian concerts. He was also a performer on several of Bill Gaither's Gaither Homecoming videos.

Influence
The trials that Oldham faced in his life were the basis for "a number of songs ... including Something Worth Living For and Thanks to Calvary (We Don't Live Here Anymore).

Ministry
Oldham was a minister of music, having been ordained in 1955. He served in that position in churches in High Point, North Carolina, Royal Oak, Michigan, Middletown, Ohio, and Indianapolis, Indiana.

In 1963, Oldham began ministering in evangelism through music. A newspaper article noted that he "served as song director and soloist for citywide preaching missions, camp meetings, youth conventions and concerts" across the United States and in other countries.

Awards and honors
Oldham's album, Something Worth Living For, was named the best gospel album of 1968 by the National Evangelical Film Foundation.

In the mid-1970s, Oldham was granted an honorary doctor of divinity degree from the California Graduate School of Theology. In 2006, he was inducted into the Gospel Music Hall of Fame.

He was the recipient of two GMA Dove Awards and an Angel Award.

In 2007, Liberty University named a campus recital hall at the Fine Arts Building, the "Oldham Recital Hall, in his honor and established the Liberty University Oldham Concert Hall Scholarship Fund at the Center for Worship.

Personal life
Oldham and his wife Laura Lee had three daughters, Paula, Karen, and DeeDee. He was the recipient of an honorary doctorate degree and was named an Honorary Colonel of Alabama.

Discography
I've A Song (TDE)
Songs that Lift the Heart (TDE)
Doug and Dr. Dale Oldham - Duets and Devotions (TDE 506)
Songs that Touch the Heart (TDE 507)
Requests and Favorites (TDE 509)
The Lord is My Song - with the Leppien Sisters (Universal 3661)
Doug Oldham Sings from the Hymnal (Universal 3667)
Sings Songs of Joy, Real Joy - with the Leppien Sisters (Universal 66621)
Doug Oldham with Jake Hess and the Imperials (Heartwarming 1930)
Something Worth Living For (Heartwarming 1959)
For Such a Time as This (Heartwarming 1977)
A Rich Man Am I (Heartwarming-Impact 1997)
I've Got To Go On (Heartwarming-Impact 3039)
Sings Jerry Falwell's Television Favorites (Impact 3062)
Have You Heard... God Loves You! (Impact 3064)
The King is Coming! (Impact 3087)
Bathing in the Sunlight of God's Love - renamed The Family of God (Impact 3099)
Sings the Best of Bill Gaither (Impact 3143)
Through It All (Impact 3156)
Get All Excited... Go Tell Everybody! (Impact 3183)
Christmas with Doug Oldham (Impact 3193)
Inspiration (Vista 1235)
Live (Impact 3211)
To God Be the Glory (Impact 3240)
Sings More Songs of Bill Gaither (Impact 3272)
The Church Triumphant ... Alive and Well! (Impact 3324)
Doug/Warm (Impact 3345)
Live... with the Speers (Impact 3353)
Doug Oldham & Friends (Impact 3393)
I Am... Because (Impact 3430)
Golden Treasury of Hymns for the Family of God (Impact 3496)
Sings the Old and New of Bill and Gloria Gaither (Impact 3529)
Special Delivery (Impact 3546)
Holiday Song (Impact 3562)
What's It Gonna Take (Impact 3707)
Golden Treasury of Hymns Volume 2 (Impact 3755)
Count Me In (Impact 3781)
Hymns of the Faith (PTL 1857)
All Rise (PTL 1996)
Poet of Praise (Lovesong)
He Saw Me (Brentwood)
The Storyteller (Song Garden)
Unmistakably Doug
My God Is Good

Book
I Don't Live There Anymore by Doug Oldham (Impact Books 1973 )

References

External links
www.dougoldham.com—Official website

1930 births
2010 deaths
American gospel singers
Southern gospel performers
Anderson University (Indiana) alumni
Singers from Indiana