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47-691: The Chalk Bluffs exposes the Ogallala , Fox Hills and Arikaree Formations . Miocene , Eocene and Paleocene vertebrate fossils are found. Most of the escarpment lies within the Pawnee National Grasslands . As the bluffs are primarily barren and protected from fire. However trees normally found in the foothills of the Rocky Mountains are found there, including: Ponderosa pine , Rocky Mountain juniper , limber pine , and mountain mahogany . Numerous raptors nest on

94-536: A biostratigraphic basis. The Ogallala's rich grass seed record was also used to develop biostratigraphic successions within the unit. Unfortunately, no correlation with any consistent rock bedding can be established over the Ogallala's range. These Nebraskan biostratigraphic classifications elevated the Ogallala to group status with three members Kimball (youngest), Ash Hollow , and Valentine (oldest). Kansas geologists attempted to carry these classifications into

141-410: A 5 km (3.1 mi) diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera). Currently, volcanic activity is exhibited via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser , plus recorded ground-swelling indicating ongoing inflation of the underlying magma chamber. The volcanic eruptions, as well as

188-464: A buffer that breaks apart the plume. Any heat from the plume that does make it to the surface is limited. Volcanic and tectonic actions in the region cause between 1,000 and 2,000 measurable earthquakes annually. Most are relatively minor, measuring magnitude 3 or weaker. Occasionally, numerous earthquakes are detected in a relatively short period of time, an event known as an earthquake swarm . In 1985, more than 3,000 earthquakes were measured over

235-475: A magnitude 4.8 earthquake struck Yellowstone, the largest recorded there since February 1980. In February 2018, more than 300 earthquakes occurred, with the largest being a magnitude 2.9. The Lava Creek eruption of the Yellowstone Caldera, which occurred 640,000 years ago, ejected approximately 1,000 cubic kilometres (240 cu mi) of rock, dust and volcanic ash into the atmosphere. It

282-613: A magnitude of 3.9. Another swarm started in January 2010, after the Haiti earthquake and before the Chile earthquake . With 1,620 small earthquakes between January 17, 2010, and February 1, 2010, this swarm was the second-largest ever recorded in the Yellowstone Caldera. The largest of these shocks was a magnitude 3.8 that occurred on January 21, 2010. This swarm subsided to background levels by February 21. On March 30, 2014, at 6:34 AM MST ,

329-548: A once-mountainous region. At least a dozen of these eruptions were so massive that they are classified as supereruptions . Volcanic eruptions sometimes empty their stores of magma so swiftly that the overlying land collapses into the emptied magma chamber , forming a geographic depression called a caldera. The oldest identified caldera remnant straddles the border near McDermitt, Nevada–Oregon , although there are volcaniclastic piles and arcuate faults that define caldera complexes more than 60 km (37 mi) in diameter in

376-419: A period of several months. More than 70 smaller swarms were detected between 1983 and 2008. The USGS states these swarms are likely caused by slips on pre-existing faults rather than by movements of magma or hydrothermal fluids. In December 2008, continuing into January 2009, more than 500 earthquakes were detected under the northwest end of Yellowstone Lake over a seven-day span, with the largest registering

423-630: A range of dramatic high bluffs that define the boundary of a "high plain". The lowest, oldest deposits filled in the shallow valleys of the weathered rocks that were exposed at that time, which ranged in age from Cretaceous in Nebraska and Kansas to Permian in Texas. As the rivers built up the alluvial fans, subsurface water circulation varied, resulting in localized formation of caliche, and shallow lakes formed between natural levees, which deposited limestone. These consolidated lenses, distributed in within

470-465: A substantial contribution to the development of geological sciences through history". The source of the Yellowstone hotspot is controversial. Some geoscientists hypothesize that the Yellowstone hotspot is the effect of an interaction between local conditions in the lithosphere and upper mantle convection . Others suggest an origin in the deep mantle ( mantle plume ). Part of the controversy

517-535: A way that could be used as a geothermal power source. If enacted, the plan would cost about $ 3.46 billion. Brian Wilcox of the Jet Propulsion Laboratory observes that such a project could incidentally trigger an eruption if the top of the chamber is drilled into. Studies and analysis may indicate that the greater hazard comes from hydrothermal activity which occurs independently of volcanic activity. Over 20 large craters have been produced in

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564-435: Is about 2.5 times bigger than scientists had previously imagined; however, scientists believe that the proportion of molten rock in the chamber is too low to allow for another supereruption. In October 2017, research from Arizona State University indicated prior to Yellowstone's last supereruption, magma surged into the magma chamber in two large influxes. An analysis of crystals from Yellowstone's lava showed that prior to

611-578: Is also classified as the Ogallala Group . Notably, it records the North American Land Mammal Ages (NALMAs) Hemphillian , Clarendonian , and Barstovian . It also includes an excellent record of grass seeds and other plant seeds, which can be used for biostratigraphic dating within the formation. The Ogallala Formation outcrops of Lake Meredith National Recreation Area preserve fish fossils. Similar specimens from

658-465: Is plainly visible today. Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption. The most recent lava flow occurred about 70,000 years ago, while a violent eruption excavated the West Thumb of Lake Yellowstone 174,000 years ago. Smaller steam explosions occur as well. An explosion 13,800 years ago left

705-584: Is relatively recent, with calderas created by large eruptions that took place 2.1 million, 1.3 million, and 640,000 years ago. The calderas lie over the Yellowstone hotspot under the Yellowstone Plateau where light and hot magma (molten rock) from the mantle rises toward the surface. The hotspot appears to move across terrain in the east-northeast direction, and is responsible for the eastern half of Idaho 's Snake River Plain , but in fact

752-523: Is the relatively sudden appearance of the hotspot in the geologic record. Additionally, the Columbia Basalt flows appeared at the same approximate time in the same place, prompting speculation that they share a common origin. As the Yellowstone hotspot traveled to the east and north, the Columbia disturbance moved northward and eventually subsided. An alternate theory to the mantle plume model

799-697: The Carmacks Group of southwest-central Yukon , Canada, which are interpreted to have been formed 70 million years ago by the Yellowstone hotspot. Progressively younger volcanic units, most grouped in several overlapping volcanic fields , extend from the Nevada – Oregon border through the eastern Snake River Plain and terminate in the Yellowstone Plateau. One such field, the Bruneau-Jarbidge volcanic field in southern Idaho ,

846-671: The Chalk Bluffs Natural Area . The bluffs are adjacent to the Cedar Creek Wind Farm . 36°28′46″N 90°09′45″W  /  36.47952°N 90.16252°W  / 36.47952; -90.16252 Ogallala Formation The Ogallala Formation is a Miocene to early Pliocene geologic formation in the central High Plains of the western United States and the location of the Ogallala Aquifer . In Nebraska and South Dakota it

893-617: The Huckleberry Ridge Tuff , was the largest, and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption . The next biggest supereruption formed the Yellowstone Caldera (640,000 years ago) and produced the Lava Creek Tuff . The Henry's Fork Caldera (1.2 million years ago) produced the smaller Mesa Falls Tuff , but is the only caldera from the Snake River Plain–Yellowstone hotspot that

940-536: The International Union of Geological Sciences (IUGS) included "The Yellowstone volcanic and hydrothermal system" in its assemblage of 100 geological heritage sites around the world in a listing published in October 2022. The organization defines an IUGS Geological Heritage Site as "a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with

987-755: The Island Park Caldera and the Huckleberry Ridge Tuff ), the Mesa Falls eruption 1.3 million years ago (which created the Henry's Fork Caldera and the Mesa Falls Tuff ), and the Lava Creek eruption approximately 640,000 years ago (which created the Yellowstone Caldera and the Lava Creek Tuff ). The caldera was the largest known until the discovery of Apolaki Caldera in 2019, which is more than twice as wide. Volcanism at Yellowstone

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1034-568: The Western United States . The caldera and most of the park are located in the northwest corner of the state of Wyoming . The caldera measures 43 by 28 miles (70 by 45 kilometers), and postcaldera lavas spill out a significant distance beyond the caldera proper. The caldera formed during the last of three supereruptions over the past 2.1 million years: the Huckleberry Ridge eruption 2.1 million years ago (which created

1081-593: The Yellowstone Supervolcano  and two from the Jemez Caldera . From bottom to top, the Ogallala was deposited as overlapping alluvial fans of sand and gravel, displaying bedding resulting from river flows and flooding. Much of this material remained unconsolidated; however, significant modification occurred as the material deepened, particularly with the cementation of the sand and gravel with calcium carbonate and silica . The top of

1128-407: The Ogallala is defined by a thick cap rock of hard limestone or caliche , broadly called "algal limestone". Patterns of thin lines in the "limestone" suggested algal origin to frontier geologists (calcite and silica deposited within mats of algae under a shallow lake). However, the material is determined to be mostly caliche that formed after deposition of the sand and gravel from the mountain rivers

1175-459: The Rocky Mountains was carried eastward on to expansive, geologically weathered plains.  This material included quartz and feldspar from Precambrian granite, but also residue from the uplifted shale, limestone, and sandstone accumulated from the Paleozoic and Mesozoic periods, as well as igneous rock from Cenozoic volcanism. Many rivers carried this material from the mountains to

1222-608: The Yellowstone Supervolcano is the volcanic field that produced the latest three supereruptions from the Yellowstone hotspot; it also produced one additional smaller eruption, thereby creating the West Thumb of Yellowstone Lake 174,000 years ago. The three supereruptions occurred 2.1 million, 1.3 million, and approximately 640,000 years ago, forming the Island Park Caldera , the Henry's Fork Caldera , and Yellowstone calderas, respectively. The Island Park Caldera supereruption (2.1 million years ago), which produced

1269-758: The cliffs including Swainson's hawks , ferruginous hawks , golden eagles , and prairie falcons . The bluffs are a favorite site for birdwatching . It has been recognized by the National Audubon Society as a site of "global importance". A 640-acre (2.6 km) portion of the Chalk Bluffs in Weld County were set aside in September 2001 by the Colorado State Parks Natural Areas Program as

1316-414: The continuing geothermal activity, are a result of a great plume of magma located below the caldera's surface. The magma in this plume contains gases that are kept dissolved by the immense pressure under which the magma is contained. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a chain reaction. If

1363-526: The east. What each river carried from different parts of the mountains varied, changing also as the geography of the Rocky Mountains evolved. Owing to the low amount of sloping, vast quantities of sand and gravel were dumped on the plains in broad and overlapping alluvial fans rather than being carried into the Mississippi River.  Over this time, many volcanic ash falls occurred and have been identified to their source, including several from

1410-416: The expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very large gas explosion. According to analysis of earthquake data in 2013, the magma chamber is 80 km (50 mi) long and 20 km (12 mi) wide. It also has 4,000 km (960 cu mi) underground volume, of which 6–8% is filled with molten rock. This

1457-495: The foreseeable future. Recurrence intervals of these events are neither regular nor predictable." This conclusion was reiterated in December 2013 in the aftermath of the publication of a study by University of Utah scientists finding that the "size of the magma body beneath Yellowstone is significantly larger than had been thought". The Yellowstone Volcano Observatory issued a statement on its website stating: Although fascinating,

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1504-542: The hotspot is much deeper than the surrounding terrain and remains stationary while the North American plate moves west-southwest over it. Over the past 16.5 million years or so, this hotspot has generated a succession of explosive eruptions and less violent floods of basaltic lava . Together these eruptions have helped create the eastern part of the Snake River Plain (to the west of Yellowstone) from

1551-551: The hydrothermal explosion that formed Mary Bay. Further research shows that very distant earthquakes reach and have effects upon the activities at Yellowstone, such as the 1992 7.3 magnitude Landers earthquake in California 's Mojave Desert that triggered a swarm of quakes from more than 800 miles (1,300 km) away, and the 2002 7.9 magnitude Denali fault earthquake 2,000 miles (3,200 km) away in Alaska that altered

1598-673: The land surface within the caldera moved upward as much as 8 inches (20 cm) at the White Lake GPS station. In January 2010, the USGS stated that "uplift of the Yellowstone Caldera has slowed significantly" and that uplift continues but at a slower pace. USGS, University of Utah and National Park Service scientists with the Yellowstone Volcano Observatory maintain that they "see no evidence that another such cataclysmic eruption will occur at Yellowstone in

1645-448: The last supereruption, the magma chamber underwent a rapid increase in temperature and change in composition. The analysis indicated that Yellowstone's magma reservoir can reach eruptive capacity and trigger a super-eruption within just decades, not centuries as volcanologists had originally thought. In respect of it being "well-known for its past explosive volcanic eruptions and lava flows as well for its world class hydrothermal system",

1692-424: The lower opaline sandstone zone and the "Algal limestone", the Ogallala has no persistent lithological marker beds beyond the stated generalities of local chert beds in the upper zone and local caliche "mortar bed" lenses in the middle zone. It may be the case that consolidation of the caliche of the "Algal limestone" occurred broadly at the same time but in whatever material was at the local surface after deposition of

1739-411: The middle portion, do not represent any particular horizon ; but do cap intermediate bluffs below valley rims. Because of their bluff-forming nature and resemblance to concrete or mortar, these lenses are described as "caprock" or "mortar beds". Various ash falls were locally deposited, supplying silica for the formation of agate and chert in the upper portion and opal in the lowest portion. Other than

1786-703: The new findings do not imply increased geologic hazards at Yellowstone, and certainly do not increase the chances of a 'supereruption' in the near future. Contrary to some media reports, Yellowstone is not 'overdue' for a supereruption. Media reports were more hyperbolic in their coverage. A study published in GSA Today , the monthly news and science magazine of the Geological Society of America , identified three fault zones where future eruptions are most likely to be centered. Two of those areas are associated with lava flows aged 174,000–70,000 years ago, and

1833-487: The past 14,000 years, resulting in such features as Mary Bay, Turbid Lake , and Indian Pond, which was created in an eruption about 1300 BC. In a 2003 report, USGS researchers proposed that an earthquake may have displaced more than 77 million cubic feet (2,200,000 m ; 580,000,000 US gal) of water in Yellowstone Lake, creating colossal waves that unsealed a capped geothermal system and led to

1880-707: The same unit are found at Alibates Flint Quarries National Monument in Texas . At the beginning of the Rocky Mountains uplift , the final floor of the Western Interior Seaway was elevated several thousand feet (thousands of meters) above sea level. The pattern of erosion of material from the northeast into the midcontinent was largely reversed from the previous drainage patterns of the Cretaceous and earlier periods so that material eroded from

1927-450: The sand and gravel ceased. And, while the "Algal limestone" is a marker bed, it does not establish correlation of the specific beds in which the caliche formed. Faced with particularly rich collections of terrestrial Neogene vertebrate fossils, Nebraska geologists recognized the distinct North American land mammal ages (NALMA) within the Ogallala; Clarendonian , Hemphillian , and Blancan sufficient to attempt definitions of formations on

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1974-544: The state; but, the state has since abandoned the three divisions. Like the remainder of High Plains states, Kansas considers the Ogallala to be a formation. However, it is convenient to informally divide the Ogallala into the three general zones with these names: Yellowstone Caldera The Yellowstone Caldera , sometimes referred to as the Yellowstone Supervolcano , is a volcanic caldera and supervolcano in Yellowstone National Park in

2021-415: The third is a focus of present-day seismicity . In 2017, NASA conducted a study to determine the feasibility of preventing the volcano from erupting. The results suggested that cooling the magma chamber by 35 percent would be enough to forestall such an incident. NASA proposed introducing water at high pressure 10 kilometers underground. The circulating water would release heat at the surface, possibly in

2068-517: Was Yellowstone's third and most recent caldera-forming eruption. Geologists closely monitor the elevation of the Yellowstone Plateau , which has been rising as quickly as 150 millimetres (5.9 in) per year, as an indirect measurement of changes in magma chamber pressure. The upward movement of the Yellowstone caldera floor between 2004 and 2008—almost 75 millimetres (3.0 in) each year—was more than three times greater than ever observed since such measurements began in 1923. From 2004 to 2008,

2115-662: Was formed between 10 and 12 million years ago, and the event dropped ash to a depth of one foot (30 cm) 1,000 miles (1,600 km) away in northeastern Nebraska and killed large herds of rhinoceroses , camels, and other animals at Ashfall Fossil Beds State Historical Park. The United States Geological Survey (USGS) estimates there are one or two major caldera-forming eruptions and a hundred or so lava extruding eruptions per million years, and "several to many" steam eruptions per century. The loosely defined term " supervolcano " has been used to describe volcanic fields that produce exceptionally large volcanic eruptions. Thus defined,

2162-522: Was proposed in 2018. It is suggested that the volcanism may be caused by upwellings from the lower mantle resulting from water-rich fragments of the Farallon plate descending from the Cascadia subduction region , sheared off at a subducted spreading rift. Others suggest that the mantle plume could not have been a dominant force in Yellowstone volcanism due to the sinking Farallon plate, as it acts as

2209-606: Was sharply reduced and the climate became arid or semiarid. This extensive and resistant material established the broad flat expanses of the High Plains. Most of the material that overlies this bed is wind-blown Pleistocene loess , while the Blanco Formation overlies the Ogallala in Texas and southwestern Kansas. Much of the underlying sand and gravel is unconsolidated or poorly consolidated such that it easily erodes away, leaving in western Kansas, Nebraska, and Texas

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