Geology

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Looking out over the Northern Range at glacial erratics, ground moraines, and Cutoff Mountain in the distance.
The physical landscape of Yellowstone National Park is the result of many geological forces. Here, glacial erratics (foreground), ground moraines (midground), and Cutoff Mountain (background) appear near Junction Butte.

NPS / Jo Suderman

 

The landscape of the Greater Yellowstone Ecosystem is the result various geological processes over the last 150 million years. Here, the Earth’s crust has been compressed, pulled apart, glaciated, eroded, and subjected to volcanism. All of this geologic activity formed the mountains, canyons and plateaus that define the natural wonder that is Yellowstone National Park.

While these mountains and canyons may appear to change very little during our lifetime, they are still highly dynamic and variable. Some of the Earth’s most active volcanic, hydrothermal (water + heat), and earthquake systems make this national park a priceless treasure. In fact, Yellowstone was established as the world’s first national park primarily because of its extraordinary geysers, hot springs, mudpots and steam vents, as well as other wonders such as the Grand Canyon of the Yellowstone River.

 
 

What Lies Beneath

Yellowstone’s geologic story provides examples of how geologic processes work on a planetary scale. The foundation to understanding this story begins with the structure of the Earth and how this structure shapes the planet’s surface.

The earth is frequently depicted as a ball with a central core surrounded by concentric layers that culminate in the crust or outer shell. The distance from the Earth’s surface to its center or core is approximately 4,000 miles (6,437 km). The core of the earth is divided into two parts. The mostly iron and nickel inner core (about 750 miles / 1,207 km in diameter) is extremely hot but solid due to immense pressure. The iron and nickel outer core (1,400 miles / 2,253 km thick) is hot and molten. The mantle (1,800 miles / 2,897 km thick) is a dense, hot, semisolid layer of rock. Above the mantle is the relatively thin crust, three to forty-eight miles thick, forming the continents and ocean floors.

In the key principles of Plate Tectonics, the Earth’s crust and upper mantle (lithosphere) is divided into many plates, which are in constant motion. Where plate edges meet they may slide past one another, pull apart from each other, or collide into each other. When plates collide, one plate is commonly driven beneath another (subduction). Subduction is possible because continental plates are made of less dense rocks (granites) that are more buoyant than oceanic plates (basalts) and thus, “ride” higher than oceanic plates. At divergent plate boundaries—like mid-ocean ridges—the upwelling of magma pulls plates apart from each other.

Many theories have been proposed to explain crustal plate movement. Scientific evidence shows that convection currents in the partially molten asthenosphere (the zone of mantle beneath the lithosphere) move the rigid crustal plates above. The volcanism that has so greatly shaped today’s Yellowstone is a product of plate movement combined with convective upwellings of hotter, semi-molten rock we call mantle plumes.

 
Steam rises from a tan-gray, rocky hillside.

Steamboat Geyser

Unpredictable and dormant for years, Steamboat Geyser has been quite active in 2018.

 

At a Glance

Although a cataclysmic eruption of the Yellowstone volcano is unlikely in the foreseeable future, real-time monitoring of seismic activity, volcanic gas concentrations, geothermal activity, and ground deformation helps ensure public safety. Yellowstone’s seismograph stations, monitored by the by the University of Utah for the Yellowstone Volcano Observatory, detect several hundreds to thousands of earthquakes in the park each year. Scientists continue to improve our capacity to monitor the Yellowstone volcano through the deployment of new technology.

Beginning in 2004, scientist implemented very precise Global Positioning Systems, capable of accurately measuring vertical and horizontal ground- motions to within a centimeter; and satellite radar imagery of ground movements called InSAR. These measurements indicated that parts of the Yellowstone caldera were rising at an unprecedented rate of up to seven centimeters (2.75 in) per year (2006), while an area near the northern caldera boundary started to subside. The largest vertical movement was recorded at the White Lake GPS station, inside the caldera’s eastern rim, where the total uplift from 2004 to 2010 was about 27 centimeters (10.6 in). The caldera began to subside during the first half of 2010, about five centimeters (2 in) at White Lake so far. Episodes of uplift and subsidence have been correlated with changes in the frequency of earthquakes in the park.

On March 30, 2014 at 6:34 am Mountain Daylight Time, an earthquake of magnitude 4.8 occurred four miles north-northeast of Norris Geyser Basin. The M4.8 earthquake was felt in Yellowstone National Park, in the towns of Gardiner and West Yellowstone, Montana, and throughout the region. This is the largest earthquake at Yellowstone since the early 1980s. Analysis of the M4.8 earthquake indicates a tectonic origin (mostly strike-slip motion) but it was also involved with unusual ground uplift of 7 centimeters at Norris Geyser Basin that lasted 6 months.

Energy and groundwater development outside the park, especially in known geothermal areas in Island Park, Idaho, and Corwin Springs, Montana, could alter the functioning of hydrothermal systems in the park.

 

More Information

 
The rainbow colors of Grand Prismatic Spring range from blue to orange.

Hydrothermal Systems

Yellowstone's hydrothermal systems are the visible expression of the immense Yellowstone volcano.

Eruption plume of Great Fountain Geyser.

Hydrothermal Features

Yellowstone preserves earth's most extraordinary collection of hot springs, geysers, mudpots, fumaroles, and travertine terraces.

Volcanic rocks along the shore, with water crashing against them.

Volcano

At the heart of Yellowstone is a large volcano.

Rocks cover the Grand Loop Road near Gibbon Falls after an earthquake.

Earthquakes

Yellowstone is one of the most seismically active areas in the United States.

The calm waters of Yellowstone Lake with tall mountains beyond.

Yellowstone Lake Geology

Yellowstone Lake covers a dynamic geologic story involving volcanoes and glaciers.

Close-up of petrified wood.

Fossils

Fossil of plants, invertebrates, vertebrates, and trace fossils found within Yellowstone document 540 million years of life.

Large boulders are strewn across a sagebrush field with a path crossing it.

Glaciers

Glaciers sculpted the volcanic landscape of Yellowstone.

The bank of a stream recently eroded shows past stream deposits.

Sedimentation and Erosion

The erosion of rock and the deposition of geologic material has created some stunning landscapes.

 

Resources

Anderson, R.J. and D. Harmon, eds. 2002. Yellowstone Lake: Hotbed of Chaos or Reservoir of Resilience? Proceedings of the 6th Biennial Scientific Conference on the Greater Yellowstone Ecosystem. Yellowstone Center for Resources and George Wright Society.

Christiansen, R.L. 2001. The Quaternary and Pliocene Yellowstone Plateau volcanic field of Wyoming, Idaho, and Montana. Reston: U.S. Geological Survey. Professional Paper 729–6.

Fritz, W.J. and R.C. Thomas. 2011. Roadside Geology of Yellowstone Country. Missoula: Mountain Press Publishing Company.

Good, J.M. and K.L. Pierce. 1996. Interpreting the Landscapes of Grand Teton and Yellowstone national parks: Recent and Ongoing Geology. Moose, WY: Grand Teton Natural History Association.

Grotzinger, J.P. and T.H. Jordan. 2014. Understanding Earth. New York: W.H. Freeman and Company.

Hamilton, W.L. Geological investigations in Yellowstone National Park, 1976–1981. In Wyoming Geological Association Guidebook.

Hendrix, M.S. 2011. Geology underfoot in Yellowstone country. Missoula, MT: Mountain Press Publishing Company.

Lillie, R.J. 2005. Parks and plates: The geology of our national parks, monuments, and seashores. New York: W.W. Norton

Smith, R.B. and L.J. Siegel. 2000. Windows Into the Earth: The Geologic Story of Yellowstone and Grand Teton national parks. New York: Oxford University Press.

Tuttle, S.D. 1997. Yellowstone National Park in Geology of national parks. Dubuque, IA: Kendall–Hunt Publishing Company.

Last updated: August 24, 2018

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Yellowstone National Park, WY 82190-0168

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