Yellowstone hotspot

The Yellowstone hotspot is a volcanic hotspot in the United States responsible for large scale volcanism in Idaho, Montana, Nevada, Oregon, and Wyoming. It formed as the North American tectonic plate moved over it, creating a chain of volcanic features.

This hotspot created the eastern Snake River Plain through a series of huge eruptions that formed large volcanic depressions called calderas. Some of these calderas include the Island Park Caldera, Henry's Fork Caldera, and the Bruneau-Jarbidge caldera.

Today, the hotspot lies under the Yellowstone Caldera, one of the most famous volcanic areas in the world. Its most recent major eruption, called the Lava Creek Eruption, happened 640,000 years ago. This eruption created the Lava Creek Tuff and shaped the current Yellowstone Caldera.

The Yellowstone hotspot is just one of a few volcanic hotspots found under the North American tectonic plate. Another example is the Anahim hotspot, located further to the west. These hotspots help scientists understand how Earth's surface has changed over millions of years.

Snake River Plain

The eastern Snake River Plain is a low area that runs across the Basin and Range mountains, following the movement of the North American Plate. Under its more recent dark rocks, called basalts, there are older light-colored rhyolite lavas and thick layers of ash from ancient eruptions, known as ignimbrites. As the Earth's outer layer, the lithosphere, moved over a hot spot deep in the Earth, it caused these eruptions. Later, volcanoes added fresh basalt lava flows in some places, such as the Craters of the Moon National Monument and Preserve.

The central part of the Snake River Plain looks similar but has lots of layers from old lakes and streams, called lacustrine and fluvial sediments. One famous spot here is the Hagerman Fossil Beds.

Nevada–Oregon calderas

The McDermitt volcanic field, located on the border of Nevada and Oregon, is often considered the starting point of the Yellowstone Hotspot. Recent studies show that the area affected by this ancient volcanic activity is much larger than previously thought. Three new silicic calderas have been found in northwest Nevada, west of the McDermitt volcanic field, along with the Virgin Valley Caldera and the McDermitt Caldera. These calderas formed between 16.5 and 15.5 million years ago during the later stages of the Steens flood basalt volcanism. The calderas in northwest Nevada range from 15 to 26 kilometers in diameter and covered about 5,000 square kilometers with high-temperature volcanic rocks.

As the hotspot moved under what is now Nevada and Oregon, it changed the local ecology by breaking up old habitats and creating more varied landscapes in western North America. The Bruneau-Jarbidge volcanic field erupted between ten and twelve million years ago, creating a wide caldera and spreading a thick layer of ash during the Bruneau-Jarbidge event. This volcanic ash was carried far by winds, covering a large part of the Great Plains. At the Ashfall Fossil Beds in northeastern Nebraska, a thick layer of ash preserved many fossils, including rhinoceroses, offering valuable insights into ancient life.

Volcanic fields

The Twin Falls and Picabo volcanic fields were active around 10 million years ago. The Picabo Caldera created the Arbon Valley Tuff about 10.2 million years ago.

The Heise volcanic field in eastern Idaho had big eruptions starting 6.6 million years ago. These eruptions created large amounts of rhyolitic magma, with the last major eruption, the Kilgore Tuff, happening 4.5 million years ago.

Yellowstone Plateau

See also: Yellowstone Caldera

The Yellowstone Plateau is a volcanic area made up of four large sunken regions called calderas. One of these, the Henry's Fork Caldera in Idaho, formed over 1 million years ago and is still clearly visible today. It is nested inside an even larger caldera called the Island Park Caldera, which stretches into Yellowstone Park.

The Island Park Caldera is much bigger, and it produced a huge amount of ash over 2 million years ago that spread far across North America. The most recent and well-known caldera is the Yellowstone Caldera, which formed around 640,000 years ago. Though it is active, with small steam eruptions still happening, scientists think it might be entering its final stages.

Eruptive history

The Yellowstone hotspot has created many volcanic eruptions across several U.S. states over millions of years. These eruptions formed large areas of lava and changed the landscape dramatically.

Notable eruptions include the Yellowstone Caldera about 640,000 years ago, which produced huge amounts of lava. Earlier, the Island Park Caldera erupted around 2.1 million years ago. Farther back, around 16 million years ago, the Columbia River Basalt Province saw massive flood basalts cover large areas of Washington, Oregon, and Idaho.