The Henry's Fork Caldera in eastern

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

is a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

located in an area known as Island Park, west of

Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowston ...

. The caldera was formed by an

eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...

1.3 million years ago of the

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, formed as the North American tectonic plate moved over it. It formed the eastern Snake Ri ...

. The eruption distributed at least 280 cubic kilometers of ash known as the Mesa Falls Tuff, covering a region including all of Wyoming and most of Colorado, Nebraska, and Kansas. The Henry's Fork Caldera is nested inside of the

Island Park Caldera The Island Park Caldera, in the U.S. states of Idaho and Wyoming, is one of the world's largest calderas, with approximate dimensions of 80 by 65 km. Its ashfall is the source of the Huckleberry Ridge Tuff that is found from southern Calif ...

, and the calderas share a rim on the western side. The earlier Island Park Caldera is much larger and more oval and extends well into Yellowstone Park. Although much smaller than the Island Park Caldera, the Henry's Fork Caldera is still sizeable at long and wide and its curved rim is plainly visible from many locations in the Island Park area. Of the many calderas formed by the

, including the later

Yellowstone Caldera The Yellowstone Caldera, sometimes referred to as the Yellowstone Supervolcano, is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States. The caldera and most of the park are located in the northwest corn ...

, the Henry's Fork Caldera is the only one that is currently clearly visible.this qualitative statement is easily verified by reviewing the Yellowstone area in Google Earth It is one of a succession of supervolcanoes and calderas that formed the

Snake River Plain image:Snake River view near Twin Falls, Idaho.jpg, The Snake River cutting through the plain leaves many canyons and Canyon#List of gorges, gorges, such as this one near Twin Falls, Idaho The Snake River Plain is a geology, geologic feature ...

. The Henrys Fork of the

Snake River The Snake River is a major river of the greater Pacific Northwest region in the United States. At long, it is the largest tributary of the Columbia River, in turn, the largest North American river that empties into the Pacific Ocean. The Snake ...

flows through the Henry's Fork Caldera and drops out at Upper and Lower Mesa Falls. The caldera is bounded by the Ashton Hill on the south, Big Bend Ridge and Bishop Mountain on the west, by Thurmon Ridge on the North and by Black Mountain and the

Madison Plateau There are nine named plateaus in Yellowstone National Park. These plateaus are part of the much larger Yellowstone Plateau and dominate areas in the park south and west of the Gallatin and Absaroka mountain ranges. Four of the plateaus are ...

on the east. The Henry's Fork caldera is in an area called Island Park, known for its beautiful forests, large springs, clear streams, waterfalls, lakes, ponds, marshes, wildlife, and fishing. Harriman State Park is situated within the caldera. The peaks of the

Teton Range The Teton Range is a mountain range of the Rocky Mountains in North America. It extends for approximately in a north–south direction through the U.S. state of Wyoming, east of the Idaho state line. It is south of Yellowstone National Park and ...

in adjacent

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

are visible to the southeast. Snowmobiling, fishing, and Nordic skiing, and wildlife viewing are popular activities in the area.

References

{{coord, 44.33, N, 111.33, W, source:frwiki_region:US_scale:100000, display=title Yellowstone hotspot Volcanism of Idaho Calderas of Idaho Volcanoes of Idaho VEI-7 volcanoes Landforms of Fremont County, Idaho Pleistocene calderas Pleistocene United States Quaternary Idaho