Island Park Caldera
Encyclopedia
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
and Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, U.S., is actually two caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
s, one nested inside the other. The Island Park Caldera is the older and much larger caldera, with approximate dimensions of 58 miles (93 km) by 40 miles (64 km). Its ashfall is the source of the Huckleberry Ridge Tuff
Huckleberry Ridge Tuff
The Huckleberry Ridge Tuff is a tuff formation created by the Huckleberry Ridge eruption that formed the Island Park Caldera that lies partially in Yellowstone Park, Wyoming and stretches westward into Idaho into a region known as Island Park...
that is found from southern California to the Mississippi River near St. Louis. This supereruption (2500 cubic kilometers) occurred 2.1 million years ago and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption.
The caldera clearly visible today is the later Henry's Fork Caldera
Henry's Fork Caldera
The Henry's Fork Caldera in Idaho is a caldera located an area known as Island Park west of Yellowstone National Park. The caldera was formed by one of the world's supervolcanos in an eruption of more than 280 cubic kilometers 1.3 million years BP, and is the source of the Mesa Falls Tuff.The...
that is the source of the Mesa Falls Tuff
Mesa Falls Tuff
The Mesa Falls Tuff is a tuff formation created by the Mesa Falls eruption that formed the Henry's Fork Caldera that is located in Idaho west of Yellowstone Park. It is the second most recent caldera forming eruption from the Yellowstone hotspot and ejected of 280 km³ of material...
. It was formed in an eruption of more than 280 cubic kilometers 1.3 million years ago. The two nested calderas share the same rim on their western sides, but the older Island Park Caldera is much larger and more oval and extends well into Yellowstone Park. The Island Park Caldera is sometimes referred to as the First Phase Yellowstone Caldera
Yellowstone Caldera
The Yellowstone Caldera is the volcanic caldera located in Yellowstone National Park in the United States, sometimes referred to as the Yellowstone Supervolcano. The caldera is located in the northwest corner of Wyoming, in which the vast majority of the park is contained. The major features of...
or the Huckleberry Ridge Caldera.
To the southwest of the caldera lies the Snake River Plain
Snake River Plain
The Snake River Plain is a geologic feature located primarily within the state of Idaho in the United States of America. It stretches about westward from northwest of the state of Wyoming to the Idaho-Oregon border. The plain is a wide flat bow-shaped depression, and covers about a quarter of Idaho...
, which was formed by a succession of older calderas marking the path of the Yellowstone hotspot
Yellowstone hotspot
The Yellowstone hotspot, also referred to as the Snake River Plain-Yellowstone hotspot, is a volcanic hotspot responsible for large scale volcanism in Oregon, Nevada, Idaho, and Wyoming, United States. It created the eastern Snake River Plain through a succession of caldera forming eruptions...
. The Plain is a depression, sinking under the weight of the volcanic rocks that formed it, through which the Snake River
Snake River
The Snake is a major river of the greater Pacific Northwest in the United States. At long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean...
winds. Other observable volcanic features in the Plain include: the Menan Buttes
Menan Buttes
The North and South Menan Buttes in southeastern Idaho are two of the world's largest volcanic tuff cones. The two cones, with four smaller associated cones, align along a north-northwest line and comprise the Menan Complex. The buttes rise about 800 feet above the surrounding Snake River plain...
, the Big Southern Butte
Big Southern Butte
Big Southern Butte is the largest and youngest of three rhyolitic domes formed over a million years near the center of the Eastern Snake River Plain in the U.S. state of Idaho. In fact, it is one of the largest volcanic domes on earth...
, Craters of the Moon
Craters of the Moon National Monument and Preserve
Craters of the Moon National Monument and Preserve is a national monument and national preserve located in the Snake River Plain in central Idaho, U.S.A. It is along US 20 , between the small cities of Arco and Carey, at an average elevation of above sea level...
, the Wapi Lava Field and Hell's Half Acre
Hell's Half Acre Lava Field
Hell's Half Acre lava field is a basaltic lava plain located on the Snake River Plain of Idaho in the United States. It is the easternmost of the basaltic lava fields on the Snake River Plain, located about west of Idaho Falls, Idaho and north of Pocatello, Idaho. In 1976 the National Park...
.
These calderas are in an area called Island Park
Island Park, Idaho
Island Park is a city in Fremont County, Idaho, United States. The city's population was 215 at the 2000 census. The city was incorporated by owners of the many lodges and resorts along U.S. Route 20 in 1947, primarily to circumvent Idaho's liquor laws that prohibited the sale of liquor outside of...
that is known for beautiful forests, large springs, clear streams, waterfalls, lakes, ponds, marshes, wildlife, and fishing. Harriman State Park
Harriman State Park (Idaho)
Harriman State Park is a state park in eastern Idaho, USA. It is located on an wildlife refuge in the Greater Yellowstone Ecosystem and is home to an abundance of elk, moose, sandhill cranes, trumpeter swans, and the occasional black or grizzly bear. Two-thirds of the trumpeter swans that winter...
is located in the caldera. Snowmobiling, fishing, and Nordic skiing, and wildlife viewing are popular activities in the area. The peaks of the Teton Range
Teton Range
The Teton Range is a mountain range of the Rocky Mountains in North America. A north-south range, it is on the Wyoming side of the state's border with Idaho, just south of Yellowstone National Park. Most of the range is in Grand Teton National Park....
to the southeast are visible from places in the caldera.