What is the Island Park Caldera?

ISLAND PARK — The volcanic feature called the Island Park Caldera is actually two calderas, one positioned 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 that 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 that is the source of the Mesa Falls Tuff. It was formed in an eruption of more than 280 cubic kilometers 1.3 million years ago. The two calderas share the same rim on their western sides, but the older Island Park Caldera is much larger and more oval and extends into Yellowstone Park. The Island Park Caldera is sometimes referred to as the First Phase Yellowstone Caldera or the Huckleberry Ridge Caldera.

To the southwest of the caldera lies the Snake River Plain, which was formed by a succession of older calderas marking the path of the Yellowstone hotspot. The Plain is a depression, sinking under the weight of the volcanic rocks that formed it, through which the Snake River winds. Other observable volcanic features in the Plain include the Menan Buttes, the Big Southern Butte, Craters of the Moon, the Wapi Lava Field and Hell's Half Acre.

These calderas are in an area called Island Park that is known for beautiful forests, large springs, clear streams, waterfalls, lakes, ponds, marshes, wildlife, and fishing. Harriman State Park is located in the caldera. Snowmobiling, fishing, and Nordic skiing, and wildlife viewing are popular activities in the area. The peaks of the Grand Tetons to the southeast are visible from places in the caldera.

From Wikipedia, to which the Island Park News contributed yet was not credited.

This is part of the online edition of Henry's Fork Country.

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