September 27, 2012 - Beauty and the Beast: Near the beauty of the Grand Tetons lurks a “beast” of unimaginable power and evil. A volcano, so powerful, it could wipe out civilization as we know it. The volcanic feature commonly called the Island Park Caldera in the state of Idaho, USA, is actually two calderas, one nested inside the other. The Island Park Caldera is the older and much larger caldera, with approximate dimensions of 58 miles (93 kilometers) by 40 miles (64 kilometers). Its ash fall is the source of the Huckleberry Ridge Tuff that is found from southern California to the Mississippi River near St. Louis. This super eruption (2,500 cubic kilometers or 1,550 cubic miles) occurred 2.1 million years BP (Before Present) 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 (174 cubic miles) 1.3 million years BP. 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 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.
The VEI (Volcanic Explosivity Index) rates volcanoes in terms of their power and violence. The scale ranges from 1 to 8, with 8 being a mega-colossal volcano. Most volcanologists rate six volcanoes in the “8” category. In order of their last major eruption they are: (1) Lake Taupo, on the North Island of New Zealand (26,500 years ago), (2) Lake Toba, Northern Sumatra, Indonesia (74,000), (3) Whakamaru; North Island, New Zealand (254,000), (4) Yellowstone Caldera, Wyoming, USA (640,000), (5) Island Park Caldera, Idaho, USA (2.1 million) and (6) La Garita Caldera, Colorado, USA (27.8 million years ago). Note that half of these mega-colossal volcanoes are in the Western United States.
There are 11 rated at VEI=7. Three are located in Japan, two USA (Long Valley Caldera in California & Valles Caldera in New Mexico), Indonesia (1), China (1), Germany (1), Italy (1), New Zealand (1) and Greece (1). Note that three are in Europe. Of these 11, two erupted in the 20th Century: (1) Mount Tambora; Sumbawa Island, Indonesia, 1815 and (2) Santorini Volcano; on the Island of Thera, Greece, 1927.
The Master of Disaster