composition, and extend as far as from their source vents. The eruptive units from the field show normal residual magnetism, suggesting that they were all formed less than 780,000 years ago, with the exception of lava within Gifford Peak's eroded core. The volcanic field also features a number of Pleistocene subglacial volcanoes, many of which formed móbergs, flat-topped peaks generated by subglacial eruptions. These mountains, such as Crazy Hills, formed pillow-like shapes when their lava interacted with ice or meltwater. The field also has tuyas, such as Lone Buttle, which formed as flat and steep volcanic cones created by lava that erupted through glaciers or ice sheets. Lone Butte in particular erupted through a glacier in the Indian Heaven field, building its upper cone above water and generating pyroclastic materials, lava flows, and tephra to reach a height of above its base. However, Lone Butte has since undergone significant glacial erosion, losing about half of its original structure. Activity at the volcanic field has occurred sporadically for the past 700,000 years. Therefore, it remains likely that volcanoes from the field will erupt in the future, generating voluminous lava flows. Nonetheless, the Volcano Hazards Program directed by the United States Geological Survey lists Indian Heaven's volcanic threat level as "Low/Very Low". To assess threats from possible lava flows at Indian Heaven or at nearby Mount Adams, geologists from the United States Geological Survey headed by W. E. Scott determined its mean burial rate in 1995, calculated as the lava volume erupted per unit time divided by the area of the lava field. They found that Indian Heaven's average burial rate was low, but noted that Indian Heaven "has had a large lava flow in the past 10,000 years." Estimating the probability of lava flows from Indian Heaven covering a certain point in the zone surrounding the field, the geologists arrived at a range between one in 100,000 to one in a million. Major vents The Global Volcanism Program of the Smithsonian Institution lists a number of major vents at Indian Heaven, including the Big Lava Bed pyroclastic cone, produced by the most recent eruption in the field; the Bird Mountain, East Crater, Gifford Peak, Lemei Rock, Red Mountain, and Sawtooth Mountain shield volcanoes; and the Lone Butte tuya volcano. The Big Lava Bed pyroclastic cinder cone has a smooth slope, and produced the Big Lava Bed flow, which represents the newest