Espenberg volcanic field

Espenberg is a volcanic field in Alaska that contains the largest maars on Earth. It was active during the Pleistocene until 17,500 years BP, when a large eruption formed the 8 by 6 kilometres (5.0 mi × 3.7 mi) wide Devil Mountain Maar and deposited tephra over 2,500 square kilometres (970 sq mi), burying vegetation and forming the largest maar on Earth. Other maars in the field are the North and South Killeak Maars and Whitefish Maar, and Devil Mountain is a shield volcano.

The large size of these maars has been attributed to the interaction between permafrost and ascending magma, which favoured intense explosive eruptions. Soils buried underneath the Devil Mountain Maar tephra have been used to reconstruct the regional climate during the last glacial maximum. The maars are part of the Bering Land Bridge National Preserve.