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.

They are the northernmost volcanoes of North America with late Pleistocene activity, lying just south of the Arctic Circle.

[20] At Kotzebue, 60 kilometres (37 mi) northeast of the volcanic field, annual temperatures fluctuate between 11.9 °C (53.4 °F) in July and −20.2 °C (−4.4 °F) in January.

[7] Native Americans used the maars as a source of fish and as hunting grounds, and remains of human activity have been identified at their shores.

[26] The non-maar vents at Espenberg appear to be over 500,000 years old, given that they are covered with vegetation and the lavas shattered by frost,[27] and are probably older than the maars.

[28] The Espenberg maars were originally considered to be of Holocene age, but research has shown that the latest eruptions occurred during the Pleistocene.

[4] It reached thickness of more than 1 metre (3 ft 3 in) over an area of 1,200 square kilometres (460 sq mi), burying soil and vegetation[21] and falling into lakes.

[22] Plant remains found buried underneath the tephra are well preserved[35] and have been used to infer climatic and biotic conditions during the last glacial maximum in the region;[36] vegetation at that time was apparently different from today[37] and there was no widespread ice cover.

They form when magma interacts explosively with surrounding rocks, excavating broad but shallow craters on the surface.

Landslides at the margins of the volcanic vents expanded the forming craters and supplied additional ice to the evaporation processes,[32] ultimately yielding the large size of the Espenberg maars.