The Espenberg Maars are the first reported example of hydromagmatic eruptions produced by interactions of magma with permafrost (Table 2).
The processes involved in the interaction of permafrost and magma at the Espenberg Maars are more than a curiosity, as the unusually large size of these four maars indicates that hydromagmatic eruptions involving permafrost can be significantly more explosive and typically excavate craters larger than those resulting from interactions with surface or groundwater (Table 2).
Water sources for selected hydromagmatic eruptions that have produced maars and tuff cones.
Pleistocene permafrost temperatures at the Espenberg Maars were probably ca.
At most maars, highly explosive conditions constitute a transient eruptive phase associated either with initially low supplies of groundwater, or with the exhaustion of available water supplies during the course of the eruption.
Lorenz (1986) suggested that maars grow as crater walls collapse into successively deeper and wider conduits.
These maars therefore grew from a combination of several processes, including the coalescence of several vents during extended eruptions and repeated collapse of landslide debris from the margins of the crater.
For instance, the depth of excavation of the maars is similar to but slightly greater than the modern thickness of permafrost.