Espenberg description and information

From Wood and Kienle (1990) ^[1]: "These are among the northernmost volcanoes in North America, being just south of the Arctic Circle. The basalt field contains 5 maars and 5 small shield-shaped volcanoes. The shields are of Pleistocene age and form tundra-covered hills as tall as 240 m. The maars are younger than the shields and range in age from >0.12 Ma to ~7,000 yr. The maars are 2 to 5 km in diameter and are filled by lakes with surfaces 60 to 80 m below surrounding topography and as much as 30 m deep. Tholeiitic and alkalic basalt of the maars contains up to several tens of percent xenoliths of basement metamorphic and sedimentary rocks as well as masses of unconsolidated Quaternary sediments which must have been frozen at the time of eruption."