Aerial view towards the north of Ukinrek Maars, Alaska
is a low-relief, broad volcanic
crater formed by shallow explosive eruptions. The explosions are usually caused by the heating and boiling of groundwater when magma invades the groundwater table. Maars often fill with water to form a lake.
- ↑ http://volcanoes.usgs.gov/Products/Pglossary/maar.html