VHP Photo Glossary: Maar

Aerial view of east Ukinrek Maar, Alaska

1. Photograph by C. Nye on 9 May 1994
Alaska Division of Geological and Geophysical Surveys


A maar 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.

Phreatic and magmatic explosive eruption of Ukinrek Maars, Alaska

2. Photograph by R. Russell on 6 April 1977 Alaska Department of Fish and Game

Photo 1:

Aerial view toward N of Ukinrek Maars, Alaska; Lake Becharof at top of photo. Water partially fills the eastern maar and completely covers a lava dome that was erupted in the 100-m deep crater during a 10-day eruption in 1977. Maar is about 300 m in diameter.

Photo 2:

Eruption column generated by phreatic and magmatic explosions rises from the larger east maar.

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