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Ukinrek maars

Ukinrek Maars

Maar · United States · 91m

Ukinrek Maars are two phreatomagmatic explosion craters that were created in an area without previous volcanic activity during a 10-day-long eruption that began on 30 March 1977. A greenish lake fills East Maar, the largest of the two in this 1994 view from the south. The smaller West Maar is surrounded by dark tephra near the left margin. Gas Rocks, an older volcanic center, forms the peninsula extending into Becharof Lake in the background.
Ukinrek Maars are two phreatomagmatic explosion craters that were created in an area without previous volcanic activity during a 10-day-long eruption that began on 30 March 1977. A greenish lake fills East Maar, the largest of the two in this 1994 view from the south. The smaller West Maar is surrounded by dark tephra near the left margin. Gas Rocks, an older volcanic center, forms the peninsula extending into Becharof Lake in the background. · Photo: Photo by Chris Nye, 1994 (Alaska Division of Geological and Geophysical Surveys, Alaska Volcano Observatory). · Wikimedia Commons
Type
Maar
Country
United States
Region
North America Volcanic Regions / Alaska Peninsula Volcanic Arc
Elevation
91m
Coordinates
57.834, -156.520
Last eruption
1977
Tectonic setting
Subduction zone / Continental crust (> 25 km)
Landform
Minor (Basaltic)
Major rock type
Basalt / Picro-Basalt
Geological summary

Ukinrek Maars are two explosion craters that were created in an area without previous volcanic activity during a 10-day phreatomagmatic eruption March-April 1977. The basaltic maars were erupted through glacial deposits in the Bering Sea lowlands 1.5 km S of Becharof Lake and 12 km W of Peulik volcano; their location is related to the regional Bruin Bay fault. The elliptical West Maar, which was the first to form, is 105 x 170 m and 35 m deep. The other maar, 600 m to the east, is 300 m wide and 70 m deep. Both maars are now filled by crater lakes; the eastern lake encircles a 49-m-high lava dome that was emplaced at the end of the eruption. Base surges were directed primarily to the NW. Juvenile material from the Ukinrek eruptions was of mantle-derived olivine basaltic composition. The dacitic Gas Rocks lava domes, of Quaternary age, are located on the shores of Becharof Lake, 3 km N of Ukinrek maars and were the site of a phreatic eruption about 2,300 years ago.

From Wikipedia

The Ukinrek maars are two volcanic craters on the north side of the Aleutian Range in Alaska that were formed by a phreatomagmatic eruption in 1977. The maars are 1.5 km south of Becharof Lake and 12 km northwest of Peulik Volcano, on a low area of the range, bordering the Bering Sea. The western of the two is elliptical in shape and up to 170 m in diameter and 35 m deep. The other lies 600 m to the east and is circular and up to 300 m in diameter and 70 m deep. The east maar has a 49 m-high lava dome within its crater lake.

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Eruption history

Summary (VEI over time)
Click a bar to see individual eruptions
350 BCE~156 BCE · 1 eruptions · max VEI ?1783~1977 · 1 eruptions · max VEI 3350 BCE23281412011783

Detailed timeline

  1. 1977VEI 3Observed
    1977-03-30 – 1977-04-09
    West and East Ukinrek Maars
  2. 350 BCEVEI ?Geological estimate
    BCE 350 – Ongoing
    Gas Rocks

External links

⚠ For reference only. Not for emergency response.