Increased seismicity under Grímsvötn volcano, Aviation Color Code raised to Yellow, Iceland
Increased seismicity was detected under the Grímsvötn volcano in SE Iceland on August 2, 2022, forcing the Icelandic Meteorological Office (IMO) to raise the Aviation Color Code for the volcano to Yellow. This is now the third volcano in Iceland with Yellow Aviation Color Code in effect – after Askja and Krysuvik. The last eruption of this volcano took place in 2011.
The decision to raise the color code was based on several earthquakes larger than M1 detected this afternoon (UTC). The largest event was M3.7 detected at 14:24 UTC at a depth of 1.4 km (0.8 miles).
This means that seismicity at the volcano is above normal activity which calls for increased monitoring in the area, IMO said.1
The last eruption at this volcano occurred in 2011 CE – May 21 to 28, 2011 (VEI 4) – and emitted about 0.8 km3 (0.20 mi3) of basaltic tephra (bulk volume).
This volcano has a history of major eruptions up to VEI 6.
Geological summary
Grímsvötn, Iceland’s most frequently active volcano in historical time, lies largely beneath the vast Vatnajökull icecap. The caldera lake is covered by a 200 m (650 feet) ice shelf, and only the southern rim of the 6 x 8 km (3.7 x 5 miles) caldera is exposed.
The geothermal area in the caldera causes frequent jökulhlaups (glacier outburst floods) when melting raises the water level high enough to lift its ice dam.
Long NE-SW-trending fissure systems extend from the central volcano. The most prominent of these is the noted Laki (Skaftar) fissure, which extends to the SW and produced the world’s largest known historical lava flow during an eruption in 1783.
The 15 km3 (3.6 mi3) basaltic Laki lavas erupted over a 7-month period from a 27 km (16.7 miles) long fissure system. Extensive crop damage and livestock losses caused a severe famine that resulted in the loss of one-fifth of the population of Iceland.2
References:
1 From Specialist remark issued by IMO at 17:03 UTC on August 2, 2022
2 Grímsvötn – Geological summary – GVP
Featured image credit: IMO
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