Iceland Mag

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Iceland Mag

Geology

Growing seismic activity in Iceland's tallest peak has scientists worried

By Staff

  • Öræfajökull glacier Iceland's tallest peak, Hvannadalshnjúkur, is located in Öræfajökull. Hiding beneath the glacier is a giant volcano. Photo/IMO, Oddur Sigurðsson

One of Iceland's most terrifying volcanoes, Öræfajökull the southernmost tip of Vatnajökull glacier, has been showing increasing activity over the past month. Geologists suspect that magma has been collecting in the volcano's magma chambers, causing the ground to rise significantly over the past two years.

Read more: All of Iceland‘s major volcanoes showing unusually high levels of activity

Öræfajökull glacier seismic monitoring stations

Monitoring the monster Location of seismic monitoring stations around Öræfajökull glacier. Photo/IMO

On October 4 a relatively powerful earthquake swarm, including a 3.4 magnitude tremor shook Öræfajökull. Earthquakes are relatively rare in the volcano. The last time a large 3+ magnitude quake hit the volcano was in 2005. Any quake in a volcano which is larger than 3 on the Richter scale is considered noteworthy and "powerful". These quakes are caused by the movement of magma from the mantle up into fissures and magma chambers in the earth's crust. Growing magma pressure increases the likelihood of an eruption.

A terrifying volcano
An eruption Öræfajökull is no joke. The volcano erupts in giant steam-blast eruptions, also known as phreatic or ultravolcanian eruptions:  One of the best known ultravolcanian eruptions in history is the 1883 Krakatoa eruption. Steam-blast eruptions occur when magma heats ground water, creating a near-instantaneous evaporation and explosion which can eject enormous quantities of ash, rock and volcanic material which is then deposited over surrounding areas.

A 1362 steam blast eruption in Öræfajökull was the second deadliest eruption in Icelandic history. It is also considered to be one of the largest tepthra eruptions in the world in the last 1000 years. It destroyed one of the most prosperous farmland regions in South Iceland, killing all inhabitants and livestock at 20-40 farms in a region which was known then as Litla-hérað. Following the eruption, which deposited 10 cubic kilometers of volcanic material over fields and farms in the region, it's name changed to Öræfi, which translates as "Wasteland" in modern Icelandic.

Better monitoring 
Scientists with the Icelandic Meteorological Office have added a number of new seismic monitors at different points on and around the volcano to keep keep it under closer scrutiny. Next month the IMO plans to add equipment which monitors the release of gasses and the condition of geothermal areas around the volcano. 

Scientists fear that an eruption in the volcano would leave very little time to evacuate the surrounding regions. Growing tourism in the foothills of Öræfajökull and in surrounding areas makes evacuation even more challenging. According to a risk assessment by the Civil Protection Agency it will take at least 40 minutes to evacuate the areas which would be affected by an eruption in the glacier. With closer monitoring scientists hope to be able to anticipate any volcanic activity with significantly greater advance knowledge.

Shrinking glaciers a possible factor
Aside from growing volcanic activity scientists believe global climate change could be a cause: As the glacier melts the weight it exerts on the underlying crust drops, causing the land to rise. At the same time pressure is released, causing earthquakes.

The most pressing question at present is the precise location of the epicenters of the recent tremors. Determining the precise depth of the epicenters will allow scientists to determine with precision the contribution of glacial melting and magma movements to the growing geological activity.

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