Thursday, October 20, 2016

Tearing us apart: Why is Iceland being hit with hundreds of earthquakes every week?

In an average week Iceland's national monitoring seismic network detects around 500 earthquakes. Now and again this number can be much higher when an earthquake swarm hits one or more of Iceland's many volcanoes.
The reason for this seismic activity is Iceland's location right on the divergent boundary between the Eurasian plate and the North American plate. Iceland is in effect slowly splitting apart along the spreading center between the plates, with the North America plate moving westward from the Eurasia plate. The rate of spreading along the Mid-Atlantic Ridge averages about 2.5 centimeters (1 inch) per year, or 25 kilometers (15.5 miles) in a million years.
As you can see on the maps above the earthquakes occur directly along the boundary between the plates. The map to the right shows earthquakes that have been recorded in the last 48 hours.
Almannagjá canyon At Þingvellir National Park. Photo/GVA
Most of the earthquakes hits without people noticing them. They don't affect daily life except when they might be a sign of an impending eruption, as happened this autumn when an earthquake swarm hit the huge Katla sub-glacial volcano, and police evacuated and closed access to nearby travel destinations.
At Þingvellir National Park, in South Iceland, you can however see clearly with your own eyes how these forces of nature are shaping Iceland's landscape. The cracks, faults and canyons which traverse the region are signs of the continental drift between the North American and Eurasian Plates. Pictured to the right is the largest one, Almannagjá canyon.
The location on the tip of the Reykjanes Peninsula is the only place in the world where you can see the Mid-Atlantic ridge rise above sea level. Close by you can walk over The Bridge Between Continents. Yes, it's a little bit of a gimmicky concept but this is indeed a location where the tectonic plates are drifting apart from each other. The bridge is located About 7km south of Hafnir by road 425.
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