Though Iceland is known for having ample earthquakes, the largest one in known history didn’t even reach seven on the richter scale. In Chile and Japan though—other well-known epicenters— many have passed nine. Why are the earthquakes in Iceland smaller?
To find out the answer to this earth-shattering question, we talked to physical chemist Dr. Helgi Rafn Hróðmarsson, aka ‘The Cosmic Chemist’.
“Earthquakes originate from tectonic plate movements that are situated just beneath the Earth’s crust. There are several tectonic plates that cover the Earth’s mantle, each named for its surface’s geography. E.g. Pacific plate, North & South American plates, etc.
Earthquakes tend to occur at the boundaries of these crustal plates, where they collide, separate, or rub against one another. Iceland is situated right at a fissure between the North American and Eurasian plates that are separating. As the plates are moving away from each other, all geological activity under Iceland originates at a much shallower level than at the cusp of tectonic collisions or in so-called subduction zones.
For example, whereas Icelandic earthquakes start tens of kilometers under sea level, earthquakes in Chile, where the Nazca plate is being subducted under the South American plate, stem from a depth of approx. 100-350 km under sea level. The further underground an earthquake is formed, the greater the seismic wave can build up, which causes the Earth’s surface to shake. Therefore, Iceland’s earthquake activity is quite mild in comparison to other regions in South America and Japan.”