Mysterious Maine earthquakes caused by Ice Age rebound

Wired : A swarm of earthquakes, all below two on the Richter scale and many too small to feel, hit Maine’s eastern coast between 30 April and 5 May. Residents called local authorities to report the sound of gunshots and unexpected blasting, but what they had heard was the sound of Earth’s crust buckling. The region is in the middle of a tectonic plate; although it experiences several earthquakes a year, swarms are rare. The last two took place in 2006 and 1967. They, along with the most recent one, were caused by Earth’s crust springing back from the Laurentide ice sheet—between one and two miles thick, it pressed the crust underneath down 500 feet. Although the ice sheet has long since melted, the crustal rebound process is still taking place.