The United States Geological Survey recorded a Magnitude 2.7 Earthquake at a depth of 5.2 km in the Yellowstone National Park in Wyoming, slightly after 8.30 pm local time on Tuesday 8 April 2014 (slightly after 2.30 am on Wednesday 9 April, GMT). This is a fairly small quake, and is unlikely to have caused any damage or injuries, though it may have been felt locally.
The approximate location of the 8 April 2014 Yellowstone National Park Earthquake. Google Maps.
The quake occurred on the northeastern fringe of the Yellowstone Caldera, a vast hotspot volcano that covers an area of roughly 55 by 75 km. Eruptions on the volcano are rare (the last happened around 70 000 years ago) and explosive eruptions even more so (the last happened around 150 000 years ago), but movement is common in the magma chamber beneath the caldera, leading to frequent, if generally rather small, Earthquakes. Magma entering a chamber beneath a volcano does not necessarily erupt as lava at the surface; it can be emplaced in structures such as sills and dykes, igneous rock formations formed entirely beneath the surface.
Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) you can report it to the USGS here.
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