quality:correction
Earthquakes

Yellowstone experiences thousands of small earthquakes every year, virtually all of which are undetectable to people. About 2/3 of the earthquakes occur in an area between Hegben Lake and the Yellowstone Caldera along a buried fracture zone left from the 2.1 mya eruption.

There have been six earthquakes with at least magnitude 6 or greater in historical times, including the 7.2‑magnitude Hebgen Lake earthquake which occurred just outside the northwest boundary of the park in 1959. This quake triggered a huge landslide, which caused a partial dam collapse on Hebgen Lake; immediately downstream, the sediment from the landslide dammed the river and created a new lake, known as Earthquake Lake. Twenty-eight people were killed, and property damage was extensive in the immediate region. The earthquake caused some geysers in the northwestern section of the park to erupt, large cracks in the ground formed and emitted steam, and some hot springs that normally have clear water turned muddy. The stress created in the fracture zone by this quake is theorized to be responsible for the current quake activity in the northwestern section of Yellowstone. A 6.1‑magnitude earthquake struck inside the park on June 30, 1975, but the damage was minimal.

For three months in 1985, 3,000 minor earthquakes were detected in the northwestern section of the park, during what has been referred to as an earthquake swarm, and has been attributed to minor subsidence of the Yellowstone caldera. Beginning on April 30, 2007, 16 small earthquakes with magnitudes up to 2.7 occurred in the Yellowstone Caldera for several days. These swarms of earthquakes are common, and there have been 70 such swarms between 1983 and 2008. In December 2008, over 250 earthquakes were measured over four days under Yellowstone Lake, the largest measuring a magnitude of 3.9. In January 2010, more than 250 earthquakes were detected over two days. Seismic activity in Yellowstone National Park continues and is reported hourly by the Earthquake Hazards Program of the U.S. Geological Survey.

On March 30, 2014, a magnitude 4.8 earthquake struck almost the very middle of Yellowstone near the Norris Basin at 6:34 am; reports indicated no damage. This was the largest earthquake to hit the park since February 22, 1980.