More than 300 earthquakes have erupted at Washington's Mount Rainier this week, the largest earthquake swarm at the volcano since 2009.

While considered an active volcano, Mount Rainier hasn’t erupted in at least a century, possibly much longer. The U.S Geological Survey said there was no physical evidence to confirm a reported 1894 eruption, nor eruptions earlier in the 18th and 19th centuries. The last eruption with strong geologic evidence happened about 1,000 years ago.