Although Washington state's Mount St. Helens has been experiencing a high volume of seismic activity, experts are allaying fears that it is a sign that the volcano is about to blow its top.
A 3.9-magnitude earthquake (considered "minor" on the Richter scale) occurred about 11 kilometres (6 miles) northeast of the volcano around 12:38 a.m. on January 3. That quake was followed by a swarm of up to 150 smaller tremors.
The stratovolcano, or a conical volcano built up by layers of strata, is approximately 80 kilometres (50 miles) northeast of Portland; 154 kilometres (96 miles) south of Seattle; and 200 kilometres (124 miles) south of Vancouver.
The 3.9-magnitude event, which was felt in Portland, Oregon, was the strongest seismic activity in the area since the volcano erupted in 1980.
However, seismologists have stated that the recent seismic pattern is different from how volcanic activity at the mountain has been measured in the past, such as in 2004 when a series of earthquakes increased in frequency and intensity, instead of decreasing.
In May 2016, over 130 small earthquakes occurred under the volcano, which the U.S. Geological Survey explained that although the tremors indicated the volcano was recharging, eruption was not imminent.
On March 20, 1980, a 4.2-magnitude earthquake occurred at the volcano, as steam began to vent and a bulge formed.
A second 5.1-magnitude earthquake on May 18 resulted in an eruption that devastated the landscape over 600 square kilometres (230 square miles). The eruption killed 57 people, caused forest fires and flooding (due to snow melt), and released ash across the Pacific Northwest. It was the first eruption to occur on contiguous United States since 1917.