Mount St. Helens National Volcanic Monument

We’re standing on the Boundary Trail at Johnston Ridge in the Mount St. Helens National Volcanic Monument. Forty years ago today, more than 44,500 hectares within Gifford Pinchot National Forest was dedicated to memorialise the deadliest and most destructive volcanic eruption in the United States. On 18 May 1980, Mount St. Helens erupted, forever changing the Washington landscape. The volcanic event started at roughly 8:30 on a Sunday morning with a 5.1 magnitude earthquake. This triggered what is known as a lateral eruption, which means the lava blast comes out of the side of the volcano, rather than the top, resulting in a massive avalanche and the destruction of about 388 square kilometres of surrounding forest.
© Don Geyer/Alamy