Forty-six years ago today at 8:32 a.m. PST, southern Washington was stunned as Mount St. Helens — a volcanic peak — unleashed a massive eruption, killing 57 people and devastating about 210 square miles of wilderness. Called Louwala-Clough, or “the Smoking Mountain,” by Native Americans, Mount St. Helens is located in the Cascade Range and stood 9,680 feet before its eruption. The volcano has erupted periodically during the last 4,500 years, and the previous active period was between 1831 and 1857. These earthquakes escalated, and on March 27, a minor eruption occurred. The volcano began emitting steam and ash through its crater and vents. Small eruptions continued daily, and in April people familiar with the mountain noticed changes to the structure of its north face.
On the morning of May 18, an earthquake of about 5.0 magnitude triggered a massive avalanche, sending the entire north face of the summit down the mountain. The giant landslide of rock and ice — one of the largest recorded in history — was followed by an enormous explosion of steam and volcanic gases, which surged northward along the ground at high speed. The lateral blast stripped trees from most hill slopes within six miles of the volcano and leveled nearly all vegetation for as far as 12 miles away. By late in the afternoon of May 18, the eruption subsided, and by early the next day it had essentially ceased.
Mount St. Helens’ volcanic cone was completely blasted away and replaced by a horseshoe-shaped crater–the mountain lost 1,700 feet from the eruption. The volcano produced five smaller explosive eruptions during the summer and fall of 1980 and remains active today. In 1982, Congress made Mount St. Helens a protected research area.
Read more on the long-lasting impact of this eruption.
