On May 18, 1980, the St. Helens in Washington state, USA exploded powerfully, causing a large earthquake. The explosion caused the top of the volcano to collapse and create a huge landslide. Notably, this landslide is considered the fastest in history with a speed of up to 402.3 km / h.
A landslide as fast as one-third the speed of sound (1,234 km/h) is just a small part of the disaster from the eruption of St. Helens in Washington in the spring of 1980. To this day, it remains the deadliest and most damaging volcanic event in American history, according to IFL Science .
Columns of ash rising from the summit of St. Helens in 1980. (Photo: History).
According to the US Geological Survey (USGS), signs of activity in Mount St. Helens began as a series of small earthquakes on March 16, 1980, leading to the mountain’s first eruption in more than 100 years on March 27 of the same year. The stream of steam and ash broke the ice cap at the summit, creating a 75-meter-wide crater, but the eruption was still quite mild compared to what was to come. Small eruptions occurred for several weeks until April 22, when the first wave of activity ceased.
By May 1980, signs of a bulge developing on the northern slopes of the mountain became increasingly apparent. That bulge is the result of magma rising below the ground , building up pressure like an inflated balloon. The worst disaster occurred on the morning of May 18, 1980 when the St. Helens was shaken by a 5.1 magnitude earthquake. As soon as the tremor struck, the top and bulge of the mountain slid down forming the largest landslide ever recorded.
While landslides took place on the northern slopes of St. Helens, the high-pressure magma chamber shot up like the cork of a champagne bottle, causing a powerful explosion that sent mud and ash across a 600 square kilometer area. The eruption completely destroyed the area in just five to nine minutes, killing all living things in that range, said USGS researcher Dan Miller.
Experts estimate the eruption released 100 million trillion joules of energy with a Volcanic Eruption Index of 5 , the highest on land in the US. But on the evening of May 18, 1980, the eruption began to slow down and stopped the next day.
A total of 57 people died in the disaster, not to mention thousands of animals living in the surrounding area. Property damage was more than billion. Volcanic ash deposits have been recorded in at least 11 US states and 5 Canadian provinces. Scientists say the St. Helens is more likely to erupt again because eruptions here usually take place after 100-300 years.