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Mount St Helens. The first eruption. In 1975, scientists warned that Mt St Helens may well erupt again before the end of the century and in 1980 after a period of 120 years with not activity at all, Mt St Helens began to give a few warning signs of the things to come.
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The first eruption In 1975, scientists warned that Mt St Helens may well erupt again before the end of the century and in 1980 after a period of 120 years with not activity at all, Mt St Helens began to give a few warning signs of the things to come. On March 20th 1980 there were several small earthquakes. These earth tremors continued until on the 27th March several small eruptions steam and ash occurred as the bulk of the magma rose up into the volcano.
Mount St Helens becomes active Seven days after the earthquakes another small eruption exploded cold black ash 3 km into the air, and the whole of the north side of the volcano began to bulge outwards, by 1.5 metres a day! At this moment scientists knew that Mt St Helens was winding up to violently explode at any time.
After seeing these small eruptions, most people, most sensible people evacuated the area. However some people, like this old man, who lived half way up the volcano, refused to leave.
Monitoring the eruption The government decided that an area 13 km wide around the volcano should be completely cleared of all people. As April rapidly approached people were still fleeing from the area. The north side of the volcano was still bulging at about 5 feet a day and the earthquakes under the volcano continued, getting stronger and stronger every day. The only people who stayed behind were the scientists who were determined to carry on watching the volcano and a few lumber jacks working in the forests. Months passed and the volcano continued to grow more and more uneasy, bulging along the whole of one side and suffering frequent earthquakes. Then on the 14th May 1980 the earthquakes stopped. To an observer the volcano looked peaceful, the rapid swelling of the north side of the volcano was the only clue that anything at all was wrong, but the scientists knew this ‘was the calm before the storm’.
The morning of the 18th May 1980 was a beautiful morning, there were no clouds and the sun was shinning, the bulging of the volcano continued but there were still no earthquakes. Everything looked peaceful. But at 08.32 am all that changed….
At 8.32 in the morning an earthquake, magnitude 5 on the Richter scale caused the bulge on the northern slopes of the volcano to move forwards and downwards.
The earthquake caused the entire northern flank of the volcano to collapse. As it did so the pressure which had been building up inside the volcano was violently released sending billions of tonnes of rock, ice, and soil racing away from the volcano.
This massive blast sent a wave of material rushing down the volcano. This blast wave known as a pyroclastic flow travels at over 100 km an hour, and is over 1000 degrees Celsius in temperature, and is the volcanoes most violent weapon.
Eruption from space The blast from the eruption in 1980 was so powerful it could be clearly seen from space.
Visitors come to St Helens For the rest of the morning a series of eruptions sent gas, ash and lumps of red hot volcanic rock known as lava bombs hurtling 20 km into the air.
Failure to escape Due to the knowledge, understanding and warnings of the scientists studying the volcano the loss of life was very minimal. Still, the blast was more intense than anyone had anticipated and the death toll reached 60 people.
Blast damage 10 km away The blast not only killed people but completely flattened the entire area surrounding the volcano. As you can see from the picture, Anything in its way was levelled, this scene 10km away from the volcano was completed deforested. All those trees and everything that lived in them, now gone.
But the volcano had one more surprise. When the volcano erupted, the sides of the mountain were still covered with ice and snow from the winter. The intense heat melted the ice and snow to release 200,000 million litres of water. The water turned the rock, ash and destroyed trees from around the volcano into huge mudflows which poured down the river valleys raising the water level by up to 200 metres in places. These raging torrents destroyed roads, bridges, railways and swept people away to their deaths.
After the eruption After the eruption had died down several days later, the ash that it had thrown into the atmosphere had completed circled the world. This ash blocked the light from the sun and lower the temperature of the earth.
Blown its top Mt St Helens is a volcano success story. Despite being one of the most explosive and violent eruptions in the last century, blowing away nearly half a kilometre in height of its summit, it killed very few people and all because of the successful monitoring and later evacuation.
