Many people live around Mount St. Helens. This is because of the very good fertile soil that surrounds the area. The fertile soil is good for farming. There are also many tourists that visit the area. Travelers from all over the world visit the area to see the Washington based volcano and to admire the large national parks that surround the volcano. There is also a national lake near the volcano called the Spirit Lake.
There has only been 1 eruption at Mount St. Helens known to us in this modern era but scientists and geologists can inspect the volcano to see if it has erupted before. They can do this by counting the rings of trees to see how old they are or by inspecting the different layers of alternate rock that made up the volcano Mount St. Helens.
The Eruption:
It was 20th of March 1980 at 3:47pm Pacific standard time. A magnitude of 4.2 earthquake on the Richter scale was detected. This was the first signal of the re-awakening of the volcano. There were a few other smaller earthquakes over the next few days. The scientists recorded that the earthquake was the start of another 10000 earthquakes.
On the 27th of March, Mount St. Helens began to let off gas and steam. It showed us that it was its first significant eruption. Magma started bubbling up and a lot of pressure started building up inside the volcano. A bulge started forming on the northern side of the volcano and this kept on increasing 1.5m a day. The public authorities closed the area surrounding the mountain after being told by geologists. Many people who lived around the area were very unhappy about the closing of the area.
By 18th May the bulge was enormous. By 8:30am ash and steam eruptions were rising from the crater of the volcano. This was the start of a massive explosion.
At 8:32am an earthquake (5 on the Richter scale) caused the bulge to start cracking. The pressure in the bulge was so great it caused a massive landslide. The landslide was made out of soil, glacial ice, snow and rock. The landslide traveled 100mph down the side of the volcano into Spirit Lake. The material with the water flung out of the lake and moved down Toutle valley as a mudflow. It eventually blocked the channel of the Columbia River 60km away from the volcano. This was the biggest landslide ever recorded.
8:33 am the landslide exposed a hole for the magma to escape. Hot volcanic gases, steam, dust and rock fragments flew out of the magma. It moved at speeds over 100kph. It flattened trees 24km away. Everything in its path was destroyed. The type of blast is called a nuee ardente.
The rest of the day the Mount St. Helens deposited ash over the whole area. Deposits were 1cm thick in the town of Yakima. Yakima is 120km away from Mount St. Helens. The air was choked by masses of gas. Volcanic debris from the magma fell onto the remains of the northern slope mountain. These deposits are called bombs or pyroclasts. The swirling ash particles caused lightning to form which started forest fires.
A day later the eruption had stopped. The cloud of ash had spread all the way to the centre of United States. Ash was found in a few cities at the northern – eastern side of United States and some also drifted across the rest of earth within a few weeks. The eruption had turned the area surrounding Mount St. Helens from day to night.
The Aftermath (Effects):
The eruption smashed everything in its way and it took 61 lives away with it. Most of their lives were taken by breathing in hot volcanic ash. More than 200 houses and cabins were destroyed. 185 miles of highways and 15 miles of railways were completely destroyed. 27 bridges were also wrecked.
More than 4 billion feet of commercial timber was damaged and only 25% of the damaged timber could be properly salvaged. It was estimated that 7000 animals were killed. Overall the cost of the destruction was estimated at $1.1 billion.
Many places with crops outside the area were covered with a thin layer of ash. This is a good long term effect because the ash would give the soil many more nutrients. Vehicles could not be used because of the lack of visibility. However it was back to normal after a few weeks.
Even though this eruption was a blow to tourism at that time, it was good for the long term because the area has been treated as a monument and many more people now visit it.
