Background information

Mount Saint Helen’s which erupted on the 18th of May 1980 at 8:32 Sunday morning, it caused a major catastrophic for its surroundings. Mount Saint Helen’s which is at United States in Washington, in northwestern United States. The volcano which is 9,677 feet high was reduced to 8,364 feet after the eruption. It erupted on the north side of the mountain and after it erupted 400 meters of the mountain had been blasted off, from America’s 9th highest peak into 30th highest peak. The longitude and latitude on the mountain is 46.2 degrees north and 122.2 degrees west.

It is on a destructive plate boundary. Oceanic plate called the Juan de Fuca plate is subducting under the continental plate called the North America plate, which means the Juan de Fuca plate in sliding under the North America plate. Which means the melting point is directly below the volcano. This volcano is in a part of the Pacific “Ring of Fire”. Mount Saint Helen’s is a composite volcano otherwise called a stratovolcano. Composite volcanoes are well known for its destructive eruptions. There was mudflow, pyroclastic flow, ash and landslides. The landslide came from the north side of the volcano. It split into three parts, one hit the Sprite Lake which caused waves to splash 225 to 275 meters high and raised the lake level by 60m. One traveled for surged up and over a 400-m-tall located 8 km due north of the volcano. The final and largest part of the landslide was diverted west by and slid 22 km down the North Fork Toutle River.

Types of hazard effects on the environment

As the north face of the mountain collapsed, expanding gases (pyroclastic flow) and steam from the molten rock hurtled rock and ash out across the land at speeds up to 670 miles per hour uprooting trees as far as 6 miles from the mountain. In would have been impossible to outrun it even in a helicopter. It is estimated that 5,000 black-tailed deer, 1,500 Roosevelt elk, 200 black bears, and 15 mountain goats fell victim along all the living organisms in the Sprite Lake just under the volcano. The pyroclastic flow went for about 5 miles north from the crater destroying everything in its way, the temperature of these pyroclastic flows was extremely hot — more than 1200 degrees Fahrenheit.

The lava melted the snow and ice on the carter therefore creating a mudflow, flowing at speeds up to 130 kilometers per hour. It reached up to a height of 60 feet. It uprooted trees, destroyed roads and bridges 40 miles down steam, and buried everything in their paths. The mudflow went over hills as high as 250 feet.

Effects on people

The major cause of the deaths is the pyroclastic. In all the eruption killed 57 people, destroyed; 250 homes, 47 bridges, 15 miles (24 km) of railways, and 185 miles (300 km) of highway were destroyed mostly by the mudflow, a bit of the pyroclastic flow and the landslide. 2000 people were evacuated from near by regions. The estimate cost for the damage is $1.1 billion for timber, civil works and agricultural losses. This does not include money for personal property losses, the cost of ash clean-up, or the loss of tourism in the area immediately after the eruption.

The eruption covered about 390 square kilometers and also sending 540 million tons of ash into the upper atmosphere there as darkening the day to the east of the volcano for more than 200 kilometers. The massive ash cloud grew to 80,000 feet (18 kilometers) in 15 minutes.  Although most of the ash fell within 300 miles of the mountain the people or animals trapped in them would certain choke and suffocate to death.

Eyewitness account

This is an eyewitness account by John l. in his helicopter,” it was a bright Sunday when suddenly the came a massive sound. As I was observing the volcano I knew it was erupting, my heart skipped a beat as the lava and ash came shooting out of the composite volcano along molten rocks. Although I could not feel it, because I was in the air, but the ground was shaking like mad. Later I found out it was at 5.1 magnitudes. The mudflow was the worst part, the brown coloured water, debris and other. The landslid creating the massive splash in the Sprite Lake was very loud. The pyroclastic flow was vaporizing everything in its path nothing stood a chance. The noise of the volcano was as loud as 100 rockets blasting off at the same time. I became deaf for a while after the eruption. Of cause it was very scary I keep on thinking that I was going to die of sure but I came out alive.”