Mt. St. Helens
Overview:
On the morning of May 18, 1980, Mt. St. Helens in Washington, USA erupted, causing immense damage to surrounding areas, affecting even those more than 100 kilometres away. Small tremors had occurred frequently in the previous months, and after a long period of increasing pressure, the volcano that had been dormant for over 100 years finally gave way to a massive explosion. At 8:30 a.m, ash and steam erupted violently, followed by a landslide composed of rock, glacier ice and soil, which sped downwards, overflowing Spirit Lake and continuing all the way to Portland. Exposed magma exploded laterally, releasing volcanic gases, steam, dust and volcanic bombs of rock.
Causes:
Mt. St. Helens in one of the many peaks in the mountain range known as the Cascades along the West Coast of the US. The Cascades are formed by the destructive margin between the Juan de Fuca and North American plates. The Juan de Fuca plate moves eastwards, and being made of oceanic crust, subducts under the North American plate, which caused it to buckle and form fold mountains: the Cascades. This tectonic movement resulted in the formation of Mt. St. Helens. Friction between the two plates cause and caused occasional earthquakes, when on May 18, 1980, an earthquake of magnitude 5 on the Richter scale triggered volcanic movement within Mt. St. Helens' mountainous body, which resulted in disastrous consequences.
Impacts:
Environmental: Mt. St. Helens itself was reduced by 390 metres due to the violent eruption. A horseshoe-shaped crater was formed; 3 kilometres long by 500 metres long, it resembled an ancient ampitheatre. The ash, dust and rocks which reached into the surrounding waterways chocked the channels, killing all fish in the area, including valuable salmon and trout. Every single tree within a 25 kilometre radius of the blast was flattened and destroyed, also causing log jams in nearby rivers. Similar to the trees, all wildlife was obliterated by the eruption.
Social: Statistics show that 61 humans died, the majority being caused by the toxic gases carried by the eruption. Settlements including several logging camps were destroyed, although fortunately not many were present at the time. Electricity supplies and telephone wires were also interrupted, and roads and bridges were hindered by the ash. Flooding and dust wrecked 12% of the local crops.
On the morning of May 18, 1980, Mt. St. Helens in Washington, USA erupted, causing immense damage to surrounding areas, affecting even those more than 100 kilometres away. Small tremors had occurred frequently in the previous months, and after a long period of increasing pressure, the volcano that had been dormant for over 100 years finally gave way to a massive explosion. At 8:30 a.m, ash and steam erupted violently, followed by a landslide composed of rock, glacier ice and soil, which sped downwards, overflowing Spirit Lake and continuing all the way to Portland. Exposed magma exploded laterally, releasing volcanic gases, steam, dust and volcanic bombs of rock.
Causes:
Mt. St. Helens in one of the many peaks in the mountain range known as the Cascades along the West Coast of the US. The Cascades are formed by the destructive margin between the Juan de Fuca and North American plates. The Juan de Fuca plate moves eastwards, and being made of oceanic crust, subducts under the North American plate, which caused it to buckle and form fold mountains: the Cascades. This tectonic movement resulted in the formation of Mt. St. Helens. Friction between the two plates cause and caused occasional earthquakes, when on May 18, 1980, an earthquake of magnitude 5 on the Richter scale triggered volcanic movement within Mt. St. Helens' mountainous body, which resulted in disastrous consequences.
Impacts:
Environmental: Mt. St. Helens itself was reduced by 390 metres due to the violent eruption. A horseshoe-shaped crater was formed; 3 kilometres long by 500 metres long, it resembled an ancient ampitheatre. The ash, dust and rocks which reached into the surrounding waterways chocked the channels, killing all fish in the area, including valuable salmon and trout. Every single tree within a 25 kilometre radius of the blast was flattened and destroyed, also causing log jams in nearby rivers. Similar to the trees, all wildlife was obliterated by the eruption.
Social: Statistics show that 61 humans died, the majority being caused by the toxic gases carried by the eruption. Settlements including several logging camps were destroyed, although fortunately not many were present at the time. Electricity supplies and telephone wires were also interrupted, and roads and bridges were hindered by the ash. Flooding and dust wrecked 12% of the local crops.
<--- Horseshoe crater
<--- Juan de Fuca/North American plate boundary
<--- Destruction caused by eruption