Presentation on theme: "The Mt St Helens Eruption May 18, 1980 Where is it? Mount St Helens in the USA has been one of the most covered volcanoes in recent years. In 1980, witnesses."— Presentation transcript:
Where is it? Mount St Helens in the USA has been one of the most covered volcanoes in recent years. In 1980, witnesses watched and filmed as the volcano erupted – killing people and creating much disaster and destruction
Mt St Helens is an active volcano in the Cascade Range of the northwestern United States. After being inactive since 1857, the mountain erupted in May 1980, causing 57 deaths and extensive damage in southwest Washington state.volcanoCascade RangeUnited StatesmountainWashington
How do volcanoes erupt? All volcanic eruptions begin deep in the earth. Magma (molten rock beneath the ground) begins to become pressurised and tries to push a path to the surface through the other rock. Sometimes this causes the top of the volcano to grow and to expand.
How do volcanoes erupt? Eventually the pressure and gas build up within the volcano becomes too much and the Volcano will blow its top The volcano will then send gas, dust, volcanic bombs, ash and lava into the air
Pyroclastic flows Within a few hours of the blast – hot mixtures of volcanic gas, pumice and ash swept down the north flank of the volcano at speeds of up to 100 miles per hour. The temp of these was more than 1200 degress Fahrenheit North of the volcano these flows deposited pumice that is up to 60 feet thick The blast from the volcano reached as far as 16 miles north of the volcano. It spread over an area of about 150 sq miles The blast stripped trees from hillsides as far away as 6 miles from the volcano