Slides in this set
Facts about the volcano:
· An active stratovolcano.
· Had fairly symmetrical sides, with alternating layers of lava and ash
· Prior to 1980 the 5th highest peak in Washington. (Before - 9,677ft, after
· Had andesitic lava, common in explosive volcanoes where the viscous
magma blocks the main vent of the volcano
· Began growing around 37,000 years ago one of the youngest in the
Cascade Range. The summit cone started growing less than 3,000 years
ago, also making it the most active within the Cascade Range.…read more
Facts about the 1980 eruption:
· 20th March 1980 a 4.1 magnitude earthquake signalled that the volcano
was active for the first time in more than 100 years.
· All through April, the north side of the volcano grew by up to 5ft a day.
· 18th May 1980 a magnitude 5.1 earthquake triggered the largest
landslide in recorded history as the volcano erupted.
· 57 people killed.
· The lateral blast flattened 9 million m3 of timber, enough to build 300,000
two bedroom houses.
· The most economically damaging volcanic eruption in US history - $2.74
· The eruption column of ash rose over 80,000ft in less than 15mins.
· Released 24 megatons of thermal energy. This is equivalent to 1,600 times
the size of the atomic bomb dropped on Hiroshima.…read more
Landslide debris covered 23 square miles and travelled up to 150mph.
· The lateral blast covered 230 square miles and travelled at least 300mph.
· Lahars travelled up to 50mph, destroying27 bridges and 200 homes.
· Pyroclastic flows reached as far as 5 miles from the crater, travelled
between 50-80mph and reached temperatures of 700°C.…read more