caused by subduction of Nazca Plate beneath the South American Plate
Forms eastern edge of the Pacific 'Ring of Fire'
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Eruption
Main eruption - 13th Nov. 1985
column of ash sent 8km skywards
Lava fragments fell onto the snow and ice around the summit
causing it to melt rapidly = millions of cubic meters swept down the side of the volcano and into the surrounding valleys
Wave of mud (or lahar) 30m deep containing glacier ice, large boulders and scalding fragments of fresh lava poured down the Lagunillas valley at 50km/h.
Town of Armero with 22000 inhabitants was destroyed
within seconds buildings were flattened or buried
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Local farmers were reluctant to leave their prosperous farms
At first there was no lava, but rocks were hurled out, dense ash and sulphur cloud rose 8km into the air - drifted 500km to the Venezuelan border - covered most of the surrounding countryside in an ash layer
The heat rapidly melted ice and snow
flood waters rushed down the local rivers sweeping away houses and bridges
The eruption dislodged ancient layers of volcanic dust, this combined with the flood waters formed an unstable volcanic mud which began to flow rapidly down the mountain.
it reached speeds of +100km/h, one flow engulfed the town of Armero
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Death toll: 22,000 = worst volcanic eruption since 1902 mount Pelée
Columbian government declared the area under military control and appealed for help
The Red Cross and UN leaning from previous disasters co-ordinated their efforts and flew in medical supplies, tents, digging equipment and personnel
The thin mountain air and thick dust made it difficult for rescue helicopters to operate + destroyed bridges made it hard for rescuers to reach the worst hit areas + shortage of hand radios for communication = bad effect on the rescue effort
The spirit of the Columbian people was one of the best resources as they we hard at work etc.
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