- in Columbia
- most northern active volcano in the Andes
- caused by subduction of Nazca Plate beneath the South American Plate
- Forms eastern edge of the Pacific 'Ring of Fire'
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- 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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