Mt St Helens 1980 0.0 / 5 ? GeographyPlate tectonicsA2/A-levelAQA Created by: andrew0699Created on: 31-05-17 10:31 Why was it vulnerable? destructive plate margin, Juan de fuca < north american plate - composite volcano 1 of 19 The main eruption? 5.1 magnitude - 600km2 blast zone (rocks/ash/lava) 2 of 19 Pyrochastic flow? pyrochastic flows, lahars and mud flows entered river channels and lakes 3 of 19 Ash? 540 million tonnes over 57,000km 4 of 19 Cost? $1.1 billion + $2.2 million to clear away ash 5 of 19 Transport? 1000 flights cancelled 6 of 19 Infrastructure? 27 bridges, 300 km roads and 24km railways 7 of 19 Rivers? mudflows and sediment caused river traffic 8 of 19 Deaths? 57 9 of 19 Homeless? 100's 10 of 19 Unemployment? rapidly rose but did return to normal 11 of 19 Forest? 240km destroyed 12 of 19 Wildlife? 7000 big game animals and 12 million young salmon 13 of 19 Lakes? the sediment and material deposited rose water level by 60m 14 of 19 Ash managment face mask were distributed and 900,000 tonnes of ask moved from transport networks 15 of 19 Shipping channels? lots of dredging or new channels 16 of 19 Deforestation management? 18.4million trees planted 17 of 19 What did USGS do? monitored 24/7 e.g. bulges/gases/temp and issued daily reports - despite this they couldn't accurately predict the eruption 18 of 19 USGS action? located hazard zones to restrict access to areas and began evacuations 19 of 19
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