Shield Volcano – Mafic Lava See how dark the rocks are & how flat the volcano is!. Basic Facts for Shield Volcanoes. Viscosity – low Gas Solubility – low Minerals – Ca feldspar, Olivine & Pyroxene Rocks – Basalt Magma type – Mafic Boundary – Divergent. Lava Tubes.
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Aa – Blocky, sharp, rocks (They got their name because they hurt when you walk on them barefoot.)
Located in Washington, Oregon & Idaho this flood covers 63,000 square miles.
Up to 3000’ thick
Fissure Eruption, Fire Curtain – Iceland 1996
Not always friendly!
Iceland – Laki 1783; huge flood basalt from a fissure eruption, caused an “Iceland Haze” of poison gas of fluorine which killed all the crops & livestock which caused 9000 people (1/4) of Iceland population to die.
1986 Cameroon Africa – Lake Nyos
Gas killed all living things in a 15 mile radius including 1,700 people.
Puu Oo – Hawaii
1902, 26,000 lives lost
nuées ardentes – “glowing clouds”, “ glowing hurricane” – blistering torrents of steam, ash, pumice, and red-hot rock that were coughed from craters and charged down volcanic slopes, obliterating everything in their path. 400 degree dust & ash moving over 100 mph
ember 13, 1985
Happen at Convergent boundary Volcanoes also.
Magma - felsic
Rocks - granite
Viscosity – very high
Gas Solubility – very high
Minerals – quartz, m.mica, k-feldspar
36,000 lost their lives in 1883 most deaths caused by tsunamis which hit 295 towns
Could be heard from 1000 miles away.
Recordable sound waves circles the earth 7 times lasting 5 days.
Ash fell 300 miles away in Singapore.
Rafts of floating pumice thick enough to support people crossed the Indian Ocean in 10 months and were still afloat two years after the eruption.
Killed 100,000 people 15,000 directly & the rest due to starvation