Shield volcano mafic lava see how dark the rocks are how flat the volcano is
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Shield Volcano – Mafic Lava See how dark the rocks are & how flat the volcano is! PowerPoint PPT Presentation


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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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Shield Volcano – Mafic Lava See how dark the rocks are & how flat the volcano is!

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Shield Volcano – Mafic LavaSee 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


Pahoehoe –rocks that are ropy & smooth.


Aa – Blocky, sharp, rocks (They got their name because they hurt when you walk on them barefoot.)


Flood Basalts happen when a Shield volcano pours out very large amounts of lava.

Located in Washington, Oregon & Idaho this flood covers 63,000 square miles.

Up to 3000’ thick


Fissure Eruptions, Curtains, and fountains – These are all “calm” volcanic features!

Fissure

Fountain

Curtain

Of fire


Hawaiian Eruptions

  • Calm

  • Fluid Lava Flows

  • Out-pouring of basaltic lava


Pele’s, the Hawaiian Goddess of Fire, Tears & Hair

Hair

Tears


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.


Ediface Collapse – this is on the edge of the Pacific Ocean


Fumarole: aka: Poison gas

1986 Cameroon Africa – Lake Nyos

Gas killed all living things in a 15 mile radius including 1,700 people.


Cinder ConesHot – the same as Shield Volcanoes except they are rock pieces & not lava flows!

Paricutin

Puu Oo – Hawaii

Parasitic –


Strombolian

  • short-lived,

  • explosive outbursts of pasty lava

  • Do not make pele’s tears or hair

  • dominated by scoria/tephra fragments

  • little or no flowing lava


Composite Volcano – Felsic & Intermediate Lava


Basic Facts - Composite

  • Viscosity - high

  • Gas Solubility - high

  • Minerals – quartz, m.mica & K-feldspar

  • Rocks - granite

  • Boundary – convergent (continent to ocean or ocean to ocean)

  • Magma - felsic


Plinian Eruption – Huge plumes of ash thrown into the Stratosphere.

  • Vesuvius – 79 AD

  • 2000 people died – covered in ash

  • Mt. St. Helen’s – 1980

  • 57 lives lost


Mt. Pelee, Nuee Ardenteaka: Pyroclastic Flows, pelean

Mt. Pelee

1902, 26,000 lives lost


Nuee Ardente

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


Laharsaka: flood

Mud Flow

Debris Flow


Lahar at Mt. St. Helens

  • The lahar carries away a bridge spanning the Toutle River about 20 miles downstream from Mount St. Helens volcano on May 18, 1980.


Deadly Lahars from Nevado del Ruiz, ColombiaNovember 13, 1985

  • Río Lagunillas, Within four hours of the beginning of the eruption, lahars had traveled 60 miles and left behind a wake of destruction: more than 23,000 people killed, and most of the town destroyed.

ember 13, 1985


Tephra aka:flying rock pieces

Ash

Bombs

Block


Fumarole: aka: Poison gas

Happen at Convergent boundary Volcanoes also.


Rhyolite Caldera Complex

Magma - felsic

Rocks - granite

Viscosity – very high

Gas Solubility – very high

Minerals – quartz, m.mica, k-feldspar


Krakatoa-phreatic explosionaka:steam eruption


Krakatoa

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.


Tambora

  • The caldera is over 3,000’ deep

  • And 5 miles in diameter

Killed 100,000 people 15,000 directly & the rest due to starvation


  • Rain, Rain Go Away - Ireland experienced persistent cold rain for 142 of the 153 summer days. The cold weather destroyed their wheat, oat and potato crops.

  • Hungary, January 1816 - Brown Snow?In January 1816, a blizzard of brown snow hit Hungary.

  • Britain, Autumn 1815 - In response to the food shortage caused by the “Year without Summer”, the British government abolished income taxes in 1816.

Tambora A Year Without Summer


Yellowstone National ParkPerhaps the largest volcano in the USA


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