Volcanoes March 2012

Eruption Types 1. Explosive ejects gases, ash, and pyroclastics shot into air and across ground caused by lots of water and gases trapped in magma

Eruption Types 2. Nonexplosive lava runs down the slopes of the volcano

Forming Volcanoes 1. Subduction Zone-most volcanoes formed this way (plate boundary) -one plate melts as it goes under the other, magma rises upward

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Forming Volcanoes 2. Hot Spots - located in middle of plates, not boundary -very thin crust allows magma to rise up, volcano forms, crust moves, starts over

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Types of Volcanoes 1. Shield Volcano Nonexplosive eruptions –Layer upon layer of hardened lava Gradual sloping sides, but can be enormous in size

Mt Etna and Mauna Kea Mt. Etna in Italy-notice how broad it is; this volcano is south of Vesuvius on the island of Sicily Mauna Loa-part of Mauna Kea, which is the largest mountain on Earth when measured from the ocean floor

Types of Volcanoes 2. Cinder Cone Volcano explosive eruptions –Layer upon layer of pyroclastics Erode quickly because they are not “glued” together by lava

Paricutin-Mexico Paricutin erupting at night. The volcano ejected materials from a hole in a cornfield until it covered a whole town. The tower from this church is all that is left of town.

Types of Volcanoes 3.Composite Volcano (aka: Statro volcano) Made from explosive and non-explosive eruptions Alternating layers of lava and pyroclastics

Stratovolcanoes Mt. St. Helens, May 18, 1980 Mt Vesuvius, Italy- notice all of the buildings and people that surround the volcano.

Predicting Eruptions Volcanologists look for: 1. 1.Faults – the Earth cracks when pressure builds up 2. 2.Gases – content and amount of gases Rockfall (RF) – landslides/deformation 4. 4.Volcano Tectonics (VT) – earthquakes in volcano

Volcanoes and Global Cooling Explosive eruptions have released enough gases and ash into the atmosphere to effect weather globally by blocking the sun’s heat

Picture Time This is some of the damage from Mt. St. Helens in May of That is volcanic ash on the right, not snow.

Iceland, Heimaey The people of Iceland live in very close proximity to many volcanoes.

Iceland-Cold with Volcanoes Volcanoes UNDER the glaciers melt the ice and make glacial lakes. This is a cinder cone volcano; it just happens to be quiet and snowy for the moment.

Surtsey, Iceland Surtsey appeared off the coast of Iceland in In four years, the island was 1 sq. mile and had elevations of 560 feet!

Mt. Etna, Italy This is just a really cool picture of lava from Mt. Etna.

Pacific Ring of Fire

Pacific Hot Spots