Chapter 8- Earth Sciences

Front 1

Definitions

Back 1

Front 2

Magma is formed (rocks melt) as a result of:

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Increasing temperature, decreasing pressure, and addition of water

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3 plate tectonic settings where magma is formed.

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Spreading centers, subduction zones, mantle plumes.

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What depth does magma form?

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50-200 km below the surface. In the lower crust and upper mantle

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Gasses given off by volcanoes..

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70%-water vapor

20%- carbon dioxide

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Acasta Gneiss

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Oldest known Rock. Located in Canada. 4.03 GA

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Oldest geological materials

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Zircon crystals from Australia. 4.2- 4.4 Ga

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Acasta Gneiss and zircon crystals

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Indicate there was continental crust more than 4 billion years ago.

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Increase in Silica content of mama increases magma _______ ?

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Viscosity

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Batholith

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A granitic pluton that is exposed for more than 100 square kilometers

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Enchanted Rock

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A batholith exposed in the llano uplift in Central TX

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Lave

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Magma that reaches the earth's surface

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2 types of basaltic lava

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Pahoehoe and Aa Aa

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Pyroclastics

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Solid materials (ash, cinders, bombs) from explosive eruptions.

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Flood Basalts

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Huge flows of basalt from cracks and fissures on land

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Mauna Loa and Mauna kea

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Both are shield volcanoes in Hawaii

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Cinder cone

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Small volcano composed of pyroclastic fragments

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Composite volcanoes (stratovocanoes)

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Consist of Alternating layers of lava and pyroclastics

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Mt St. Helen's and Mt. Hood

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Both stratovolcanoes in the cascade Mt, western US

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Mt. Vesuvius

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Stratovolcano near Naples, Italy

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Ash flows

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Extremely rapid flows of pyroclastic materials and gas

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Caldera

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The very large, circular depression left when the summit of a volcano collapses.

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The largest volcanic eruptions in the US in the last 2.1 Ma occurred WHERE?

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Yellowstone

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How can volcanic eruptions affect climate?

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Make it cooler or warmer