volcanic stones the origins of magma and igneous rocks introduction to geology

Volcanic StonesThe Origins of Magma and Igneous Rocks

Introduction to Geology

The Rock Cycle

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Accumulates into rising magma body

Partial melting of source

Forms magma chamber (solidifies or rises)

Eruption as lava or ash

The Formation of Igneous Rocks

The Origins of Magma

The four main factors that influence the origins of magma are:

* Temperature * Water Content

* Pressure * Mineral Composition

Geologic Settings in which Magma Originates

Magma Formation and the Geothermal Gradient

The Formation of Magma

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The Formation of Magma

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Melting Rocks

Solid

Increasing temperate vibrates atoms and can break bonds

Liquid

Pressure tends to hold lattice together

The Formation of Magma

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Decompression melting

Solid asthenosphere rises to fill gap

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The Formation of Magma

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Sheeted dikes of basalt

Pillow basalt

Gabbro

Mantle

The Formation of Magma

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Dec

ompr

essi

on

Cru

stal

Hea

ting

The Formation of Magma

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Few volcanoes

Burial and heating of crustal rocks

Melting during subduction before collision (but shuts off)

Felsic rocks (granite)

The Formation of Magma

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Oceanic island

Rising mantle plume

Crustal melting and caldera in continent

Huge basalt

flows on continents

The Formation of Magma

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Mafic magma melts crust

Adding water melts mantle

Mostly felsic and intermediate rocks

The Formation of Magma

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Add water to hot mantle

Mostly mafic and intermediate rocks

The Formation of Magma

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Water in minerals released at depth

Hot water circulates in ridge; added in pores and in minerals

The Formation of Magma

Mantle Melting and Plate TectonicsThe Formation of Magma

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Mid-ocean ridge

Oceanic hot spot

Subduction beneath continent

Continental hot spot

Continental collision

Observe these settings where large magma chambers form, and propose causes of melting for each site

The Formation of Magma

Volcanic StonesThe Origins of Magma and Igneous Rocks

This Concludes