Igneous Rocks

Flashcards about Igneous Rocks

Igneous Rock

Form from freezing of molten rock

Sedimentary Rock

Form from cementing or precipitating of other rocks, minerals, chemicals

Metamorphic Rock

Form from one rock changing to another from high heat/pressure

Magma

Melted rock below ground

Lava

Melted rock above ground

Extrusive Igneous Rock

Rocks that freeze in air or water above ground (Lava flows, Volcanic ash, Pyroclastic debris)

Intrusive Igneous Rock

Rocks that freeze slowly below ground

Decompression Melting

A way rocks can melt; occurs when pressure decreases

Magma Composition Factors

Source compositions, partial melting, mixing of magmas

Felsic Magma

Silica content of 66-76%

Intermediate Magma

Silica content of 52-66%

Mafic Magma

Silica content of 45-52%

Ultramafic Magma

Silica content of 38-45%

Viscosity

Controls how fast/easily magma flows

Fractional Crystallization

As different minerals crystallize, the magma changes its composition

Extrusive Rock Textures

Glassy (obsidian) or full of holes (pumice)

Sills

Horizontal intrusions of magma

Dikes

Vertical intrusions of magma

Plutons/Laccoliths/Batholiths

Frozen remnants of ancient magma chambers

Phaneritic Texture

Can see the crystals

Aphanitic Texture

Cannot see crystals

Porphyritic Texture

2 distinct sizes of crystals

Fragmental Texture

Made of small bits of volcanic rock

Glassy Texture

"Shock" frozen igneous rocks