Earth Sciences (Rocks and Volcanoes 1)

Flashcards about Igneous Rocks and Volcanoes

Solidus Line

The boundary between the solid and partially liquid state of the mantle.

Decompression Melting

Decrease in pressure with no great change in temperature

Partial Melting

Caused by:
decompression melting

hot mantle plume melting

Fluid flux melting

Hot mantle plume melting

Increase in temperature

Fluid-flux melting

Addition of fluids (water-rich)

Crystallizing magma

Crystals (minerals) + melt (liquid) + gas bubbles (H2O, CO2, SO2)

Bowen’s Reaction Series

As magma cools, minerals crystallize in a systematic fashion.

Magma differentiation

The combination of cooling, crystallization, and melt composition change.

Assimilation

A magma may change composition by incorporating and melting the surrounding host rock

Magma Mixing

A magma may change composition when one magma intrudes into another magma with a different composition.

Batholiths

Very extensive plutons usually assembled over millions of years.

Dikes

Thin magmatic intrusions. Cross-cut existing geological layers. Kind of like veins

Sills

Thin magmatic intrusions. Parallel to existing geological layers. Kind of like veins

Igneous Rocks

form from very hot, liquid (molten) rock called magma

Rock texture

Overall appearance of the rock based on the size, shape, and arrangement of its interlocking crystals; result mainly from different cooling histories.

Rock composition

Composed of minerals – consequence of the chemical makeup of its parent magma.

Step 1 of mafic magma → felsic magma

Partial melting of ultramafic mantle rock generates basaltic
(mafic) magma

Step 2 of mafic magma → felsic magma

Basaltic (mafic) magma buoyantly rises through the lithosphere and ponds beneath less dense crystal rocks

Step 3 of mafic magma → felsic magma

Partial melting of continental crust generates magma with a
felsic-intermediate composition

Pegmatitic texture

Very large grains (<2.5cm). Very slow cooling, typically intrusive.