Rocks Igneous Sedimentary Metamorphic Rocks Naturally formed nonliving

Rocks Igneous Sedimentary Metamorphic

Rocks • Naturally formed, nonliving, firm and coherent mass of solid earth material. • Rocks are classified by their origin (how they formed)

Igneous Rocks • • • Form from the crystallization of a molten mixture of minerals and dissolved gasses. magma - molten rock underground lava - molten rock at the surface

• As the molten rock cools, the ions in the liquid slow down and join into molecules of minerals.

Intrusive • If cooling is slow as would happen inside the earth, large/coarse mineral grains will form

Extrusive • If cooling is quick as would happen at or near the surface, small/fine mineral grains will form

• If cooling is too quick, minerals may not form. (amorphous/glassy texture)

• In rare cases, magma begins to cool slowly at depth, then rises quickly and cools forming porphyry.

• If gas bubbles are escaping from lava as it cools, a vesicular texture forms

Composition • The mineral composition of igneous rocks depends on the magma from which it solidifies.

Felsic Magma/Felsic Rocks • • Light color Low density Usually form on continents. Forms rocks that are pink, white, grey

Mafic magma/Mafic Rocks • • Dark color High density Usually form in oceans. Forms rocks that are black, green, dark grey

There’s always an exception • The one exception to this rule is obsidian, which is black in color, but felsic in composition

Using the Earth Science Reference Tables • What can we get from the Earth Science Reference Tables: 1. 2. 3. 4. 5. 6. Environment of formation Texture Grain Size Color Composition Density