Igneous Sedimentary Metamorphic 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 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: Environment of formation Texture Grain Size Color Composition Density