I. How to Identify Rocks?

1. Composition

The chemical makeup of a rock.

Scientist study rock by looking at two types of criteria: composition and texture.

I. How to Identify Rocks?

2. Texture: Is based on the size shape and position of mineral grain/crystals.

Scientist study rock by looking at two types of criteria: composition and texture.

II. 3 Ways Magma Forms

III. Texture

Igneous pattern Metamorphic pattern Sedimentary pattern

A. Texture of Igneous Rock1. Intrusive Igneous Rock

Rock formed from the cooling and solidification of magma beneath the Earth’s surface.

Slow cooling results in the formation of large crystals.

(Coarse-grained Texture)

Interactive Rock Sim

A. Texture of Igneous Rock2. Extrusive Igneous Rock

Rock that forms as a result of volcanic activity at or near the Earth’s surface

Fast cooling results in the formation of small crystals.

(Fine-grained Texture)

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Interactive Rock Sim

Four Igneous Rocks Web Activity

1. Felsic Rock Light colored

rocks. Composed of

aluminum, potassium, silicon, and sodium.

2. Mafic Rock Dark colored

rocks. Composed of

calcium, iron, and magnesium.

Course-grained Fine-grained

Course-grained Fine-grained

B. Composition of Igneous Rock