Rocks

RocksMixture of two or more different minerals that have been: cemented togethersqueezed and heated together

melted and cooled together

The Rock Cycle The diagram of the rock cycle shows

how rocks change slowly over time.

Types of Rocks1. Igneous 2. Metamorphic 3.

Sedimentary

1. Igneous Rocks

Most igneous rocks are produced deep underground by the cooling and hardening of magma (melted rock).

“Igneous” comes from Latin for “fire”

1. Granite 2. Obsidian 3. Pumice

Formation of Igneous Rocks

A. Intrusive Rocks- form from magma that cools below

the surface of the earth. Ex. Granite

B. Extrusive Rocks- form as lava cools on the surface of

the earth.

Ex. Obsidian

Examples: Formation of Igneous Rock

-Extrusive- Formed from lava; volcanic

Intrusive- Formed deep within the earth

Obsidian Pumice

Granite

Textures of Igneous Rock 1. Glassy

3. Fine-grained

2. Coarse-grained

Obsidian Granite

Basalt

2. Metamorphic Rocks Formed from heat and pressure

changing the original or parent rock into a completely new rock. The parent rock can be either sedimentary, igneous, or even another metamorphic rock.

1. Schist 2. Marble 3. Slate

Classifying Metamorphic Rocks

1. Foliated- when mineral grains flatten and line up in parallel layers.

2. Unfoliated-when mineral grains grow and rearrange but do not form layers.

Foliated

Gneiss

Unfoliated

Marble

3. Sedimentary Rocks Form when sediments are

pressed and cemented together, or when minerals form from solutions.

Usually consist of layers

1. Siltsone2. Conglomerate

3. Shale

Classification of Sedimentary Rocks

1. Detrital Sed. Rocks- (Clastic Rocks)- Made of the broken fragments of other rocks.

A. Weathering- the process of breaking rocks into smaller pieces. Happens when rock is exposed to air, water, or ice.

B. Erosion- the movement of weathered material.

C. Compaction- when the sediments stick together and

form solid rock.

D. Cementation- when large sediments are held together

by natural cements that are produced when water soaks through

rock and soil.

E. Shape & Size-

1. Conglomerate- when the sediments are rounded

2. Breccia- when the sediments have sharp

angles.

Clastic Rocks Conglomerate

1. Sandstone

2. Mudstone

2. Chemical Sed. Rocks- Formed when dissolved material

comes out of solution by inorganic processes such as

evaporation.

Examples are

1. Limestone

and

2. Rock Salt

3. Organic Sedimentary Rocks- Rocks made

from the remains of once-living things

Coquina

Organic Sed. Rock Examples

1.

Chalk

2. Coal

Fact about the Mississippi River

Did You Know?

The Mississippi River carries an average of 436,000 tons of sediment each day

It moves an average of 159,000,000 tons of sediment a year

Distribution of Rocks in the U.S.