Chapter 4

The Rock Cycle

• Make sure your rock cycle is drawn!!

The Rock Cycle

• Processes that shape the earth– Weathering- water, wind, ice, and heat break

down rock– Erosion- process where water, wind, ice or gravity

transports soil and sediment from one location to another

– Deposition- process which material is at rest– Uplift- process where movement in the earth

causes rocks from the inside of earth to move

The Rock Cycle

• Pg 92-93

The Rock Cycle

• Various paths to the rock cycle- pg 94• The rock cycle can vary and change in different

ways.• Three rock types– Sedimentary– Igneous– Metamorphic

Rock Cycle

After rock is classified into one of the 3 rock types it can be classified further- Composition- chemical makeup of a rock- Texture- size, shape, or position of a rock’s

grains

Igneous Rock

• Igneous rock begins as magma• Magma can form by– When rock is heated– When pressure is released– When rock changes compositions

Igneous Rock

• Composition and texture of igneous rock– Light colored rocks-less dense, rich in aluminum,

potassium, silicon, and sodium called felsic rocks– Dark colored rocks- mafic rocks, rich in calcium,

iron, and magnesium– Texture determined by how fast magma cools

Igneous Rock

• Igneous Rock Formations– Intrusive igneous rock: course grained texture,

cools slowly, pushes into rock below– Extrusive igneous rock: forms from magma that

erupts, cools rapidly

Sedimentary Rock

• Sedimentary rock forms near the surface of earth

• Materials that have been weathered form a natural cement that bonds rock and mineral fragments together

• Strata- most noticeable feature- layers

Sedimentary Rock

• Composition of Sedimentary rock- classified by way it is formed– Clastic- fragments of minerals together– Chemical- forms from solutions of dissolved

minerals and water– Organic- formed from fossils (limestone or coral)

coal is also organic

Sedimentary Rock

• Sedimentary rock structures– Most important feature of sedimentary rock-

stratification- rocks in layers– Sed. Rocks sometimes record motion of wind on

lakes, oceans, rivers, and sand dunes in features called ripple marks

– Mud cracks form when find grained sediments at the bottom of water are exposed to the air and dry out.

Metamorphic Rock

• Rocks in which the structure, texture, or composition have been changed.

• Contact metamorphism- heated with nearby magma, occurs near igneous intrusions

• Regional metamorphism- pressure builds up in a rock that is deep below the surface, occurs a distance away from earth’s surface

Metamorphic Rock

• Composition: occurs when temperature or pressure inside the earth’s crust change

• Texture: – Foliated- mineral grains arranged in planes or

bands – Nonfoliated- mineral grains not arranged in planes

or bands

Metamorphic Rock

• Deformation- change in the shape of a rock caused by a force placed on it. Folds or bends indicate a rock has been deformed.