Rocks, Rocks, and More Rocks

Types of Rocks

• Igneous rock– Forms when magma cools and hardens – Can form underground or above ground– Types of igneous rock:

• Granite• Scoria• Pumice• Obsidian

Pumice

ObsidianScoria

• Wind and water can break igneous rock into sediments.

• When the sediments are cemented into a layer over time, igneous rock becomes sedimentary rock.

• What causes the cementation?

Types of Rocks

Sedimentary Rock

SedimentsIgneous Rock

Wind and Water

Cementation

Types of Rocks

• Sedimentary Rock– Common types include chalk, limestone, and

clay– Often contains fossils – Types of Sedimentary rocks

• Clastic: made up of different rock fragments• Biogenic: contain materials from organisms such

as corals• Precipitate: rocks formed when water evaporates

such as halite (rock salt left behind after sea water evaporates)

Types of Rocks

• Weathering and erosion will revert sedimentary rocks back to sediments.

• Heat and pressure change sedimentary rock to metamorphic rock.

Metamorphic Rock

Sedimentary Rock

Sediments

Weathering and Erosion

Heat and Pressure

Types of Rocks

• Metamorphic Rock– Make up a large part of the Earth’s crust– Common examples include slate, shale, and

mudstone– Can go through foliation, a process where the

randomly distributed minerals in the rock become organized in a parallel manner

– Foliation can cause cleavage or breakage of the rock at weak cracks

Foliation

The disorganized minerals become more organized.

Cleavage

Weak areas are prone to breakage.

Types of Rocks

Metamorphic Rock

Sediments MagmaWeathering

and Erosion

• Very high heat melts metamorphic rock into magma.

• Weathering and erosion will change metamorphic rock back to sediments.

Melting

Magma (molten rock)

• A hot liquid made of melted minerals

• Called lava when it appears on Earth’s surface, usually from volcanic vents

• The temperature of magma can range from 650 to 1200 °C

• Created by heating rock under extreme temperatures

• Cooling magma creates igneous rock

What do compaction and

cementation do to sediments?

What does melting metamorphic rock

create?

What does cooling magma create?

What do weathering and erosion do to all types of rock?

What does the melting of igneous

rock create?

Rock Cycle

Igneous Igneous RockRock

Metamorphic Metamorphic RockRock

SedimentsSediments

Sedimentary Sedimentary RockRock

MagmaMagmaWhat do

weathering and erosion do to this

type of rock?

What do heat and pressure to do

sedimentary rock?

Weathering and Erosion

Heat and Pressure

Cementation

Cooling

Melting

Which rock becomes metamorphic rock

under heat and pressure?

Minerals

• Rocks are made up of one or more types of minerals.

• True minerals have the following characteristics:– Solid– Have a crystal structure– Inorganic and naturally occuring– Defined chemical composition

Minerals

• Ways to classify minerals:– Hardness: how hard the material is– Luster: how the surface interacts with light– Metallic: metallic qualities such as

reflectivity– Color: what color the material is– Magnetism: the rock’s ability to attract other

metals– Fluorescence: appearance under UV light

Erosion

• Erosion is the movement of particles by wind, water, ice, or gravity.

• Erosion is a natural process that can be increased by human land use.

• Steep slopes, lack of vegetation, and land use can increase the rate of erosion.

• How does erosion differ from weathering?

Erosion

Erosion

• Types of erosion include:– Gravity erosion– Water erosion– Shoreline erosion– Ice erosion– Wind erosion

• Can you explain what occurs in each of these types of erosion?