Weathering And Erosion

WeatheringWeatheringAnd And

ErosionErosion

WeatheringAnd

Erosion

WeatheringThe breaking down of the Earth’s crust into smaller

pieces. It is caused by physical, chemical, or biological means.

The Different Types of Weathering

Physical WeatheringProcess by which rocks are broken down into smaller pieces by external conditions.

Types of Physical Weathering Frost heaving and frost wedgingPlant rootsFriction and impactBurrowing of animalsTemperature changes

Frost Wedging

Frost Heaving

Frost Action or ice wedging slowly breaks up this sedimentary rock into

unusual shapes.

Root PryThe tree is

growing in the rock and soon the rock will break apart

because of the tree roots.

Plant Roots

Friction and Repeated Impact

Burrowing of Animals

Temperature • Temperature can produce mechanical

weathering. During the day, the sun’s energy heats a rock’s surface. During the night, the rock’s surface cools. The repeated change from hot to cold may cause the rock to peel or flake layers that are parallel to the rock’s surface. This peeling or flaking is known as exfoliation.

Temperature Changes

This is a picture of the

Half Dome. The rock is

peeling away from the

mountain in layers just

like an onion. This is

exfoliation.

These rocks have been blasted by wind and sand causing them to become rounded.

WIND ABRASION

Chemical Weathering• The process that breaks down rock

through chemical changes.• The agents of chemical weathering

– Water– Oxygen– Carbon dioxide– Living organisms– Acid rain

Water• Water weathers rock by dissolving it

Oxygen• Iron combines with

oxygen in the presence of water in a processes called oxidation

• The product of oxidation is rust

This rock is red because of the oxidation of iron in the

sediment when the rock was being formed.

Carbon Dioxide• CO2 dissolves in rain water and creates

carbonic acid• Carbonic acid easily weathers

limestone and marble

Living Organisms• Lichens that grow on rocks produce weak

acids that chemically weather rock

Acid Rain• Compounds from burning coal, oil and gas

react chemically with water forming acids.• Acid rain causes very rapid chemical

weathering

Acid Rain

1908 to 1969

Acid rain has eaten away this limestone statue.

Karst Topography• A type of landscape in rainy regions where

there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams.

• Created by chemical weathering of limestone

Features of Karst: Caves

Features of Karst: Disappearing Streams

Features of Karst: Sinkholes

Erosion• The process by which water, ice, wind or gravity

moves fragments of rock and soil.• Erosion loosens & transports sediment formed by

weathering.

ErosionThere are many kinds of

Erosion.Here are a few:• Wave Action

• Running Water• Landslides

• Avalanche•Glaciers• Slump

•Creep • Rock Fall• Mud Flow

Erosion Moving water & wind cause changes to existing land forms & create new landforms such as valleys, plateaus, flood plains, canyons, caves or dunes

Colorado River as it winds its way through the Grand Canyon.

Grand Falls, near Leup, Arizona

Water Erosion

• Rivers, streams, and runoff

Wave action is when waves hit the rocks and pieces of rock

break off.

In this picture the running water eroded the sides of

this canyon and created the V-shaped valleys.

Ice Erosion

• Glaciers

This is a picture of a glacier which carves out a U-shaped valley

where it flows dragging rocks and boulders along the way.

Wind Erosion

Mass Movements• Landslides, mudslides, slump and creep

This is a picture of a landslide. A type of mass

wasting.

This is a picture of an avalanche. It is similar to a landslide with ice and

snow instead of rock.

Mudslide

This is a diagram of creep. The hillside slowly slips over many

years from temperature or water.

Creep

In this picture the land has slumped

into the road below.