Weathering and Erosion

Weathering and Erosion

Mr.Mendoza

What is Weathering?

Is the breaking down and changing of rocks near Earth’s surface

Two Types:

Mechanical (physical)  

Chemical

What is Mechanical Weathering?

Physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition.

Three Types of

Mechanical Weathering

Frost Wedging

Unloading

Biological Activity

Frost Wedging

Expansion of freezing water in cracks and crevices

Eventually breaking rocks into pieces

Sections of rock that are wedged loose are called talus

Unloading

The uplift and erosion of rocks overlying igneous rocks because pressure on igneous rocks is reduced

Exfoliation—slabs of outer rock separate and break loose

Biological Activity

The activity of organisms, including plants, burrowing animals, and humans

Plant roots wedge into rocks breaking them apart

What is Chemical Weathering?

the transformation of rock into one or more new compounds.

Chemical Weathering: Water

Water dissolves minerals and rocks.

-This results in the formation of clay minerals.

Chemical Weathering: Oxygen

Oxygen in atmosphere combines with iron in rocks & minerals.This results in rust (red rocks).

Chemical Weathering: Carbon Dioxide

Carbon Dioxide combines with water (H2O) in atmosphere or soil forming weak carbonic acid. This results in clay or caves.

Chemical Weathering: Acid Precipitation

Acid precipitation … rain, snow, sleet mixed with gases in the atmosphere that turn these forms of water into a weak acid (pH < 5.0).

Chemical Weathering: Acid Precipitation

sulfur dioxide and nitrogen oxide The most common source – coal-fired power plants

It is also known as acid rain

Chemical Weathering: Acid Precipitation

It causes lakes to become more acidic than living things can handle. AND… It chemically weathers nonliving things like statues and buildings

Erosion

The wearing away and moving of surface materials by gravity, water, wind, or glaciers.

The wearing away and moving of surface materials by gravity, water, wind, or glaciers.

4 Agents of Erosion: 

1.Wind

2.Water

3.Gravity

4.Glaciers