Weathering Ch. 10

By: Kelsey Bowman and Tiffany Gee

What is weathering?• Weathering is the breakdown of

rock into smaller pieces.

What are the two types of weathering?

• The two types of weathering are chemical and mechanical. – Chemical weathering is the breaking

down of rock and minerals into new substances by chemical means.

–Mechanical weathering is the breaking down of rock into small pieces by physical means.

Mechanical Weathering • Abrasion is the action of rocks and

sediments grinding against each other and the wearing away of exposed surfaces.

– For example, abrasion occurs in the body of rivers when rocks and pebbles roll along the bottom. They eventually become river rocks.

Mechanical Weathering cont.• Mechanical weathering also occurs

with plants and animals.

– The root wedging in plants is an example of mechanical weathering.

– Ice wedging is the process of which water seeps into a crack in a rock and freezes. This is a form of mechanical weathering.

– Earthworms separating the soil is also an example of mechanical weathering.

Chemical Weathering• Acid precipitation contains acid

that is a form of chemical weathering.– For example, acid precipitation occurs in bronze statues.

It also occurs in granite and makes the bonds between mineral grains weaken as chemical weathering continues.

How does rust form?• Oxidation is the chemical reaction

in which an element such as iron combines with oxygen to form an oxide. Rust is the most familiar result of oxidation.

Caves• Caves are a form of chemical

weathering

Differential Weathering• The process by which softer, less

weather-resistant rocks wear away, leaving harder, more weather-resistant rocks behind.

– For example, the Devil’s Tower is a landform known as a volcanic neck. When the molten solidified it was protected from weathering by the softer rock of the volcano.

What are soil and bedrock?• Soil is a loose mixture of small mineral

fragments and organic material.

• Beneath the soil, is a layer of rock know as bedrock.

• Sources of soil: parent rock. This rock forms from granite that forms from limestone soil.

Things that involve soil:

• Humus is small particles of decay plant and animal material. Humus is located in Horizon A which is a layer of topsoil.

– Topsoil is the top layer of soil.

– When rainwater travels down through the horizons of the soil, it dissolves the nutrients and minerals which is known as the process of leaching.

The Importance of soil:• It’s very important for our soil to be

taken care of, because it has many benefits for our planet.

– One way you can help the soil is by soil conservation. This is the various methods by which humans take care of the soil.

– We can also try to prevent erosion in the soil. Erosion is the process by which wind and water transfer soil and sediment from one location to another.

Summary of Vocabulary• During this

PowerPoint presentation, you have learned the following vocabulary words that deal with weathering and erosion. Just in case you have forgotten here is a recap of the words:

Weathering Mechanical Weathering Abrasion Chemical Weathering Acid Precipitation Oxidation Differential Weathering Soil Bedrock Parent Rock Humus Topsoil Leaching Soil Conservation Erosion