Weathering and Soil Formation Chapter 10 Standard: S6E5.d Describe process that change rocks and the surface of the earth.

What you will review: Describe how ice, water, wind, gravity, plants, and animals cause mechanical weathering. Describe how water, acids, and air cause chemical weathering of rocks.

The Big Idea???? Weathering is a continuous process that results in the formation of soil and the development of landforms.

2. Mechanical weathering The process by which rock materials are broken down by the action of physical or chemical processes. The breakdown of rock into smaller pieces by physical means. Examples: ice, wind, water, gravity, plants, and animals.

Abrasion: Wind, Water, and Gravity Abrasion is the grinding away of rock surfaces through mechanical action. Wind – sand/silt blown against exposed rock. Water – rocks/pebbles roll & bump/scrape each other. Gravity – Rocks fall on each other from a mountainside.

Ice The alternate freezing & thawing of soil /rock is called frost action. Ice wedging is when water seeps into cracks during warm weather, freezes during cold, expands, and pushes against the sides of the rock causing cracks.

Check point Name three things that can cause abrasion. Wind Water Gravity

More Mechanical Weathering Plants –strong roots grow slowly over time forcing the rocks to expand & crack.

Animals- burrowing in the ground breaks & loosen rocks to be exposed to weathering. Ex: Moles, prairie dogs, insects, worms, and gophers

Chemical weathering The process by which rocks break down as a result of chemical reactions.

Acid precipitation - Rain, sleet, or snow, that contains a high concentration of acids. Examples: sulfuric and nitric acids from volcanoes, burning of fossil fuels.

Acids in Groundwater - Carbonic or sulfuric acids in groundwater dissolve rocks & form caverns. Mammoth Cave, Kentucky

Living things – Lichens produce acids that can slowly break down rock. Air – oxidation: Iron combines with Oxygen to produce a chemical reaction called rust.

Review Which one is which? A rock fall on a mountainside mechanical A rusty bridge chemical Lichens and mosses growing on a boulder An alpine glacier advancing down a valley