Weathering and Soil Formation Chapter 10, Section 1

What is weathering? Weathering is the process by which rocks are broken down. This can be either: Mechanical Chemical

Mechanical a.k.a. Physical Mechanical weathering is the breakdown of rock into smaller pieces by a physical means. For example: Wind Water Animals Plants Ice Gravity

Think about it! Which of the following things cannot cause mechanical weathering? A. Water B. Acid C. Wind D. Animals

Ice Wedging Water seeps into cracks in rock. Then when it freezes it expands. This causes the cracks to enlarge.

Ice/Frost WEDGING

Pot Holes: a common form of ice wedging

Abrasion The weathering of rocks due to them rubbing against other rocks or particles.

Wind, Water, Gravity These are all ways that abrasion occurs.

Formed by wind abrasion Valley of Fire State Park (Nevada)

ABRASION OF WIND AND WATER

Formed by wind abrasion Arches Nation Park (Utah)

Think about it! What are three ways abrasion occurs in nature?

Think about it! What are three ways abrasion occurs in nature? Answer: Wind, Water, & Gravity

Plants Some plants can easily break through rocks.

Plant Activity: Roots Split Rock

Animals Burrowing animals such as rats, earthworms, ants, coyotes, and rabbits cause a lot of weathering.

Which method of mechanical weathering is shown below

Which method of mechanical weathering is shown below

Which method of mechanical weathering is shown below

Which method of mechanical weathering is shown below

Chemical Weathering Chemical weathering is the process by which a rock is broken down as a result of a chemical reaction.

Water Water is the main ingredient in chemical weathering. It may take thousands of years, but water can even break down granite.

Acid Precipitation Acid precipitation is any rain, sleet, or snow that contains large amounts of acid. All precipitation is naturally acidic, however, acid precipitation contains more than normal.

Acid can also be found in groundwater or in the air. Oxidation is the chemical reaction that occurs when elements react with oxygen.

Think about it! Why does acid precipitation weather rocks faster than normal precipitation?

Think about it! Why does acid precipitation weather rocks faster than normal precipitation? Answer: Acid precipitation is more acidic than natural precipitation. Stronger acids break down rocks faster.

Summary Questions 1. Explain the difference between mechanical and chemical weathering.

Answers Q: Explain the difference between mechanical and chemical weathering. A: Mechanical weathering is the breaking down of rock into smaller pieces by physical means only and chemical weathering is the process of breaking down rocks as a result of a chemical reaction.

Summary Questions 1 . Describe how humans contribute to the process of chemical weathering.

Answers Q: Describe how humans contribute to the process of chemical weathering. A: Humans produce man-made gasses by burning so much fossil fuel (coal, oil, natural gas). These gases react with water and produce acid rain. This acid rain literally “eats” away at rocks.