Chapter 10 Section 1 - Weathering

weathering

Weathering is the breakdown of rock into smaller pieces (called sediment) by physical and chemical processes.

karst landscapes

When ground water containing acids reacts with limestone it breaks it down (chemical weathering). This creates landscapes or formations like caverns/caves.

Which of the following things cannot cause mechanical weathering? a. water b. acid c. wind d. animals

b. acid

Describe three ways abrasion occurs in nature.

Abrasion can be caused by wind, water, and gravity. Each of these causes rocks to grind against each other and break down by physical methods.

Making Inferences: Why does acid precipitation weather rocks faster than normal precipitation?

Acid precipitation is more acidic than natural precipitation. Stronger acids break down rocks faster

acid precipitation

Acid precipitation is rain, sleet, or snow with a high concentration of acid.

Describe the similarity in the ways tree roots and ice mechanically weather rock.

Both tree roots and ice can force cracks in rocks to expand.

chemical weathering

Chemical weathering is a process by which rocks break down because of chemical reactions. (Chemicals react to one another weakening the bonds between two different materials. This makes the materials break apart.)

Describe five sources of chemical weathering.

1. water 2. acid precipitation 3. acids in groundwater 4. acids in living things 5. air

Substances that have a pH of less than 7 are acidic. For each pH unit lower, the acidity is ten times greater. For example, normal precipitation is slightly acidic at a 5.6 pH. If acid precipitation were measured at 4.6 pH, it would be 10 times more acidic than normal precipitation. How many times more acidic would precipitation at 3.6 pH be than normal precipitation? Show your work below.

10 × 10 = 100 times more acidic

Making Comparisons Compare the weather processes that affect a rock on top of a mountain and a rock buried beneath the ground.

A rock on top of a mountain tends to be weathered more because it is exposed to wind, precipitation, and the effects of gravity. A rock buried underground does not experience weathering from wind, precipitation, or gravity.

mechanical weathering

Mechanical weathering is the breakdown of rock into smaller pieces by physical means (like abrasion, grinding, or rubbing together).

List three things that cause chemical weathering of rocks.

Water, acids, and air. The chemicals in each react with the material to cause it to weather (or break down).