Weathering Study Guide
Weathering includes mechanical weathering and chemical weathering. Mechanical weathering is any process that breaks up rock without changing its chemical composition. Chemical weathering is any process in which water, air, or other substances react with the minerals in the rock and change the chemical composition of the rock.
Use the words in the box to fill in the blanks of the paragraph below.
Plants / Pieces / Moisture / Frost wedging / Acids / Carbonic-Freezing / Chemical / Oxidation / Temperatures / Minerals / acid
Climate / Desert / Mechanical / Cracks / Reacting
Weathering is the breaking down of rocks into __(1)__. There are two main types of weathering. __(2)__ weathering involves breaking rocks without changing their chemical composition. In __(3)__, water trapped in rocks freezes and expands, forcing rocks apart. __(4)__ can also cause mechanical weathering. As their roots grow and put pressure on rocks, __(5)__ widen and rock fragments may fall off. __(6)__ weathering involves water, air, and other substances’ __(7)__ with the minerals in the rocks. When metal is exposed to water and oxygen, __(8)__ occurs and rust forms. __(9)__ in plant roots and mosses can also react with the __(10)__ in rocks. Water and carbon dioxide combine to form __(11)__, which reacts with minerals such as calcite in limestone. How rapidly weathering occurs in an area depends on the __(12)__. Chemical weathering happens more slowly in __(13)__ areas due to a lack of __(14)__. Low __(15)__ in polar regions keep chemical weathering to a minimum there. Whenever __(16)__ and thawing alternate, mechanical weather becomes an important form of weathering.
Decide if the following descriptions are examples of mechanical weathering or chemical weathering. Write the word “mechanical” or “chemical” for each statement.
17. Mosses growing on the surface of rocks, producing pits in the rocks.
18. The wedging of tree roots along natural joints in granite outcrops.
19. Limestone dissolved by carbonic acid.
20. The oxidation of minerals that contain iron.
21. Animal burrows dug in rock that let in water and air.
22. Repeated freezing and thawing of water that cracks rock.
23. The action of water, salt, and air on car fenders and panels.
24. Acids from plant roots which break up rocks.
25. Formation of potholes in streets during severe winters.
26. Lifted sections of sidewalk along tree-lined streets
27. A small rock falling from a cliff.
28. Feldspar mixing with acidic groundwater and producing clay minerals.
29. Halite in rocks dissolving in water.
30. Decaying plants dissolving some of the minerals in rocks.
31. Tree roots cracking the concrete foundation of a house.
Sequence the following processes in each section (1-4) by which factors in mechanical weathering break down rocks and minerals.
Temperature
32. _____ Freezing water exerts pressure on the rocks and make them split.
33. _____ Water collects in the cracks of rocks and rock layers.
34. _____ Water thaws and the cycle, called frost wedging repeats.
35. _____ Water expands as it freezes.
Pressure
36. _____ Successive layers of rock are stripped away in a process called exfoliation.
37. _____ The bedrock surface expands and long cracks form parallel to the surface of the rock.
38. _____ The overlying rock layers are removed and the pressure on the bedrock is reduced.
39. _____ Bedrock at the great depths is under pressure from the overlying rock layers.
- Which long-term atmospheric changes would increase the rate of chemical weathering on surface bedrock?
- Decreasing temperature and decreasing precipitation
- Decreasing temperature and increasing precipitation
- Increasing temperature and decreasing precipitation
- Increasing temperature and increasing precipitation
- Explain your answer for #40.
Outline information about how water, oxygen, and carbon dioxide contribute to chemical weathering. (see p. 156-157)
- Water
- Important in chemical weathering because: ______
- Hydrolysis is ______.
- It occurs in the decomposition of: ______.
- Oxygen
- Like water, it can: ______.
- This chemical reaction is called: ______.
- ______.
- Produced by: ______.
- Combines with water in the atmosphere to form: ______.
- Carbonic acid reacts with minerals to: ______.
- Limestone caverns can form when: ______.