Unit 7 Weathering and Erosion Study Guide KEY
Standards for this unit
#1 Students will investigate the scientific view of how the earth’s surface is formed.
Describe processes that change rocks and the surface of the earth.
Explain the effects of physical processes (plate tectonics, erosion, deposition, volcanic
eruption, gravity) on geological features including oceans (composition, currents, and
tides).
Describe soil as consisting of weathered rocks and decomposed organic material.
Explain the effects of human activity on the erosion of the earth’s surface.
Describe methods for conserving natural resources such as water, soil, and air.
Questions – students will be asked to answers these questions throughout the unit.
#1 What are the characteristics of weathering
#2 What are the different kinds of weathering processes?
#3 How are weathering and erosion different?
#4 How are weathering and erosion related?
#5 How does the formation of soil relate to the processes of weathering and erosion?
Soil
1. Soil is a non-renewable resource.
2. Soil is comprised of a mixture of rock particles (minerals), decomposed organic materials, minerals, air, and
water.
3. A soil horizon is a layer of soil with properties that differ from those of the layer above and below it.
4. Soil is extremely valuable. It is responsible for all of the food that people eat. Soil is considered to be a nonrenewable resource because if we do not use good farming technique, we will run out of topsoil.
5. Although weathered rock is the basic component of soil, the composition and texture of soil and its fertility
and resistance to erosion are greatly influenced by plants and other organisms.
6. Decomposing plant and animal material in soil is also known as humus.
7. The three types of soil:
Sandy Soil – has the biggest particles does not hold water well and warms and dries out quickly.
Clay Soil – has lots of clay particles and small air pores. Holds water and drains water poorly.
Loam Soil - consists of sand, silt and clay. It is considered to be the perfect soil. It holds water easily and
drains well.
8. The type of soil that is best for drainage is sandy and the best type for growing crops is loamy.
9. Good soil stores water, provides nutrients for plants, and provides homes for animals.
Weathering
10. Weathering is the process that breaks down rock and other substances at Earth’s surface.
11. Weathering is the breaking apart of rock.
12. The two main types of weathering are mechanical, and chemical.
13. Mechanical weathering is breaking down rocks by physical force.
14. Mechanical weathering includes ice wedging, exfoliation, and organisms breaking down rocks.
15. Chemical weathering is the breakdown of rocks by chemical reactions that change the rocks makeup or
composition.
16. Chemical weathering includes dissolution (soluble rocks and minerals dissolve in acidic waters), hydrolysis
(feldspars alter to clay), and oxidation (rusting of iron).
17. Hydrolysis is the chemical weathering that refers to a chemical change to a substance when it interacts with
water.
18. Water is the main cause of chemical weathering.
19. The dirt on Mars is red because of rust / oxidation. This is an example of chemical weathering.
20. Acid rain causes rocks to weather much faster than they would naturally.
Erosion
21. Weathering and erosion are two very different processes that tend to act sequentially.
22. Erosion is the movement of rock particles.
23. Erosion transports weathered rock material.
24. Water, wind and ice are agents of erosion.
25. Deposition occurs where the agents (forces) of erosion lay down sediment.
26. Dirt from mountain tops can be carried downhill to fill in valleys. This is called deposition.
27. Waves erode the shoreline.
28. What are the three major ways in which erosion moved sediment? water, wind and ice.
29. Weathering and erosion wear down, and deposition fills in Earth’s surface.
30. The agent of erosion that carries the largest rocks is glaciers.
31. Rivers can carve a valley through rock with a river flowing through it while a glacier can carve a valley
where only rocks remain. When the glacier retreats or melts it leaves behind a valley without water.
32. Wind, water, and gravity all combine to move dirt around. Of the three, water is responsible for moving the
most amount of soil.
Humans Impact
33. Human intervention can increase and decrease erosion.
34. Human activities, such as reducing forest cover and intensive farming, have changed Earth’s surface.
35. One simple way to keep soil healthy is to ensure that the soil is never bare. That means keeping plants in
dirt for as long as possible.
36. Humans can increase erosion through poor farming practices or disturbing the land through development.
37. Man-made structures along the coastline often have the unwanted side effect of enhancing coastal erosion.
38. Man-made structures are sometimes built to help control erosion.
39. Construction on steep slopes can lead to mass wasting (erosion by gravity), including slumps and landslides
40. Due to misusing soil, desertification, nutrient depletion of soil, and mass wasting can occur.
41. Mass movement and mass wasting is the downhill movement of large amounts of surface material caused
by gravity.
42. Examples of mass movement and mass wasting are creep, rock falls, avalanches, mudslides, mudflow, and
rock slides.
43. Creep is a very slow mass movement that goes on for years or even centuries. You can't see creep
happening but leaning fences and poles and broken retaining walls show where it has taken place. Creep is the
slowest type of mass movement.
Vocabulary
soil horizon - is a layer of soil with properties that differ from those of the layer above and below it
deposition – the part of the erosion process in which sediment is placed in a new location
erosion – the process in which weathered particles are picked up and moved from one place to another
soil horizon – a layer of soil with properties that differ from those of the layers above or below it
weathering – the breaking down and loosening of rock near the surface of the earth
mechanical weathering - breaking down rocks by physical force
chemical weathering - the breakdown of rocks by chemical reactions that change the rocks makeup or
composition
mass wasting – the downhill movement of masses of rock and soil.
landslide – fast movement of rock and soil
mudflow – movement of mud or soil
humus – decomposed/dead plant and animal material in soil
nonrenewable resources – any natural resource in limited supply and cannot be replaced if it is used up;
examples - oil and coal
renewable resources – any resource that can or will be replenished naturally in the course of time; examples –
solar and wind.
organic matter – made from living matter or related to living matter