7th Grade Weathering and Erosion Party Planner
Answer Key
- Explain the two types of weathering:
- Mechanical weathering produces physical changes in rocks:
Ice wedging
Pressure release-causes rock to expand, cracking and leading to exfoliation
b.Chemical weatheringBreakdown of rocks by chemical reactions that change the rocks composition (what it is made up of)
- Explain exfoliation and give an example.
Exfoliation is a process in which layers of exfoliationrock gradually break off.
- Plant root growth
- Abrasion-wearing down by friction, the rubbing of one object or surface against another (example: running river)
- Explain chemical weathering and give an example.
Chemical weathering is the breakdown of rocks by chemical reactions that change the rocks composition (what it is made of)
- Water (dissolving)
- Rusting
- Explain the three ways that controls the rate of chemical weathering:
- Surface area-the more exposed area, the faster the break down of rock (chemical)
- Rock composition ex: Granite compared to limestone
- Climate:
Chemical weathering occurs in wet, hot areas faster than cold, dry regions
Mechanical weathering caused by freezing and thawing
- Where does chemical weathering occur?
Chemical weathering occurs in wet, hot areas faster than cold, dry regions
- Where does mechanical weathering occur?
Mechanical weathering caused by freezing and thawing
- Explain how soil is formed.
Weathering and organic processes form soil
- What is soil?
A mixture of weathered rock particles and other materials
- What is humus?
Humus-decayed organic (living things) in the soil
10. List six ways that affects soil formation:
a.Rock in an area
b.Climate: tropical, desert, temperate, artic
c.Landforms: mountains and valleys
d.Plant cover: provide organic matter
e.Living organisms: microorganisms and animals
f.Time
- Define soil horizon.
A layer of soil with properties that is different than the layers above and below it.
- Explain soil profile.
Soil horizons are in a specific area
- Explain four properties of soil.
a.Texture-determined by size of weathered rock particles it contains
b.Color-most comes from iron and humus
c.Pore space-the spaces between the particles
d.Chemistry-minerals and organic nutrients
(Does it react with water such as bubbling?)
- Explain three ways human activities that increase soil erosion.
a.Farming-soil loss and overgrazing results in desertification- expansion of desert in areas where natural plant cover has been destroyed
b.Construction and development
c.Mining
- Strip mining
- Open pit
- List and draw pictures the five ways that we can conserve soil.
a.Crop rotation
b.Conservation tillage
c.Terraces
d.Contour plowing
e.Windbreaks
- Explain how climate is different from weather and the climate we have in Missouri.
Weather is what is happening now while climate is weather over a long period of time.
Temperate soils form in region with moderate rainfall and temperatures.
- Explain three soil horizon types.
a.The A horizon- is the upper layer of soil and is commonly called topsoil.
It contains the most organic matter out of all the horizons due to the humus that it contains gives it the dark color
(Moderate pore space).
b. This layer lies just below the A horizon. It has a little organic matter and is usually brownish or reddish color and contains clay (very little pore space for water) and minerals.
c.This is the deepest layer of soil. This layer contains the largest and least-weathered rock particles. It is usually light yellowish brown (sand which has high amount of pore space).
- Draw a picture of the three soil horizon types with details of what objects can be found in each layer along with the approximate depth of each layer in inches.