Erosion and Weathering Study Guide
Test Date: 11/18
1: Explain the difference between physical and chemical weathering
Rocks are physically weathered by breaking them into smaller and smaller pieces. Rocks are chemically
weathered when compounds in the rock react chemically with another chemical.
Also true: The difference is that physical weathering is a process that weathers rock without a chemical
change. And chemical weathering changes the composition of rocks and it involves a chemical change.
All of the mechanisms of physical weathering have one important thing in common, they do not
change the chemical composition of the materials they act upon. Rocks are broken to smaller
and small pieces, but they are simply smaller pieces of the same compounds.
1a. What is a physical property and how does this help you answer
question 1?
A physical property is something that does not change the composition of the rock while observing it.
This helps me answer question because i know physical change and weathering will be alike because it
does not change that substance.
1b. What is a chemical property and how does this help you answer
question 1?
A chemical property is something that is changed and evident from a chemical reaction. This helps me
answer question one because chemical weathering will involve chemical changes.
2. Explain why “Rocks and soil are transported from one place to
another” more accurately describes what happens in erosion than
“Rocks are broken down into smaller pieces”.
It describes it better because when rocks are broken down into smaller pieces just tells us that its being
broken down. When the soil and rock is transported it will also be broken down while transported.
3. Identify and define the 3 materials which make up soil.
- Organic material, big and small chunks of dirt
- gravel, hard rock that can be small
-sand, small weathered rock
4. Explain how each of the following could cause physical weathering:
·
Growing tree roots- The roots themselves are down in the ground and can crack things like
cement
·
Rain-
When the rain falls into the cracks of rocks it can cause freeze thaw
·
Freezing and thawing ice - Water goes into a rock, then when freezes it expands the rock.
The rock cracks which is physical weathering
Frost wedging is caused by the freezing of water that has seeped into the crevices of rocks.
When water freezes, it expands by about 10%. This force essentially pries the rock apart. When
a rock cracks by frost wedging, more rock face is exposed for chemical weathering. Physical
weathering can therefore speed the rate of chemical weathering.
5. Explain why marble gravel would chemically weather faster than a
large stone statue and a quartz gravel.
It would weather faster because the marble would react with acid rain. We simulated this process in our
lab with calcium carbonate and hydrochloric acid.
In addition, small pieces are more likely to be weathered than larger pieces because more surfaces are
exposed to chemical weathering.
6. Sheila lives on a hill and is concerned about erosion damaging her
house. What could she do in order to reduce erosion around the
house? (Test question will be somewhat similar but the test question
will be open ended without a template. Here is a template to make sure
your answer covers all areas).
Sheila could add trees or other plants to her property. Vegetation decreases erosion by slowing the flow
of water and catching and preventing soil from flowing down the hill. She could also add other obstacles
such as large stones or fence.s. These too will decrease erosion by slowing the flow of water and by
catching a preventing soil from flowing down the hill.
7. How do you know that the particles that make up soil are normally
NOT all the same size?
Soil can be made up of many different components that are all different in sizes and shape. Some of the
components are humus, rock particles, gravel, and organic components.
8. A sieve can be used to analyze soil. Circle the sentence that most
accurately describes how a sieve analyzes soil. Then, explain why each
incorrect answer is incorrect and why the one you chose is correct.
A. They break soil down into small particles. incorrect because it does
not break down soil it separates the soil
B. They separate the organic part of soil from the inorganic parts.
incorrect because it separates all of the parts in soil
C. They separate soil by particle size. correct because the sieve does
separate it by the size of the particles.
D. They remove all gravel from soil. incorrect because it does not
remove the gravel it separates it.
9. State how you know that it may take thousands of years to weather
a rock into smaller particles.
I know because when I did a lab about weathering a rock we could not even weather the rock, when we
tried with a scoop for about ten minutes. In nature it would take thousands and thousands of years to
move the particles from place to place while reducing the particles.
10. Decide which of the following is least likely to speed up chemical
weathering in an area. Then, explain why it is least likely AND why the
other selections may indeed speed up chemical weathering. Feel free to
refer to question 1a and 1b to help distinguish and tell the difference
between chemical and physical.
A. Wind blowing over a field.
- Least Likely because it doesn’t involve chemical
aspects.
B. Plants releasing oxygen into the air- Plants secrete acids that
subject rock to chemical weathering.
C. Animals releasing carbon dioxide into the air Animals burrow into soil,
exposing new surfaces to weathering and erosion.
D. Power plants releasing sulfur dioxide into the air. Chemical
weathering by acids, naturally occurring or accelerated by various types of
pollutants introduced into the ecosystem by industry, acts by softening and
decomposing rock.
11. Circle the items which allow erosion to take place. Then, for each
of the following, explain how it allows erosion to take place or why it
does not allow erosion to take place.
A. Water - Yes it allows erosion to take because it helps the flow.
B. Trees - Does not allow erosion to take place because it’s an obstacle
C. Wind - Helps erosion take place to speed it up or does not help it depending on the
way it is facing
12. Physical weathering contributes to the formation of soil. Circle the
answer choice that contributes to the formation plants.
A. It breaks down dead remains of plants and animals into an organic
component
B. It breaks large rock into small pieces
C. It transports soil material and helps accumulate in certain places
D. It creates nutrients for plants and animals.
13. Physical and chemical weathering actually combine to weather
rocks. How does this happen?
By breaking rocks into smaller pieces, physical weathering exposes more of a rock’s surface to chemical
weathering. The combination
of the two speeds the overall process of weathering.
For example when a rock is hit on with rain and forms cracks thats physical weathering. When the rock is
cracks acidic rain can come in a make a chemical reaction which is chemical weathering.
The following answers may be worded in a number of ways. If you would like me to review your
answer, please show me your response in school no later than Monday 11/17.
14. This question will be an exact question on the test. Pick 2 of the
following concepts. Define each.
Geologic Time Concept,
Big Bang Theory, Continental Drift, Makeup of the earth (Crust, core, mantle)
Plate tectonics -
15. This question will be an exact question on the test. Pick 2 that you
did not pick on question 14 and explain how this topic connects to
erosion and weathering.
Geologic Time Concept Big Bang Theory
Continental Drift
Makeup of the earth (Crust, core, mantle) Plate tectonics