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Questions and Answers
Which process is primarily responsible for breaking down rocks through interaction with water and gases?
Which process is primarily responsible for breaking down rocks through interaction with water and gases?
What is the main action of erosion agents such as wind and water?
What is the main action of erosion agents such as wind and water?
Which type of mass wasting process occurs when rock and debris slide down a slope under the influence of gravity?
Which type of mass wasting process occurs when rock and debris slide down a slope under the influence of gravity?
How can human activities influence erosion processes?
How can human activities influence erosion processes?
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Which factor is crucial in determining the rate of weathering in a given area?
Which factor is crucial in determining the rate of weathering in a given area?
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What mechanism of mechanical weathering involves the expansion and contraction of water in rock cracks?
What mechanism of mechanical weathering involves the expansion and contraction of water in rock cracks?
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What role does abrasion play in the weathering process?
What role does abrasion play in the weathering process?
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What type of biological weathering occurs when plants grow in cracks and expand them?
What type of biological weathering occurs when plants grow in cracks and expand them?
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Which type of mass wasting involves the rapid movement of water-saturated soil and weak rock down a slope?
Which type of mass wasting involves the rapid movement of water-saturated soil and weak rock down a slope?
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What causes landslides to occur at the base of cliffs formed from resistant materials?
What causes landslides to occur at the base of cliffs formed from resistant materials?
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Which process describes the removal of loose sediments by wind, lowering the land surface?
Which process describes the removal of loose sediments by wind, lowering the land surface?
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What is the main factor that determines the effectiveness of wind as an agent of erosion?
What is the main factor that determines the effectiveness of wind as an agent of erosion?
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Which of the following statements about soil creep is accurate?
Which of the following statements about soil creep is accurate?
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Which agent of erosion typically results in a wave-cut notch at the base of coastal cliffs?
Which agent of erosion typically results in a wave-cut notch at the base of coastal cliffs?
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What main weathering process contributes to rockfalls at cliffs?
What main weathering process contributes to rockfalls at cliffs?
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Where do large sand movements typically occur due to wind?
Where do large sand movements typically occur due to wind?
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What role do fungi and algae play in the weathering of rocks?
What role do fungi and algae play in the weathering of rocks?
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Which of the following processes is primarily responsible for the formation of rust in rocks?
Which of the following processes is primarily responsible for the formation of rust in rocks?
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Which type of rock is likely to weather the fastest?
Which type of rock is likely to weather the fastest?
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What is one of the main agents of erosion?
What is one of the main agents of erosion?
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How does climate influence the rate of chemical weathering?
How does climate influence the rate of chemical weathering?
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In what way can human activities increase the rate of weathering?
In what way can human activities increase the rate of weathering?
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Which statement is true regarding surface area and weathering?
Which statement is true regarding surface area and weathering?
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What is the main difference between physical and chemical weathering in cold/moist climates?
What is the main difference between physical and chemical weathering in cold/moist climates?
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Study Notes
Exogenic Processes
- Exogenic processes are geological processes that occur at or near the Earth's surface.
- Uniformitarianism is the theory that the Earth's changes over geological time are the result of continuous, uniform processes.
- Key exogenic processes include: erosion, weathering, and deposition.
Erosion
- Erosion is the breaking down and transportation of rocks and other materials by natural forces.
- Agents of erosion include wind, water (streams and waves), and gravity (mass movements).
- Mass wasting is when gravity pulls weathered sediments down slopes.
Weathering
- Weathering is the breaking down of rocks and other materials at or near the Earth's surface.
- There are two main types of weathering: mechanical and chemical.
Mechanical Weathering
- Mechanical weathering physically breaks down rocks into smaller pieces without changing their chemical composition.
- Common causes include:
- Animal actions: burrowing animals loosen soil and break apart rocks.
- Freezing and thawing: water seeps into cracks, freezes, expands and breaks apart rocks (frost wedging).
- Release of pressure: erosion removes material from a rock mass, reducing pressure and causing the outside to crack and flake off.
- Plant growth: roots enter cracks in rocks, forcing them apart as the plant grows.
- Abrasion: rocks hitting each other wear down and break apart.
Chemical Weathering
- Chemical weathering breaks down rocks by changing their chemical composition.
- Common causes include:
- Water: Dissolves minerals and carries other substances that break down rocks.
- Oxygen: Combining with iron creates rust, making rocks soft and crumbly.
- Carbon dioxide: Dissolving in water creates carbonic acid which weathers rocks like marble and limestone.
- Living organisms: Plant roots produce weak acids that break down rocks.
- Acid rain: Burning fossil fuels puts sulfur, carbon, and nitrogen into the air, which react with water vapor to create acid rain. Acid rain accelerates chemical weathering.
Deposition
- Deposition is the process in which sediment (eroded material) is laid down in new locations.
Rate of Weathering
- Factors influencing weathering rates include:
- Type of rock: Soft minerals like those in limestone wear down faster than hard minerals.
- Surface area: Larger surface areas allow for more contact, accelerating weathering.
- Climate: More moisture increases both physical and chemical weathering, while cold/moist climates increase physical weathering.
Agents of Erosion
- Agents of erosion are the forces that move sediment from one place to another.
- These include gravity, wind, running water (streams), and waves.
Gravity
- Gravity is the force that pulls weathered sediments downhill.
- Types of mass wasting include:
- Fast: Landslides and mudslides.
- Slow: Soil creep and slump.
Running Water
- Running water is the dominant form of erosion.
- The amount of water in a stream is called discharge.
- Erosion occurs where the water flows the fastest, usually near the outside of curves in a river channel (meander).
Wind
- Wind can move sand and small sediments, but rarely moves material more than a meter above the ground.
- Deflation: Wind removes loose sediment, lowering land surfaces.
- Abrasion: Wind-blown sand wears down rocks.
Waves
- Waves erode cliffs and transport sediment.
- The process occurs at the base of cliffs where waves are most powerful.
Landforms
- Oxbow lakes: Created when a meander of a river is cut off.
- River deltas: Sediment deposited at the mouth of a river.
- Other landforms include landslides and rockfalls.
Waves
- Wave size depends on how long the wind blows in one direction.
- Water particles move in circular paths over deep ocean water.
- When a wave reaches shallow water, friction causes the bottom to move more slowly, and the wave "breaks".
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Description
Explore the fundamental concepts of exogenic processes that shape the Earth's surface, including erosion, weathering, and deposition. Understand how natural forces like wind, water, and gravity contribute to these geological changes. Discover the differences between mechanical and chemical weathering.
