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Questions and Answers
What is the primary process of mechanical weathering that involves the expansion of freezing water?
What is the primary process of mechanical weathering that involves the expansion of freezing water?
Which type of weathering involves the chemical transformation of rocks into new compounds?
Which type of weathering involves the chemical transformation of rocks into new compounds?
What is the most important agent of chemical weathering?
What is the most important agent of chemical weathering?
What results from the weathering of potassium feldspar?
What results from the weathering of potassium feldspar?
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What process generates rounded rocks through weathering?
What process generates rounded rocks through weathering?
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Which process creates onion-like layers in rocks?
Which process creates onion-like layers in rocks?
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What type of erosion typically involves the movement of materials by water, wind, or ice?
What type of erosion typically involves the movement of materials by water, wind, or ice?
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What do silicate minerals produce as a result of weathering?
What do silicate minerals produce as a result of weathering?
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What is the primary difference between residual soil and transported soil?
What is the primary difference between residual soil and transported soil?
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Which soil horizon is primarily composed of organic and mineral matter?
Which soil horizon is primarily composed of organic and mineral matter?
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How does slope orientation affect soil development?
How does slope orientation affect soil development?
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What do the zones O and A collectively represent in a soil profile?
What do the zones O and A collectively represent in a soil profile?
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Which factor does NOT influence soil formation?
Which factor does NOT influence soil formation?
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What is meant by the term 'solum' in the context of soil profiles?
What is meant by the term 'solum' in the context of soil profiles?
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Why do steep slopes often have poorly developed soils?
Why do steep slopes often have poorly developed soils?
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What classification system is used in the United States to categorize soils?
What classification system is used in the United States to categorize soils?
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What is a primary factor influencing the natural rate of soil erosion?
What is a primary factor influencing the natural rate of soil erosion?
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Which type of erosion accounts for approximately 2/3 of all soil erosion in the U.S.?
Which type of erosion accounts for approximately 2/3 of all soil erosion in the U.S.?
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Which practice is NOT commonly used to control soil erosion?
Which practice is NOT commonly used to control soil erosion?
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What is mass wasting primarily influenced by?
What is mass wasting primarily influenced by?
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What condition causes saturation of materials that can lead to mass wasting?
What condition causes saturation of materials that can lead to mass wasting?
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What effect does oversteepening of slopes have on soil stability?
What effect does oversteepening of slopes have on soil stability?
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Which factor does NOT contribute to soil erosion by wind?
Which factor does NOT contribute to soil erosion by wind?
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How do tree windbreak barriers help in controlling soil erosion?
How do tree windbreak barriers help in controlling soil erosion?
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What characterizes the movement in a rockslide?
What characterizes the movement in a rockslide?
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Which mass wasting process is specifically associated with the saturation of soil and typically occurs on hillsides in humid regions?
Which mass wasting process is specifically associated with the saturation of soil and typically occurs on hillsides in humid regions?
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What distinguishes a debris flow from other mass wasting processes?
What distinguishes a debris flow from other mass wasting processes?
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Which type of mass wasting involves slow movement and is recognizable by tilting fences or utility poles.
Which type of mass wasting involves slow movement and is recognizable by tilting fences or utility poles.
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What is a unique characteristic of solifluction?
What is a unique characteristic of solifluction?
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Which of the following describes the term 'liquefaction' in relation to mass wasting?
Which of the following describes the term 'liquefaction' in relation to mass wasting?
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Which type of mass wasting is characterized by rapid movement along a curved surface?
Which type of mass wasting is characterized by rapid movement along a curved surface?
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Which of the following statements about fall, slide, and flow in mass wasting is true?
Which of the following statements about fall, slide, and flow in mass wasting is true?
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What aspect of rock characteristics primarily influences weathering rates?
What aspect of rock characteristics primarily influences weathering rates?
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Which two factors are most crucial for chemical weathering to occur effectively?
Which two factors are most crucial for chemical weathering to occur effectively?
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What is differential weathering primarily a result of?
What is differential weathering primarily a result of?
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Which component is NOT a part of the soil system?
Which component is NOT a part of the soil system?
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What characteristic of soil refers to the proportions of different particle sizes?
What characteristic of soil refers to the proportions of different particle sizes?
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Which soil texture is best suited for plant life?
Which soil texture is best suited for plant life?
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Which of the following is NOT one of the basic soil structures?
Which of the following is NOT one of the basic soil structures?
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What role does regolith play in the soil system?
What role does regolith play in the soil system?
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Study Notes
Earth's External Processes
- Weathering is the disintegration and decomposition of material at or near the surface.
- Mass wasting is the transfer of rock material downslope under gravity's influence.
- Erosion is the incorporation and transportation of material by a mobile agent, typically water, wind, or ice.
Weathering
- Two types of weathering:
- Mechanical weathering: breaking rocks into smaller pieces.
- Chemical weathering: changing rocks' internal structure by removing or adding elements.
Mechanical Weathering
- Four key processes:
- Frost wedging: expansion of freezing water.
- Salt crystal growth: generates onion-like layers and exfoliation domes.
- Sheeting: generates onion-like layers and exfoliation domes in igneous rocks.
- Biological activity: physical and chemical alteration of rocks by living organisms, such as tree roots.
Increase in Surface Area by Mechanical Weathering
- Mechanical weathering increases the surface area, exposing more rock to chemical weathering.
- A smaller rock volume has a larger surface area than a larger rock volume.
Chemical Weathering
- Alters minerals by removing or adding elements, primarily water.
- Key agents are water dissolved oxygen and carbon dioxide (forming carbonic acid).
- Chemical weathering of granite produces clay minerals, soluble potassium salts and silica (in solution), but quartz remains mostly unaltered.
- Weathering of silicate minerals creates insoluble iron oxides and clay minerals.
Spheroidal Weathering
- Weathering that rounds rocks by acting inward from exposed surfaces.
- Water penetrates extensively, decomposing minerals and enlarging joints.
- Rocks are primarily attacked at corners and edges; rounded shapes.
Rates of Weathering
- Factors that influence weathering speed:
- Advanced mechanical weathering aids chemical weathering by increasing the surface area.
- Rock characteristics: mineral composition and solubility, physical features like joints.
- Climate: temperature and moisture are the most crucial factors.
Rock Type Influences Weathering
- Different rock types weather at varying rates.
- Granite, despite weathering, shows less weathering than Marble on structural and inscriptions.
Soil
- Interface in the Earth system, a combination of mineral matter, water, and air.
- Regolith is the layer of unconsolidated rock and mineral fragments over bedrock.
- Soil supports plant growth.
Soil Components
- Soil is made up of:
- 45% mineral matter
- 25% water
- 25% air;
- 5% organic matter.
Soil Texture and Structure
- Soil texture describes the proportions of different particle sizes (sand, silt, and clay).
- Loam (a mixture of all three) is best for plant life.
- Soil structure refers to how soil particles clump together. Four common structures are platy, prismatic, blocky, and spheroidal .
Soil Profile
- Soil-forming processes occur from the surface downward.
- Horizons (zones or layers of soil) include:
- O: organic matter
- A: organic and mineral matter
- E: little organic matter; zone of eluviation and leaching
- B: zone of accumulation
- C: partially altered parent material (bedrock)
- Topsoil is the O and A horizons combined.
- The solum (true soil) includes O, A, E, and B horizons
Controls of Soil Formation
- Factors affecting soil formation:
- Parent material (bedrock, transported soil).
- Time: varies among soil types.
- Climate.
- Plants and animals contribute organic matter and impact chemical and physical properties.
- Slope: steep slopes often have poorly developed soils.
Slopes and Soil Development
- Soil development depends on slope angle and orientation.
- Steep slopes have thinner soil due to erosion.
- Flatter slopes support thicker soil.
Soil Erosion
- Soil erosion is the natural process of soil material removal.
- Natural rates depend on soil characteristics, climate, slope, and vegetation type.
- Processes causing soil erosion include raindrops dislodging soil particles, wind erosion, and flowing water carrying soil away
- Human activities can exacerbate soil erosion
Soil Conservation Methods
- Techniques for controlling soil erosion include terraces, crop strips, windbreaks, and grassed waterways.
Mass Wasting
- Downward movement of rock, regolith, and soil due to gravity's influence.
- Gravity is the primary driving force.
Mass Wasting Triggers
- Triggers for mass wasting include:
- Saturation of material with water- destroys particle cohesion and adds weight
- Oversteepening of slopes- unconsolidated material assumes a stable angle of repose
- Removal of anchoring vegetation.
- Ground vibrations from earthquakes
Mass Wasting Processes
- Classified by:
- Material involved (rock, debris, mud, earth, etc.)
- Movement (fall, slide, flow)
- Speed (fast or slow)
Mass Wasting Forms
- Distinct types of mass wasting include:
- Slumps (curved surface)
- Rockslides (rapid movement of bedrock)
- Debris flows (with water) and lahars (volcanic debris)
- Earthflows (saturated soil)
- Creep (slow, continuous movement)
- Solifluction (slow movement in permafrost areas)
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Description
Test your understanding of Earth's external processes including weathering, erosion, and mass wasting. Explore the types of weathering and key mechanisms of mechanical weathering. Learn about how these processes affect the landscape around us.
