Earth's External Processes Quiz

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)