Notes on Earth Processes — Weathering, Erosion, Sedimentation, Mass Wasting, and Endogenic/Exogenic Dynamics
EXOGENIC PROCESSES
Natural forces that change the landscape: weathering, erosion and deposition. Earth surface processes include:
weathering; sediment production by weathering and biochemical or chemical precipitation;
erosion, transport, and deposition of sediment under gravity, flowing water, air, and ice;
earthquakes and Earth surface motions; volcanic eruptions and movement of volcanic ejecta.
TYPES OF EARTH PROCESSES
Exogenic vs Endogenic (surface vs interior processes)
Exogenic processes operate at or near the Earth’s surface and sculpt/degrade the surface.
Endogenic processes originate from inside the Earth and move rock and landforms through internal energy.
EXOGENIC PROCESSES
Are processes that take place at or near the earth's surface that make the surface water away. These are very destructive, responsible for degradation and sculpting the earth's surface.
TYPES OF EXOGENIC PROCESSES
Weathering
Erosion
Sedimentation
Mass Wasting
1. WEATHERING
The process that breaks down rock into smaller pieces. Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms.
TYPES OF WEATHERING
A. PHYSICAL WEATHERING
Rock is physically broken into smaller pieces; also called mechanical weathering or disaggregation; disintegration of rocks without chemical change.
B. CHEMICAL WEATHERING
Chemicals in rainwater alter minerals in a rock; CO2 dissolved in rainwater makes it slightly acidic; reactions alter rock minerals.
A. PHYSICAL WEATHERING
Happens when rock is physically broken into smaller pieces; no chemical change.
B. CHEMICAL WEATHERING
Involves chemical reactions between minerals and atmospheric/aqueous species (e.g., water, CO2).
FACTORS AFFECTING PHYSICAL WEATHERING
1. ICE WEDGING
Frozen water seeps into cracks; as ice melts and refreezes, it widens crevices and breaks rock with repeated cycles.
2. RELEASE OF PRESSURE
Rock formed under high pressure reaches surface; overlying rock erodes away; fractures form parallel to rock surface.
3. GROWTH OF PLANTS
Roots grow in cracks, widen and break rock over time.
4. ANIMALS
Burrowing activity and movement can break rock; tree roots illustrate mechanical weathering.
5. ABRASION
Rock-to-rock or rock-to-particle impacts; gravity, water flow cause rocks to grind down.
4. ANIMALS
Burrowing animals contribute to weathering by disturbing rock and soil.
5. ABRASION (remainder of mechanical weathering)
Describes rocks bumping against each other, aided by gravity or moving water.
B. CHEMICAL WEATHERING
Chemical weathering describes changes to minerals caused by chemicals in rainwater; CO2 from air dissolves in rainwater, creating acidity that reacts with rocks.
FACTORS AFFECTING CHEMICAL WEATHERING
1. WATER
Hydration changes chemical bonds; example: anhydrite reacts with groundwater to form gypsum:
2. OXYGEN
Oxygen reacts with iron forming iron oxide (rust) and weakens rock.
3. CARBON DIOXIDE
CO2 dissolves in rainwater forming carbonic acid which weather rocks (e.g., silicon-rich rocks).
4. LIVING ORGANISM
Decaying plant/fungal matter forms carbonic acid; bacteria weather rock to access nutrients.
5. ACID RAIN
Rainwater acidity accelerates chemical weathering; reiterates CO2 dissolution effect.
2. OXYGEN (detailed)
Oxygen reacts with minerals (e.g., iron) to form oxides; color changes and fragility increase.
3. CARBON DIOXIDE (detailed)
Volcanic CO2 dissolves in rainwater, enhancing chemical weathering of continental rocks.
4. LIVING ORGANISM (detailed)
Organisms produce acids and facilitate mineral dissolution; bacteria contribute to mineral weathering.
5. ACID RAIN (repeated concept)
Acidic rain enhances mineral dissolution; chemical weathering descriptions summarize this effect.
PHYSICAL VS CHEMICAL WEATHERING
Physical weathering: disintegration without chemical change.
Chemical weathering: decomposition/alteration of minerals via chemical reactions.
SUMMARY OF WEATHERING IMPACT
Weathering prepares rock for soil formation; provides resources (e.g., clay for pottery, bauxite for aluminum).
Weathering weakens rocks, aiding erosion and mining.
Weathering shapes landforms and supports life by enabling soil formation.
2. EROSION
Erosion involves detachment, movement, and deposition of rocks and minerals by agents such as water, ice, wind, gravity, etc.
It transports materials and reshapes landforms.
AGENTS OF EROSION
Water
Ice
Wind
Gravity
EROSION OF WATER
Water erosion detaches and removes soil; rate varies with soil type, landscape, and weather; may be natural or human-accelerated.
Wears away earth's surface.
EROSION BY WIND
Wind erodes land by removing soil, especially on flat, dry or sandy areas; forms dunes and desert features.
EFFECTS: can bury or sandblast structures; transport dust; impact environment and health.
EXAMPLES: dunes sculpted by wind; rock formations shaped by wind.
EFFECTS ON HEALTH, ENVIRONMENT, ECONOMY, and PROPERTY noted (airborne dust, crop degradation, dust storms affecting transport).
ELEMENTS contributing to wind erosion: industrial activity, agriculture, deforestation, roadwork, urban sprawl, climate change, weather, tillage, crop growth, decomposition, erosion, soil factors.
EROSION BY ICE
Glaciers erode landscapes over long timescales via gravity-driven movement and abrasion.
EROSION BY GRAVITY
Gravity drives erosion by causing rocks/soil to move downslope; major mechanism behind landslides, rockfalls, mudslides, and mass weathering processes.
Gravity transports material from higher to lower elevations.
Landslides and mudslides are direct results of gravitational erosion.
SEDIMENTATION (deposition following erosion)
Sedimentation is the deposition of rock fragments, soil, organic matter, or dissolved material that has been eroded/transported by water, wind, ice, or gravity.
Depositional environments where sediments accumulate.
Process involves particles settling out due to forces (gravity, centrifugal acceleration, electromagnetism) and coming to rest against a barrier.
Settling is the falling of suspended particles; sedimentation is the final result of settling.
3. MASS WASTING
Mass wasting (mass movement) is the movement of rock or soil down slopes primarily under gravity.
Differs from erosion in that debris is not entrained in a moving medium (water, wind, or ice).
Triggered by various factors.
TRIGGERS OF MASS WASTING
Oversteepened slopes: stable angle for loose particles is roughly depending on particle size/shape; exceeding this makes mass movements more likely.
Removal of vegetation: roots stabilize slopes; loss increases likelihood of movement.
Earthquakes: sudden shaking dislodges rock/soil, initiating movement.
Other notes in the source slide show additional factors, but these are the primary listed triggers.
CLASSIFICATIONS OF MASS WASTING (A–H)
A. Slump
A coherent mass moves down slope along a concave-upward or planar surface; movement is relatively rapid but remains coherent.
B. Solifluction
Slow downhill flow of saturated soil in Arctic regions; slow, uniform through the thickness of soil.
C. Earth Flow
Viscous flow of fine-grained, water-saturated material; intermediate between creep and mudflow.
D. Mudflow
Mass of water and sand-sized particles that mixes and flows rapidly; water-laden debris flow; mudslides differ in common usage.
E. Debris Slide
Dry or relatively dry rock/soil debris moves downslope, speeds vary; mass slides and rolls forward without backward rotation.
F. Debris Flow
Water-laden masses of soil and fragmented rock rush down mountainsides; entrain objects; deposit thick muddy material in valleys.
G. Rock Flow
Plastic deformation and flow of rock materials; slow movement due to internal rock deformation, vibrations, weathering effects.
H. Soil Creep
Very slow downward progression of rock/soil down shallow slopes; slow deformation from prolonged stress.
OTHER MASS WASTING CONSIDERATIONS
Types of mass wasting (rock slide, landslides, debris flows, lahar/mudflow, etc.) appear in illustrated lists; common categories include rock fall, rock slides, rock avalanches, slides, and looser debris movements on disturbed terrain.
ENDOGENIC PROCESSES
Endogenic processes are geological processes that occur beneath the Earth’s surface; energy originates in the Earth’s interior; the ground is always moving.
Forces within the Earth cause ground movement and landform destruction/creation.
HOW IT WORKS
Ground movement breaks, twists, and shakes rock layers at the surface; land is destroyed in some places and created in others.
MAIN ENDOGENIC PROCESSES
A. FOLDING
Two opposing forces compress rock layers; folds form (anticline, syncline, axial plane); folds can be symmetrical or asymmetrical; various fold types include overfold, recumbent, etc.
B. FAULTING
Fracturing and displacement of brittle rock along a fault plane due to tension or compression; a fault line often marks lines of weakness.
TYPES OF FAULTING
1. NORMAL FAULT (CONVERGENCE)
Crust is spreading; common at plate boundaries or interior faults.
2. REVERSE FAULT (DIVERGENCE)
Hanging wall moves up relative to the footwall; occurs in compression zones.
3. TEAR FAULT (TRANSFORM)
Strike-slip faults; localized faults associated with folds and thrust faults; strike direction perpendicular to thrust front.
SUBSEQUENT ENDOGENIC PROCESSES
1. VOLCANISM (MAGMATISM)
Magma beneath crust under great pressure; cracks and lines of weakness allow magma to move; release pressure in magma during folding/faulting; leads to volcanic activity, lava flows, ash, etc.
Effects/phenomena listed include floods, lava flow, burning effects of eruptions, ash and chemicals in air, colored sunsets, mudflows, destruction, formation of new land masses, etc.
2. EARTHQUAKES
Sudden shaking or vibration due to rapid release of energy after rock or plate movement along faults.
Why earthquakes happen: rocks stick due to friction, pressure builds; eventual break releases energy as seismic waves; ground shakes as plates move.
IMPORTANCE OF WEATHERING
Weathering breaks initial rock mass into smaller fragments, forming soil.
Clay is used for pottery; bauxite (aluminum ore) is a product of weathering used in aluminum extraction.
Weathering weakens rocks, aiding mining/exploitation.
Weathering prepares land for agents of erosion and transportation to act.
Agents of erosion subsequently modify landforms, influencing human activities and land use.
Weathering is essential for supporting life (soil formation and nutrient cycling).
In sum, weathering explains landform formation, provides resources, and shapes human use of landscapes; it can be seen as both a source of beauty and a disaster in some contexts (A BEAUTIFUL DISASTER).
SUMMARY POINTS
Exogenic vs Endogenic processes describe surface vs interior forces shaping Earth.
Weathering transforms rocks into soils and resources; it has physical and chemical pathways with distinct drivers.
Erosion transports weathered material via water, wind, ice, and gravity, leading to deposition (sedimentation).
Mass wasting describes gravity-driven downslope movement of rock/soil, with multiple classifications (A–H) including slumps, mudflows, creep, etc.
Endogenic processes include folding and faulting, plus subsequent volcanism and earthquakes that rework the crust.
The angle of stability for slopes is typically in the range
Weathering underpins soil formation, resource availability, mining feasibility, and landscape development; erosion, sedimentation, and mass wasting continually reshape those landscapes; human activities influence these processes (deforestation, urbanization, pollution, etc.).
CLOSING REMARKS
The interconnected cycle of weathering, erosion, sedimentation, and mass wasting, driven by exogenic and endogenic forces, continually crafts Earth’s surface and affects ecosystems, economies, and health.