Exogenic Processes PDF

WHAT IS EXOGENIC PROCESS? Exogenic Process – processes that take place at or near the surface that make the surface wear away. Endogenic Process – geodynamic processes (seismic activities). TYPES OF EXOGENIC PROCESSES Degradation: o Weathering o Mass wast...

WHAT IS EXOGENIC PROCESS? Exogenic Process – processes that take place at or near the surface that make the surface wear away. Endogenic Process – geodynamic processes (seismic activities). TYPES OF EXOGENIC PROCESSES Degradation: o Weathering o Mass wasting o Transportation o Erosion Aggradation: o Deposition WEATHERING The physical breakdown and/or chemical alteration of rocks; Breaking down of Rocks. Can be mechanical or chemical: o Mechanical weathering: Breaking up of large rocks into smaller fragments without changing the rock’s mineral composition. o Chemical weathering: Decomposes rocks through chemical change. MECHANICAL WEATHERING 1. Frost Wedging/Frost Weathering: a. Occurs in regions where the temperature fluctuates above and below freezing point. b. Water enters rock spaces, expands when frozen, weakening the rock through repeated freeze-thaw cycles. 2. Thermal Stress/Insolation Weathering: a. Results from the expansion and contraction of rocks caused by temperature changes. b. The outer surface of rocks is warmer/colder than the inner portions. c. Peeling off process is called exfoliation. 3. Pressure Release/Unloading: a. Occurs when overlying rock is eroded away, causing the outer layer to expand and separate from the rock body. b. Evident in intrusive igneous rocks. c. The exfoliation due to pressure release is often called sheeting. 4. Organic Activity: a. Anthropogenic activities become the primary cause of weathering like road construction, mining or even simple walking. CHEMICAL WEATHERING 1. Oxidation: a. Oxygen dissolved in water oxidizes some minerals (e.g., iron-rich minerals), producing rust which weakens rocks. b. Composition: Iron  2. Hydrolysis: a. Water dissolves minerals (affects carbonate minerals) and leaves behind chalky new minerals. 3. Carbonation: a. Carbon dioxide in rainwater forms carbonic acid, which reacts with calcium carbonate to form calcium bicarbonate. 4. Biological Action: a. Decaying remains of dead plants in soul may form organic acid and, when dissolved in water, may cause chemical weathering. MASS WASTING Involves the movement of rocks, soil, and regolith, driven by gravity. Types: o Rock and Debris Fall: ▪ Rock falls from steep cliffs; debris falls include soil and vegetation. o Landslides: ▪ Sudden fast movements of soil, rock, or regolith due to failure of slopes. ▪ Two types: Translational Slides: Movement along a well-defined surface. Rotational Slides (Slumps): Movement along a concave upward surface. o Flows: ▪ Material behaves as a liquid; prone in humid areas. ▪ Slurry Flows (20%-40% water): Solifluction: moves at around 1cm/yr and occurs in water-saturated areas. Debris Flows: Caused by heavy rains, move at around 1 m/yr to 100m/h. Mudflows: High-velocity mixtures of sediment and water, result from heavy rains. ▪ Granular Flows (0%-20% water): Creep: Slow movement, seen in bent trees and fences. Earthflows: velocities ranges from less 1 cm/yr to less than 100 m/h. Debris Avalanches: High-velocity flows of large rock and regolith. EROSION Transports materials (sediments) from one place to another by water, wind, or ice. Opposite of deposition. Agents: o Water: ▪ Primary agent, can cause splash, sheet, gully, valley, and bank erosion. o Wind: ▪ Carries dust, sand, and ash from one place to another, common in deserts and beaches. o Ice: ▪ Involves glaciers that erode land by plucking (removing chunks of rock) or abrasion (scratching bedrock with debris). TYPES OF WATER EROSION 1. Splash Erosion: a. Raindrops detach and move tiny particles of soil.  2. Sheet Erosion: a. Raindrops break apart soil structure, moving it down slopes as water flows. 3. Gully Erosion: a. Narrow channels are eroded into great depth by heavy rains. 4. Valley Erosion: a. Continuous water flow erodes valleys deeper. 5. Bank Erosion: a. Streams and rivers wear out their banks. 6. Coastline Erosion: a. Ocean waves pound rocks into pebbles and sand, altering coastlines. 7. Seaside Cliff Erosion: a. Waves erode cliffs, forming caves and arches; continuous pounding can leave sea stacks (rock columns). WIND EROSION Wind: o Carries dust, sand, and ash, polishing rocks and cliffs. o Forms sand dunes and ventifacts. o Can be damaging and is common in deserts and beaches. ICE EROSION Plucking: Fractured bedrock is incorporated into the ice. Abrasion: Ice and debris scratch bedrock, leaving grooves. TRANSPORTATION OF MATERIALS Materials transported in four ways: o Solution: Dissolved in water. o Suspension: Particles carried by air, water, or ice. o Traction: Rolling, sliding, and shuffling particles along surfaces. o Saltation: Particles move from surface to medium in repeated cycles. DEPOSITION Occurs when eroded materials settle in a location. WATER AND LANDFORMS When stream velocity decreases, it decreases, it deposits the sediments it carries. Material deposit of a stream is called alluvium. 1. Deltas: a. Formed when a river loses energy as it flows into slow-moving water like a lake or sea. 2. Alluvial Fans: a. Formed when a stream reaches a flat area (piedmont or gently sloping plain), depositing materials. 3. Flood Plains: a. Wide expanses of alluvium that cover flat areas prone to flooding. They form when silts are deposited on a flat surface during floods.  4. Levees: a. Small natural embankments formed alongside a river channel when the river overflows its banks, depositing coarse sediments as its velocity decreases. GLACIER AND LANDFORMS Glacial Till: Unsorted deposits left by glaciers. Moraines: Ridges of glacial till. Eskers: Winding ridges formed by glacial streams. Drumlins: Streamlined asymmetrical hills. Kames: Steep-sided hills formed by glacial deposits. WIND AND LANDFORMS Loess: Wind-deposited silt forming broad layers. Sand Dunes: Hills of coarse materials formed by wind action in deserts and coastal areas.