Lithosphere Exogenic Processes Exercise Solutions | KalviGavani

| Feature | Physical Weathering | Chemical Weathering | |---|---|---| | Process | Mechanical breakdown | Chemical decomposition | | Change | Size decreases, composition unchanged | Composition changes | | Climate | Cold and dry | Hot and humid | | Examples | Frost action, exfoliation | Oxidation, carbonation, hydration | | Products | Smaller rock fragments | New minerals (e.g., clay, rust) |

Mass wasting is the downward movement of rock, soil, and debris under the influence of gravity, without a transporting medium. Three types: 1. Creep: Very slow, continuous movement of soil downslope 2. Landslide: Rapid sliding of a large mass of rock and soil 3. Mudflow: Rapid flow of water-saturated soil and rock

Erosional landforms: V-shaped valley, waterfalls, meanders Depositional landforms: Alluvial fans, floodplains, deltas

Stalactites: Icicle-like formations hanging from the ceiling of limestone caves, formed by deposition of calcium carbonate from dripping water. Stalagmites: Mound-like formations rising from the cave floor, formed by deposition of calcium carbonate from water dripping onto the floor. When stalactites and stalagmites meet, they form a column.

1. Physical (Mechanical) Weathering: Breakdown of rocks into smaller fragments without changing their chemical composition. - Frost action (freeze-thaw): Water enters cracks in rocks, freezes and expands (by ~9%), widening the cracks. Repeated freezing and thawing eventually splits the rock. Common in cold climates. - Exfoliation (onion weathering): Outer layers of rock peel off due to daily temperature changes. The rock expands during the day and contracts at night, causing the outer layers to flake off. Common in deserts. - Thermal expansion: Rocks expand when heated and contract when cooled, causing stress and cracking. - Abrasion: Rocks grind against each other by wind, water, or ice, wearing them down. 2. Chemical Weathering: Decomposition of rocks through chemical reactions, changing their composition. - Oxidation: Reaction of minerals with oxygen. Iron-bearing rocks rust (turn reddish-brown). Fe + O₂ → Fe₂O₃ (rust) - Carbonation: Reaction with carbonic acid (H₂CO₃ formed by CO₂ + water). Limestone (CaCO₃) dissolves, forming caves and karst landscapes. CaCO₃ + H₂CO₃ → Ca(HCO₃)₂ (soluble) - Hydration: Minerals absorb water and expand, causing rocks to crack. Feldspar + water → clay minerals - Solution: Soluble minerals dissolve in water. Rock salt (NaCl) dissolves easily. 3. Biological Weathering: Breakdown of rocks by living organisms. - Plant roots: Roots grow into cracks, exerting pressure and splitting rocks - Burrowing animals: Earthworms, ants, and rodents dig into soil and rocks - Lichens and mosses: Secrete acids that dissolve rock surfaces - Decaying matter: Organic acids from decaying plants and animals react with rocks

Erosional Landforms of Rivers: 1. V-shaped valley: Formed in the upper course by vertical erosion (downcutting). The river cuts deep into the ground, and the valley sides are steep, forming a V-shape. 2. Waterfalls: Formed when a river flows over a band of hard rock followed by soft rock. The soft rock erodes faster, creating a step and eventually a waterfall. Example: Niagara Falls. 3. Gorges: Deep, narrow valleys formed by intense vertical erosion, usually in hard rock areas. 4. Meanders: Bends in the river course formed by lateral erosion on the outer bank and deposition on the inner bank. 5. Oxbow lakes: Formed when a meander loop is cut off from the main river. The neck of the meander narrows and eventually breaks through. Depositional Landforms of Rivers: 1. Alluvial fans: Fan-shaped deposits of sediment formed where a river leaves a mountain and enters a plain. The river's velocity drops suddenly, depositing its load. 2. Floodplains: Flat areas on either side of the river that get covered with water and sediment during floods. Very fertile for agriculture. 3. Levees: Raised banks along the river formed by repeated flooding and deposition of coarse sediment near the river channel. 4. Deltas: Triangular depositional landforms formed where a river meets a sea or lake. The river splits into distributaries as it deposits its sediment load. Example: Sundarbans Delta (Ganges-Brahmaputra). 5. Oxbow lakes (also partly depositional): When a meander is cut off, the crescent-shaped lake is filled with still water and sediment over time.

Erosional Landforms of Wind: 1. Mushroom rocks (rock pedestals): Wind erodes the lower part of a rock more than the upper part (because wind carries more sand near the ground), creating a mushroom shape. Common in deserts. 2. Yardangs: Elongated ridges of rock carved by wind erosion, aligned in the direction of the prevailing wind. 3. Deflation hollows: Shallow depressions formed by wind removing loose sand and dust from the surface. 4. Ventifacts: Rocks faceted (flattened) on one or more sides by wind abrasion. Depositional Landforms of Wind: 1. Sand dunes: Mounds of sand deposited by wind. Types include barchan (crescent-shaped), longitudinal (parallel to wind), transverse (perpendicular to wind), and parabolic dunes. 2. Loess: Fine, yellowish, wind-blown silt deposited far from its source. Very fertile soil. Found in northern China, central USA, and the Rhine Valley in Europe. 3. Ripple marks: Small ridges formed on sand surfaces by wind, similar to water ripples. Factors affecting wind erosion: - Wind speed and duration - Vegetation cover (less vegetation = more erosion) - Particle size (fine particles eroded more easily) - Rock hardness (softer rocks erode faster)