Surface Processes: Weathering, Erosion, and Landscapes
What this domain tests
Surface processes explain how rock is broken down, moved, and deposited at Earth's surface. Expect questions on weathering, soils, mass wasting, streams, groundwater, glaciers, wind, and coasts, with emphasis on linking a process to its landform or sediment.
Weathering and soils
Physical weathering includes frost wedging, salt-crystal growth, unloading, thermal expansion, and biologic activity. Chemical weathering includes dissolution, hydrolysis (feldspar to clay), and oxidation. Soil is regolith plus organic matter, organized into O, A, E, B, C, and R horizons. Warm wet climates favor chemical weathering; cold or dry climates favor physical breakdown.
Mass wasting and streams
Mass wasting is downslope movement under gravity. Triggers include saturation, steepening, vegetation removal, and earthquakes. Streams erode, transport, and deposit sediment; gradient, discharge, and load control behavior. Competence is the largest clast a stream can carry; capacity is the total load. Meanders, floodplains, and deltas record deposition where velocity falls.
Groundwater, glaciers, wind, and coasts
Porosity is pore space; permeability is connected pore space that transmits water. The water table separates saturated from unsaturated rock. Glaciers erode by abrasion and plucking; till is unsorted, outwash is sorted. Wind transports by saltation and produces dunes and loess. Waves refract, and longshore drift moves sediment along coasts, building spits and bars.
Worked example
A river drops from 1,200 m to 700 m over 100 km. Gradient = 500 m / 100,000 m = 0.005, or 5 m/km. The steeper upstream reach has faster flow and more erosion; the downstream reach has a lower gradient, so deposition dominates. This explains why boulders and gravel appear upstream while sand and mud collect downstream.
Traps
- Weathering breaks rock in place; erosion transports the debris.
- High porosity does not guarantee high permeability.
- Till is unsorted; outwash is sorted by water.
- Mass wasting does not require water, though water often triggers it.
- Longshore drift direction follows the dominant wave approach, not the wind alone.