Geomorphic Processes

A crevasse is a deep crack, fissure, or fracture in a glacier or ice sheet, typically formed by stress and movement of the ice. These deep, often hidden cracks pose significant danger to mountaineers and glacier travelers.

A drainage basin is an area of land where all water that falls as precipitation or collects within it drains to a common outlet point, such as a river, lake, or ocean. It includes the main stream and all its tributaries.

River velocity directly determines the energy available to erode and transport sediment. Higher velocity increases erosion capacity and carries larger particles, while lower velocity leads to deposition. Gradient, channel shape, and discharge influence velocity but are secondary factors.

Hydraulic action (force of moving water), solution (chemical dissolution), and abrasion (particle grinding) are the three primary mechanisms by which streams erode their channels and transport sediment. Deposition is the opposite process.

Cobble-sized particles (64-256mm) are too large to be suspended and instead travel as bed load, rolling, sliding, or bouncing along the streambed. Suspended load carries silt and clay; dissolved load contains minerals in solution.

Point bars form on the inner curve of meanders where slower water velocity allows sediment deposition. Cut banks (option A) form on the outer curve where faster water erodes the bank, making them the opposite feature.

A delta is a wedge-shaped sediment deposit formed where a stream enters a standing body of water (lake or ocean). Alluvial fans (option A) form on land, while submarine fans (option B) form underwater but are not typically wedge-shaped in the same way.

Erosion is the process of topsoil and rock removal by natural forces like wind, water, or ice. Corrosion refers to chemical degradation of materials, not physical removal. Desalination removes salt from water, and detoxification eliminates toxic substances.

Gully is the correct answer. A gully is a narrow channel formed in the earth by water erosion, typically on a hillside or mountainside. They are smaller than canyons and form when water cuts through soil or soft rock. A fissure is a deep crack, a crack is a general fracture, and a gorge is a larger, deeper valley. The question correctly describes gullies.

Valley is the correct answer. A valley is an elongated depression in the land surface, typically situated between mountain ranges or hills. Valleys are drained by rivers and their tributaries, which shape them over geological time. A canyon is a deep gorge with steep sides, a plain is flat land, and a plateau is elevated flat land. The question accurately describes a valley.

An ox-bow lake forms when a river meander is cut off as the river finds a shorter path, leaving a crescent-shaped stagnant lake beside the main channel. A meander is the bend itself, not the resulting lake.

When a glacier calves, a large chunk of ice breaks off from its terminus and falls into a body of water, becoming an iceberg. Option A describes crevasses, which are internal cracks, not calving. Option B incorrectly suggests the glacier splits and flows in a different direction. Option D describes crack formation, which is a precursor to calving but not calving itself.

Weathering is the breakdown and decomposition of rocks in place through physical and chemical processes. Erosion involves removal and transportation of weathered material. Denudation is the overall lowering of land surface including both weathering and erosion. Mass washing is not a standard geological term.

Diagenesis is the process of compaction, cementation, and chemical changes that convert loose sediment into solid sedimentary rock over time.