Geology and Landforms: Key Concepts for Earth Science

Dynamic equilibrium

Balance between tectonic uplift and reduction by weathering/erosion.

Angle of repose

The steepest stable slope angle for loose material (~35° for sand, ~45° for gravel).

Regolith

Weathered rock material covering bedrock.

Mudflows

Mass movement with moisture.

Rockfalls

Mass movement without moisture.

Karst topography

Landscape from dissolution of limestone (≥80% CaCO₃), forming sinkholes, caves, disappearing streams.

Continental divides

High terrain separating drainage to different oceans.

Erosion vs. deposition

Erosion removes material; deposition drops it.

Water velocity significance

Higher velocity increases transport capacity and particle size moved.

Point bar

Depositional feature on inside bend of meander.

Cut bank

Erosional feature on outside bend of meander.

Oxbow lake

U-shaped lake from cutoff meander.

Base level

Lowest erosion level (usually sea level).

Eolian landscape

Shaped by wind (erosion, transport, deposition).

Abrasion vs. deflation

Abrasion = sandblasting; deflation = lifting/removing loose particles.

Loess

Wind-blown silt deposits from glacial outwash (e.g., Midwest, China).

Desertification

Fertile land becomes desert due to drought, deforestation, poor agriculture.

Sand dune types

Crescent (1 wind direction), linear (2 directions), star (>2 directions).

Glacier

Persistent ice mass moving under its own weight.

Alpine vs. continental glaciers

Alpine in mountains; continental cover large areas (Greenland = continental).

Depositional landforms

Lateral moraine (sides), medial moraine (middle), terminal moraine (end).

Permafrost

Ground frozen ≥2 years.

Weathering

Breaks down rock in place.

Physical weathering

Breaks rock without chemical change.

Chemical weathering

Alters rock composition.

Drainage patterns

Dendritic: tree-like; Trellis: parallel with right-angle tributaries; Radial: outward from central high point.

How glaciers form

Glaciers form where snow accumulation exceeds ablation (melting/evaporation) over years.