Earth Science Practice Test: Weathering and Erosion

Water expands by about 9% when it freezes, pushing the crack wider each time. This is a type of mechanical (physical) weathering, because the rock's minerals do not change.

Rainwater absorbs carbon dioxide and forms weak carbonic acid, which dissolves calcite in limestone. Over thousands of years this chemical weathering opens caves underground.

Chemical reactions speed up with heat, and water is needed for most of them, so warm, humid regions weather fastest. Cold, wet climates favor frost wedging, which is mechanical.

Weathering breaks or dissolves rock where it is, and erosion is the transport of that material by water, wind, ice or gravity. The first option swaps the two terms.

Glaciers fill a whole valley and scrape its sides and floor, leaving a U shape. Rivers cut downward in a narrow channel and usually make V-shaped valleys.

Slower water has less energy, so it drops the largest, heaviest particles first. Gravel settles near the river mouth, while fine clay stays suspended longest and settles farthest out.

When a river reaches standing water it slows sharply and drops its sediment, building a delta, like the Mississippi Delta. A moraine is a ridge of sediment left by a glacier.

Landslides are mass movement, which is erosion driven by gravity. The rain soaks the slope, adds weight and reduces friction, but gravity pulls the material downhill.

The 2 cm cube has 6 × 4 = 24 cm². It splits into 8 small cubes, each with 6 cm², for 48 cm². More exposed surface is why broken rock weathers faster.

Wind picks up sand grains and blasts them against exposed rock, wearing and polishing it like sandpaper. Frost wedging splits rock along cracks; it does not polish faces.