Weathering, Erosion, and River Systems

This set of vocabulary flashcards covers the processes of physical, chemical, and biological weathering, the distinctions between erosion and deposition, and the characteristics of river courses.

Weathering

The slow breakdown of rocks, soil, and minerals into smaller pieces in situ, meaning there is no movement of the weathered material.

Physical weathering

A process where rocks break into smaller pieces without changing their chemical composition.

Granular disintegration

A type of physical weathering where rocks break into small grains or pieces, such as sand or gravel, often caused by expansion and contraction.

Exfoliation

A weathering process where rocks are peeled off in layers due to repeated heating and cooling causing outer layers to expand and break away.

Block separation

Physical weathering where rocks break into large blocks along cracks or joints, often expanded by temperature changes or water.

Chemical weathering

The breakdown of rocks into particles with a different chemical composition from the original rock, involving agents like water, oxygen, and $CO_2$.

Solution

A type of chemical weathering where minerals, such as salt, dissolve in water.

Hydration

A chemical weathering process where minerals absorb water and expand, which can contribute to the physical breaking of the rock.

Hydrolysis

A chemical reaction between minerals and hydrogen ions in rainwater that can change rock-forming minerals into clay minerals.

Oxidation

A chemical process where rock minerals react with dissolved oxygen to form red/yellow oxides, similar to rusting; common in tropical areas.

Carbonation

A process where $CO_2$ dissolves in water to form a weak carbonic acid that weathers rocks like limestone and chalk.

Biological weathering

The breakdown of rocks caused by living organisms, such as plant roots growing into cracks or animals digging.

Mining

A human activity that speeds up weathering by digging up and breaking large rocks, exposing more surfaces to the elements.

Burning fossil fuels

A human impact that releases chemicals into the atmosphere, contributing to acid rain which weathers limestone and buildings.

Building roads

A human activity where rocks are blasted with explosives and broken into smaller pieces, facilitating faster weathering.

Erosion

The process by which soil and rock are removed from the Earth's surface and transported to another location by agents like water, wind, or glaciers.

Deposition

The process where eroded material is dropped or deposited in a new location once the movement stops.

Gravity

The underlying force behind many types of erosion that causes materials, rocks, and rivers to move downhill from higher elevations.

Upper Course

The beginning of a river (upstream) characterized by steep slopes, fast-moving water, vertical erosion, and $V$-shaped valleys.

Rapids

Fast-flowing parts of a river caused by steep slopes, typically found in the upper course.

Middle Course

The stage of a river with more gradual slopes, wider valleys, lateral erosion, meanders, and $U$-shaped valleys.

Meanders

Bends or curves in a river that typically develop during the middle and lower courses.

Lower Course

The stage close to the mouth (downstream) where water flows slowly, meanders are frequent, and deposition is the dominant process.

Oxbow Lake

A $U$-shaped lake formed in the lower course when a river bend is cut off from the main river channel.