Earth Science: Weathering, Erosion, Mass Movements, and Surface Water

Comprehensive vocabulary flashcards covering the processes of mechanical and chemical weathering, water and wind erosion, sediment transport and deposition, mass movement hazards, and surface water drainage.

Weathering

The breakdown or change of rock at or near Earth's surface, either breaking it into smaller pieces or changing its minerals over time.

Mechanical (physical) weathering

A process where rock is broken into smaller pieces while its chemical composition and minerals stay the same.

Chemical weathering

A process where minerals in rock react and change, causing the chemical composition of the rock to change.

Frost wedging

A mechanical weathering process where water enters a crack in rock, freezes and expands, widening the crack until rock fragments separate.

Exfoliation

A mechanical weathering process where the outer layers of rock peel or split away in sheets due to pressure release and temperature changes.

Root pressure

A mechanical weathering process in which plant roots grow into small rock cracks and thicken, pushing against the rock and widening the cracks.

Oxidation

A chemical weathering reaction in which oxygen and moisture react with iron-containing minerals in rock, forming a reddish-brown mineral surface.

Erosion

The removal of weathered rock or sediment from its original location.

Transport

The movement of removed weathered material or sediment elsewhere by agents such as flowing water or wind.

Deposition

The dropping or settling of transported material or sediment after transport when the transporting medium loses energy.

Sediment

Small pieces of rock, soil, or other transported material.

Velocity

The speed of moving water, often measured in $\text{cm/s}$ in river investigations.

Slope

A property describing how steep a river channel or hillside is.

Discharge

The quantity of water flowing through a channel in a given time.

Independent variable

The factor deliberately changed in an investigation, such as channel slope.

Dependent variable

The result observed or measured in an investigation, such as water velocity or sediment movement.

Controlled variable

Conditions kept unchanged in an investigation, such as starting sediment, flow, width, and rain setting.

Mass movement

The downslope movement of soil, rock, or other weathered material on slopes under the continuous pull of gravity.

Creep

A very slow downhill movement of soil, evidenced by leaning trees, tilted fences, or tilted posts.

Landslide

A rapid downhill movement of rock and soil producing a large displaced mass.

Mudflow

A rapid downhill flow of a thick mixture of wet mud and water, typically occurring after heavy rain.

Rockfall

A mass movement where pieces of rock fall from a steep slope or cliff, leaving fallen rocks at the base.

Avalanche

A mass movement where snow and ice move rapidly down a snowy mountain.

Suspension (wind)

A mode of wind transport where very small and light particles, such as dust, remain lifted in moving air.

Saltation

A mode of wind transport in which sand grains bounce in short hops near the ground.

Surface creep (wind)

A mode of wind transport in which heavier particles, coarser grains, and small pebbles roll or slide along the ground surface.

Deflation

A wind-erosion process in which wind lifts and removes loose, fine particles from the ground surface.

Desert pavement

A surface layer of coarser pebbles and rocks left behind after wind removes fine particles through deflation.

Abrasion

A wind-erosion process in which wind-driven sand grains hit, rub, polish, and wear down solid rock surfaces.

Ventifact

A rock that has been smoothed, grooved, or shaped by the scraping action of wind-driven sand grains.

Sand dune

A ridge or mound formed by wind-blown sand that migrates as sand moves up a gentler windward slope and slides down a steeper leeward slope.

Loess

A thick, wind-deposited accumulation of fine silt that has settled out of the air.

Runoff

Water from rainfall that flows downhill across the land surface into streams, wadis, or other surface channels.

Infiltration

The process by which rainwater soaks downward into the ground through soil and rock pores or cracks.

Evaporation

The process in which liquid water changes to water vapour and moves into the air.

Groundwater

Water stored beneath Earth's surface that moves through connected rock pores and cracks after infiltration.

Drainage basin

The area of land where water drains into one main river system.

Divide

The high ground or elevated boundary that separates neighbouring drainage basins.

Tributary

A smaller stream or river that joins and feeds into a larger river.

Confluence

The place where two streams or rivers meet.

Mouth

The location where a river enters a lake, sea, or another receiving body of water.

Runoff percentage formula

The mathematical relationship used to calculate surface runoff: $\text{Runoff (\%)} = \left(\frac{\text{runoff collected}}{\text{water added}}\right) \times 100$.

Weathering

The breakdown or change of rock at or near Earth's surface in place, occurring without moving the material elsewhere.

Mechanical (physical) weathering

The process where rock is broken into smaller pieces while its chemical composition remains unchanged.

Chemical weathering

The process where minerals in a rock react and change, altering the rock's overall chemical composition.

Frost wedging

A mechanical weathering process in which water enters cracks, freezes and expands, widening the cracks until rock fragments separate.

Exfoliation

A mechanical weathering process in which the thin outer layers of rock peel or split away in sheets due to pressure release and temperature changes.

Oxidation

A chemical weathering reaction between oxygen and minerals in rocks, such as forming a reddish-brown mineral surface on iron-rich rocks exposed to air and moisture.

Erosion

The removal and initial movement of weathered rock or sediment from its original place.

Transport

The process of carrying eroded sediment from one location to another by agents such as flowing water or wind.

Deposition

The dropping or settling of transported material and sediment when moving water or wind loses energy.

Sediment

Small pieces of rock, soil, or other transported loose material.

Velocity

The speed of moving water, often measured in $\text{cm/s}$ during stream simulations.

Slope

A measure of how steep a river channel or hillside is.

Discharge

The quantity of water flowing through a stream channel in a given amount of time.

Independent variable

The factor deliberately changed by an investigator in a scientific experiment, such as channel slope.

Dependent variable

The result observed or measured in an experiment, such as water velocity or sediment movement.

Controlled variables

Conditions intentionally kept unchanged during an investigation to ensure a fair test, such as starting sediment, flow, channel width, and rain setting.

Mass movement

The downslope movement of soil, rock, or other weathered material under the direct influence of gravity.

Creep

The extremely slow downhill movement of soil, characterized by clues such as leaning trees or tilted fences and posts.

Landslide

The rapid downward movement of a large, displaced mass of rock and soil down a slope.

Mudflow

A rapid downhill flow of a thick mixture of wet mud and water, typically triggered after heavy rainfall.

Rockfall

A mass-movement event where individual pieces of rock detach and fall freely from a steep cliff or slope, accumulating at the base.

Avalanche

The rapid downslope movement of snow and ice down a mountain.

Suspension (wind)

A mode of wind transport in which very small, lightweight particles such as dust remain lifted and airborne in moving air.

Saltation

A mode of wind transport in which sand grains bounce along the ground surface in short hops.

Surface creep (wind)

A mode of wind transport where heavier, coarser sand grains and small pebbles roll or slide along the surface pushed by wind.

Deflation

The process of wind erosion where wind lifts and removes loose, fine particles from the ground surface.

Desert pavement

A gravel-covered ground surface of larger pebbles and rocks left behind after wind deflation blows away fine material.

Abrasion

The mechanical wearing down, scraping, and polishing of exposed solid rock by the impact of wind-driven sand grains.

Ventifact

A rock that has been shaped, smoothed, or grooved by the abrasive action of windblown sand particles.

Loess

A thick, extensive deposit formed by fine wind-blown silt that has settled out of the air.

Sand dune

A ridge or hill of wind-deposited sand that migrates downwind with a gentler windward slope and a steeper leeward slope.

Runoff

Precipitation that moves downhill across Earth's land surface instead of soaking into the ground, entering streams or wadis.

Infiltration

The downward movement of water soaking into soil and rock through pores or cracks.

Evaporation

The physical process in which liquid water changes into water vapour and returns to the atmosphere.

Groundwater

Water that is stored beneath Earth's surface within connected pore spaces and rock fractures.

Drainage basin

The total geographic area of land where surface water drains into a single main river system.

Divide

A ridge or area of higher ground that serves as the boundary separating adjacent drainage basins.

Tributary

A smaller stream or river that flows into and feeds a larger main river.

Confluence

The geographic location where two or more streams or rivers meet and merge.

Mouth (river)

The point where a river empties into a lake, ocean, or another receiving body of water.