Crust of the Earth: Erosion and Mass Wasting

These flashcards cover key vocabulary and definitions related to erosion, mass wasting, processes of sediment transport, and fluid dynamics as discussed in the geology lecture.

Weathering

The processes involved in the breakdown of rock.

Erosion

The set of processes whereby regolith is picked up and transported from one place to another.

Fluid

Substances which change their shape easily under their own weight.

Shear Force

A force acting in a direction parallel to a surface or to a planar cross section of a body.

Shear Stress

The response to a shear force.

Laminar Flow

A flow where streamlines are parallel and do not cross.

Turbulent Flow

A flow where streamlines twist, turn, and cross each other.

Reynolds Number

A dimensionless number used to determine whether a fluid’s flow is laminar or turbulent.

Regolith

A layer of loose, heterogeneous material covering solid rock.

Alluvial

Sediments deposited by the action of water.

Eolian

Sediments transported and deposited by wind.

Ventifacts

Rock surfaces smoothed by wind abrasion.

Suspended Load

The fine portion of sediment kept in constant suspension by water.

Dissolved Load

The fraction of sediment in solution as ions.

Bed Load

The portion of sediment that cannot be kept in constant suspension.

Creep

A slow, continuous movement of soil or rock down a slope.

Landslide

A rapid mass movement in rock or soil.

Talus

Coarse rubble that accumulates at the foot of a slope prone to rockfalls.

Mudflow

A flow that contains large quantities of water.

Earthflow

A movement of relatively fine-grained materials traveling quickly.

Debris Flow

A flow containing material coarser than sand.

Debris Avalanche

The fastest unconsolidated flow, moving down steep slopes.

Slump

A type of mass wasting where the surface at the top of the slide remains undisturbed.

Angle of Repose

The steepest angle at which loose material will remain at rest without sliding.

Gravity

The simplest mechanism of sediment transport, moving particles down a slope.

Surface Tension

The attractive force between molecules at a surface.

Chatter Marks

Crescent-shaped gouges formed by rock fragments dragged by a glacier.

Striations

Linear gouges left in bedrock by glaciers.

Slope Stabilization

Measures taken to reduce the potential for landslides.

Hydraulic Action

Erosive action caused by the movement of water.

Mass Wasting

The downslope movement of soil and rock under the influence of gravity.

Solifluction

A type of mass wasting common in permafrost where the water-saturated active layer moves downslope over frozen ground.

Rockfall

The fastest form of mass wasting where rocks fall vertically or bounce down a steep cliff face.

Rockslide

A rapid movement of a cohesive block of bedrock along a planar surface of weakness such as a bedding plane or joint.

Submarine Landslide

Mass wasting events occurring on the seafloor, often along the continental slope or the flanks of volcanic islands.

Liquefaction

The process by which saturated, unconsolidated soil loses its strength and behaves like a liquid, often triggered by earthquakes.

Scarp

The steep, exposed cliff face or crown left at the upslope edge of a slump or slide.

Toe of the Slide

The lower, downslope part of a landslide where the displaced material accumulates.

Debris Slide

A rapid sliding movement of a mass composed of soil and weathered rock fragments.

Rock Avalanche

A high-speed, catastrophic flow of fragmented rock debris resulting from a massive rockfall or rockslide.

Sensitive Clays

Clays that can lose nearly all their shear strength and flow like a liquid when disturbed or shaken.

Solifluction

A type of mass wasting common in permafrost where the water-saturated active layer moves downslope over frozen ground.

Rockfall

The fastest form of mass wasting where rocks fall vertically or bounce down a steep cliff face.

Rockslide

A rapid movement of a cohesive block of bedrock along a planar surface of weakness such as a bedding plane or joint.

Submarine Landslide

Mass wasting events occurring on the seafloor, often along the continental slope or the flanks of volcanic islands.

Liquefaction

The process by which saturated, unconsolidated soil loses its strength and behaves like a liquid, often triggered by earthquakes.

Scarp

The steep, exposed cliff face or crown left at the upslope edge of a slump or slide.

Toe of the Slide

The lower, downslope part of a landslide where the displaced material accumulates.

Debris Slide

A rapid sliding movement of a mass composed of soil and weathered rock fragments.

Rock Avalanche

A high-speed, catastrophic flow of fragmented rock debris resulting from a massive rockfall or rockslide.

Sensitive Clays

Clays that can lose nearly all their shear strength and flow like a liquid when disturbed or shaken.

Economic Loss

The financial impact of mass wasting, including damage to infrastructure and loss of property value.

Landslide Dam

A temporary dam formed by a landslide that blockades a river, creating a flood risk upstream and downstream if it fails.

Deforestation

The removal of vegetation that otherwise stabilizes slopes through root systems and moisture regulation.

Undercutting

The removal of the base of a slope by natural processes or human construction, leading to slope failure.

Oversteepening

The construction or excavation of slopes to an angle greater than the natural angle of repose.

Artificial Loading

The addition of weight to a slope, such as buildings or fill material, which increases the downslope force.

Irrigation

A human activity that can increase pore-water pressure and decrease shear strength in soil, triggering mass movements.

Drainage Control

A preventive measure that redirects water away from a slope to prevent saturation and pore-water pressure buildup.

Retaining Walls

Structures built at the base of a slope to provide physical support and resist shear forces.

Rock Bolts

Tensioned steel rods used to anchor unstable rock masses to deeper, more competent bedrock.

Shotcrete

Reinforced concrete sprayed onto rock surfaces to prevent weathering and fragmentation.

Benching

The process of cutting steps into a slope to reduce the overall gradient and catch falling material.

Slope Grading

Physical reshaping of a slope to a shallower, more stable angle.

Gabions

Metal cages filled with rock used to stabilize banks and slopes against erosion.

Rock Fence

A mesh barrier designed to catch and stop falling rocks or small debris flows.

Snow Shed

A structure designed to protect roads or rails from avalanches by allowing snow to pass over the top.

Hazard Mapping

The scientific analysis and spatial identification of areas prone to mass wasting to inform urban planning.

Buttressing

Adding heavy material to the toe of a slope to counteract the driving forces from above.

Geogrids

Polymeric materials used to reinforce soil mass inside a slope or retaining wall.

Ground Displacement Monitoring

The use of instruments like inclinometers to detect small movements in a slope before catastrophic failure occurs.