GEOL 101: Mass Movement, Hydrology, Glaciology, Drylands, and Coastal Processes

Vocabulary practice cards defining key terms from GEOL 101 lectures and quizzes, covering mass wasting, rivers and surface water, hydrogeology, glaciers, arid systems, and shoreline dynamics.

Mass Movement

The downslope transport of rock, regolith, and soil under the direct influence of gravity.

Angle of Repose

The steepest angle at which a pile of particles or sediments remains stable.

Liquefaction

A phenomenon occurring in saturated material during an intense earthquake where strong shaking causes the slope or material to fail and flow like a liquid.

Geologic Hazard

A natural geologic process that can cause harm to people or property if they are exposed to it.

Geologic Risk

The probability that exposure to a geologic hazard will cause harm, expressed as $\text{Risk} = \text{Hazard} \times \text{Exposure}$.

Fall (Mass Movement)

A type of mass movement involving the free fall of detached individual pieces of material of any size.

Slide (Mass Movement)

The movement of material along a distinct zone of weakness or flat surface, divided into rotational slumps and translational slides.

Flow (Mass Movement)

Material moving downslope in a viscous, turbulent, and fluid-like manner, typically associated with saturation.

Hydrologic Cycle

The continuous movement of water on Earth involving ocean evaporation, plant transpiration, condensation, precipitation, infiltration, and runoff back into oceans.

Water Balance

The annual volume of water passing through each component of the hydrologic cycle (about $380,000\,\text{km}^3$ or $91,000\,\text{cubic miles}$), wherein global precipitation equals global evaporation.

Drainage Basin

The total area of land (also known as a watershed) where rainfall collects into a single river or river system through rills, gullies, and streams.

Headwaters

The upper part of a drainage network (the zone of sediment production) where the most erosion occurs in a river system.

Trunk Stream

The section of a river drainage network (the zone of transportation) that usually features the longest transport of sediment load.

Mouth (River)

The terminal portion of a drainage network (the zone of deposition) where a stream loses energy and deposits most of its sediment load.

Delta

A depositional landform that develops where a river or stream enters a standing body of water such as a lake, inland sea, or ocean.

Abrasion (Stream)

An erosional process caused by the physical bombardment of a stream channel by moving water and sediment.

Quarrying

The removal of blocks of rock or material from a stream bed during high flow velocities.

Corrosion

The gradual chemical dissolution of channel bedrock (primarily soluble rocks like limestone) by flowing water.

Dissolved Load

Soluble mineral matter and chemical compounds carried in solution by a stream, mostly contributed by groundwater.

Suspended Load

Fine physical sediment particles (such as fine sand, silt, and clay) held aloft in the water column, constituting the bulk of a river's sediment load.

Bed Load

Coarser sediment particles that move along the bottom of a stream channel by rolling, sliding, or saltating.

Meandering Channel

An alluvial river channel that flows in sweeping, continuous bends and transports the majority of its sediment load in suspension.

Braided Channel

A complex network of converging and diverging channels threading around gravel bars or islands, formed where sediment is coarse and discharge varies widely.

Groundwater

Subsurface liquid water stored within the pore spaces, fractures, and voids of rock, soil, and sediment (representing $30.1\%$ of Earth's freshwater).

Water Table

The upper surface or level of groundwater saturation beneath the land surface, which generally mimics surface topography.

Porosity

The percentage of the total volume of rock or sediment that consists of open pore spaces.

Permeability

A measure of how well interconnected pore spaces are in a subsurface material, dictating how easily water can flow through it.

Aquifer

A permeable, porous subsurface layer of sediment or rock (such as sand or gravel) that enables groundwater to flow freely.

Aquitard

A subsurface layer of rock or sediment (such as sandy clay) that slows down or restricts groundwater movement.

Aquiclude

An impermeable subsurface layer that can store and contain water within its structure but does not permit groundwater to flow through it.

Aquifuge

A completely impermeable, solid rock layer possessing zero porosity that neither stores nor transmits groundwater.

Cone of Depression

A localized drawdown or depression in the water table centered around a well where groundwater is actively being pumped out.

Artesian System

A hydrogeologic system where groundwater in a tilted, confined aquifer bounded by aquitards is under sufficient pressure to rise above the level of the water table on its own.

Spring

A natural outflow where the water table intersects Earth's surface to produce an outcropping of water.

Geyser

An eruptive thermal feature in volcanic rock where groundwater in deep subterranean chambers is superheated under immense pressure until it flashes into regular steam eruptions.

Karst

A landscape and set of subterranean features created by the acidic dissolution of soluble carbonate rocks like limestone by groundwater.

Glaciation

The geologic process of continuous accumulation, compaction, and recrystallization of snow on land to form glacial ice.

Plastic Flow

The internal movement and ductile deformation of ice within a glacier, occurring once ice thickness reaches approximately $165\,\text{feet}$ ($\ge 165\,\text{feet}$).

Basal Slip

The physical sliding of an entire glacier along the bedrock or underlying surface at its base.

Plucking

A glacial erosion process where meltwater penetrates fractures in underlying bedrock, freezes, and tears large loosened blocks of rock into the moving ice mass.

Moraine

A bar-shaped ridge or mound of poorly sorted glacial debris deposited along the margins or front of a glacier, marking its maximum extent.

Glacial Erratics

Massive, transported boulders dropped by retreating or melting glaciers that differ in lithology from the underlying local bedrock.

Dryland

A climate region covering approximately $30\%$ of Earth's land where the potential rate of evaporation exceeds average precipitation.

Desert

A fully arid dryland region characterized by extremely low precipitation and brief surface water retention.

Steppe

A semi-arid transitional climatic zone between a desert and a humid region that supports scrub vegetation.

Rain Shadow

A dry geographic area on the leeward side of a mountain range formed because rising air cools and drops its moisture on the windward slope.

Ephemeral Stream

A short-lived desert stream channel (also known as a wadi) that flows only during or immediately following heavy precipitation events.

Deflation

The wind erosion process involving the lifting and removal of loose, dry, fine-grained particles across an arid landscape.

Aeolian

Sedimentary processes and deposits, such as sand dunes and wind-blown silt, that are shaped or deposited by wind.

Cross-Bedding

A large-scale sedimentary structure found within sandstones that indicates preservation of ancient wind-blown sand dunes.

Erg

A vast, continuous regional sand sea, such as the Rub' al Khali (Empty Quarter) on the Arabian Peninsula.

Ocean Wave

Energy traveling through seawater, predominantly generated by the friction of wind blowing across the surface of the ocean.

Longshore Current

A current flowing parallel to the coastline created by incoming refracted waves that drives the transport of sediment (beach drift) along a shore.

Emergent Coast

A shoreline formed where tectonic uplift or falling sea levels expose land, characterized by steep cliffs, wave-cut platforms, and marine terraces (e.g., the western US).

Submergent Coast

A shoreline characterized by relative sea-level rise or land subsidence, featuring barrier islands, marshes, and drowned river valleys/estuaries (e.g., the eastern and Gulf US).

Spring Tide

The highest high tide and lowest low tide occurrence resulting from the gravitational alignment of the Sun and Moon during new and full moon phases.

Hard Stabilization

Engineered coastal structures such as jetties, groins, breakwaters, and seawalls built to interrupt sediment transport or protect property from erosion.

Beach Nourishment

The soft coastal management practice of mechanically adding large quantities of hauled sand to maintain an eroding shoreline.