Geology Exam Review: Geologic Time, Surface Processes, and Earth Systems

Vocabulary practice flashcards covering geologic time, mass wasting, surface streams, hydrogeology, glaciology, desert landforms, and coastal processes.

Relative Age Dating

The geological practice of placing rocks, structures, or events in a sequential chronological order to determine whether they are older or younger without determining their exact numerical age.

Mass Wasting

The downslope movement of rock, regolith, and soil under the direct pull of gravity, influenced by factors such as relief, moisture content, and geological layering.

Soil Creep

The exceptionally slow, steady downhill movement of soil and loose surface debris caused by gravity and repetitive expansion-contraction cycles.

Soil Slump

A form of mass movement occurring when a cohesive block of unconsolidated material or soil slips downward along a curved, spoon-shaped rupture surface.

Rockfall

The rapid and free-falling descent of individual rocks or detached bedrock fragments down a steep cliff or slope.

Rock Slide

A fast and destructive mass wasting event in which a sheet or block of bedrock slides downslope along a planar surface of structural weakness.

Stream Discharge

The volume of water passing through a defined cross section of a stream channel over a given interval of time.

Stream Gradient

The slope of a stream channel, typically expressed as the vertical decrease in elevation over a given horizontal distance.

Base Level

The lowest limit to which a stream or river can downcut and erode its channel.

Alluvial Fan

A fan-shaped or cone-shaped accumulation of sediment deposited where a fast-flowing, confined mountain stream exits onto an open, flatter plain.

Delta

A depositional sediment landform constructed at the mouth of a river where it enters a standing body of water like a lake or ocean.

Oxbow Lake

A crescent-shaped body of standing water created when a meandering river cuts a straight path through a narrow neck, isolating an abandoned meander loop.

Drainage Basin (Watershed)

The comprehensive land area that collects and directs all surface runoff and precipitation into a common river system or body of water.

Water Table

The upper surface of the underground saturated zone, where all opening pore spaces within rock or sediment are filled with water.

Capillary Fringe

A subsurface zone directly above the water table where water is drawn upward into pore spaces against gravity via surface tension.

Aquitard

A layer of sediment or rock with very low permeability that impedes or severely limits the transmission of groundwater.

Aquifer

A permeable, water-bearing underground rock or sediment unit capable of yielding usable quantities of groundwater to springs and wells.

Porosity

The ratio or percentage of open void spaces within the total volume of a given rock, sediment, or soil sample.

Permeability

The measure of a porous material's capacity to allow fluids to pass through its interconnected network of pore spaces.

Hydraulic Gradient

The slope of the water table or potentiometric surface, which drives the direction and velocity of groundwater flow.

Artesian Well

A well tapping into a confined aquifer where hydrostatic pressure forces water to rise naturally above the top of the aquifer without the need for pumping.

Cone of Depression

A localized, conical depression in the water table centered around a pumping well caused by the active withdrawal of groundwater.

Saltwater Intrusion

The landward migration of saline coastal groundwater into freshwater aquifers, often triggered by heavy pumping and overdrafting of coastal wells.

Karst Topography

A distinctive landscape marked by sinkholes, sinking streams, caverns, and subsurface drainage resulting from the dissolution of soluble bedrock such as limestone.

Crevasse

A deep, vertical fracture formed in the brittle upper zone of a glacier as the ice moves and stretches over uneven topography.

Glacial Surge

A brief, sudden acceleration during which a glacier flows downhill at speeds significantly higher than its normal baseline velocity.

Glacial Budget

The balance between the total accumulation of snow and ice and the total ablation (loss by melting, evaporation, or calving) across a glacier over time.

Calving

The process by which large blocks of ice break away from the edge or terminus of a glacier into an ocean, lake, or bay to form icebergs.

Till

Unsorted and unstratified sediment dumped directly onto the landscape by melting glacial ice.

Moraine

A ridge or mound of unsorted glacial debris and till deposited along the front, margins, or base of an active or retreating glacier.

Esker

A winding, sinuous ridge composed of stratified sand and gravel left behind by meltwater streams flowing through tunnels within or under stagnant ice.

Drumlin

An asymmetrical, streamlined hill of glacial till aligned parallel to ice movement, featuring a steep upstream side and a gentle downstream slope.

Kettle Lake

A body of water occupying a steep-sided basin formed when a stranded, sediment-buried block of glacial ice melts.

Glacial Subsidence

The downward bending or sinking of Earth's lithosphere caused by the tremendous weight of an overlying ice sheet.

Desertification

The progressive transformation of productive, semiarid or subhumid lands into desert terrain primarily as a result of human activities and climate stresses.

Ventifact

A stone or pebble shaped, grooved, or polished by the abrasive action of windblown sand in arid settings.

Desert Pavement

A closely fitted surface layer of interlocking gravels and stones left behind after wind and running water remove finer sediment.

Desert Varnish

A dark, thin patina of iron oxides, manganese oxides, and clay minerals that coats exposed rock surfaces in arid regions over long periods.

Blowout

A shallow, wind-excavated depression or basin created in loose, unconsolidated sand where vegetative cover is absent or disturbed.

Loess

A widespread, unstratified deposit of windblown, silt-sized sediment typically derived from deserts or glacial outwash plains.

Barchan Dune

A solitary, crescent-shaped sand dune whose tips or horns point in the downwind direction, forming in environments with limited sand and unidirectional wind.

Transverse Dune

A prominent, straight sand ridge oriented perpendicular to the dominant wind direction, characteristic of regions with abundant sand and sparse vegetation.

Parabolic Dune

A crescent-shaped sand dune whose horns point upwind, typically anchored by vegetation in coastal or semiarid blowout areas.

Longitudinal Dune

A long, parallel ridge of sand oriented roughly parallel to the prevailing regional wind directions where sand supplies are moderate.

Submerged Coastline

A shoreline that has been partially flooded or drowned due to a relative rise in regional sea level or tectonic sinking of the coastal landmass.

Emergent Coastline

A coast that has been exposed or elevated above sea level due to tectonic uplift of the land or a drop in global sea level.