Environmental Geology Vocabulary Review

Comprehensive vocabulary flashcards covering major geological, environmental, and climatological terminology across all 15 chapters of Environmental Geology by Steve Earle.

Earth System Science

An interdisciplinary field based on the premise that the Earth behaves as a single, self-regulating planetary system of physical, chemical, biological, and human components interconnected by complex transfers and feedbacks of matter and energy.

Albedo

The reflectivity of an Earth surface, measured as the proportion of incoming solar radiation that is reflected back into space rather than absorbed and converted to heat.

Faint Young Sun Paradox

The apparent contradiction where the early Sun was approximately $20\%$ to $30\%$ less luminous than today, yet early Earth did not freeze over because of a denser atmosphere rich in greenhouse gases such as carbon dioxide ($\text{CO}_2$) and methane ($\text{CH}_4$).

Gaia Theory

The hypothesis proposed by James Lovelock and Lynn Margulis that living organisms and their inorganic environment on Earth evolve and interact as a self-regulating system that maintains conditions suitable for the persistence of life.

Climate Feedback

A secondary process that either amplifies (positive feedback) or dampens (negative feedback) an initial climate forcing effect, such as the ice-albedo feedback or the release of greenhouse gases from thawing permafrost.

Silica Tetrahedron

A structural building block of all silicate minerals consisting of four oxygen ions ($\text{O}^{2-}$) covalently and ionically bonded to a central silicon ion ($\text{Si}^{4+}$), yielding an overall tetrahedral shape with a net charge of $-4$ ($\text{SiO}_4^{4-}$).

The Rock Cycle

The continuous series of geological processes through which igneous, sedimentary, and metamorphic rocks are formed, altered, transported, buried, uplifted, and remelted over geological time.

Asthenosphere

A ductile, semi-molten layer of the upper mantle between approximately $100\,\text{km}$ and $250\,\text{km}$ depth where temperatures are close to or slightly above the melting point of mantle rock, allowing it to slowly deform and flow.

Hydrolysis

A chemical weathering reaction in which hydrogen ions or water split mineral molecules apart, such as the reaction of carbonic acid ($\text{H}_2\text{CO}_3$) with silicate minerals like feldspar to form clay minerals and dissolved ions while consuming atmospheric $\text{CO}_2$.

Milanković Cycles

Cyclical variations in Earth's orbital geometry—specifically eccentricity (approx. $100{,}000\text{-year}$ cycle), axial tilt or obliquity (approx. $41{,}000\text{-year}$ cycle), and precession or tilt direction (approx. $23{,}000\text{-year}$ cycle)—that alter the seasonal and latitudinal distribution of solar insolation.

Thermohaline Circulation

Global deep-ocean circulation driven by density differences resulting from variations in water temperature ('thermo') and salinity ('haline'), which plays a critical role in transferring heat from low to high latitudes.

Dansgaard-Oeschger Cycles

Rapid millennial-scale climate oscillations of $6$ to $10\,^{\circ}\text{C}$ recurring roughly every $1000$ to $2000\,\text{years}$ during glacial periods, driven primarily by changes in North Atlantic salinity and thermohaline circulation strength ('salinity oscillator').

Glacier

A long-lasting body of ice on land that is thick enough (at least tens of metres) and expansive enough (at least hundreds of metres) to flow under its own weight under the influence of gravity.

Equilibrium Line

The boundary on the surface of a glacier that separates the zone of accumulation (where annual snow accumulation exceeds melting) from the zone of ablation (where annual melting exceeds accumulation).

Basal Sliding

The mechanism of glacier movement in which an entire glacier slides across bedrock or sediment facilitated by a lubricating thin film of subglacial liquid water at a warm base.

U-Shaped Valley

A steep-sided, flat-bottomed valley formed through glacial erosion as an alpine glacier carves deeply across its floor and sides, widening a pre-existing stream valley.

Cirque

A bowl-shaped, steep-walled amphitheatre basin carved into the side of a mountain at the head of a glacial valley by alpine glacial erosion and freeze-thaw processes.

Arête

A sharp, narrow, jagged knife-like ridge of rock formed between two adjacent parallel U-shaped glacial valleys or adjacent cirques.

Horn

A steep, pyramidal mountain peak formed by headward glacial and freeze-thaw erosion carving into the rock on three or more sides from adjacent cirques.

Till

Unsorted, unstratified sediment deposited directly by glacial ice, ranging in clast size from microscopic clay minerals up to immense boulders.

Sandur

A broad, gently sloping proglacial outwash plain formed of stratified sand and gravel deposited by meltwater-fed braided streams issuing from the margin of a glacier.

Esker

A long, winding, sinuous ridge of stratified sand and gravel deposited by a subglacial stream flowing in an ice-walled tunnel within or beneath a glacier.

Mass Wasting

The down-slope failure and movement of rock, regolith, or unconsolidated sediment under the direct influence of gravity without the primary transport of an erosional medium such as water, wind, or ice.

Angle of Repose

The maximum, steepest slope angle at which a pile of loose, dry unconsolidated sediment can remain stable without sliding or failing under gravity (typically around $30^{\circ}$ to $35^{\circ}$ for dry sand).

Sackung

The exceptionally slow, deep-seated gravitational sagging or translational sliding motion of a large block of rock (on the order of millimetres to centimetres per year) on a steep slope.

Rock Avalanche

A rapid, catastrophic mass wasting failure where a detached body of rock disintegrates into fragments that flow in a fluid-like manner, frequently supported on a cushion of entrapped air at speeds exceeding tens of metres per second.

Creep

The imperceptibly slow (millimetres to centimetres per year) downslope movement of soil or unconsolidated regolith, often facilitated by cyclical freeze-thaw or wetting-drying processes and manifested by curved 'pistol butt' tree trunks.

Slump

A rotational slide occurring within thick unconsolidated materials where coherent masses of sediment move downward and outward along a concave-upward curved failure surface.

Debris Flow

A fast-moving, water-saturated slurry of unconsolidated sediment containing sand, gravel, boulders, and organic debris that rushes rapidly down steep stream channels.

Lahar

A volcanic mudflow or debris flow consisting of water-saturated volcanic ash, tephra, and rock debris, typically mobilized by the rapid melting of snow and ice during an eruption or by torrential rainfall on volcanic slopes.

Earthquake

The shaking of the ground caused by the sudden rupture and displacement of strained rock bodies along a fault beneath the Earth's surface, releasing stored elastic energy as seismic waves.

Elastic Rebound

The mechanism by which rocks deform elastically under tectonic stress until the rock's shear strength is exceeded, resulting in brittle rupture and instantaneous snapping back to an unstressed configuration.

Rupture Surface

The specific area across a fault plane over which brittle failure and relative displacement occur during an earthquake.

Episodic Tremor and Slip (ETS)

Periodic, slow slip accompanied by non-earthquake seismic tremor occurring along the intermediate, ductile-to-locked transition zone of a subduction plate boundary (such as the Cascadia subduction zone roughly every $14\,\text{months}$).

Moment Magnitude ($M_W$)

An earthquake magnitude rating scale based on the seismic moment, calculated from the surface area of the fault rupture, the average displacement along the fault, and the rigidity modulus of the rock.

Liquefaction

The process whereby water-saturated, cohesionless sediment temporarily loses its shear strength during intense seismic shaking and transforms into a pressurized fluid slurry.

Tsunami

A series of ocean waves with extremely long wavelengths generated by sudden vertical displacement of the seafloor, most commonly during a large ($M \ge 7$) subduction earthquake.

Effusive Eruption

A non-explosive volcanic eruption characterized by the gentle, steady outpouring of low-viscosity, gas-poor (typically mafic) lava onto the surface.

Composite Volcano

A steep-sided, conical volcanic mountain (also called a stratovolcano) constructed from alternating layers of pyroclastic debris and viscous lava flows, typically found along subduction plate boundaries.

Shield Volcano

A broad, gently sloping volcano with a low-angle profile resembling a warrior's shield, built almost entirely from successive fluid mafic (basaltic) lava flows originating from mantle plumes or divergent boundaries.

Cinder Cone

A small (tens to hundreds of metres high), steep-sided conical hill formed from accumulated vesicular fragments of mafic tephra (cinders) ejected during a monogenetic, gas-rich explosive eruption phase.

Caldera

A large, basin-shaped volcanic depression exceeding $2\,\text{km}$ in diameter formed by the subsidence or collapse of the volcano's summit into an evacuated underlying magma chamber.

Pyroclastic Density Current

A fast-moving, high-temperature (up to $1000\,^{\circ}\text{C}$) ground-hugging avalanche of incandescent volcanic gas, ash, pumice, and rock fragments moving downslope at speeds of hundreds of kilometres per hour.

Large Igneous Province (LIP)

An extensive accumulation of predominantly mafic extrusive and intrusive rocks covering up to millions of square kilometres formed by massive, short-duration magmatic pulses from mantle plumes.

Kimberlite

An ultramafic igneous pipe-like rock originating deep within the mantle at depths of $150$ to $450\,\text{km}$ that ascends rapidly to the surface, potentially carrying diamond crystals mined from ancient cratonic roots.

Volcanogenic Massive Sulphide (VMS) Deposit

A stratiform metal sulfide ore deposit formed on or near the sea floor where hydrothermal fluids discharge at submarine volcanic vents ('black smokers'), precipitating sulfide minerals like chalcopyrite, sphalerite, galena, and pyrite.

Porphyry Deposit

A large-tonnage, low-to-medium-grade hydrothermal ore deposit of copper, molybdenum, or gold hosted in and around a fractured, porphyritic felsic-to-intermediate stock in the upper crust.

Acid Rock Drainage (ARD)

Acidic, metal-laden drainage generated when iron sulfide minerals (predominantly pyrite, $\text{FeS}_2$) are exposed to atmospheric oxygen and water, oxidizing to produce sulfuric acid and releasing toxic dissolved metals.

Tailings

The fine-grained slurry of crushed rock residue and processing chemicals left behind after the economic ore minerals have been physically extracted from pulverized rock.

Oil Window

The specific depth (typically $2$ to $4\,\text{km}$) and temperature range ($60$ to $120\,^{\circ}\text{C}$) within the Earth's crust where sedimentary organic matter is thermally converted into liquid petroleum.

Hydraulic Fracturing (Fracking)

The extraction process of injecting water, proppants, and chemicals at extremely high fluid pressure into deep, impermeable source rocks (such as shale) to induce fractures and facilitate the recovery of oil and natural gas.

Capacity Factor

The ratio of the actual electrical energy produced by a power-generating facility over a specified period to its potential output if it had operated continuously at full rated capacity.

Run-of-River Hydro

A hydroelectric generation facility that diverts a portion of natural river flow through a penstock and turbine without requiring the construction of a large water-storage reservoir dam.

Geo-Exchange System

A ground-source heat pump system that utilizes the relatively constant year-round thermal reservoir of the shallow subsurface (maintained by solar energy) for heating in winter and cooling in summer.

Exfoliation

A mechanical weathering process in which concentric curved sheets or slabs of rock fracture and peel away parallel to an exposed surface due to the release of confining pressure (pressure unloading).

Frost Wedging

A mechanical weathering process occurring when water seeps into rock fractures, freezes, and expands by approximately $9\%$, progressively prying the crack wider during repeated freeze-thaw cycles.

Soil Horizons

Distinct, sub-horizontal textural and compositional layers within a developed soil profile, classically designated as O (organic), A (topsoil), E (eluviated), B (subsoil accumulation), and C (partially weathered parent material).

Podsol

A Canadian soil order typical of cool, humid coniferous forest regions, characterized by intense leaching (eluviation) of iron, aluminum, and clay from the upper horizons and accumulation in the B horizon.

Chernozem

A fertile grassland soil order characteristic of sub-humid to semi-arid prairie regions, distinguished by a dark, organic-rich A horizon that is at least $10\,\text{cm}$ thick.

Smectite

A group of 2:1 (tetrahedral-octahedral-tetrahedral) swelling clay minerals that have significant cation exchange capacity and expand dramatically by absorbing water molecules directly between molecular interlayer sheets.

Porosity

The percentage of the total bulk volume of an unconsolidated sediment or rock that is occupied by void or pore spaces.

Hydraulic Conductivity ($K$)

A measure of the ease with which water can move through pore spaces or fractures within a permeable sediment or rock, typically expressed in units of velocity ($\text{m/s}$).

Aquifer

A permeable, saturated geological unit of rock or unconsolidated sediment capable of storing, transmitting, and yielding economically significant quantities of water to wells or springs.

Potentiometric Surface

An imaginary surface representing the total hydraulic head of groundwater in a confined aquifer, equal to the elevation to which pressurized water will naturally rise in an artesian well.

Darcy's Law

An empirical equation stating that total groundwater discharge ($Q$) is proportional to hydraulic conductivity ($K$), hydraulic gradient ($i$), and cross-sectional area ($A$): $Q = K \times i \times A$.

Cone of Depression

A funnel-shaped localized depression of the water table or potentiometric surface centered around a pumping well, formed because water is extracted faster than it can be replaced by aquifer flow.

Drainage Basin

The total geographic catchment area of land that gathers precipitation and surface runoff to deliver it into a single stream network or body of water, bounded topographically by drainage divides.

Base Level

The lowest elevation to which a running stream or river can chemically and mechanically erode its channel floor.

Recurrence Interval ($R_i$)

The statistical average time interval in years between flood discharge events of a specific magnitude, calculated as $R_i = \frac{n + 1}{r}$, where $n$ is the years of record and $r$ is flood rank.

Runoff Coefficient

A dimensionless empirical factor representing the fraction of precipitation falling on a drainage surface that becomes direct overland surface runoff rather than infiltrating into the subsurface.

Karst

A distinctive landscape characterized by sinkholes, sinking streams, caves, and complex subterranean drainage systems, formed primarily through the chemical dissolution of soluble bedrock such as limestone by slightly acidic water.

Karren

A collective term describing minor superficial solutional channels, flutes, furrows, and grooves developed on exposed bare limestone surfaces.

Epikarst

The upper, highly weathered boundary zone of solutionally enlarged fractures and cavities in a karst landscape, extending up to $10$ to $30\,\text{m}$ below the surface, connecting surface infiltration to the deep endokarst.

Sinkhole

A topographically closed, funnel-shaped surface depression in a karst landscape formed by the dissolution of bedrock, the collapse of underlying cave roofs, or the suffosion of overlying sediment.

Swallet

A distinct point opening or sink point in a karst landscape where an entire surface stream or runoff disappears underground into the subterranean karst network.

Vadose Zone

The unsaturated aerated subterranean zone extending from the ground surface down to the water table where geological pores, fractures, and cave passages contain both air and water.

Phreatic Zone

The saturated subterranean zone situated beneath the water table where all pore spaces, fractures, and karst cavities are completely filled with water.

Speleogens

Centimetre-to-metre-scale erosional bedrock relief features sculpted into the internal rock surfaces of caves by dissolution or mechanical abrasion, including scallops, pendants, and notches.

Speleothems

Secondary mineral deposits precipitated inside caves from karst groundwater degassing carbon dioxide, encompassing stalactites, stalagmites, columns, draperies, and flowstone.

Troglobites

Obligate, subterranean-adapted organisms that are physically restricted to cave environments, typically exhibiting loss of pigmentation, rudimentary or missing eyes, and specialized sensory organs.

Phreatic Loop

A deep, water-filled U-shaped conduit that develops beneath the water table in the phreatic zone, connecting an input recharge site to an output spring along a preferential bedrock pathway.

Leachate

Highly mineralized, oxygen-depleted contaminated water that has percolated through solid waste in a landfill, dissolving organic and inorganic matter, heavy metals, ammonia, and organic acids.

Biochemical Oxygen Demand (BOD)

A standardized measure of the dissolved oxygen consumed by aerobic microorganisms while biologically decomposing organic matter present in water or wastewater over a specified incubation period (typically $5\,\text{days}$, $\text{BOD}_5$).

Landfill Gas

A mixture of biogenic gases generated by microbial decomposition of putrescible organic waste inside an anaerobic landfill, consisting predominantly of methane ($\text{CH}_4$, $45$ to $60\%$) and carbon dioxide ($\text{CO}_2$, $40$ to $60\%$).

Permafrost

Ground (soil, sediment, or bedrock, along with contained water and organic matter) that remains continuously frozen at or below $0\,^{\circ}\text{C}$ for at least two consecutive years.

Storm Surge

An abnormal coastal rise in sea level accompanying an intense storm or tropical cyclone, caused by strong onshore winds pushing water inland, deep atmospheric low pressure, and superimposed high waves.