GEOG 212: Geomorphological Processes and Landforms Lecture Series

Comprehensive practice vocabulary flashcards covering the definition, history, and physical processes of geomorphology including tectonics, weathering, mass wasting, fluvial, aeolian, and coastal landforms.

Geomorphology

The study of the nature of earth’s landforms and the processes that shape the earth’s surface; derived from the Greek words 'ge' (earth), 'morphe' (form), and 'logos' (discourse).

Principle of Uniformitarianism

The fundamental concept that the same physical processes and laws that operate today operated throughout geologic time, summarized by the phrase: 'the present is the key to the past'.

Orogenic forces

Internal forces shaping the Earth’s surface, including tectonic movements, volcanic activities, and earthquakes.

Exogenic forces

External forces associated with denudation processes such as weathering, mass wasting, and the actions of glaciers, rivers (fluvial), and wind.

Catastrophism

The theory popularised by George Cuvier that Earth's features are formed in single, worldwide catastrophic events such as great floods or volcanic eruptions.

James Hutton

Conceiver of the Theory of Uniformitarianism and often referred to as the 'Father of Modern Geology'.

Geographical Cycle of Erosion

A model developed by W.M. Davis describing landscape evolution through stages of youth, maturity, and old age (peneplanation).

Base level

The lowest elevation to which a stream can erode, with the ocean serving as the ultimate base level.

Grove Karl Gilbert

Acknowledged as the Father of modern geomorphology, he systematically discussed weathering, bedrock erosion, and the dynamic equilibrium theory of landforms.

Landscape evolution model

A mathematical expression represented as $I - O = \triangle S$, where $I$ is input of sediment, $O$ is output, and $\triangle S$ is change in storage.

Barysphere (Core)

The Earth's center with a thickness of approx. 3500\text{\nkm}, composed of Iron and Nickel ($\text{NIFE}$) and temperatures reaching $1927^{\text{o}}C$.

SIAL

Continental crust rocks composed of silica and alumina, typically felsic rocks like granite with a density of $2.7$.

SIMA

Oceanic crust rocks composed of silica, iron, and magnesium, typically mafic rocks like basalt with a density of $3$.

Mohorovic (“Moho”) Discontinuity

The interface or boundary between the Earth's crust and the upper mantle marked by a change in earthquake wave transmission and rock density.

Lithosphere

The cold, rigid, and brittle layer composed of the crust and the uppermost mantle, ranging from 60-150\text{\nkm} in thickness.

Asthenosphere

The semi-liquid, plastic soft layer upon which the lithospheric plates float.

Pangea

A supercontinent theorized by Alfred Wegener that existed 200\text{\nmillion years} ago before splitting into Laurasia and Gondwanaland.

Subduction

The tectonic process in which one plate (typically oceanic) slides or is dragged beneath another plate into the Earth's mantle.

Plastic Strain

Deformation where a body is bent or molded and does not return to its original shape after stress is removed.

Anticline

An upward-arching fold in rock layers.

Syncline

A downward-curving fold in rock layers.

Horst

An uplifted block of land between two reverse faults caused by compression or a central block being pushed upwards.

Graben (Rift Valley)

A block of land that has subsided between faults, often caused by tension.

Batholith

A massive igneous pluton formed beneath the Earth's surface by the intrusion and solidification of magma.

Sill

A concordant igneous rock body that solidifies parallel to the pre-existing bedrock layers.

Dyke

A discordant igneous rock body that cuts across pre-existing rock beds, mostly along fault lines.

Viscosity of Magma

Controlled by silica content; basic lava (basalt) contains 50\text{\n%}\text{ SiO}_2 and flow easily, while acidic lava (granite) contains 70\text{\n%}\text{ SiO}_2 and is highly viscous.

Shield Volcano

A gently sloping, dome-shaped landform built from highly fluid basaltic lava flows, such as Mauna Loa in Hawaii.

Elastic Rebound Theory

The theory that earthquakes occur when rocks are bent by tectonism until the strain is relieved by sudden slippage along a fault, releasing energy as seismic waves.

P-waves (Primary waves)

Compressional longitudinal waves that travel fastest through any material (5000\text{\nm/s} in granite) and arrive first at seismograph stations.

S-waves (Secondary waves)

Transverse shear waves that displace the ground perpendicularly; they only travel through solids and move at approximately 60\text{\n%} the speed of P-waves.

Richter scale

A quantitative scale ranging from $0-10$ that measures the magnitude or quantity of energy emitted by an earthquake.

Modified Mercalli Scale

A descriptive ordinal scale numbered from $I$ to $XII$ used to measure earthquake intensity based on observed destruction and human sensation.

Bowen’s Reaction Series

The sequence of temperature-dependent mineralization in igneous rocks, where minerals like Olivine crystallize first at high temperatures.

Goldich Stability Index

A measure of the relative weathering rate of minerals; it demonstrates that minerals formed at high temperatures (like Olivine) weather faster than those formed at low temperatures (like Quartz).

Haloclasty

Mechanical weathering caused by salt crystal growth in rock openings, common in arid and coastal regions, often forming 'tafoni' or honeycomb surfaces.

Exfoliation

A type of physical weathering where rock breaks apart in layers parallel to the surface due to pressure release.

Carbonation

A chemical weathering process where rainwater containing $\text{CO}_2$ forms weak carbonic acid ($\text{H}_2\text{CO}_3$) that reacts with calcium carbonate ($\text{CaCO}_3$) to form soluble calcium bicarbonate.

Chelation

A biological weathering process where organisms like lichens produce substances (chelates) that decompose minerals by removing metallic cations.

Factor of Safety ($FS$)

The ratio of resisting forces (shear strength) to driving forces (shear stress); a slope is stable if $FS > 1$.

Solifluction

The slow downslope movement of water-saturated sediment over a permafrost layer, typical of tundra regions in summer.

Gelifluction

A seasonal mass movement in periglacial regions describing the slippage of topsoil along a slide plane when it becomes waterlogged during a thaw.

Lahar

A mudflow specifically triggered by volcanic eruptions where falling ash or dust is turned into mud by rain or snowmelt.

Hydraulic action

Fluvial erosion caused by the physical force of moving water sweeping up loose material and breaking up weak solid rocks.

Corrasion (Abrasion)

The wearing away of a river bed or coastal cliff using the transported load as a grinding tool.

Saltation

A mode of transportation where small pebbles and stones are bounced along a river bed or desert floor.

Hjustrom Curve

A graph showing the relationship between water velocity and the erosion, transport, or deposition of different sized particles.

Ox-bow lake

A crescent-shaped lake formed in the lower course of a river when a meander loop is cut off from the main channel by deposition.

Delta

A fan-shaped alluvial area at the mouth of a river formed by the deposition of sediment as the river meets a calm body of water like a sea or lake.

Erg

A sandy desert characterized by a 'sea of sand' and ripples formed by wind direction.

Hamada

A rocky desert consisting of large stretches of bedrock swept clear of sand and dust by wind.

Yardang

A streamlined ridge carved from bedrock by wind abrasion and deflation, typical in vertically layered rocks.

Ventifacts

Pebbles or rocks that have been polished, pitted, or grooved by wind-driven sand; those with three faceted faces are called 'dreikanter'.

Barchans

Migrating crescent-shaped sand dunes with horns pointing downwind, formed where winds blow in a consistent direction.

Loess

An unstratified, wind-blown silt deposit ($20-50$ micrometers) that is typically loamy, porous, and highly fertile.

Playa

A temporary lake in a desert basin with no outlet that collects water periodically, leading to the deposition of salt and mud upon evaporation.

Alluvial fan

A triangle-shaped deposit of gravel and sand found at the foot of mountains where a rapid change in slope causes sudden sediment deposition.

Bajada

A broad slope of debris formed by the coalescence (merging) of multiple alluvial fans in front of a mountain.

Fetch

The distance of open ocean or lake surface over which the wind blows in a constant direction to produce waves.

Constructive waves

Coastal waves with a strong swash and weak backwash, leading to more deposition than erosion.

Longshore Drift

The zig-zag movement of sediment along a coastline caused by waves (swash and backwash) hitting the shore at an angle.

Tombolo

A coastal depositional landform where a spit or sandbar joins the mainland to an offshore island.

Wave-cut platform

A horizontal bench in the tidal zone extending from the base of a retreating sea cliff.

Blow-hole

A vertical shaft from a sea cave to the cliff top through which sea water and air are forced out by wave action.

Geo

A long, narrow coastal inlet that develops when the roof of a sea cave collapses.