TheGeoRoomGeomorphology

Definition of the Day
River Competence
The largest particle that can be carried by a river

Geomorphology Glossary

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A
aa
A fluid lava flow with a rugged appearance.
alcrete
A type of duricrust composed of aluminium minerals.
Amphibole
Class of rocks having aluuminosilicate minerals e.g. granite
Andesite
A fine and dark coloured igneous rock containing pagioclase feldspars and hornblende.
Arkose
A coarse grained sedimentary rock (sandstone) containing quartz and feldspars.
Anticline fold
An arch shaped symmetrical fold. See Folds
Ash
Small debris particles of less than 4mm extruded from a volcano. See Volcanoes
asthenosphere
A zone in the uppermost mantle consisting of weak volcanic rocks. This layer keeps the plates floating. See Plate Tectonics
Avalanche
A type of mass movement containing ice and debris. See Mass Movements
B
Basal Surface
An unweathered rock lying beneath the earth's surface. Also known as bedrock. See Deep weathering
Basalt
A mafic (dark coloured) igneous rock containing plagioclase feldspars, pyroxenes and or olivine. Easily weathered.
Basin
A depressed land area either from folding (Folding) or other land depressors e.g ice.
Batholith
A large pluton (intrusive) that often show up as a mountain when it is exposed to the surface by erosion or uplift. See Plutons, Intrusive Features
Blind valley
A valley common in karst regions closed at the end by a hard strata or slope which diverts any channel down the limestone. See Karst landscapes
body waves
Earthquake waves that travel below the surface. See earthquakes.
Bornhardt
A dome shaped inselberg rising abruptly from a plain. SeeGranitic Inselbergs
Breccia
A sedimentary rock with large, angular fragments of quartz.
Bysmalith
A pluton that has a fault across it. See Intrusive Volcanic Features: Plutons
Calcite
A white mineral composed of calcium carbonate common in limestone rocks. See Limestone Properties
Calcrete
A duricrust of dried up calcite. SeeDuricrust
Caldera
A large depression formed when super eruptions blows and collapse the flanks of a volcano. SeeVolcanoes
canyon
See gorge.
carbonation
A type of chemical weathering were acidulated water containing carbon dioxide reacts with limestone rocks containing caclite (calcium carbonate) turning it into calcium bicarbonate.
castle kopje
An inselberg with balanced rocks on top of each other forming a castle appearance. See Granitic Inselbergs
chalk
A white and soft sedimentary rock composed of calcite (calcium carbonate) and formed from dead organic matter such as sea creatures and plants.
chemical weathering
Weathering by means of reactions between rock and different elements such as water and acids. See Chemical Weathering
chelation
The weathering of rocks by acids released from decayed organic matter. See Chemical Weathering
cinder cone
A small volcano which mainly extrudes fragmented lava (scoria)
cliff
See scarp
clint
The troughs found on a limestone pavement formed when carbonated water attacks and deepens vertical joints.
cockpit
Star shaped depressions separating conical hills in a limestone terrain formed when water attacks lines of weakness.
Cohesion
The ability of particles to strongly stick together resisting movement.
Colluvium
Debris washed down at the foot of a slope
conical karst
In a karst topography water attacks lines of weakness leaving behind conical and circular hills.
composite cone
A cone shaped and catastrophic volcano which mainly generates ash and pyroclastic materials. See Volcanoes
concordant
Small volcanic intrusions (plutons) running across the bedding planes of large volcanic plutons. See Plutonic Forces
convergent boundary
A catastrophic plate boundary between oceanic and continental, oceanic and oceanic or continental and continental plates that collides generating volcanic activities, mountains and earthquakes. See Plate Boundaries
continent
The land area of a plate consisting of sial. See Plate Tectonics
continental crust
The outermpst continental section consisting of sial which is more thicker than the oceanic crust. See Plate tectonics
continental shelf
The extended part of a continent into the ocean.
corestone
Small to medium sized circular rocks constituting saprolite of deep weathered profile. See Deep weathering
concave slope
The lower unit of a slope. See Slope Profiles
conglomerate
A sedimentary rock with interbedded pebbles and cobbles.
convex slope
The upper unit of a slope. See Slope Profiles
crater
A circular blowout left on top of a volcano when an eruption occurs. See Volcanoes
crust
The outermost layer of the earth.
cumulo-dome
A dome shaped volcano that extrudes viscous, less runny lava that quickly solidifies.
D
Debris
All loose weathered or eroded material found on the surface.
Deep weathering
The weathering of underground rocks by water and humic acids that percolate through the soil.
dip
The angle made by a stratum with the horizontal surface.
divergence boundary
A plate boundary where plates split (move apart) creating an opening that oozes magma to the top.
dome
A more folded anticline.
duricrust
A hard layer(crust) found on top of hills or plateaus made from mineral precipitation.
dike/dyke
An often small discordant pluton that runs across existing rocks
diorite
A coarse grained igneous rock consisting of quartz, feldspar and hornblende.
dolerite
A dark, medium coarse grained igneous rock that forms many sills and dykes.
dry valley
A dried up valley with traces of prior water flow that percolated down a limestone. See karst landscape
dwala
A low lying basal surface exhumed from underground by the stripping of regolith. See Granitic inselberg
E
earthquake
A sudden movement in the earth's crust caused and triggered by plate movements and volcanoes. See
endogenic
Denoting all processses occurring internally the earth's surface.
epicenter
The area on the ground, above the focus, where an earthquakes first hits. See earthquakes.
etchplanation
The weathering of underground rocks producing deep regolith which is then stripped away revealing weathered rocks as inselbergs. See Inselberg Formation
exfoliation
A type of physical weathering were a rock's outer layer peels off caused by repeated expansion and contraction by insolation. See Physical Weathering
exhumation
The stripping away of regolith revealing underground basal surfaces or piling boulders as inselbergs.
Exogenic
Denoting all processes occurring on or out of the earth's surface.
Felsic
Denoting dark coloured minerals in igneous rocks
flowstone
Calcite that flows along cave walls and dry out.
Free face
See Cliff
focus
The origin of an earthquake deep in the lithosphere.
Foot slope
See Concave Slope
freeze-thaw action/ frost shattering
A type of physical weathering were ice exerts tremendous pressure against a rock causing it to disintegrate. See Physical Weathering
fumarole
Emitted hot gases through cracks around a volcano.
geomorphology
The study of earth's landforms, their form, shape and structure.
Gabbro
A hard, dark and coarse grained igneous rock.
gorge
A narrow steep sided valley.
Gully
On slopes, these are widened and deepened rivulets. See Processes on Slopes
Geyser
An volcanic landform where steam is ejected by the heating of water by underground hot rocks.
graben
A downthrow block of land between two upthrowns called horsts.
grike
An acid eaten trough found along a limestone pavement separated by ridges known as clints. See Karst Landscape
gypsum
A soft whitish sedimentary rock consisting of hydrated calcium sulphate.
H
half graben
A fault in which a block of land (downthrow) slides down over one curved fault line. See Faults
Hogback
A steep fold of about 45o.
Hortonian Overland flow
The concentrated or unconcentrated flow of water in rills or as sheetwash respectively down a slope. See Hortonian Overland flow
Hotspot
An intensely hot area where magma is constantly supplied. Mainly found in plate interiors. See Volcanic Hotspots
Hot spring
A spring of natural hot water heated by underground rocks.
Humification
See Chelation
Hydration
A type of chemical weathering were repeated absorption of water and swelling disintegrates a rock. See Chemical Weathering
Hydrolysis
A type of chemical weathering were rock minerals reacts with water causing them to disintegrate into fine soil. See Chemical Weathering
hypabyssal
Small plutons (intrusive features) that solidify just below the surface.
I
igneous rocks
Rocks formed from the solidification of magma at depth or lava on the surface.
Inselberg
A small to medium isolated hill rising abruptly from a plain. See Inselberg Formation
interfluve
An upland area between two adjacent watercourses.
isoclinal fold
A fold with limbs that run parallel in the same direction. See folds
L
laccolith
Are dome shaped intrusive features made from viscous lava that quickly solidifies at depth. See intrusive volcanic landforms
Lahar
A type of mudflow consisting of volcanic debris mixed with water. See Volcanoes
landslide
The sliding of blocks (en mass) of land along a slip plane. See mass movements
Lapilli
Small pyroclastic particles between 4 and 30 mm. See Volcanoes.
lapolith
A saucer shaped pluton often as large as a batholith. See Intrusive Volcanic features
laterite
A red brownish soil reach in insoluble iron minerals.
lava
The molten rock found on the earth's surface. See Volcanoes
limestone
A soft sedimentary rock containing the mineral calcite (calcium carbonate). See Limestone
limestone pavement
An small or large outcrop of limestone usually demoted with grikes and clints. See karst landscape
lithification
The conversion to rock.
lithosphere
Rigid part of the earth consisting the uppermost mantle and the crust. Also known as plate.
lithology
Denoting to rocks, their structure and form.
M
maar
A shallow and broad volcano (crater) that erupts on the surface with groundwater. See volcanoes.
magma
The molten rock below the earth's surface.
mantle
The region between the outer core and the crust consisting of dense silicate rock.
mantle plume
A rising column of magma forming a massive dome of magma just below the surface or a hotspot on the surface. See Hotspots
metamorphic rocks
Rocks formed by intense heat and pressure on other rocks (igneous, sedimentary or metamorphic).
mica
A shiny silicate mineral commonly found in granite
mineral precipitation
The process where water evaporates from minerals or the process where minerals are deposited from a solution.
monandock
An isolated hill rising abruptly from a plain. Also known as inselberg
monocline
An asymmetrical fold with raised limb. See folds
mudflow
A fast mass movement carrying water laden coarse sediments. See Mass Movements
mudstone
A dark sedimentary rock with a consolidated mixture of clay and silt
N
nubbin
A small mound of exhumed granitic boulders. See Granitic Inselbergs
Nuée ardent
A fiery cloud of ash and pyroclastic debris. See volcanoes
O
orogenesis
The building up of mountains by tectonic processes
overland flow
The unconcentrated or concentrated movement of water on a slope as sheetwash or in rills respectively.
Oxidation
A type of chemical weathering where water reacts with iron rich rocks causing a reddish colouration(rust). See chemical weathering
P
Pahohoe
A viscous lava with a smooth and wrinkled pattern
parallel retreat
According to C.King, a process where scarps retreat back inland, maintaining steepness, leaving a pediplain behind. See Slope Evolution
passive margin
A boundary found within continents away from major tectonically active margins.
Plant Root Action
A type of physical weathering where a rock disintegrates due to plant roots between cracks exerting pressure against the rock. See Physical Weathering
Pediplain
According to C.King, a flat and extensive land area left when scarps retreat. See Inselberg Formation Theories
Pediment
A gently sloping extension of a plateau or hill (inselberg). See Inselbergs
permeable
Allowing water to pass through
pervious
See permeable.
Peneplain
According to W.M Davis, this represents the last stage of erosion characterised by a levelled land surface. See Slope Evolutional Theories
polje
A near steep sided valley with a flat floor found in a karst landscape. See Karst Landscape
ponor
See sinkhole
porphyry
A rock, usually igneous, with coarse grains interbedded in a fine groundmass (small grains)
pressure release
A physical weathering type where underground rocks are subjected to differential pressures and temperatures on the surface causing them to develop cracks running parallel to the surface.
Q
quartz
A crystal shiny mineral mostly native to igneous rocks such as granite.
R
rainsplash
The process whereby raindrops dislodge and erode soil grains on a surface. See Slope processes
rectilinear slope
The middle transportation unit of a slope where the gradient is constant. See Slope Profiles
recumbent fold
Extremely folded rocks forming a "Z like" pattern. See Folds
regolith
All the unconsolidated debris covering the bedrock below the earth's surface. See Deep weathering
reverse fault
A fault where the downthrow slides up the upthrow. See faults
rills
Tiny streams created by running water along slopes
rivulet
See rill
rift valley
A downthrow (valley/graben) which slides down between two fault lines. See Rift Valley
rockfall
A mass movement where weathering, water or earth movements collapse rock boulders along a scarp. See mass movements
runoff
Water running down a slope as overland flow or throughflow. Runoff encompasses all types of water flow. See Slope Processes
S
sandstone
A hard sedimentary rock cemented with fragments of quartz and sand.
salt crystallisation
A type of physical weathering where salts within rock cracks expand causing the eventual disintegration of the rock. See physical weathering.
saprock
The first deep weathered layer consisting of boulders. See deep weathering.
saprolite
A deep weathered layer comprising of weathered corestones. See Deep weathering
scarp
A steep and resistant rock face uncovered by debris found on the edges of plateaus, valleys and or inselbergs. Also called scarp.
schist
A coarse grained metamorphic rock.
scree
Pile of weathered or eroded material covering a slope.
sedimentary rock
A rock type formed from grains of other rocks or remains of dead plants and animals.
shale
A fine clay sedimentary rock.
sheetwash
A type of overland flow where water moves unconcentrated collecting soil in the path. See Processes on slopes
sial
Denoting chemical composition of the continental crust
sill
A discordant pluton (intrusive feature) running horizontally to existing sedimentary rocks. See plutons.
slicrete
A duricrust of silica.
sima
Denoting chemical composition of the oceanic crust.
slip fault
See transform fault
slope
Any inclined surface.
slope decline
(W.M Davis) The process where the landscape lowers into a flat undulating plain with time. see Slope evolution
slope replacement
(W. Penck) The engulfing of the entire slope by a growing basal surface (debris) with time. See Slope evolution
slope retreat
(C. King) The denudation of scarps causing them to wear backwards. see Slope evolution
slump
A rotational slide where blocks of land sits on top of another. see Mass movement
soil creep
The slow movement of soil grains down a slope. See Mass movements
solifluction
A periglacial mass movement where debris moves atop the impermeable frozen bedrock/surface. See mass movements
speleotherms
Denoting all deposits of calcite in a cave
surface waves
Earthquake waves that travel along the surface.
sub-surface flow
See throughflow
super-volcano
See composite cone
sycline
Saucer shaped symmetrical fold.
T
tafoni
A hollowed out depression on a rock surface eaten out by weathering.
talus
Weathered or eroded material (usually small stones) on the foot of scarp.
terracing
The process of building steps along a slope to minimise mass movements.
tors
Small to large boulders piling on top of another exhumed from underground. See Granitic inslebergs
tower karst
Tall towers of limestone of 200m or more created when acidulated water widens and deepens joints on a limestone terrain. See Karst Landforms
transform fault
A plate boundary where plates slide past each other or together.
translational slide
See landslide
travertine
A limestone with an inorganic origin. See limestone properties
U
uvala
An enormous depression found in a karst landscape formed from the coalescence of several sinkholes or tectonic depressions.
V
vadose
Denoting underground water lying above the water table.
valley
A depression between hills, plateaus or mountains usually with a river in between.
viscous lava
A thick and less runny lava that congeal and solidifies quickly.
W
weathered mantle
See regolith
weathering
The breakdown of rocks by physical or chemical means.
weathering front
The boundary separating the weathered regolith from the bedrock. See Deep weathering
whaleback
See Dwala
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