Tips & Guides
Tips & Guides
Definition of the Day
Atmospheric Instability A condition in the atmosphere where air parcels are heated and therefore are warmer than the surrounding atmosphere resulting in unstable weather conditions such as heavy rains and hailstorms. See Atmospheric Stability & Instability
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. See
Granitic 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. See
Duricrust Caldera A large depression formed when super eruptions blows and collapse the flanks of a volcano. See
Volcanoes 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)
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.
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.
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 45
o. 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.
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.
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
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.
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
nubbin A small mound of exhumed granitic boulders. See
Granitic Inselbergs Nuée ardent A fiery cloud of ash and pyroclastic debris. See volcanoes
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
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.
quartz A crystal shiny mineral mostly native to igneous rocks such as granite.
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
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
composite cone sycline Saucer shaped symmetrical fold.
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.
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.
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
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