Glossary

Acid volcanics	Light coloured volcanic rocks containing more than 66 per cent silica, free quartz and a minimum of dark coloured minerals.
Aeolian	Moved by the wind.
Alluvial	Deposited by streams.
Alluvial fan	Fan shaped alluvial deposit of sediment where streams disperse after leaving confined valleys. Steepness (gradient) relates to sediment grain size.
Amphibolite	Metamorphic rock composed essentially of amphiboles or dark coloured minerals such as hornblende. Usually derived from submarine basalt.
Anabranch	Branch of an anastomosing stream that leaves the main channel and rejoins it some distance down stream.
Anastomosing	Multi-branched stream system.
Backplain	Parts of a river floodplain furthest from the channel.
Barrier	See coastal barrier.
Basalt	Dark coloured, fine grained volcanic rock composed of olivine, pyroxene and feldspar. No free quartz.
Basement rock	General term to describe older rocks beneath a sedimentary basin.
Bedrock	Hard rock beneath a superficial cover of soils and sediments.
Black earth	Dark coloured pedal clay soils usually found in valleys and often derived from basalt.
Blockstream	Periglacial landform composed of a "river" of boulders on low angle slopes.
Braided river	River in which the main channel is braided with multiple paths that split and join frequently. Usually a gravel or sand bed stream.
Caldera	Large volcanic crater created by explosion or internal collapse of a volcanic cone.
Cambrian	Period of geologic time 500-570 million years ago.
Carboniferous	Period of geologic time 280-345 million years ago.
Cauldron subsidence	See caldera.
Central volcano	A single major volcanic vent responsible for a large area of volcanic rocks.
Chert	Fine grained siliceous rock usually formed in deep sea environments either as a chemical precipitate, or as accumulated remains of siliceous single celled organisms such as radiolaria.
Cirque	Small glaciers and the basins they excavate at the head of valleys.
Claystone	Sedimentary rock composed of clay. Also referred to as mudstone.
Cliff top dunes	Sand dunes located well above the beach from which the sand was derived.
Coastal barrier	Complex landscape of beach, dunes and enclosed lagoon or swamps that form between headlands during rising sea levels.
Colluvial	The movement and deposition of sediment and debris on slopes.
Columnar lava	Basalt or other volcanic rocks with well developed columns (organ pipes) formed by cooling joints.
Competence	The ability of a stream to carry sediment of different size.
Conglomerate	Sedimentary rock composed of particles coarser than sand, for example, pebbles.
Contact metamorphic	Metamorphic change induced in rock that comes in contact with a heat source such as a granite intrusion.
Continental shelf	Shallow seas adjacent to the continent. Most were exposed during times of low sea level in the Pleistocene ice age.
Contour banding	Alternating zones of different soil, sediment and vegetation approximately following the contour on gentle slopes in the arid zone. Often stony and stone-free bands.
Cracking clay	Alluvial clays with high shrink/swell potential that crack deeply on drying.
Cretaceous	Period of geologic time 65-136 million years ago.
Debris dam	Floating load debris (logs etc.,) that have accumulated across a river channel and that may divert the stream.
Dendritic	Multiple branching pattern like a tree.
Desert pavement	Lag gravel surface of gibbers (pebbles and boulders) on the soil surface.
Devonian	Period of geologic time 345-395 million years ago.
Diatomite	Very light weight sedimentary rock composed of the remains of diatoms.
Diatreme	Pipe like vertical volcanic vent filled with broken and cemented country rock created by a single explosion.
Dip-slope escarpment	Asymmetric landform where rock bedding controls the cross-sectional shape of ridges. Cliffed on one side with a gentle slope following the dip of bedding planes on the other side.
Discharge	Volume of water flowing past a point in a stream over time.
Dolerite	Medium grained igneous rock with composition similar to basalt. Usually found in dykes or sills.
Downs	Extensive undulating and gently rolling plains.
Dune	Sand accumulating and moving in dune forms.
Dyke	Vertical sheet of intrusive igneous rock.
Endemic	Restricted distribution.
Ephemeral	Lasting only a short time.
Escarpment	A cliff or the steep slopes of a plateau edge.
Fault	Fracture zone in rock along which there has been movement of the crust.
Feldmark	Community of prostrate plants growing on a stony pavement in an extreme alpine environment.
Floodout	Area of an alluvial fan where the stream disperses across a plain.
Fold belt	Region in which all the bedrock has been subject to similar phases of disturbance by folding and faulting.
Footslope	Lower part of a hillslope merging with the alluvial plain.
Gabbro	Coarse grained igneous rock with composition similar to basalt.
Gibber	Stones in a desert pavement.
Gilgai	Hummocky micro-relief pattern common in heavy alluvial clays.
Glacio-marine	Poorly sorted sandstones and conglomerates formed in an environment where icebergs move glacial debris offshore.
Gneiss	High grade, coarse grained metamorphic rock with an overall composition similar to granite.
Gondwana	Name given to the super continent formed when Australia, Antarctica, Africa, India and South America were all joined.
Gorge	Steep narrow river valley.
Gradational Soil	A soil with a gradual increase in texture (ie. becomes more clayey) as the profile deepens.
Granite	Light coloured, coarse grained plutonic rock with free quartz. Usually composed of potassium feldspar, quartz and mica.
Granodiorite	Coarse grained plutonic rock, similar to granite but with less quartz and more dark minerals.
Great Artesian Basin	Extensive area of inland Australia filled with Mesozoic sedimentary rocks and containing an important resource of artesian water.
Great Dividing Range	Eastern highlands of Australia that separate coastal streams from those flowing inland and particularly the Murray-Darling Basin.
Great Escarpment	Eastern margin of the Great Dividing Range where the most rugged topography is found.
Groundwater window	Place where the topography is lower than the groundwater table and a lake or salina forms.
Guano	Accumulation of bird (or bat) faeces and the soil it interacts with.
Gypsum	A common mineral of evaporates in inland salt playas. Calcium sulphate
Harsh clay	Hard, dense clay with high shrink/swell potential and highly dispersible. See also: Mellow clay.
Horizon	Layers in a soil formed by surface processes, by convention A and B horizons are equivalent to topsoil and subsoil.
Hypersaline	Very saline brines. Salt concentration greater than sea water.
Igneous	Rocks formed from melts in the Earth's crust. eg. Granite, gabbro or basalt.
Inner barrier	Older coastal barrier system sometimes found on the landward side of the outer (or modern) barrier.
Intrusives	Igneous rocks that have intruded other rocks. eg. A granite body or an igneous dyke.
Island arc	Complex of volcanic islands, and shallow seas adjacent to an oceanic trench. For example, Indonesia.
Joints	Natural fractures in a body of rock that cause it to break into regular blocks on weathering or when quarried.
Jurassic	Period of geologic time 136-190 million years ago.
Karst	Landforms created by solution of rock in which most of the drainage is by underground channels that may lead to the formation of caves. Normally refers to limestone karst but can occur in other rock types.
Lava field	Extensive area of volcanic rock derived from many small volcanic vents rather than a central volcano.
Leucitite	Rare basalt dominated by the felspathoid leucite, rather than the more common calcic plagioclase.
Lignite	Soft brown coal.
Limestone	Any sedimentary rock composed essentially of calcium carbonate.
Linear dunes	Sand dunes forming regular lines oriented parallel to dominant winds.
Lithic sandstone	Sandstone composed of sand sized rock fragments.
Loam	Soil material with approximately equal quantities of sand, silt and clay.
Lunette	Crescent shaped beach and dune complex found on the eastern sides of lakes in arid Australia. Usually composed of quartz sand but can also be partly or wholly composed of sand sized clay pellets and occasionally gypsum sand (copi or seed gypsum).
Meander	River with a single channel that sweeps back and forth in smooth curves.
Mellow clay	A soft stable clay with minimum shrinkage potential.
Mesa	Small flat topped hill. See also Tableland.
Mesozoic	Era of geologic time 65-225 million years ago.
Metamorphic	Any rock formed from a pre-existing rock by application of heat and pressure. For example, quartzite, slate, schist, or gneiss.
Meta-sediments	Low grade metamorphic rock derived from sedimentary rocks and retaining some original structure or composition.
Monocline	One sided fold in a geological basin.
Monzonite	Coarse grained igneous of the granite type.
Mound spring	Point of surface flow of artesian water. Mounds normally formed by concentration of soluble minerals.
Mulga groves	Contour banded pattern of mulga growth on extensive sandplains.
Ordovician	Period of geologic time 430-500 million years ago.
Overflow lakes	Lakes fed by floodwaters from a stream.
Pagoda country	Sandstone landscapes formed by erosion with tall rock pillars that look like pagodas.
Palaeodrainage	Abandoned river patterns evident in the landscape formed under different climatic conditions.
Palaeozoic	Era of geologic time 225-570 million years ago.
Parabolic dunes	Curved dune patterns oriented parallel to dominant winds. May be a pre-cursor to linear dunes.
Pedal	Natural aggregates in soils, often with a geometric shape. eg. blocky or prismatic.
Pegmatite	Very coarse grained rocks of granitic composition containing large mineral crystals.
Peneplain	A lowland plain formed by erosion to the extent that rock structure and composition no longer influence the landscape. Supposed to be the end phase of an erosion cycle, which is an old concept that is not universally accepted.
Periglacial	Environments dominated by ground ice and freeze/thaw processes, as in the tundra.
Permian	Period of geologic time 225-280 million years ago.
Phyllite	Fine grained metamorphic rock with well developed cleavage, derived from shale.
Pillow lava	Volcanic rock with unusual pillow structure caused by lava cooling under water.
Plateau	Generally high ground with more or less concordant summits and low relative relief.
Playa	Clay plain that is temporarily flooded to form a lake or swamp after exceptional rainfall.
Pleistocene	Epoch of geologic time 10,000 to 1.8 million years ago.
Pliocene	Epoch of geologic time 1.8 - 5 million years ago.
Ploughing block	Large boulder moved through the soil mantle by periglacial processes, or by high snow loads.
Plugs	Bodies of igneous rock that have cooled in the throat of a volcano and subsequently been exposed by erosion. Often columnar jointed.
Podsol	Soil profile with distinctive horizons of a bleached lower topsoil and cemented iron oxide pans in the subsoil. Formed in quartz sand under special conditions and special vegetation. Common in coastal dunes.
Porphyry	Any igneous rocks with a porphyritic texture, that is, coarse crystals in a fine groundmass. Indicates that two phases of cooling were involved.
Prior streams	Relic channels and channel traces on an alluvial fan created by streams in a different climate.
Psuedokarst	Cave-like land forms and features in non-soluble rocks such as granite boulders.
Quartz sandstone	Sandstone composed largely of quartz sand grains.
Quartzite	Metamorphosed quartz sandstone.
Quartzose	General term for a sedimentary rock composed of quartz grains that is intermediate between a quartz sandstone and a quartzite.
Quaternary	Period of geologic time 0-1.8 million years ago.
Rain shadow	Area of low average rainfall such as the region behind a mountain range.
Regolith	All layers of weathered rock, sediments and soil material covering the surface.
Residual	A soil material or landform that remains in place from the past.
Rhyolite	Fine grained, light coloured volcanic rock with a high proportion of quartz, equivalent in composition to granite.
Rock platforms	Coastal rock benches in the inter-tidal zone.
Runoff	Precipitation that flows across the ground surface and enters streams leading to lakes or oceans.
Run-on sites	Parts of footslopes or alluvial fans that receive runoff from upper slopes.
Sandplains	Extensive sheets of aeolian sand that do not exhibit dune forms.
Sandstone	Sedimentary rock composed of sand sized particles.
Scarp	See Escarpment
Schist	Foliated, high grade metamorphic rock
Sedimentary	Rocks composed of sediments. For example, claystone, sandstone, conglomerate.
Serpentinite	A green metamorphic rock composed of hydrated magnesium silicates formed by the alteration of olivines and pyroxenes usually in a submarine environment.
Shale	Sedimentary rock composed of silt and clay sized particles, weakly cemented.
Shield volcano	Very large composite and symmetric volcano.
Silcrete	Fine grained orthoquartzite formed by cementation of shale or siltstone with silica.
Sill	Horizontal sheet of intrusive igneous rock.
Silurian	Period of geologic time 395-430 million years ago.
Slate	Fine grained metamorphic rock with perfect cleavage formed by metamorphism of shale.
Snow patch	Area of persistent summer snow on a protected aspect.
Solifluction lobes	Lobes and bulges of deformed soil and vegetation on hillslopes subject to periglacial activity.
Structure	Overall geometry of folds, faults and joint patterns in a rock mass.
Subsoil	B horizon usually derived from rock by in situ weathering.
Swale	Valley between dunes.
Tableland	Large flat top hill, extended mesa or small plateau. Also used to describe a plateau.
Terminal channels	River channels that terminate in an inland region without reaching the sea or a lake.
Terraces	Level areas of valley floors that are not flooded. Abandoned floodplains.
Tertiary	Period of geologic time 1.8-65 million years ago.
Texture contrast profile	Soil profile in which the topsoil (A horizon) has a sandier texture than the subsoil (B horizon). Typically a sandy loam over a clay.
Throughflow	Water moving through the soil between the A and B horizons. Or, water passing through a swamp in a valley.
Topsoil	Surface layer of soil with higher organic content, A horizon.
Tor	Large outcrop of bedrock. In granite country tors are typically round boulders.
Trachyte	Fine grained igneous rock equivalent in composition to a syenite. Contains a small amount of free quartz.
Triassic	Period of geologic time 190-225 million years ago.
Tuff	Consolidated volcanic ash.
Turbidites	A suite of deep marine sedimentary rocks formed as a result of sediment transport by turbidity currents.
Ultrabasic rock	Igneous rocks containing less than 45 per cent silica. Usually coarse grained and contain no free quartz or feldspar.
Unconformity	Surface between two rock units of different ages with different attitudes, represents an interval of time.
Uniform textured soils	Soils in which the topsoil and subsoil have very nearly the same textures.
Veins	Thin body of mineral such as quartz, intruded through a rock, usually following structural weaknesses such as joints.
Volcanic	Igneous rocks that have been formed on the Earth's surface as from a volcano.