Nature conservation

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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.

Page last updated: 18 April 2016