Glossary

erosion

the wearing away of any part of the Earth's surface by natural agencies. These include mass wasting and the actions of waves, wind, streams and glaciers. Fundamental to the process of erosion is that material must be picked up and carried away by such agents (transportation).

 

estuarine

originating in an estuary - formed where a deeply cut river mouth is drowned following a land subsidence or a rise in sea level. Fresh water intermixes with seawater and tidal effects occur.

 

extinction

the dying-out of a plant or animal species. This may have arisen from a variety of causes, for example increased competition for certain niches, variation in the physical environment such as climatic changes or fluctuations in sea-level, which affect the range of habitats available.

 

faulting

the action or process of fracturing and displacement that produces a fault - a fracture in earth materials, along which the opposite sides have been relatively displace parallel to the plane of movement. The surface along which movement takes place is known as the fault plane, or fault surface. Faulting may mark the walls of the fault plane with slickensides - a striated and polished surface from the grinding and sliding of two rock masses against one another.

 

glacial pavement

bedrock surface with fine-cut parallel or near-parallel lines made by rock fragments carried in a glacier which travelled over the bedrock

 

Glossopteris

a late Palaeozoic genus of fossil plants (tongue-ferns) found throughout the glaciated regions of the Southern Hemisphere. Glossopteris flora bore clusters of simple spatulate leaves.

 

gneiss

a foliated metamorphic rock formed under conditions of high grade regional metamorphism. It is usually coarse grained and characterised by a layered appearance due to the segregation of ferromagnesian from quartzo-feldspathic minerals in discontinuous layers or lenticles.

 

Gondwana

the southern supercontinent taking its name from the Gondwana system of India, dating to the late Palaeozoic and early Mesozoic, and containing glacial tillites below coal measures. Similar rock sequences of the same age, containing identical fossil flora (Glossopteris) show connection of the southern continents of Antarctica, Africa, South America, Australia and India

 

granite

a light coloured medium to coarse-grained plutonic(of deep seated origin) igneous rock composed mainly of quartz and feldspar with biotite and/or hornblende as the commonest ferromagnesian minerals.

 

greenstone belt

embedded in the ancient granite and gneiss terrains of South Africa and Australia are greenstone belts. These are islands of ancient deformed rock, metamorphosed from basaltic lava and topped by sediments. They are between 2.5 and 3.5 billion years old. Because greenstone belts contain pillow lavas, geologists believe that they are ancient pieces of oceanic crust that formed under the sea in back-arc basins as the continents grew larger.


 

Sources Consulted:
Farndon, J. (1998). Concise Encyclopedia Earth, Dorling Kindersley, Great Britain, 192.
Lapidus, D.F. (1987) Collins Dictionary of Geology, Winstanley, I. (Ed.), HarperCollins, Great Britain, 565pp.


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