G Flashcards
Gabbro
An intrusive basalt.
G8
See Group of Eight.
Gamma index
A measure of connectivity in a network which compares actual number of edges (e) with maximum possible number of edges for the vertices (v) in that network.
γ or e(max) = e x 100/3(v-2)
Garden city
In the UK, a planned settlement with low housing density. The brainchild of Ebenezer Howard as a result of social concern for poor urban and rural living conditions for working people. The first was begun in 1903 at Letchworth in Hertfordshire and a full history of the movement can be found at: www.letchworthgardencity.net.
Garden festival
In the UK, a large scale renovation of derelict inner-city land by designating it for the planting of specially designed gardens. The improved image of the area would then assist the development of economic and residential projects in the area.
Garrigue
The shrub vegetation of the Mediterranean region where soils are thin and dry and have been converted to growth of herb plants e.g. thyme and rosemary.
GATT
See General Agreement on Tariffs and Trade.
Gavelkind
See Fragmentation.
GDP
See Gross Domestic Product.
Gelifluction
A form of mass movement in which thawed upper soil layers move over permafrost.
General Agreement on Tariffs and Trade
Precursor to the World Trade Organisation.
General circulation
In the atmosphere, the general pattern of wind and pressure at a global scale. See tricellular model.
Genetically modified crop
The placing of a gene from one organism into another so that the latter can take on a quality of the former that it does not otherwise have. Thus organisms can be modified to grow larger, faster etc. or to be made immune to certain diseases. Currently highly controversial. Proponents see a wealth of agricultural, nutritional and medicinal problems solved this way. Those against warn of the unknown side effects for the environment and our bodies.
Gentrification
The renovation of the housing fabric in an old, usually inner-city area, when more affluent groups displace lower income groups en masse over a relatively short period of time. May be triggered by a clear event such as the improvement or provision of a better transport link, or by something less tangible such as a fashion trend taking off in the housing market.
Geodesy
The science of measuring the surface of the earth.
Geographic Information System
The creation of a database of geographic information from a variety of sources which allow the cross-referencing and compilation of different data sets so that relationships may be observed or postulated.
Geologic time
The total time involved since formation of the earth to the present time.
Geologic time scale
See http://www.geosociety.org/science/timescale/timescl.htm
Geomorphology
The science of understanding landform formation.
Geostationary orbit
An orbit path that keeps a satellite over the exact same point on the earth’s surface at all times.
Geostrophic wind
Wind blowing parallel to isobars because of deflection of the pressure-gradient force by the Coriolis Force.
Geothermal
Heat from within the earth. By pumping water down to hot rock layers where magma is close to the surface, we can use the resultant steam to drive turbines and produce electricity. On a smaller scale the water can be used directly to heat swimming pools and spas and the like.
Ghetto
An area, usually in slum condition, where an ethnic group is dominant.
Gini coefficient
G = ½ Σ(Xi -Yi)
Xi and Yi are two sets of data expressed as a percentage.
The coefficient shows how alike they are from identical (0) to as unidentical as they could be (100).
GIS
See Geographical Information System.
Glacial
Defined as of or pertaining to a cooler period of climate during which glaciers advance (ice age).
Glacial budget
The net result of accumulation and ablation.
Glacial diversion
See diffluence.
Glacial erosion processes
Two main types:
1. Plucking - glacial ice freezes on to bedrock and, when it moves, pulls away pieces of rock, which are then added to the sides and base of the glacier.
2. Abrasion - rocks incorporated into the glacier scrape away at valley floors and sides, leaving grooves and smooth surfaces behind.
Freeze-thaw weathering is also important, as it fractures rock and creates debris which falls on to glaciers and increases their erosional force.
Glacial landform
A landform produced by glacial erosion or deposition.
Glacial movement
Two types:
- Basal slipping - pressure between the ice and the surface creates friction and heat which slightly melts ice in contact. This lubricates the underside of the glacier allowing it to flow.
- Internal distortion - gravitational forces can cause some parts of the glacier to move more quickly then others which can eventually lead to cracks appearing in the ice.
Glacial retreat
When ablation exceeds accumulation causing a net loss of ice from the glacier. This usually involves the snout being found at a point in the valley short of the farthest it ever reached. Note that ice still moves downslope but that the zone of ablation now extends further up the valley.