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E - Earthquake to Extrusive - Geography Dictionary

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Earthquake – sudden release of energy through the earth’s crust in the form of seismic waves. Tension builds up within the crust as convectional forces in the mantle try to move the plates above but are prevented from doing so by friction between plates. When friction is overcome, an earthquake occurs.

Earthquake intensity - a measure of how much damage an earthquake causes. Several scales are in use which have developed over time from the very crudest, subjective observations of the 19th century, to relatively sophisticated, empirical forms today. ie: Rossi-Forel Scale; Omori Scale; Mercalli Scale; MCS Scale; MMI Scale; MM56; MSK64 Scale; EMS-98 Intensity Scale; JMA Seismic Intensity Scale.

Earthquake magnitude – a mathematical measure of the strength of an earthquake based on the maximum amplitude of the seismic waves produced. See Richter Scale.

Earth tremor – technically any earthquake can be said to consist of earth tremors, as the word tremor simply means shaking. However, it is generally accepted that the phrase earth tremor should relate only to smaller earthquakes, i.e. those of low magnitude and intensity. These would ordinarily cause little or no damage but may have a greater impact if they come in the immediate aftermath of a high magnitude and intensity earthquake which has already weakened and destabilized many structures. Where the line should be drawn is not agreed.

Easting– the vertical gridlines on a map so called because their numeric value increases from west to east.

Ebb tide – a falling tide.

EC – see European Community.

Ecology - study of the ecosystem with particular reference to the relationships between plants and animals and the environment.

Economic activity -work or industry undertaken for economic purposes. Four sectors:

  • Primary - exploitation of raw materials

  • Secondary -processing and production

  • Tertiary -service provision

  • Quaternary -high-technology industry such as research, or IT.

Economic growth -the growth of gross national product over time. Calculation is highly complex and does not necessarily relate to improvements in the economic experience of the general population as great disparities of wealth can occur with the bulk of the wealth becoming concentrated in the hands of a small elite.

Economic man -assumption used in many models of economic geography that human decision-making and subsequent behaviour is based on rational economic motives. A weakness in these models as modern studies have shown great variation in motive as well as ability to make decisions and access to information. Poor ability and information will lead to poor decision-making even if following an economic motive.

Economic rent -also known as locational rent, the profit to be derived from land. Proposed by von Thunen, it is calculated by subtracting the costs of production and transport of a unit of produce from the market price for that unit and multiplying by the total yield for the area of land in question.

Economically less developed country (ELDC) -previously known as undeveloped, Third World, The South, less developed and less economically developed country (LEDC). A country whose development has yet to lead to the presence of welfare criteria that allow the country to be termed economically more developed. Terminology has changed to try and avoid unwarranted perceptions that people in different places may in some way be better than, or superior to, people in other places.

Economically more developed country (EMDC) -previously known as developed, First World, The North, more developed and more economically developed country (MEDC). A country whose development has led to the presence of welfare criteria that allow the country to be termed economically more developed. These are generally the wealthiest countries in the world although anomalies occur. Some oil-rich Middle Eastern countries are very wealthy but do not display social welfare criteria. Some former Second World countries struggle economically but display complex, modern political structures. Terminology has changed to try and avoid unwarranted perceptions that people in different places may in some way be better than, or superior to, people in other places.

Economies of scale -lower per unit costs achieved by large-scale output. Two kinds:

  • internal -benefit the firm: specialized labour is more efficient, fixed costs spread over more units of production, purchasing is cheaper with bulk buying, larger firms can enjoy lower cost of borrowing.

  • external -benefit the industry: specialized labour pool, attract pool of suppliers.

Ecosystem -a system existing in a particular region, at a variety of scales, where organisms exist in communities and interact with the abiotic environment around them.

Ecotone - the transition zone between very diverse ecosystems e.g. from tropical rainforest to savanna.

Ecotourism -maintenance of very small-scale, low density tourist developments, usually in locations where the environment is particularly fragile or sensitive to human activity, so that degradation does not occur in those areas.

Edaphic -lit. of the soil. Any soil properties which affect plant growth and distribution.

EEC -see European Economic Community.

Effective precipitation -precipitation available for actual use by plants.

Effluent - water released to the environment after treatment.

EFTA -see European Free Trade Association.

ELDC -see economically less developed country.

ELDW - economically less developed world -collectively all the economically less developed countries (ELDCs).

Elevation -height above sea-level.

el Nino -a periodic reversal in the usual pressure, wind and precipitation patterns of the tropical Pacific region which can have severe implications for human activity. Excellent background and explanations here:

ELR -see environmental lapse rate.

Eluviation -removal of material from a soil horizon, usually downward.

Embargo -an order to prohibit trade with a particular country.

Embryo dune – very small dune of sand trapped by grasses at the back of the beach.

EMDC -see economically more developed country.

EMDW -economically more developed world -collectively all the economically more developed countries (EMDCs).

Emergent coast -a coast that has experienced net sea level fall and the characteristics particular to it as a result.

Emergent plants -see aquatic plants.

Emigration -movement of people away from an area, region or country.

Employment sector -the broad types of economic activity within which jobs are provided: primary, secondary, tertiary and quaternary.

Employment structure -the percentage of people employed in each of the four major employment sectors.

Enclosure -in the UK 1450-1820, the move from an agricultural system based on open, or shared, crop fields with common land for grazing and resource collection (e.g. for firewood) to one where individual farmers occupy private holdings whose boundaries are delimited or which may be enclosed by hedges and walls.

Endemic-the presence, regularly or exclusively, of a plant or living organism in a particular area or population. Most usually used in reference to disease causing organisms.

Endogenetic -all factors and processes internal to the Earth.

Energy budget -for the Earth, the net balance between insolation and outgoing radiation. The net gain of the surface and net loss of the atmosphere keeps energy transferring from the former to the latter by conduction, radiation and latent heat (vertical transfers). Also, net surpluses in lower latitudes and net deficits in higher latitudes maintain energy transfers between the two zones through wind and ocean currents (horizontal transfers).

Energy conservation-attempts to limit energy use so that the growth in overall global energy use is slowed. Idealists wish to see absolute reduction in energy use but perhaps a lower per capita usage is a more appropriate goal. Strategies may be threefold:

  • abstention -people deliberately consume less

  • greater efficiency -either through new technologies or through changing habits

  • developing renewable sources of energy

Energy source-the direct source of all the fuels and other forms of energy that we use e.g. coal, oil, wind, tidal. With the exception of geothermal energy and nuclear energy, all of these have originated at some point in time from the sun.

Englacial -within a glacier.

English Heritage -in England, a private body, originating from central government, charged with regeneration and conservation of buildings considered to have a high historical value and thus maintenance of the cultural landscape.

Enterprise zone -in the UK, a policy of the 1980s to encourage economic growth, often in deprived inner city areas, by making it easier and cheaper to establish industrial activity through tax and rates allowances and exemptions and simpler planning procedures. Poorly implemented and ultimately unsuccessful, they were discontinued by the 1990s.

Entrainment -the taking up of river sediment into transport.

Entrepreneur -a risk taker in the business world. Usually applied to a person who sets up as a business owner using their own money or an obligation on borrowed money.

Environment -two meanings:

  • most commonly the physical surroundings in which organisms live.

  • also, any identifiable structure or set of conditions within which people operate e.g. the political environment.

Environmental impact assessment -the identification, prediction and evaluation of the impact that a proposed development may have so that either strict regulations can be laid down governing its construction or the project can be rejected.

Environmental lapse rate (ELR) -change in temperature with altitude above a particular point at a particular time. Average is 6.5蚓 per 1000m. Actual rates slower at lower altitude. In summer, rates tend to be quicker than in winter for the same place.

Environmentalism -the politicization of concern for the environment and demands for action to protect and conserve it.

Environmentally sensitive areas (ESAs) -in the UK, rural areas identified as being of importance for conservation. Farmers are encouraged to maintain both the human and the natural landscape, and to undertake less intensive farming practices. They may receive payment for participating.

Epeirogenic -gentle but large-scale uplift of the crust, or ontinent building-

Ephemeral - in rivers, flowing seasonally or occasionally in response to increased water availability e.g. due to a rainfall event or snowmelt. Compare with intermittent.

Epicentre -the point on the surface directly above the focus of an earthquake.

Epidemic -widespread occurrence of a disease in a particular area or population.

Epiphytes -plants in tropical rainforest which live on the branches or trunks of larger trees. This strategy is purely to achieve greater access to sunlight. They are NOT parasitic as they do not live at the expense of the 'host' Their roots trap falling litter and water on which they survive.

Epoch -geological time period. See geologic time scale.

Equator -the line of latitude (0- bisecting the northern and southern hemispheres equally and thus at the maximum circumference of the globe and perpendicular to the polar circumference.

Equatorial climate -within 5-to 10-of the equator at elevations up to 1000m. annual rainfall exceeds 2000mm and falls nearly every day. Temperatures are high: 30-32蚓 in the day, rarely falling below 20蚓 at any time. Annual temperature range of about 3蚓. Humidity is therefore very high.

Erosion -the degradation and removal of rock material by an agent (water, wind or ice). See abrasion, attrition, hydraulic action, solution, wave-pounding.

Erratic -a large, extremely heavy boulder found in an area of entirely different geology. As the boulder clearly did not form in this area it must have come from another, and source areas are usually pinpointed within a few kilometres but up to a couple of hundred kilometres distant. Currently accepted, along with other evidence in the area, as being glacial debris.

Eruption -the escape of gases, steam and lava from within the crust to the surface or into the atmosphere. May be explosive enough to also send pyroclastic material, such as rocks and dust, into the air at the same time.

Escarpment -an elongated, steep slope at the edge of an upland area such as a plateau or cuesta.

Esker-a low, winding ridge of fluvioglacial deposits which have been laid within sub-glacial channels, therefore found running along the floor of glacial valleys.

Estancia -a ranch in Spanish-speaking S. America.

Estuary -area of a lower river valley or mouth influenced by tidal change.

Ethnic -having one or all of the following: common national or cultural tradition; common language; commonality relating to race or descent thereof.

Ethnic group -a particular group of people within a larger population distinguished by ethnic characteristics.

Ethnic segregation -the clustering of people by ethnic group into spacially distinct parts of urban areas.

EU- see European Union.

Euro -the single European currency.

European Central Bank -controlling institution of monetary policy for the single European currency -the Euro.

European Commission -the civil service of the European Union. Can propose legislation to the European Parliament.

European Community (EC) -class="d-title" name for European Union prior to 1st November 1993 when the Maastrict Treaty of 1992 was ratified.

European Currency Unit -the forerunner of the Euro, this was a stable means of exchange between the former national currencies as they prepared to give way to the single currency.

European Economic Area (EEA) -1991 agreement between European Community and European Free Trade Association.

European Economic Community (EEC) -the original class="d-title" name of the European Union when it was established in 1957 by the Treaty of Rome by the 'original six'-Belgium, France, Germany, Italy, Luxembourg and the Netherlands - also known as the Common Market.

European Free Trade Association -established in 1959 to rival the EEC. See

European Parliament -the elected body of representatives who draft legislation appropriate to the pan-European members of the EU.

European Union -see

Eustatic adjustment -changes in sea level due to changes in the volume of water held in the ocean store.

Eutrophication -an increase in the chemical nutrients to be found in any particular ecosystem. Of particular concern to geographers as poor farming practices can introduce excessive nutrients to waterways, increasing the primary productivity of algal plants which suffocate other primary producers in the water. The increased decomposition activity then reduces the oxygen content of the water which can impact on oxygen reliant organisms such as fish.

Evaporation -the transformation of water liquid to water gas (or vapour) by energy from heat or air movements.

Evapotranspiration -total moisture lost through evaporation and transpiration.

Exfoliation -the 'peeling' away of outer layers of rock in a process of physical weathering found where diurnal temperature range is very wide. Originally thought to be a wholly independent process, now thought to require hydration to prepare the rocks first.

Exogenetic - all factors and processes external to the Earth i.e. working on the surface.

Exotic river-one which maintains its course through an area in which precipitation is not enough to support channel flow. Flow is instead maintained by high volume source areas such as a body of water, or area of high snowmelt. e.g the Nile.

Exotic species -one found in an area to which it is not native.

Expanded town -a town deliberately tagged for expansion to try and alleviate population pressure on a nearby, larger urban area. Large urban centres naturally attract more than their air share-of immigrants and policy has been to try and intercept these people by offering a viable alternative.

Extending flow -in a glacier, when gradient becomes steeper and ice accelerates and becomes thinner.

Extensive agriculture -cultivation of a large land area producing a relatively low per unit yield.

Extrusive-lit. forced out. In geography, applied to volcanic material that reaches the surface. May be lava, pyrolclasts or gases.

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