Ice Age -see glacial.

Iceberg-a mass of ice formed from fresh water floating in the ocean. They are break-away fragments from ice sheets or glaciers. Due to the buoyancy, only 10% of the mass appears above the surface.

Ice cap -a large area of ice. Smaller than an ice sheet, a common division is made at 50000km². The term is also often applied to the ice sheets found in polar regions, though this is a more popularist use.

Ice core -two types:

• the ice found in the middle of a pingo.

• a sample of ice taken from the inner/lower parts of a glacier or larger body of ice. Analysis of this ice can give us information on past climate.

Ice lens -in periglacial areas, as winter sets in, land not under continuous permafrost will experience freezing of water in the surface layer. Water from below this layer is then drawn up through capillary action. Frozen patches form in a lens shape parallel to and just below the surface. This causes stones to roll to the edges of the lens forming patterned ground.

Ice sheet -a large area of ice, usually over 50000km². Currently found in Greenland and Antarctica.

Ice wedge -when temperature fall below -15蚓, ice in soil contracts. This causes cracks to open in the ground. These may fill with water which then freezes to form an ice wedge. During interglacials, or periods of retreat, the ice melts away and the crack may fill with solid material which stands out and may show the shape of the old ice wedges within the profile of the soil (fossilized ice wedge).

Igneous -a rock formed through the cooling of magma or lava. The slower the cooling, the larger the rock crystals and the harder the rock, although all igneous rocks are very hard.

Illuviation -inward movement of clays, minerals and organic matter to a low soil horizon  From one above.

IMF -see International Monetary Fund.

Immature soil -one which has not had time to develop. It will be made mostly of regolith. Organic components are minimal.

Immigration -inward movement of people to a country.

Impermeable -a rock which cannot absorb water and does not allow it to pass through.

Import controls -measures imposed by governments to restrict the import of particular goods or goods from a particular country. May involve mild measures such as lots of ed-tape-requirements, through tariffs and quotas, to embargoes in the most extreme form.

Import penetration -the proportion of the market for a particular product-type taken up by imports.

Import substitution -the establishment and/or explicit government support for an industry producing goods that were formally exclusively, or nearly exclusively, imported. Usually used in the ELDW to try and add value to domestic raw materials and reduce the flow of money out of the country.

Incised stream -one which has cut deeply down into the landscape.

Income - money received. Can be considered at three scales:

• wages and salaries for individuals

• revenue (turnover) for businesses

• taxes, tariffs, duties and others for governments.

Independent variable - one which is not affected by another e.g. depth is not affected by water temperature but the water temperature will vary with depth (it is the dependent variable).

Indigenous -originating in a particular area, region or nation. Usually applied to flora, fauna and people.

Industrial estate -planned area of integrated buildings and roads for industrial use, especially by modern industrial businesses. Often built on brownfield sites as part of urban regeneration projects.

Industrial inertia -the continuing presence of industry in an area, or at a location, after the initial locational factors have ceased to apply.

Industrialisation -the move from an economy dominated by agricultural output and employment to one dominated by manufacturing.

Industrial location theory -any theory attempting to explain why industries are found to have located in the places they are found. Relate locational factors to the goals of the industry such as minimizing costs (least-cost location) or maximizing profits.

Industrial revolution -a fundamental change in the way that goods are produced and the behaviour of the people who produce them. Essentially two have occurred:

• 17^th and 18^th century move from small-scale, low-tech., often home-based, production by thousands of individuals to machine-based mass production in factories owned by a few and employing people to do the work.

• 20^th century to present appearance of hi-tech industry which is footloose and less dependent on economies of scale.

Infant mortality -the number of deaths of infants below one year of age as a proportion of every thousand live births in that population in that year.

Infield-outfield -farming system, largely obsolete now, where the fields closest to the farm buildings receive the most attention and most intensive cropping. The fields further away may only be used for grazing or even left fallow.

Infiltration -movement of water from the surface into the soil.

Infiltration rate -the rate at which water moves into the soil. Dependent on:

• amount of water already in the soil, especially near the surface. Very wet and very dry soils have the slowest rates of infiltration.

• soil texture which determines the size of pore spaces and thus how easily water can pass through.

• soil structure as some ped shapes block water.

• amount and type of vegetation. Vegetation will influence rate at which water arrives at the surface as well as the nature of the soil.

Informal sector-self-employment and the jobs that are done by self-employed people, and which are neither declared to, nor regulated by, the authorities.

Information technology (IT) -technology tasked with processing, storing and communication of information e.g. computers, mobile phones, PDAs. Geographical effects have been widespread as the advances in IT have begun to dramatically change behaviour e.g. working from home, reducing business trips, shopping from home. The irony of IT advances so far is that a technology that essentially disperses activities (by not requiring people to be at particular locations) has led to greater concentration of economic wealth at the global level as it is the EMDW, and particular regions within it, that have been able to adopt and adapt IT most effectively.

Infrastructure -the collective class="d-title" name for all the communication links and basic utility links that get built across a country to facilitate movements. Good infrastructure requires high levels of capital input, expertise, and political will. Differences in infrastructure quality are a defining feature between the EMDW and ELDW.

Inner-city -the older parts of large urban areas found near to the CBD and containing both residential and industrial landscapes, sometimes integrated. They are the remnants of nineteenth century urban expansions that were at the heart of the first industrial revolution. By the 1970s they were identified with decline and deprivation but since the late 20^th century, many have been redeveloped or gentrified. 

Inorganic - non-living things. Also abiotic.

Input -in systems theory, any element introduced to the system from outside.

Inselberg - lit. sland mountain-(from the German). A stand-alone mountain or hill which rises steeply from much flatter surroundings.

Insolation -incoming solar radiation measured from when the atmosphere is engaged.

Instability -the continued rising of an air mass as it is warmer than the surrounding, or environmental, air. This is especially common after the rising mass has passed the dew point and so cools at the saturated adiabatic lapse rate as the release of latent heat keeps the mass warmer. The term instability is used as the continued rising leads to further opportunity for condensation and thus the build up of large, dense storm clouds.

Intensive agriculture -the application of high levels of capital and/or labour inputs to units of land area. Thus is can be true of agriculture in both the ELDW and the EMDW.

ab> Inter-basin transfer -the transfer of water between drainage basins by humans.

Interception -when precipitation deposits onto a surface that Is not the actual land such as vegetation or animals.

Interdependence -the connections between different components of systems or between separate systems which mean that changes in one will necessarily cause changes in another.

Interglacial -a period of warmer climate conditions between glacial periods.

Interlocking spurs -the landform resulting from the winding path of a river in its upper course cutting a V-shaped valley. The slopes on the inside of each bend jut out giving an interlocking appearance.

Intermediate technology -see alternative technology.

Intermittent -in rivers, flowing most of the time but seasonally or occasionally ceasing to flow in response to decreased water availability e.g. increased evapotranspiration or bed seepage. Compare with ephemeral.

International dateline-a line of longitude at approximately 180˚ which is internationally agreed as the official start point of each day.

International Monetary Fund (IMF) -an organization framework for international economic co-operation conceived by the United Nations. http://www.imf.org/external/np/exr/facts/glance.htm

Interquartile range -statistical measure of the spread of values around the median. When the upper, or higher, 25% of values and the lower 25% of values are removed, the spread of the remaining, interquartile, values is derived.

Interstadial -a relatively short and temporary period of warming during a glacial. Not long enough to be classed as a proper interglacial.

Inter-tidal zone -the land between the low tide mark and high tide mark. See also littoral.

Intertropical convergence zone-where the surface level winds from the two Hadley Cells come together. The term was introduced to take into account the seasonal movement of the heat equator which causes the cells to change position through the year.

Interventionist -belief in significant government presence in modifying markets to improve their efficiency and to protect consumers from unscrupulous or irresponsible business behaviour. Such government action could include:

• fines for firms who break standards across a range of criteria

• laws to impose standards and minimum wage levels

• protection for consumers and workers

• regional policies to maintain balance across the national space

• support to start-up businesses or ailing older ones

• training schemes

Intrazonal soil -one whose main characteristics are controlled by a single local factor. Climate is not dominant and so they occur in localized places rather than zones.

Intrusive landform -one produced by the cooling of magma into solid igneous rock within the crust.

Invisible export-the sale of a service to a customer overseas, particularly of financial products such as banking and insurance.

Invisible import -the buying of a service from an overseas provider.

Invisible trade -import and export of services in industry sectors such as banking, tourism and education. Forms part of the balance of payments.

Irrigation -when humans water the land, usually for agriculture but also for leisure (e.g. golf courses), either during a period of dry weather or to bring areas of land in drier zones into use.

Island arc -a chain, often arc-shaped, of volcanic islands. These are undersea volcanoes which have grown through repeated eruptions to break the surface. They are the product of a subduction zone where either the continental plate is so low lying that its edge is submerged, or two pieces of oceanic plate have collided, the denser being subducted.

Isobar - A line on a weather map that connects points of equal pressure. On a weather map, isobars extend around areas of high and low pressure.

Isodapane - line connecting points of equal total transport cost.

Isopleth map -a map which uses lines joining points of an equal value to show variations in that value e.g. contour lines on a topographical map, isobars on a weather map.

Isostatic- the rise and fall of the land relative to the sea (as opposed to eustatic) due to the removal or addition of ice sheets respectively.

Isostatic depression -the sinking of a landmass due to the overlying weight of ice.

Isostatic rebound -the rising of a landmass after the removal of ice.

Isotim-a line connecting points of equal transport costs. Intersecting isotims for multiple materials/products allow isodapanes to be drawn by connecting the points of intersection.

Isotope - some elements have more than one form. They differ only in nuclear terms rather than chemical ones and have different relative atomic mass as a result. They may behave slightly differently which allows us to use them in geography for a number of measurements relating to constructing past conditions.

Isotropic - physically uniform in all directions. Usually used to describe flat plains with uniform soil and climate properties in models seeking to isolate other variables.

ITCZ -see Intertropical Convergence Zone.