An oil‐refining process that breaks large hydrocarbon molecules into smaller ones. …
A procedure used in North America in which hazardous materials are identified and tracked as they are produced, treated, transported, and disposed of by a series of permanent, linkable, descriptive documents (manifests). Also known as manifest system . …
Landform created by glacial scour and (like a r?che moutonn?e) formed around resistant rock underneath moving ice, which has a rocky, angular upstream (crag) side and a gently sloping downstream (tail) side. …
A very large, ancient, stable core area within the continental crust, made of highly deformed metamorphic rocks, which are effectively the roots of the continents. Also known as shield . …
An opening in a forest that is created by the application of even‐agedsilviculture practices. See also clearcut. …
The doctrine that all of the universe (including each species of organism) was created separately, in much its present form, by a supreme being or deity. …
US legislation that authorized the President of the USA to set aside public lands as public reservations. …
An amount by which a particular country has actually reduced its pollution emissions, particularly of greenhouse gases, beyond the agreed or required amount. See also certified emissions reduction, emissions reduction unit. …
The extremely slow continuous movement of unconsolidated soil or rock debris down a slope in response to gravity. A very slow form of mass movement. Also known as soil creep . …
Any plant (such as ivy) that grows by sending out a shoot that grows along the ground, rooting all along its length. The term is also applied to a tight‐clinging vine. …
The final geological period of the Mesozoic era that began 145 million years ago and ended 65 million years ago, during which deciduous trees evolved and grew over a wide area and shallow seas submerged much of the surface of the Earth. Dinosaurs became extinct after this period, in a mass extinction. …
A rare brain disease in humans, which usually affects in middle age, is usually fatal, is characterized by progressive dementia and gradual loss of muscle control, and is caused by a prion protein. See also Bovine Spongiform Encephalopathy. …
A deep crack in the ice of a glacier or ice sheet that is caused by ice movement. …
1 Management of a crisis: measures that are taken to identify, acquire, and plan the use of resources to anticipate, prevent, and/or resolve a threat (for example to public safety arising from terrorism). 2 Management in a crisis: decision‐making based on a seat‐of‐the‐pants response to the immediate issue, with little if any consideration of longer‐term effects. …
A group of common air pollutants (sulphur dioxide, carbon monoxide, particulates, hydrocarbons, nitrogen oxides, photochemical oxidants, and lead) that pose the greatest threat to human health and are regulated in the USA by the Environmental Protection Agency. Also known as conventional pollutant . See also designated pollutant, hazardous air pollutant. …
The environmental factor that is closest to a tolerance limit for a given species at a given time. See also limiting factor. …
An area that has been designated (usually by government) as critical for the survival and recovery of threatened or endangered species. …
The maximum amount of a particular pollutant that an environment or ecosystem can tolerate without suffering long‐term damage. …
A species which, according to the IUCNRed List, faces an extremely high risk of extinction in the wild in the immediate future. See also extinct, endangered, vulnerable species. …
In project management, a technique that is used to plan and control the activities in a project, based on identifying the series of successive activities which take up most time (the ?critical path?). This determines the total lead time of the project. Also known as programme evaluation and review technique . …
A habitat that is vital to the health and survival of one or more species, because it provides such features as nesting sites, food sources, and breeding grounds. …
Scottish name for a small farm, generally run on a subsistence basis. …
1 A plant (such as cereals, vegetables, or fruit plants) that is cultivated and harvested for use by people or livestock. See also companion crop. 2 See crop yield. …
The application of pesticides to plants by a low‐flying plane. …
Land that is used for the production of cultivated crops for harvest, either alone or in rotation with grasses and legumes. …
The layout of crops and fallow in a given area of land, and how these vary through the year. …
The way in which crops are grown. See also crop rotation. …
A subsystem of the farming system, or a unit of land use, that comprises the soils and plants, water, nutrients, labour, and other inputs that are used to produce food, feed, fuel, and fibre. …
A measure of efficiency, that is, output (production) per unit of input over time; for example grams of biomass per square metre per day, or crop yield expressed in tonnes per hectare per season. Can also be expressed in terms of labour or financial inputs, solar energy inputs, and so forth. …
The portion of a plant or crop that is left in the field after harvest. …
The practice of planting an area with different crops from year to year, in order to maintain soil fertility and organic matter content, and reduce soil erosion. Most rotations include legume‐type crops to rebuild stores of nitrogen in the soil. See also rotation pasture. …
The amount of a crop that is harvested from a given area of land (such as a field) in a single growing season, usually expressed as yield per unit area (for example, tonnes per hectare). Also known as crop . See also harvest. …
The production (breeding) of a hybrid plant or animal by deliberately mixing different species, breeds, or varieties. Also known as crossing . …
1 The transfer of micro‐organisms from one place or food to another, usually by direct contact. 2 The movement of underground contaminants from one level or area to another. …
The fertilization of a flower by pollen from a different plant of the same species, which creates an offspring with a different genetic makeup from either of the parent plants. See also crossbreeding. …
A view or representation of the interior of an object, viewed along a plane. …
The top or highest part of a tree and the canopy in a forest, made of branches and foliage. See also overstorey. …
A classification of individual trees in a forest, based on dominance relative to adjacent trees, which reflects position in the canopy and amount of sunlight received. The four classes, in descending order of crown height and size, are dominant, codominant, intermediate, and suppressed. …
The growth of the crowns of trees in a forest so that they touch and effectively block out sunlight from the area below. See also closed canopy. …
An intense forest fire that burns the top of living trees as well as the plants below it. …
The distance from the ground to the base of the crown in a tree. …
The number of live births in a given year, per thousand individuals in that population. …
The number of individuals who die in a given year, per thousand individuals in that population. Also known as crude mortality rate . …
The outer layer of the Earth, which varies in thickness between 6 and 48 kilometres, and floats on and surrounds the mantle. It comprises oceanic crust and continental crust, and the thick continental crust and much thinner oceanic crust are separated from the mantle below by the Mohorovicic discontinuity. The crust is made largely of oxygen (47%) and silicon (28%), with much smaller amounts of al…
An aquatic invertebratearthropod of the class Crustacea that lives in freshwater or seawater, has a segmented body, paired jointed limbs, and a hard shell. Examples include shrimp, crabs, lobsters, and crayfish. …
The bending up or down of rocks in the Earth's crust that is caused by pressure, either from within the Earth (for example by mountain building) or from on top of it (for example by crustal subsidence or crustal rebound). Deformation includes faulting, folding, shearing, compression, and extension caused by tectonic forces. …
Large sections or blocks of the Earth's crust, which are curved to the spherical shape of the Earth and fit together like a jigsaw. There are seven major plates (the North American, South American, African, Eurasian, Indo‐Australian, Pacific, and Antarctic plates) and at least twelve minor plates. These plates float on the asthenosphere, allowing them to move relative to one another, driven by s…
The raising of part of the Earth's crust after the melting of heavy continental ice sheets. …
The depression of part of the Earth's crust that is caused by the immense weight of continental ice sheets. …
1 The branch of physics that studies the production and effects of very low temperatures. 2 The preservation of living organisms in a dormant state by freezing, drying, or both. …
The in vitro preservation of organic material (such as embryos, sperm, or eggs) by freezing, usually in liquid nitrogen. Also known as cryogenic storage . …
The frozen part of the Earth's surface, which includes the polar ice caps, continental ice sheets, mountain glaciers, sea ice, snow cover, lake and river ice, and permafrost. …
Behaviour or coloration that helps to conceal an animal. See also cryptic coloration. …
A form of camouflage, in which many animals develop hereditary colouring and markings which match and conceal them in their usual surroundings, in order to protect themselves against predators. See also cryptic. …
Non‐vascular plants such as fungi, mosses, lichens, and liverworts. …
A single‐celled micro‐organism that is commonly found in lakes and rivers, is highly resistant to disinfection, and causes acute diarrhoea, abdominal pain, vomiting, and fever in humans. …
A homogeneous regularly shaped solid with flat surfaces (faces) and specific angles between the faces. The crystal form varies from one substance to another, reflecting the atomic, molecular, or ionic structure of the crystal. …
1 An organism or other object that is rejected or set aside because it is of inferior quality. 2 The process of killing designated animals in a particular place, as part of a management plan, in order to reduce the number of individuals within the population. …
A domesticated variety of plant that has been cultivated by selective breeding and is not normally found in wild populations. Also known as cultivated species . …
1 To prepare and use land for growing crops. 2 To adapt a wild plant to a new environment. See also domesticate. …
The accelerated extinction of species that is caused by human activities such as the over‐hunting of animals, over‐collection of plants, introduction of non‐native species, removal of habitat, and induced environmental change (for example, related to pollution). …
Natural landscape that has been modified (both by accident and by design) by humans. …
The physical remains (including artefacts, objects, and structures) of past human activities. Contrast aesthetic resource. See also resource. …
1 The growth of cells or an organism in a prepared medium, under laboratory conditions. 2 A set of beliefs, attitudes, and rules for behaviour that are commonly held in a particular society. …
A drain or pipe that carries surface water under a built structure such as a road or railway. …
Effects that result from separate, individual actions that collectively become significant over time. …
The sum of exposures that an organism has to a pollutant over a period of time. …
Having the appearance or character of cumulus clouds. …
A tall cumuluscloud (sometimes reaching an altitude of 9000 metres (30?000 feet)?), formed in turbulent, rising air. They are usually grey or dark grey. Their tops may be smooth or striated or be flattened into an anvil shape, and they often bring heavy rain or hail (formed in the strong vertical uplift) and are sometimes associated with thunderstorms. …
A type of cloud that is associated with rising air currents, usually below about 2400 metres (8000 feet). In Latin cumulus means heap. They are dense, well‐defined mounds with dark bases and white rounded upper regions. Relatively thin cumulus clouds, which are common on warm summer afternoons in middle latitudes, indicate fair weather and relatively stable conditions. …
An instrument used to monitor wind speed, via the rotation of cups by the movement of air. …
An obsolete measure of radioactivity, equal to 3.7 ? 1010 (37?000?000?000) nuclear disintegrations per second. Replaced by the *becquerel. …
1 A horizontal movement of water, for example along a stream or through an ocean. 2 The movement or flow of electricity. 3 Occurring in or belonging to the present time. …
1 A waxy film made of cutin that covers the external surface of the stems and leaves of plants, which helps to prevent water loss. 2 The exoskeleton made of chitin that is secreted by invertebrates. …
A waxy substance that, together with cellulose, forms the outer layer of the skin (cuticle) of many plants. …
A part (stem, leaf, or root) that is removed from a plant and is capable of developing into a new plant through rooting or grafting. …
A river in northeast Ohio, USA, into which industries around Cleveland dumped oily wastes, and which has literally caught fire on numerous occasions. The most serious fire occurred on 23 June 1969 , and that event triggered a series of important pollution control initiatives including the Clean Water Act ( 1972 ) and the Great Lakes water quality agreement, and the creation of federal and state e…
A group of inorganic salts that contain the cyanide ion (CN-). They are highly poisonous and are used in ore processing to extract gold and silver from crushed rock. …
Bacteria, also known as blue green algae, that contain chlorophyll and can photosynthesize. They can form large coloured mats on the surface of lakes and rivers. One species causes a red tide. …
A system that continuously changes in response to feedback. …
A hypothetical model of how landscapes evolve through a progressive sequence of stages, starting from an uplifted surface dissected by some rivers, through a youthful landscape with steep valley sides and steep long profiles, to a mature landscape dominated by low hills and low river slopes, to the gentle undulating or flat landscape of old age. Also known as geomorphic cycle . …
The development of low‐pressure systems (depressions) in the atmosphere. See also frontogenesis. …
1 The name for a hurricane in the Indian Ocean. 2 See depression. 3 See tornado. …
The movement of air around a depression. In the northern hemisphere the flow is anti‐clockwise, and in the southern hemisphere it is clockwise. …
Rain that occurs in a depression, when warm air rises above cold air and cools adiabatically, causing the condensation of water vapour and formation of raindrops. Also known as frontal rain . …
The contents of a cell, other than the nucleus. See also protoplasm. …
The mineral layer beneath the B‐horizon within a soil profile, which is relatively unaffected by biological activity and is composed of only partially weathered material. See also soil horizon, a‐horizon. …
Relating to the production of milk or milk products, such as butter and cheese. …
A computer model developed by James Lovelock to illustrate his Gaia hypothesis on any planet that supports life, based on how black and white daisies adapt to changes in radiation and temperature. …
An artificial barrier constructed across a river or valley, usually for flood control, irrigation, and/or power generation. See also reservoir. …
Evaluation of the magnitude, physical extent, and types of damage that a biological or physical resource experiences as a result of an event such as a natural hazard. …
The condition of being susceptible to harm or injury, for example as a result of exposure to a natural hazard. …
The 19th‐century British naturalist ( 1809 ? 82 ) who is widely considered to be the father of the theory of evolution. His landmark work, On the Origin of Species, published in 1859 , supported the idea of evolution by means of natural selection. …
An international celebration of science and humanity that is held on 12 February each year, to celebrate the birth of Charles Darwin in 1809 . …
An international agreement reached in Darwin, Australia in 1988 , in response to the United Nations Framework Convention on Biological Diversity, that countries should work together to improve knowledge and understanding of the world's biological diversity. …
The theory put forward by Charles Darwin that species originate and develop by evolution from simpler species, and that evolution is driven mainly by natural selection. …
A collection of facts (usually created by measurement) from which conclusions may be drawn. See also information. …
The processing of large amounts of data in order to extract new kinds of useful information from it, based on patterns and relationships. See also informatics. …
A reference (such as mean sea level) against which to measure heights or depths. …
The first light of day, in the eastern sky before sunrise. Also known as daybreak. See also dusk. …
1 A 24‐hour period of time that begins at midnight and ends the following midnight, during which the Earth makes a complete rotation on its axis. 2 The time between sunrise and sunset, when it is light outside. Contrast night. …
Light that is received from the Sun and the sky, during the daytime. …
1 Using sunlight to provide supplementary lighting for the interior of a building. 2 The act of cutting back vegetation bordering a road, in order to encourage the growth of new herbs and shrubs. …
A colourless insecticide (dichlorodiphenyltrichloroethane), which is persistent and can collect in the fatty tissues of certain animals. It was used during the Second World War to control the spread of typhus and malaria by insects, and was widely used as an agricultural pesticide during the 1950s and 1960s. It has been banned in the US since 1973 as a result of growing public concern because of…
The number of individuals in a population who die in a given year, usually expressed as a ratio (number of deaths per year per 1000 individuals). Also known as fatality rate, mortality . …
Dead organic material (leaves, twigs, etc.) and sediment. …
A type of overland or submarine mass movement involving a downslope flow of a saturated mass of soil and rock debris, with more than half of the material being particles larger than sand size. Slower than a debris slide. Also known as a flow . …
A rapid downslope movement of an unconsolidated mass of mud, sediment, and rock. Faster than a debris flow. Also known as a slide . …
An emerging approach to the conservation of wildlife, which involves conservation organizations (usually from developed countries) acquiring part of the international debt of a particular developing country at an agreed discount price. The organization then redeems the debt in local currency, and uses it to fund conservation activities such as the setting up and running of nature reserves and nati…
The 1970s, when a large number of the most important US policies towards the environment were passed because of greater public engagement, broader support for environmental policies in Congress, pro‐environmental leadership from Republican and Democratic presidents, and favourable interpretations of statutory laws by key US courts (particularly the Supreme Court). …
To pour of draw off the upper layer of liquid after the heavier material has settled. For example, drawing off water after a solid pollutant has settled out, as a means of cleaning up polluted water. …
The rate of radioactive decay, which is characteristic of the given nuclide. The decay constant is the probability that an atom of the radionuclide will decay within a stated time (it is measured in units of reciprocal time). …
An element (which may itself be radioactive) that is formed by the radioactive decay of another element, which may be stable or may itself be radioactive. Also known as daughter product . …
The partial or complete removal of chlorine from a substance, for example by using activated carbon and sulphur dioxide. …
A unit that measures the intensity or loudness of sound. …
A tree or plant that sheds its leaves at the end of the growing season (autumn) each year. Examples include ash, beech, hickory, maple, and oak. Also known as hardwood . Contrast coniferous, evergreen. …
A temperate or tropical forest in which the deciduous trees shed their leaves during either cold or dry seasons. It is relatively fertile (because of the abundant leaf litter), plant biodiversity is high, and typical trees include oak, hickory, maple, ash, and beech. Found in areas with moderate rainfall and marked seasons. …
The process of acting upon the best information available in order to determine the most appropriate course of action. …
1 A downward slope or bend. 2 Angular distance north or south of the celestial equator. 3 The angle between magnetic north and geographical north. …
To permanently shut down a facility (such as a nuclear reactor or power plant) or withdraw it from service or active use Contrast commission. …
The waste materials that are produced when a facility (such as a nuclear power plant) is decommissioned. …
1 The breakdown of organic matter into smaller particles by organisms such as bacteria and fungi, releasing energy, simple organic material (such as sugars and proteins), and inorganic compounds (nutrients) back into the environment where they become available to plants. 2 The chemical weathering of rock. …
Removal of harmful substances (such as chemicals, bacteria, or radioactive material) from exposed individuals, rooms, and furnishings in buildings or from the exterior environment. …
Reasoning from the general to the particular, for example by developing a hypothesis based on theory and then testing it from an examination of facts. Also known as deduction . Compare inductive reasoning. …
A worldview or set of beliefs that calls for a major shift in human attitudes, values, and behaviour that rejects anthropocentrism and directs personal action to protect nature and improve the environment. Contrast shallow ecology. See also ecocentric, radical ecology. …
Areas of the oceans that are seaward of the continental shelf. …
Any area of open water that is deeper than two metres or covers the deepest emerging vegetation. …
A well‐defined layer in the ocean that reflects sonar and indicates the presence of fish, squid, or other large marine organisms. …
Disposal of waste fluid (particularly hazardous waste) by pumping it into a deep well, where it is stored underground in permeable rock surrounded by impermeable layers. …
The removal of clay and dust from dry soil by wind. See also desert pavement. …
The breakdown of clusters of soil particles. The term is usually applied to clay soils. …
The removal of excess fluoride in drinking water in order to protect teeth from damage or staining. …
A chemical herbicide that causes the leaves to fall from trees and growing plants. See also agent orange. …
To remove the leaves from plants, trees, or shrubs. …
The permanent clearance of a forest, usually rapidly by cutting or burning over a large area, without replanting or natural regeneration. Also known as forest clearance . Contrast afforestation. …
A change in the original shape of a material, such as a layer of sedimentary rock that has been affected by folding. See also crustal deformation. …
In the UK, the Department for Environment, Food and Rural Affairs, formerly MAFF. …
The removal of dissolved gases from water in order to purify it. …
The melting (ablation) and receding of ice sheets and glaciers, which uncovers the land beneath. Contrast glaciation. …
Able to be broken down or separated into a simpler form, using chemical, physical, or biological means. See also biodegradable. …
1 The chemical or biological breakdown of a complex compound into simpler compounds. 2 General lowering of land surfaces by erosion. Contrast aggradation. …
The process of changing the designated status of a particular resource, such as removing a species of animal or plant from the IUCNRed List, or removing a Superfund waste site from the National Priorities List in the USA. …
A method of long‐term forecasting or decision‐making based on expert judgement. It involves a number of stages: experts are interviewed anonymously and separately, in order to gain their views on a particular issue or problem; the results are combined and fed back to the experts as a group; each expert is then interviewed again, in the light of peer group opinion. In theory, the process contin…
A fan‐shaped alluvial deposit at the mouth of a river, built up by the deposition of successive layers of fine‐grained sediment is caused by a reduction in velocity of the current so that the sediment drops out. …
The ability and desire to buy goods and services, or the quantity of a good or service that is needed in order to meet the requirements of the user. See also market equilibrium, supply. …
An approach to the allocation of scarce resources that is based on minimizing wastage, restricting supply, and educating people to use less of the resource and use it more carefully. Also known as demand‐side management . …
The relationship between price and quantity demanded of a good or service, which shows how much would be bought or consumed at various prices at a particular point in time. …
Native and desired non‐native species of plants and animals that have a high social, cultural, or economic value. …
Fish and aquatic animals that live at or near the bottom of a sea or lake. …
The removal of dissolved minerals and mineral salts from a liquid, particularly water. …
Relating to populationstatistics, changes, and trends based on measures of fertility, mortality, and migration. …
An equation that is used to calculate population changes from one year to the next in a given area, based on number of births, deaths, and migrations. The general form of the equation is a mass balance equation, in which end population = starting population ? natural increase ? net migration, where natural increase = births ? deaths, and net migration = immigrants ? emigrants. At the global scale …
Any of the three factors (fertility, mortality, and migration) that determine the level, composition, and distribution of population in a particular place or area. See also demographic balancing equation, demographic transition model. …
Statistics that describe the characteristics of a population, such as age, sex, race, family size, income, and location of residence. …
The growth pattern that many human populations go through as countries develop, undergo industrialization and urbanization, and improve their standard of living. Birth and death rates converge and zero population growth is achieved. …
A four‐stage model that shows how birth rates and death rates change through time in a particular country or area, giving rise to phases of population stability and change. During stage one the death rate is usually very high because of poor health and difficult living conditions, life expectancy at birth is less than 30 years, but birth rates are also high and so population growth rate is zero …
The statistical study of the characteristics of populations, including distribution, age structure and composition, and patterns of fertility, mortality, and migration. …
A rain‐proof, weather‐tight cavity in a tree or a space dug by animals among rocks or in soil. See also den tree. …
A type of drainage pattern that develops as a random network and has branches like a tree. …
The use of growth rings in trees to date when timber was felled, transported, processed, and used for construction. …
A dating technique based on the analysis of growth rings in trees. The number of rings indicates age, and the width of individual rings indicates climatic conditions at the time of growth and is used in dendroclimatology. See also tree ring. …
A technique used to reconstruct past climate, based on analysis of growth rings in trees, as proxy climate indicators. Ring width reflects the climatic conditions of the growing season, and rings can be counted to give ages. See also tree ring. …
A branching, tree‐like diagram, which usually has a single source, and shows relationships produced by classification. See also cladogram. …
The study of the identification, habits, and distribution of trees. See also silviculture. …
The biological process in which nitrates are reduced to nitrogen gas, by denitrifying bacteria, in soil under anaerobic conditions. Contrast nitrification. …
Free‐living bacteria in soil that convert nitrates to gaseous nitrogen and nitrous oxide. …
A cloud with its base on the ground surface, that reduces visibility to 0.5 kilometres or less. …
A liquid that does not dissolve in water, and which is also denser than water so it sinks. Many chlorinated solvents are DNAPLS. …
1 The mass of a substance per unit volume (kilograms per cubic metre, kg m-3). 2 The number of individuals of a defined group that are present in a given area at a particular time. See also frequency, population density. …
A current in water that flows because of differences in density. For example density currents in the ocean are caused by differences in temperature, salinity, and turbidity. …
The creation of layers in a water body due to differences in density, which may be caused by differences in temperature and in concentrations of dissolved solids and suspended solids. …
The regulation of the size of a population by mechanisms that are controlled by population density (such as the availability of resources, or the incidence of contagious disease), and that become more effective as density increases. Contrast density‐independent. …
A factor that influences the individuals in a population in ways that do not vary with population density. Contrast density‐dependent. …
A tree with cavities in which birds, mammals, or insects (such as bees) can nest. Also known as cavity tree . …
The wearing down of the land surface by natural geological processes, which involves weathering, mass movement, and erosion. …
The long‐term history of landscape development by denudation. See also cycle of erosion, erosion surface. …
Laid bare, stripped of all vegetation cover, often as a result of a disturbance such as a landslide. …
The consumption of oxygen in water by aquatic organisms, as they decompose (oxidize) organic materials. …
In conservation assessment, the reliance of a species, community, or ecological process on a particular location (such as a feeding ground or a migration corridor) or structure (such as a coniferous forest) for survival. …
In a given human population, the number of economically dependent, non‐working members (who are younger than 15 or older than 65) compared with the number of productive, working members (aged 15 to 64). …
A theory that the relationships between advanced capitalist societies (the wealthy First World) and undeveloped, poor Third World countries has always been exploitative. Development of the former has resulted in underdevelopment of the latter; the latter are kept dependent on the former by the capitalist system, and as a result the former continue to exploit the latter for their own gain. …
Decline in availability that results from using abiotic (non‐renewable) resources, or from using biotic (renewable) resources faster than they can be renewed. …
The time it takes to use up a non‐renewable resource. …
1 An accumulation of sediment, minerals, and precipitated substances. See also alluvium, colluvium, boulder clay. 2 A facility where things can be stored for safekeeping. …
1 The accumulation or laying down of sediment. 2 The conversion of water vapour directly into ice, without first becoming a liquid. In chemistry this is known as sublimation. …
Any part of the environment in which sediment is deposited, such as a lake, coast, or river. …
Tiny particles in the atmosphere on which an ice crystal can grow by the process of deposition. Also known as ice nuclei . …
A cyclonic circulation of winds towards the low pressure at the centre, where convergence occurs. It can produce violent, damaging thunderstorms with winds of force 12 or above on the Beaufort scale. Depending on where it occurs a depression is also known as a low, tropical cyclone (or just cyclone), hurricane or typhoon. …
A drainage system having no obvious pattern. Sometimes found in areas of low relief, low slope, and large sediment loads, and typical of recently glaciated areas. …
In cladistics, a feature that is shared among members of smaller groups or clades and is believed to have evolved at a later date than primitive features. Also known as advanced character . …
The demand for a particular resource (such as bricks) that is created by the desire to satisfy the demand for some other resource (such as houses). …
Contact between a gas, liquid, or solid (such as a pollutant) and the skin. …
The ability of a pesticide or toxic chemical to poison an organism (including people and animals) by contact with the skin. …
The removal of salt from water, usually by distillation, freezing, electrodialysis, or reverse osmosis. …
A person who is descended from a particular ancestor or race, as an offspring. …
A dry biome that is common in the subtropics, and contains plants and animals that are adapted to extreme water shortage. It is created by an arid climate in which evaporation exceeds precipitation, and precipitation is infrequent, unpredictable, and less than 25 centimetres of rain a year. See also tropical desert, temperate desert, cold desert, sand desert. …
Different climates produce tropical deserts, temperate deserts, and cold deserts, but they have in common wide diurnal variations in temperature, low relative humidity, limited precipitation, more or less continuous sunshine throughout the year, little cloud cover and clear skies, and occasional intense local convectional showers. Middle‐latitude deserts are cooler than the low‐latitude desert…
A hard surface layer that develops in a desert climate, caused by the evaporation of water from the ground which leaves calcium carbonate, gypsum, or other cementing materials as a precipitate. Contrast desert pavement. …
A North American grassland vegetation that grows in semi‐arid climates on bajadas and in valley bottoms where clay‐rich soils prevent water from draining. It is often dominated by bunch grasses or (where disturbed) various shrubs. …
The spread of desert‐like conditions in semi‐arid regions due to human activities (including overgrazing, deforestation, or soil erosion), prolonged drought, and/or climatic change (global warming), which cause long‐term changes in the soil, climate, and plants and animals of an area. The term was originally used to mean the spread of desert conditions over adjacent areas as a result of clim…
A type of hot desert in the form of a depression, which is often salty and receives drainage from inflowing streams. …
Gravel and stones left after wind and water erosion have removed finer material from a desert floor. Contrast desert crust. …
A region of the Earth in which deserts are found. There are five main desert provinces: the Sahara, southern Africa, South America, North America, and Australia. …
A book by Edward Abbey who regarded the wilderness as a place where people can separate themselves from society but from which they need to return to society refreshed and ready to deal with the problems of society. Regarded by some as a latter‐day Walden. …
A dark, hard, shiny coating of iron and manganese oxides that is found on rocks in arid regions. …
A hot, dry, dusty wind that blows outwards from a low air pressure cell over a desert, desiccating surrounding areas and withering plants. Examples include the sirocco and the harmattan. …
Any material (such as a chemical) that absorbs moisture. …
The process of drying out as a result of the removal of water. …