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| The point at which the longitudinal profile of a stream is abruptly broken by a change in GRADIENT. (a waterfall, rapids, or cascade). (11) |
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| An interior sunken portion of a composite volcanic crater; usually steep-sided and circular, sometimes containing a lake; also found in conjugation with shield volcanoes. (9) |
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| A general term referring to all processes that cause degradation of the landscape. (weathering, mass movement, erosion, and transport). (10) |
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| The SIDEWAYS and DOWNWARD movement of the edge of a plate of the earth's crust into the mantle beneath another plate. SUBDUCTION ZONE: an area where two plates of crust collide and the denser oceanic crust dives beneath the less dense continental plate, forming deep oceanic trenches and seismically active regions. (8) |
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| Base level: a hypothetical level below which a stream cannot erode its valley, and thus the lowest operative level for denudation processes; in an absolute sense, represented by sea level extending back under the landscape. BASE LOAD: those coarser materials dragged along a streambed by a stream's traction. (11) |
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| A high water level that overflows the natural (or artificial) banks along any portion of a stream. (11) |
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| An element or combination of elements that form an inorganic natural compound; described by a specific formula and qualities of a specific nature. (8) |
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| A mass of intrusive igneous rock that has cooled slowly in the crust; forms in any size or shape. The largest partially exposed pluton is a BATHOLITH. (8) |
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| The largest plutonic form exposed at the surface; an irregular intrusive mass (>100km^2; >40mi^2) that invades crustal rocks, cooling slowly so that crystals develop. (8) |
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| Loss of glacial ice through melting, sublimation, wind removal by deflation, or the calving off of blocks of ice. (14) |
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| A scooped-out, amphitheater-shaped basic at the head of an alpine glacier valley; an erosional landform. (14) |
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| A sharp ridge that divides two cirque basins; means "fish bone" in French. Arêtes form sawtooth and serrated ridges in glaciated mountains. (14) |
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| A pyramidal, sharp-pointed peak that results when several cirque glaciers gouge an individual mountain summit from all sides. (14) |
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| General descriptive term for clay, silt, and sand, transported by running water and deposited in sorted or semi-sorted sediment on a floodplain, delta, or streambed. (11) |
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| A small mountain lake, especially one that collects in a cirque basin behind risers of rock material. (14) |
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Direct ice deposits that appear unstratified and unsorted; a specific form of GLACIAL DRIFT. (14)
Till Plains: Large, relatively flat plains composed of unsorted glacial deposits behind a terminal or end moraine. Low-rolling relief and unclear drainage patterns are characteristic. |
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| The reflective quality of a surface, expressed as the percentage of reflected insolation to incoming insolation; a function of surface color, angle of incidence, and surface texture. (3) |
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| A self-regulating association of living plants, animals, and their nonliving physical and chemical environment. (16) |
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| The state or process of a species, family, or larger group being or becoming extinct. |
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Upward-faulted blocks produced by pairs or groups of faults; characterized by the mountain ranges of the interior of the western United States.
Graben: Pairs or groups of faults that produce downward-faulted blocks; characteristic of the basins of the interior western US. (9) |
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Forms when soil or rock temperatures remain below 0*C (32*F) for at least 2 years in areas considered periglacial; the criterion is based on temperature and not on whether water is present.
Periglacial: cold-climate processes, landforms, and topographic features along the margins of glaciers, past and present, that occupy more than 20% of Earth's land surface; including permafrost, frost action, and ground ice. (14) |
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| Undulating horizontal motions in the upper-air westerly circulation at middle and high latitudes. (4) |
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| A natural process in which lakes receive nutrients and sediment and become enriched; the gradual filling and natural aging of water bodies. (16) |
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| The most prominent movement in the upper-level westerly wind flows; irregular, concentrated, sinuous bands of geostrophic wind, traveling at 300 kmph (190 mph). (4) |
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| ITCZ (Intertropical convergence zone); Equatorial low-pressure trough |
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| A thermally caused low-pressure area that almost girdles Earth, with air converging and ascending all along its extent. (4) |
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A lake that was formerly part of the channel of a meandering stream, isolated when a stream eroded its outer back, forming a cutoff through the neck of a looping meander.
Meandering stream: The sinuous, curving pattern common to graded streams, with the outer portion of each curve subjected to the greatest erosive action and the inner portion receiving sediment deposits.
Graded stream: A condition in a stream of mutual adjustment between the load carried by the stream and the relate landscape through which the stream flows, forming a state of dynamic equilibrium among erosion, transported load, deposition, and the stream's capacity. (11) |
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| An explosively ejected rock fragment launched by a volcanic eruption; sometimes described by the more general term TEPHRA. (9) |
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| Large quantities of fine-grained clays and silts left as glacial outwash deposits and subsequently blown by the wind great distances and redeposited as a generally unstratified , homogeneous blanket of material covering existing landscapes. In China, loess originated from desert lands. (12) |
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| A depositional feature of glaciation; a small hill of poorly sorted sand and gravel that accumulates in crevasses or in ice-caused indentations in the surface. (14) |
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| Formation made when an isolated block of ice persists in a ground moraine, an outwash plain, or a valley floor after a glacier retreats; as the block finally melts, it leaves behind a steep-sided hole that frequently fills with water. (14) |
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| Marginal glacial deposits (lateral, medial, terminal, ground) of unsorted and unstratified material. (14) |
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| The transport of sand grains (usually larger than 0.2 mm, or 0.008 in.) by stream or wind, which bounce the grains along the ground in asymmetrical paths. (11, 12) |
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| A graph of stream discharge over a period of time (minutes, hours, days, years) at a specific place on a stream. The relationship between stream discharge and precipitation input is illustrated on the graph. (11) |
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| Mechanical wearing and erosion of bedrock accomplished by the rolling and grinding of particles and rocks carried in a stream, moved by wind in a "sandblasting" action, or imbedded in glacial ice. (11, 12, 14) |
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| The inner portion of a stream meander that receives sediment fill. (11) |
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| Fan-shaped fluvial landform at the mouth of a canyon; generally occurs in arid (dry) landscapes where streams are intermittent (occur irregularly). (12) |
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| An area of salt crust left behind by evaporation on a desert floor, usually in the middle of a bolson or valley; intermittently wet and dry. (12) |
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| A continuous apron of coalesced alluvial fans, formed along the base of mountains in arid climates; presents a gently rolling surface from fan to fan. (12) |
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| In arid landscapes, a surface formed when wind deflation and sheet flow remove smaller particles, leaving residual pebbles and gravels to concentrate at the surface; resembles a cobblestone street. (12) |
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| The joining of carbon dioxide and hydrogen in plants under the influence of certain wavelengths of visible light; releases oxygen and produces energy-rich organic material (sugars and starches). (16) |
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| A principle of ecology and biogeography: The more diverse the species population in an ecosystem (in number of species, quantity of members in each species, and genetic content), the more risk is spread over the entire community, which results in greater overall stability, greater productivity, and increased use of soil nutrients, as compared to a monoculture of no diversity. (16) |
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| A glacial erosion feature; an asymmetrical hill of exposed bedrock displaying a gently sloping upstream side that has been smoothed and polished by a glacier and an abrupt, steep downstream side. (14) |
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| A landlocked body of water which has a concentration of salts (mostly sodium chloride) and other minerals significantly higher than most lakes (often defined as at least 3g of salt per L). In some cases, salt lakes have higher concentration of salt than sea water, but such lakes would also be termed hypersaline lakes (Caspian Sea, Aral Sea, and Lake Balkhash). (13) |
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| Analysis of the distribution of pollen grains of various species contained in surface layer deposits, especially peat bogs and lake sediments, from which a record of past climate may be inferred. Because the lake sediments accumulate over time, a core of the mud will show that the mud at the bottom will be the oldest and the mud at the top will be the newest. By separating the samples of the core, we can get a record of how the vegetation around that site has changed. This has shown us that the area around the Great Lakes was tundra 11,000 years ago. |
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| Also known as a sinkhole, a natural depression or hole in the surface topography caused by the removal of soil or bedrock, often both, by water. |
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| A geoengineering technique for long-term storage of carbon dioxide or other forms of carbon to mitigate global warming. CO2 is usually captured from the atmosphere through biological, chemical or physical processes. It has been proposed as a way to mitigate accumulation of greenhouse gases in the atmosphere, which are released by burning fossil fuels. |
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| Valleys carved by tributary glaciers and left stranded high above the glaciated valley floor following the removal of previous slopes and stream courses by the glacier. (HV are sites of spectacular waterfalls as streams plunge down the steep cliffs). |
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| A circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10-15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface. This circulation is intimately related to the trade winds, tropical rainbelts, subtropical deserts and the jet streams. |
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| A kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Modern smog comes from the vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. Smog is also caused by large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. |
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A term used to describe the distinct, and often symmetrical geometric shapes formed by ground material in periglacial regions. Typically found in remote regions of the Arctic, Antarctica, and the Australian outback, but also found anywhere that freezing and thawing of soil alternate.
The geometric shapes and patterns associated with patterned ground are often mistaken as artistic human creations. |
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| A kind of air pollution; Photochemical smog comes from the vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. Industrial smog is that caused by large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. |
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Frost action forces expansion and contraction that results in the transport of stones and boulders. As the water-ice volume changes and an ice wedge deepens, coarser particles move toward the surface. An area with a system of ground ice and frost action develops sorted and unsorted accumulations of rock at the surface that become organized forms, or patterned ground. PG may include polygons of sorted rocks that coalesce (come together) into stone polygon nets.
A term used to describe the distinct, and often symmetrical geometric shapes formed by ground material in periglacial regions. Typically found in remote regions of the Arctic, Antarctica, and the Australian outback, but also found anywhere that freezing and thawing of soil alternate.
The geometric shapes and patterns associated with patterned ground are often mistaken as artistic human creations. |
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| If the slope of an established meandering stream is suddenly increased it will resume downward erosion- this happens when the base level of the stream is reduced, for example due to tectonic uplift of the region, a global fall in sea-level, collapse of moraine-dammed lake downstream, or by capture of the stream by a steeper one. As the stream erodes downwards, its established meandering pattern will remain as a deep valley known as an incised meander or entrenched meander. (San Juan River, rivers in the Colorado Plateau and streams in the Ozark Plateau; form desirable locations for the construction of fortifications). |
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| An elevated area of land with a flat top and sides that are usually steep cliffs. It is a characteristic landform of arid environments, particularly the southwestern US. (the largest mesa in the world is considered to be the Grand Mesa located in western Colorado in the US). |
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A conspicuous isolated hill with steep, often vertical sides and a small, relatively flat top; it is smaller than mesas, plateaus, and tables.
("butte" means "small hill" in French; Because of their distinct shapes, buttes are frequently key landmarks in both plains and mountainous areas).
Mesa has a top wider than its height, while a butte's top is narrower.
Ex. Scotts Bluff in Nebraska; Crested Butte in Colorado; Elephant Butte in New Mexico. |
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The angle of a slipface is the angle at which loose material is stable.
The minimum angle made by the inclined plane with the horizontal surface such that the body lying on the inclined plane is just at the verge of sliding down along the inclined plane.
All mass movements occur on slopes. If we try to pile dry sand on the beach, the grains will flow downward until an equilibrium is achieved. The steepness of the slope that results when loose sand comes to rest depends on the size and texture of the grains; this is the ANGLE OF REPOSE.
This angle represents a balance of driving and resisting forces (gravity and friction) and commonly ranges between 33* and 37* (measured from a horizontal plane). |
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Soil's most permanent attribute; refers to the size and organization of particles in the soil.
A soil property used to describe the relative proportion of different grain sizes of mineral particles in a soil. Particles are grouped according to their size into what are called soil separates. These separates are typically named CLAY, SILT, and SAND. Soil texture classification is based on the fractions of soil separates present in a soil. The soil texture triangle is a diagram often used to figure out soil textures.
Individual mineral particles are SOIL SEPARATES. Particles range from the finest clays, to silts, to coarser sands, to larger pebbles and gravels. |
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Used by scientists to describe the current period in the Earth's history when human activities have had a significant global impact on the Earth's ecosystems.
It has no precise start date, but may be considered to start with the Industrial Revolution (late 18th century). |
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| The branch of the science of biogeography that is concerned with the geographic distribution of ANIMAL SPECIES and their attributes. That makes zoogeography the study of how patterns of animal biodiversity vary over space and through time. |
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The branch of biogeography that is concerned with the geographic distribution of PLANT SPECIES.
Phytogeography is concerned with all aspects of plant distribution, from the controls on the distribution of individual species ranges (at both large and small scales) to the factors that govern the composition of entire communities and floras. |
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The study of the record of the EARTH'S MAGNETIC FIELD preserved in various magnetic minerals through time.
It has demonstrated that the Earth's magnetic field varies substantially in both orientation and intensity through time. |
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The evolutionary process by which new biological species arise.
There are four geographic modes of speciation in nature, based on the extent to which speciating populations are geographically isolated from one another: allopatric, peripatric, parapatric, and sympatric. Speciation may also be induced artificially, through animal husbandry or laboratory experiments. |
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A species movement away from an existing population or away from the parent organism.
Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population genetics, and species distributions. |
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Carbohydrates, the organic result of the photosynthetic process, are combinations of carbon, hydrogen, and oxygen. They form simple sugars, such as glucose (C6H12O6). Plants use glucose to build starches, which are more complex carbohydrates and the principal food stored in plants. PRIMARY PRODUCTION refers to the rate at which energy is stored in such organic substances.
It is the production of organic compounds from atmospheric or aquatic carbon dioxide, principally through the process of photosynthesis, with chemosynthesis being much less important. All life on earth is directly reliant on primary production.
The organisms responsible for primary production are known as PRIMARY PRODUCERS or autotrophs, and form the base of the food chain. (mainly plants; aquatic ecoregions algae). |
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The disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings.
This means electrochemical oxidation of metals in reaction with an oxidant such as oxygen. (iron rusting). |
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An erosional feature of streams. Found in abundance along mature or meandering streams, they are located on the OUTSIDE of a stream bed, known as the meander.
They are shaped much like a small cliff, and are formed by the erosion of soil as the stream collides with the river bank. As opposed to a point bar which is an area of deposition, a cut bank is an area of EROSION. (aka river cliff). |
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Smaller plutons (intrusive igneous rock bodies) include the magma conduits of ancient volcanoes that have cooled and hardened. Those that form parallel to layers of sedimentary rock are SILLS.
Those that CROSS layers of rock they invade are DIKES.
A type of sheet intrusion referring to any geologic body that cuts discordantly across 1. planar wall rock structures, such as bedding or foliation or 2. massive rock formations, like igneous/magmatic intrusions and salt diapirs. (8) |
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The Ogallala Aquifer, aka the High Plains Aquifer, is a vast yet shallow underground WATER TABLE AQUIFER located beneath the Great Plains in the US.
One of the world's largest aquifers (174,000 mi^2) covers portions of 8 states. |
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Aeolian processes pertain to the activity of the WINDS and more specifically, to the winds' ability to SHAPE the surface of the Earth and other planets.
Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of unconsolidated sediments.
Although water is a much more powerful eroding force than wind, aeolian processes are important in ARID environments such as deserts. |
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Was a massive SHEET OF ICE that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern US, between c. 95,000 and c. 20,000 years before the present day.
Its southern margin included the modern sites of NYC and Chicago, and then followed quite precisely the present course of the Missouri River up to the northern slopes of the Cypress Hills, beyond which it merged with the Cordilleran Ice Sheet.
The ice coverage extended approximately as far south as 38 degrees latitude in the mid-continent. |
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A type of mudflow or landslide composed of pyroclastic material and water that flows down from a volcano, typically along a river valley.
An Indonesian word referring to MUDFLOWS OF VOLCANIC ORIGIN.
Ex. Nevado del Ruiz; erupted in a lateral explosion. The hot eruption quickly melted ice on the mountain's snowy peak, liquefying mud and volcanic ash, sending hot mudflow downslope. Such a flow is a LAHAR. |
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Approx. the last 11,500 years
The youngest epoch (division of time) in the geologic time scale, characteristic of postglacial conditions since the retreat of the continental glaciers.
Began approx. 12,000 years ago and continues into present. It is part of the Quaternary period. |
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Rain or any other form of precipitation that is unusually acidic (elevated levels of hydrogen ions; low pH).
It can have harmful effects on plants, aquatic animals, and infrastructure through the process of wet deposition.
Acid rain is caused by emissions of compounds of ammonium, carbon, nitrogen, and sulfur which react with the water molecules in the atmosphere to produce acids. |
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The autotrophic component of the plankton community.
Most phytoplankton are too small to be individually seen with the unaided eye. When present in high enough numbers, they may appear as a green discoloration of the water due to the presence of chlorophyll within their cells. |
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