RVDE Glossary

Glossary - RVDE

RVDE Glossary

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(Source): Letters indicate source listed at bottom of page.

abiotic: The nonliving or physical part of an environment.

albedo: The percentage of incoming radiation that is reflected by a natural surface such as the ground, ice, snow, water, clouds, or particulates in the atmosphere.

alluvial fan: A fan-shaped, gently sloping deposit of sediment left by a stream where it issues from a mountain valley onto a broad, relatively flat plain or valley. Alluvial fans are common in semiarid regions.

alluviation: The deposition or formation of alluvium or alluvial features (such as cones or fans) at places where stream velocity is decreased or streamflow is checked; the process of raising the level of a stream bed through sediment deposition, or of covering or filling a surface with alluvium. (a)

ambient: Prevailing or surrounding environmental conditions.

annual vegetation: Plants that live for only one growing season or one year.

anthropogenic: Manmade or resulting from human activities.

aspect: The direction toward which a slope faces with respect to the compass or to the rays of the Sun. (a)

biological soil crusts: A highly specialized community of cyanobacteria, mosses, lichens, and their by-products, which create a crust of soil particles bound together by organic materials. Biological soil crusts are also known as cryptogamic, microbiotic, cryptobiotic, and microphytic crusts. (d)

biomass: The total mass of all living organisms or of a particular set of organisms in an ecosystem or at a specific level in a food chain; usually expressed as a dry weight or as the carbon, nitrogen, or caloric content per unit area. (c)

biotic: The living part of the environment; pertaining to living organisms.

bioturbation: The disturbance of sediments caused by living organisms as they feed and/or burrow.

botanic habitat: A habitat of plants.

cohort: A group of organisms with common characteristics.

cryptobiotic crusts: See biological soil crusts.

cyanobacteria: Photosynthetic bacteria formerly called blue-green algae whose growth forms tend to be filamentous; a component of biological soil crust. (d)

debris flow: A moving mass of rock fragments, soil, and mud, more than half of the particles being larger than sand size. (a) Debris flows usually occur on fairly steep slopes. Term also refers to the material that occurs in such a flow and that can be recognized in sedimentary deposits.

deflation: A form of wind erosion; the sorting out, lifting, and removal of loose, dry, fine-grained particles (clay and silt sizes) by the turbulent eddy action of the wind, as along a sand-dune coast or in a desert. (a)

digital elevation model (DEM): A digital cartographic/geographic dataset of elevations (topography) in xyz coordinates. The terrain elevations for ground positions are sampled at regularly-spaced horizontal intervals. DEMs are derived from contour lines and/or photogrammetric methods using USGS 7.5-minute, 15-minute, 2-arc-second (30- by 60-minute), and 1-degree (1:250,000-scale) topographic quadrangle maps. Digital elevation models are typically used to represent terrain relief.

ecoregion: Any geographical region characterized by distinctive flora or fauna (such as a biome or a province). (c)

ecosystem: A community of organisms and their physical environment that interact as an ecological unit. (c) Any natural unit or entity including living and non-living parts that interact to produce a stable system through cyclic exchange of materials. (b)

El Niño: A warming of the surface waters of the eastern equatorial Pacific that occurs at irregular intervals of 2-7 years, usually lasting 1-2 years. Along the west coast of South America, southerly winds promote the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustains abundant sea birds, whose droppings support the fertilizer industry. Near the end of each calendar year, a warm current of nutrient-poor tropical water replaces the cold, nutrient-rich surface water. In most years the warming lasts only a few weeks or a month, after which the weather patterns return to normal and fishing improves. However, when El Niño conditions last for many months, more extensive ocean warming occurs and economic results can be disastrous. El Niño has been linked to wetter, colder winters in the United States; drier, hotter summers in South America and Europe; and drought in Africa. Because this condition often occurs around Christmas, it was named El Niño (Spanish for boy child, referring to the Christ child). (b)

El Niño/Southern Oscillation (ENSO): Interacting parts of a single global system of climate fluctuations. ENSO is the most prominent known source of interannual variability in weather and climate around the world, though not all areas are affected. The Southern Oscillation (SO) is a global-scale seesaw in atmospheric pressure between Indonesia/North Australia, and the southeast Pacific. In major warm events El Niño warming extends over much of the tropical Pacific and becomes clearly linked to the SO pattern. Many of the countries most affected by ENSO events are developing countries with economies that are largely dependent upon their agricultural and fishery sectors as a major source of food supply, employment, and foreign exchange. New capabilities to predict the onset of ENSO event can have a global impact. While ENSO is a natural part of the Earth's climate, whether its intensity or frequency may change as a result of global warming is an important concern. (b)

ephemeral stream: A stream or reach of a stream that flows briefly only in direct response to precipitation in the immediate locality and whose channel is at all times above the water table. (a)

evapotranspiration: Loss of water from the soil both by evaporation and by transpiration from plants. (c)

extratropical: The part of the Northern Hemisphere that has atmospheric circulation disconnected from tropical circulation processes. The intertropical convergence zone (ICTZ), which delineates the two regions, changes on an annual cycle.

geographic information system (GIS): 1. A system for archiving, retrieving, and manipulating data that has been stored and indexed according to the geographic coordinates of its elements. The system generally can utilize a variety of data types, such as imagery, maps. table, etc. (b) 2. An organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information. (f)

geomorphic processes: Processes that pertain to the formation of surface features of the Earth.

geomorphology: The study of present-day landforms, including their classification, description, nature, origin, development, and relationships to underlying structures. Also, the history of geologic changes as recorded by these surface features. The term is sometimes restricted to features produced only by erosion and deposition. (b)

georeference: To establish the relationship between page coordinates on a planar map and known real-world coordinates. (f)

geospatial data (spatial data): Information about the location, shape of, and relationships among geographic features, usually stored as coordinates and topology. (g)

geostatistics: 1. Statistics as applied to geology; the application of statistical methods or the collection of statistical data for use in geology. 2. A branch of applied statistics that deals with the phenomena that fluctuate in two- or three-dimensional space. Geostatistics is concerned with assessing properties that may be physically continuous (hence cannot be truly random variables) but are too variable to describe by deterministic means; it offers a way of describing the spatial continuity that is an essential feature of many natural phenomena. (a)

hillslope run-off: Precipitation that flows off hillsides and appears in surface streams.

hydrography: (hydrographic) Relating to the characteristic features of bodies of water, such as depth and flow. (c)

hydrology: The science that deals with global water systems (both liquid and solid), its properties, circulation, and distribution, on and under the Earth's surface and in the atmosphere, from the moment of its precipitation until its return to the atmosphere through evapotranspiration or its discharge into the ocean. (a)

infiltration: The flow of a fluid into a solid substance through pores or small openings; specifically, the movement of water into soil or porous rock. (a)

Landsat, Landsat 7: Land Remote Sensing Satellite Program managed by the U.S. Geological Survey. The Landsat Satellite series began in 1972 to gather information about land surface features of the planet. Landsat 5, launched in 1984 and Landsat 7, launched in 1999, are still operational. Data from the satellites have been used for monitoring land cover conditions, geological/mineralogical exploration, urban growth, and cartography. Global coverage is available and data sets are provided by the USGS at the cost of reproduction. (g)

microclimate: The climate that prevails in a small area, usually in the layer near the ground. (c)

microtopography: Topography on a small scale. The term has been applied to features having relief as small as 1–10 cm as well as to those involving amplitudes of 50–100 meters and wavelengths of a few kilometers. (a)

model: A mathematical approximation or simulation of a real system, process, or object that omits all but the most essential variables, developed to understand its behavior or to make predictions. The representation always involves certain simplifications and assumptions. (b)

mucilaginous sheath material: External coating formed by some filamentous cyanobacteria that is sticky and can hold soil particles in place. (d)

Pacific Decadal Oscillation: A long-lived El Niño-like pattern of Pacific climate variability. The Pacific Decadal Oscillation operates at something on the order of a 20- to 30-year time scale, while El Niño/La Niña events are typically on the order of 6 to 18 months in length. Both phenomena correlate with relatively wetter or drier periods in the western portion of North America.

parent material: The source from which a soil is primarily derived, usually from unconsolidated bedrock, sediment, or organic material.

pedogenic: Of or pertaining to soil formation. (a)

percolation: Slow, non-turbulent movement (usually downward) of water through small openings within a porous material. (a)

perennial: A plant that normally lives for more than two seasons and which, often after an initial period, produces flowers annually. (c)

pixel: Picture element of a digital image data set corresponding to a specific area of ground. (b)

remote sensing: Methods for gathering data on a large or landscape scale which do not involve on-the-ground measurement, such as satellite photograph and aerial photography; often used in conjunction with Geographic Information Systems. (c)

repeat photography: The technique of taking a duplicate photograph of a specific site after a period of time for use in analysis. Repeat photography is a simple and inexpensive tool for reconstructing past environmental changes and monitoring future ones. As a first approximation, past environmental change can be measured by locating the site of a historical photograph, reoccupying the original camera position, and making a new photograph of the same scene. Differences between the present and past provide a basis for identifying and even quantifying changes, while the new photograph establishes a benchmark for future evaluation. (e)

run-on: Water from streams, or water flowing downslope in a layer, that provides moisture in addition to the moisture provided by precipitation alone.

soil compaction: Compression of the soil which results in reduced soil pore space (the spaces between soil particles), decreased movement of water and air into and within the soil, decreased soil water storage, and increased surface runoff and erosion.

spatial model: A model that describes variations through space, using analytical procedures applied with a GIS. There are three categories of spatial modeling functions that can be applied to geographic features within a GIS: (1) geometric models, such as calculating the straight-line distance between features, generating buffers, calculating areas and perimeters, and so on; (2) coincidence models, such as topological overlay; and (3) adjacency models (pathfinding, redistricting, and allocation). (f)

surficial geology: Geology of surficial deposits, including soils; surficial deposits include unconsolidated and residual, alluvial, or glacial deposits lying on bedrock or occurring on or near the Earth’s surface; they are generally unstratified and represent the most recent of geologic deposits. The term is sometimes applied to the study of bedrock at or near the Earth’s surface. (a)

synoptic: Relating to conditions as they exist simultaneously over a broad area, as of the atmosphere or weather. (c)

temporal model: A model that describes changes over time. Commonly applied to climate or landscape conditions changing over various periods of time, from seasons to decades.

tensile strength: The maximum applied pull stress (in force per unit area) that a specimen can withstand before breaking. (a)

turbidity: The state, condition, or quality of opaqueness or reduced clarity of a fluid, due to the presence of suspended matter. (a)

UNESCO Global Humidity Index: A humidity index developed by UNESCO (United Nations Educational, Scientific, and Cultural Organization) to classify the level of aridity. For more information, see Global Humidity Index from GRID and UEA/CRU

vascular plant: A plant with a specialized conducting system for the transport of water and nutrients that includes xylem and phloem; includes familiar higher plants such as trees, shrubs, and grasses. (c)

Sources:

a. Jackson, Julia, A., ed., 1997, Glossary of Geology, Fourth Edition: Alexandria, Virginia, American Geological Institute

b. Earth Observatory Glossary: National Aeronautics and Space Administration (NASA) website

c. Status and Trends of the Nation’s Biological Resources: USGS website (see Glossary)

d. Crust 101: An Introduction to Biological Soil Crusts USGS and partners website

e. Landscape Changes in the Southwestern United States: Techniques, Long-term Data Sets, and Trends: USGS website

f. ESRI Glossary of GIS Terms: Reprinted from ESRI Glossary of GIS Terms with permission. Copyright© ESRI.

g. Landsat Project Glossary: USGS website

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