L<sub>dn</sub>The day-night average sound level. It is the average A-weighted sound level over a 24-hour period that gives additional weight to noise that occurs during…
L<sub>eq</sub>Equivalent/continuous sound level. Leq is the steady sound level that would contain the same total sound energy as the time-varying sound over a given…
LaccolithAn igneous intrusion that has been forced between two layered rock units. The top of the intrusion is arched upwards and the bottom of the intrusion is…
Lacustrine wetlandWetlands that are generally larger than 20 acres and having less than 30% cover of vegetation such as trees, shrubs, or persistent emergent plants.
Lag gravelResidual deposit of coarse material that has had the finer fraction removed by a transporting agent, usually wind or water.
LaharA mudflow composed of water and volcanic ash. Lahars can be triggered by the flash melting of the snow cap of a volcanic mountain or from heavy rain.
Land areaIncludes dry land and land temporarily or partially covered by water, such as marshlands, swamps, and river flood plains; streams, sloughs, estuaries, and…
Land coverThe physical coverage of land, usually expressed in terms of vegetation cover or lack of it.
Land disturbanceDiscrete event or process that alters soil and/or kills or damages vegetation. From an ecological and hierarchical perspective, disturbance is a change in…
Land subsidenceThe sinking or settling of land to a lower level in response to various natural and man-caused factors.
Land UseThe manner in which a parcel of land is used or occupied.
Land Use PlanA set of decisions that establish management direction for land within an administrative area, as prescribed under the planning provisions of FLPMA; an…
Land withdrawalWithdrawals are governed by regulations issued under FLPMA, contained in 43 CFR Part 2300.
LandformAny feature of the Earth's surface having a distinct shape and origin. Landforms include major features (such as continents, ocean basins, plains…
LandmarkType of reference point external to the observer. Usually a simply defined physical object.
LandscapeA region consisting of interacting ecosystems determined by geology, soils, climate, biota, and human influences.
Landscape characterThe arrangement of a particular landscape as formed by the variety and intensity of the landscape features and the four basic elements of form, line…
LavaMagma that reaches the Earth's surface and issues from volcanoes.
Lava flowAn outpouring of lava onto the land surface from a vent or fissure. Also, a solidified tongue-like or sheetlike body formed by outpouring lava.
Lava tubesNatural conduits through which lava moves beneath the surface of a lava flow during a volcanic eruption.
Law of the RiverA complex body of laws, court decrees, contracts, agreements, regulations and an international treaty used to govern allocation and management of Colorado…
Laydown areaAn area that has been cleared for the temporary storage of equipment and supplies.
LeadA gray-white metal that is listed as a criteria air pollutant. Health effects from exposure to lead include brain and kidney damage and learning…
Leasable mineralsFederal minerals such as coal, oil shale, oil, gas, phosphate, potash, sodium, tar sands, geothermal resources, potassium, asphaltic materials, and all…
LeaseA contract transferring the use of property or occupancy of land, space, structures, or equipment in consideration of a payment (e.g., rent).
LimestoneA sedimentary rock made mostly of the mineral calcite (calcium carbonate). Limestone is usually formed from shells of once-living organisms or other…
Lithic debitageDebris produced during stone (lithic) tool manufacture.
Lithic scatterA distribution of cultural items that consists primarily of lithic (stone) material.
Livestock guzzlerA watering system for cattle and other livestock that maintains a set water level as water is used.
Livestock watering areaWater used for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs.
LoamA soil consisting of an easily crumbled mixture of clay, silt, and sand.
Locatable MineralsMinerals or materials subject to disposal and development through the Mining Law of 1872 (as amended).
LODEA mineralized ledge, vein or mineral deposit in place.
Lode mining claimA claim based on the presumption that the valuable mineral is a part of a bed-rock lode, vein, stockwork, stratum, or intrusion and is not dominantly a…
LoessA group of windblown soils, largely comprising silt, weakly cemented by calcite.
Low-income populationPersons whose average family income is below the poverty line. The poverty line takes into account family size and age of individuals in the family.
Low-level magnetic fieldsFields of force that are generated whenever electric current flows. The sun's average large-scale magnetic field, and the Earth's, exhibit a north and a…
LuminaireA complete lighting unit consisting of a lamp(s), housing, and connection to the power circuit.