MaarA volcanic crater that is produced by an explosion in an area of low relief, is generally more or less circular, and often contains a lake, pond, or marsh.
Macrophyte (aquatic)An aquatic plant that is large enough to be observed with the naked eye. It grows in or near water.
Mafic (or maphic)A term used to describe an igneous rock that has a large percentage of dark-colored minerals such as amphibole, pyroxene, and olivine.
MagmaMolten or partially molten rock at temperatures ranging from 1,260 F to 2,880 F (700 C to 1600 C).
Maintenance areaAny geographic region of the United States previously designated nonattainment pursuant to the CAA Amendments of 1990 and subsequently redesignated to…
MammalsA group of air-breathing animals whose skin is more or less covered with hair or fur and who have mammary glands.
ManoA stone with a flat side that was primarily held in one's hand or hands and used to grind edible substances, typically corn, grains, and nut meats.
MantleThe main bulk of the Earth, between the crust and core, ranging from depths of about 40 to 3,480 kilometers.
Mantle hot spotA region of continental or oceanic crust below which a mantle plume causes melting of the overlying crust, resulting in a broad regional topographic swell…
MarshAn area of low-lying wetlands dominated by grasslike plants.
Maximum Contaminant Level (MCL)The highest level of a contaminant that is allowed in drinking water. MCLs ensure that drinking water does not pose either a short-term or long-term…
MeanA statistics term. The average value in a set of measurements. The mean is the sum of a set of numbers divided by how many numbers are in the set.
Mean sea level (MSL)The arithmetic mean of hourly water elevations observed over a specific 19-year tidal epoch.
Median household incomeDivides households into two equal segments, with one-half of households earning less than the median household income and the other half earning more.
Median housing valueDivides housing units into two equal segments, one-half of housing units less than median housing value and the other half valued more.
MegafaunaA number of species of presently extinct mammals including mammoths and mastodons.
MegawattOne thousand kilowatts, or 1 million watts; standard measure of electric power plant generating capacity.
Megawatt electrical (MWe)One million watts of electrical energy; a measure of electrical power capacity, use in PEIS is synonymous with MW.
MesaA broad, flat-topped elevation with one or more steeply-sloping to vertical sides.
Mesic habitatA habitat type characterized by the presence of a moderate amount of moisture or water. Compare: hydric; opposite: xeric.
MesozoicAn era of geologic time between the Paleozoic and the Cenozoic, spanning the time between 251 and 65 million years ago.
Metamorphic rockA sedimentary or igneous rock that has been changed by pressure, heat, or chemical action.
MetateA portable stone slab upon which seeds and other grains are milled with a mano using a push-pull, back-and-forth motion. See also Mano
MicrositeA small area within an environment with unique features, conditions, or characteristics relative to the surrounding area.
Migration corridorA route followed by animals such as big game, birds, or fish when traveling between winter and summer habitats.
Migratory Bird Treaty Act (MBTA)The MBTA implements various treaties and conventions between the United States, and Canada, Japan, Mexico, and the former Soviet Union for the protection…
Military Training Route (MTR)A designated corridor of airspace with defined vertical and lateral dimensions established for conducting military flight training at airspeeds in excess…
Mineral Leasing Act of 1920 (MLA)Authorizes the agency to issue rights-of-way grants for oil and gas gathering and distribution pipelines and related facilities not already authorized…
Mineral materialsWidespread deposits of common clay, sand, gravel, or stone which are not subject to disposal under the 1872 Mining Law, as amended.
Mining claimThat portion of the public mineral lands which a miner, for mining purposes, takes and holds in accordance with the mining laws.
Mining water useWater use during quarrying rocks and extracting minerals from the land.
Minority populationIncludes Hispanic, American Indian, or Alaskan Native; Asian; Native Hawaiian or Other Pacific Islander; Black (not of Hispanic origin) or African…
MioceneAn epoch of the upper Tertiary period, 23 to 5.3 million years ago.
MirrorA reflecting surface of various physical shapes (parabolic, nearly flat, or flat) used to reflect and/or concentrate the sun's energy to specific…
MitigationTerm usually used to refer to various changes or improvements made in a home; for instance, to reduce the average level of radon.
Mitigation (measures)Methods or actions that will reduce adverse impacts from solar facility development.
moduleThe smallest self-contained, environmentally protected structure housing interconnected photovoltaic cells and providing a single dc electrical output…
Molten saltsMixtures of sodium nitrate and potassium nitrate in various proportions that are used as a heat transfer or heat storage medium in CSP Solar Energy…
MontaneThe highland area located below the subalpine zone. Montane regions generally have cooler temperatures, and often have higher rainfall than the adjacent…
MortarA stone bowl or bowl-shaped depression (such as in a rock) in which seeds, berries, nuts, meats, and other items are ground or pulverized with a pestle…
MossesLow-growing, nonvascular plants that are common to moist habitats.
Multijunction solar cellA photovoltaic device comprised of two or more semiconductor materials or cell junctions, each capable of producing electricity with the photovoltaic…
Multiple useA combination of balanced and diverse resource uses that takes into account the long-term needs of future generations for renewable and nonrenewable…
Multiple Use ClassesClass C is for lands designated either as wilderness or for wilderness study areas. These lands are managed to protect their wilderness values.
Multiple use managementCoordinated management of the various surface and subsurface resources, without permanent impairment of the productivity of the land, that will best meet…