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Micrite
Micrite is a limestone composed of microcrystalline calcite, or carbonate mud with grains typically 1 to 4 μm, named by Robert L. Folk in 1959 for his carbonate rock classification.
Microbial carbon pump
The microbial carbon pump (MCP) is an ocean carbon sequestration mechanism, proposed in 2010, in which marine microorganisms transform labile dissolved organic carbon into recalcitrant forms persisting for millennia.
Microbial food web
The microbial food web is the portion of aquatic food webs made up of bacteria, archaea, protists, and viruses that recycle nutrients and dissolved organic matter.
Microbialite
A microbialite is an organosedimentary deposit that accretes through interaction between benthic microbial communities and sediments, a term introduced by Burne and Moore in 1987 that includes stromatolites and thrombolites.
Microburst
A microburst is a small downburst of sinking, rain-cooled air that strikes the ground and spreads damaging winds; the term was coined by Ted Fujita in 1975.
Microclimate
A microclimate is the climate of a small, specific area like a forest canopy or city street, whose temperature, humidity, and wind differ measurably from the surrounding region.
Microcline
Microcline is a triclinic potassium feldspar (KAlSi₃O₈), one of the most abundant rock-forming minerals of the continental crust, best known for its cross-hatched tartan twinning and its bluish-green gem variety amazonite.
Microphysics scheme
A microphysics scheme is a parameterization in atmospheric and climate models that computes cloud and precipitation processes, such as condensation and particle growth, at subgrid scales.
Microplate
A microplate is a small, relatively rigid block of lithosphere that moves independently of the major tectonic plates, with oceanic examples like the Easter microplate.
Microseismic monitoring
Microseismic monitoring is a passive geophysics method that records very small earthquakes from hydraulic fracturing and fluid flow, used to image subsurface fractures and stress changes.
Microwave radiometry
Microwave radiometry is the passive measurement of thermal microwave emission from the atmosphere, ocean, or land, retrieving temperature and moisture in all weather, day or night.
middle Kaub Formation
Middle Kaub Formation: clay-rich middle part of the Kaub Formation (Lower Emsian, Lower Devonian) in the Hunsrück, Germany; five members, laminated slates with Chondrites, source of the Bundenbach Hunsrück Slate fossils.
Midland Basin
The Midland Basin is a sub-basin of the Permian Basin in West Texas, whose Wolfcamp shale alone was assessed by the USGS at a mean 20 billion barrels of recoverable oil.
Midnight sun
The midnight sun, or polar day, is the summer phenomenon of the sun staying above the horizon for 24 hours a day north of the Arctic Circle.
Migmatite
Migmatite is a composite metamorphic rock with two or more distinct parts, at least one formed by partial melting, named by Jakob Johannes Sederholm in 1907 from the Greek for mixture.
Migration velocity analysis
Migration velocity analysis (MVA) is a seismic imaging method that estimates the subsurface velocity model by repeatedly migrating data, measuring kinematic errors in prestack images, and tomographically inverting them into velocity updates.
MIKE 11
MIKE 11 is a one-dimensional river modeling software package developed by the Danish Hydraulic Institute (DHI) for simulating water levels, flows, and water quality in rivers and estuaries.
Milankovitch cycles
Milankovitch cycles, or Milankovitch variations, are periodic changes in Earth's orbital eccentricity, axial tilt, and precession that redistribute sunlight and pace ice ages, named for Serbian mathematician Milutin Milankovitch.
Mild-slope equation
The mild-slope equation, derived by J. C. W. Berkhoff in 1972, is an elliptic partial differential equation describing water waves over slowly varying seabeds, widely used in coastal engineering.
Millennium Drought
The Millennium Drought, also called the Big Dry, was a prolonged 2001–2009 drought in southeast Australia, the region's lowest rainfall since 1900, which reshaped Australian water policy.
Millstone Grit
Millstone Grit, now formally the Millstone Grit Group, is a Namurian-age succession of coarse-grained sandstone, siltstone, and mudstone in Great Britain, named for gritstones quarried as millstones.
Min Min light
The Min Min light, or Min-min, is an unexplained floating, often colored light in the Australian outback that follows travelers, reported chiefly along the Winton–Boulia road in western Queensland.
Mineral
A mineral is a naturally occurring, normally crystalline solid element or compound formed by geological processes, and the building block of rocks; over 6,100 species are recognized.
Mineral Park
Mineral Park is an open-pit copper, molybdenum, and silver mine in the Cerbat Mountains of north-western Arizona, 18 miles north of Kingman, first mined in the 1870s and restarted in 2025.
Mineral resource classification
Mineral resource classification assigns estimated mineral quantities to categories like Measured, Indicated, and Inferred Resources and Proved and Probable Reserves, under national codes including JORC and NI 43-101.
Mineralogical Society of America
The Mineralogical Society of America (MSA) is a United States scientific membership organization, founded in 1919, that advances mineralogy, crystallography, geochemistry, and petrology and publishes American Mineralogist.
Mineralogy
Mineralogy is the branch of Earth sciences concerned with the formation, properties, uses, and classification of minerals, the crystalline building blocks of rocks, spanning fields from crystallography to gemmology.
Mining district
A mining district is a named geographic area where minerals have been extracted at considerable, often long-lasting scale, focused on related ore types, with boundaries traditionally recognized rather than administrative.
Mining industry of South Africa
The mining industry of South Africa, also known as the mineral industry of South Africa, supplied 70% of the world's platinum and 46% of its chromium in 2024.
Minoan eruption
The Minoan eruption, also known as the Santorini or Thera eruption, was a huge Late Bronze Age eruption of the Santorini volcano in the Aegean Sea that buried Akrotiri.