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Monazite
Monazite is a rare-earth phosphate mineral and principal ore of the rare earth elements and thorium, occurring mainly in placer sands and supplying most rare earth production until 1964.
Monazite geochronology
Monazite geochronology is a dating method that determines the ages of rocks and metamorphic events from the uranium–thorium–lead isotope system preserved in the phosphate mineral monazite.
Monin–Obukhov similarity theory
Monin–Obukhov similarity theory (MOST) is a semiempirical framework in boundary-layer meteorology, set out by Obukhov in 1946 and Monin in 1954, that remains the standard method for computing surface fluxes in weather and climate models.
Mono Lake Volcanic Field
Mono Lake Volcanic Field: basalt-to-rhyolite vents in and around Mono Lake, Mono County, California, near Lee Vining. Features Black Point, Negit, Paoha Island; last activity about 300 years ago; moderate USGS threat potential.
Monolith
A monolith is a large rock body or landform standing as one piece, left standing by erosion, famously including Devils Tower in Wyoming and Uluru in Australia.
Monsoon
A monsoon is a thermally driven wind that reverses direction seasonally, bringing alternating wet and dry seasons, and shaping life for more than two-thirds of the world's population.
Monsoon Experiment (MONEX)
The Monsoon Experiment (MONEX) was an international field program under the Global Atmospheric Research Programme that studied the winter and summer monsoons of Asia and Africa in 1978 and 1979.
Monsoon of South Asia
The monsoon of South Asia, also called the Indian monsoon, is the seasonal reversal of winds that delivers most of the subcontinent's rainfall, chiefly from June to September.
Monsoon trough
The monsoon trough is an elongated zone of low surface pressure where trade winds and monsoon winds converge, a semi-permanent feature of monsoon circulation that brings rain, depressions, and tropical cyclones.
Monsoon-influenced humid subtropical climate
The monsoon-influenced humid subtropical climate (Subtropical Monsoon) is a Köppen climate type, Cwa, with mild winters, hot summers, and rain concentrated in summer rather than winter.
Monterey Bay Aquarium Research Institute
The Monterey Bay Aquarium Research Institute (MBARI) is a non-profit oceanographic research center in Moss Landing, California, founded by David Packard in 1987 to advance marine science and technology.
Monterey Formation
The Monterey Formation is a Miocene marine sedimentary rock unit in California, built from diatom remains, that generated much of the oil in the state's coastal basins.
Montmorillonite
Montmorillonite is a soft aluminum silicate clay mineral of the smectite group that swells when it takes up water, forms most of the rock bentonite, and is used in drilling muds and absorbents.
Montney Formation
The Montney Formation is a Lower Triassic, siltstone-dominated rock unit in the Western Canada Sedimentary Basin, spanning about 130,000 km² across northwestern Alberta and northeastern British Columbia, and is Canada's largest source of natural gas.
Monzogranite
Monzogranite is a variety of granite, a coarse-grained plutonic igneous rock containing 20 to 60 percent quartz and roughly equal amounts of alkali feldspar and plagioclase, defined in the QAPF classification.
Monzonite
Monzonite is a coarse-grained plutonic igneous rock in which alkali feldspar and plagioclase occur in roughly equal amounts, with little quartz; it sits between syenite and diorite.
Moon rock
A Moon rock, also called a lunar sample, is a piece of the Moon's crust or regolith brought to Earth by Apollo, Luna, and Chang'e missions or found as meteorites.
Moonstone (gemstone)
Moonstone is a gem-quality feldspar named for adularescence, a soft glow that floats below the polished surface, caused by thin orthoclase and albite layers; it is a June birthstone.
Mooring (oceanography)
An oceanographic mooring is a anchored line with a surface or subsurface buoy and attached instruments that measure ocean conditions at one fixed station continuously, for months to years.
Morenci mine
The Morenci mine is an open-pit copper and molybdenum mining complex in Greenlee County, southeastern Arizona, worked since the 1870s and now one of the world's largest open-pit copper mines, run by Freeport-McMoRan.
Morphodynamics
Morphodynamics is the study of the mutual adjustment of topography and fluid dynamics involving sediment transport, a feedback loop that shapes shores, estuaries, riverbeds, and dunes.
Morrison Formation
The Morrison Formation is a Late Jurassic rock unit across the western United States, deposited about 157 to 150 million years ago and famous for dinosaur fossils.
MOSAiC expedition
MOSAiC was an international Arctic expedition in which the German icebreaker Polarstern drifted frozen in sea ice from 2019 to 2020, studying the Arctic climate.
Moskstraumen
Moskstraumen, also called Moskenesstraumen, is a strong tidal current and maelstrom in the Lofoten archipelago of Nordland, Norway, running between Lofotodden and the island Mosken; it inspired Poe's "A Descent into the Maelström".
Mosquito Fire
The Mosquito Fire was a 2022 wildfire in Placer and El Dorado counties, California, that burned 76,788 acres and became the state's largest wildfire of 2022.
Mount Batur
Mount Batur (Gunung Batur) is an active stratovolcano in northeastern Bali, Indonesia, rising 1,717 m above Lake Batur within a double caldera and a UNESCO Global Geopark.
Mount Bromo
Mount Bromo (Gunung Bromo) is an active volcanic cone, 2,329 m high, standing in the Tengger caldera in East Java, Indonesia, with more than 50 recorded eruptions since 1804.
Mount Cattlin
Mount Cattlin, also written Mt Cattlin, is an open pit lithium mine near Ravensthorpe, Western Australia, that produced spodumene concentrate from 2010 until care and maintenance in 2025.
Mount Damavand (دماوند)
Mount Damavand (دماوند), also spelled Demavend, is a dormant stratovolcano in the Alborz Mountains of northern Iran, the highest peak in the Middle East at 5,610 m.
Mount Holland
Mount Holland is an integrated lithium project in Western Australia's Wheatbelt, owned equally by Wesfarmers and SQM, mining the Earl Grey spodumene deposit and refining lithium hydroxide near Perth.