Earth Science, Geologic Time & Fossils, MEX-NOT
Planet Earth has billions of years of history, from the time when it was an inhospitable ball of hot magma to when its surface stabilized into a variety of diverse zones capable of supporting many life-forms. Many are the species that lived through the various geologic eras and left a trace of their existence in the fossils that we study today. But Earth is never done settling, as we can see from the earthquakes, tsunamis, volcanic eruptions, and other phenomena manifested in Earth’s crust, oceans, and atmosphere.
Earth Science, Geologic Time & Fossils Encyclopedia Articles By Title
Mexico City earthquake of 1985
Mexico City earthquake of 1985, severe earthquake that occurred on September 19, 1985, off the coast of the Mexican......
Miacis
Miacis, genus of extinct carnivores found as fossils in deposits of the late Paleocene Epoch (65.5–55.8 million......
mica
mica, any of a group of hydrous potassium, aluminum silicate minerals. It is a type of phyllosilicate, exhibiting......
Michell, John
John Michell was a British geologist and astronomer who is considered one of the fathers of seismology, the science......
Michelson, A.A.
A.A. Michelson was a German-born American physicist who established the speed of light as a fundamental constant......
micrite
micrite, sedimentary rock formed of calcareous particles ranging in diameter from 0.06 to 2 mm (0.002 to 0.08 inch)......
microburst
microburst, pattern of intense winds that descends from rain clouds, hits the ground, and fans out horizontally.......
Microclimate
Microclimate, any climatic condition in a relatively small area, within a few metres or less above and below Earth’s......
micropegmatite
micropegmatite, quartz and alkali feldspar intergrowth so fine that it can be resolved only under the microscope;......
Mid-latitude steppe and desert climate
Mid-latitude steppe and desert climate, major climate type of the Köppen classification characterized by extremely......
migmatite
migmatite, in geology, rock composed of a metamorphic (altered) host material that is streaked or veined with granite......
Milankovitch, Milutin
Milutin Milankovitch was a Serbian mathematician and geophysicist, best known for his work that linked long-term......
Mill, Hugh Robert
Hugh Robert Mill was a British geographer and meteorologist who exercised a great influence in the reform of geography......
Miller, Hugh
Hugh Miller was a Scottish geologist and lay theologian who was considered one of the finest geological writers......
millerite
millerite, a nickel sulfide mineral (NiS) found in carbonate veins, as at Keokuk, Iowa, or as an alteration product......
Milne, John
John Milne was an English geologist and influential seismologist who developed the modern seismograph and promoted......
mimetite
mimetite, arsenate mineral, lead chloride arsenate [Pb5(AsO4)3Cl], in the pyromorphite series of the apatite group......
mineral
mineral, naturally occurring homogeneous solid with a definite chemical composition and a highly ordered atomic......
- Introduction
- Occurrence, Formation, Compound
- Crystal Structures, Chemical Compounds
- Polymorphism, Crystalline Structure, Chemical Compounds
- Composition, Variation, Classification
- Chemical Bonding, Structure, Properties
- Crystal Habit, Aggregation
- Hardness, Mohs Scale, Crystalline
- Classification, Properties, Types
- Sulfides, Crystals, Properties
- Oxides, Hydroxides, Compounds
- Halides, Crystals, Properties
- Carbonates, Calcite, Dolomite
- Nitrates, Chemical Compounds, Properties
- Borates, Structure, Properties
- Sulfates, Crystals, Properties
- Phosphates, Crystalline Structure, Chemical Compounds
- Silicates, Crystalline, Structure
- Nesosilicates, Structure, Chemistry
- Associations, Phase Equilibrium, Crystallization
- Phase Diagrams, Crystallography, Chemistry
mineral deposit
mineral deposit, aggregate of a mineral in an unusually high concentration. About half of the known chemical elements......
mineral processing
mineral processing, art of treating crude ores and mineral products in order to separate the valuable minerals......
mineral water
mineral water, water that contains a large quantity of dissolved minerals or gases. Mineral water from natural......
mineralogy
mineralogy, scientific discipline that is concerned with all aspects of minerals, including their physical properties,......
Miohippus
Miohippus, genus of extinct horses that originated in North America during the Late Eocene Epoch (37.2–33.9 million......
mirabilite
mirabilite, a widespread sulfate mineral, hydrated sodium sulfate (Na2SO4·10H2O), that forms efflorescences and......
Mist
Mist, suspension in the atmosphere of very tiny water droplets (50–500 microns in diameter) or wet hygroscopic......
Modiolopsis
Modiolopsis, extinct genus of pelecypods (clams) found as fossils in Ordovician rocks (about 488 million to 444......
Moeritherium
Moeritherium, extinct genus of primitive mammals that represent a very early stage in the evolution of elephants.......
Mohorovičić, Andrija
Andrija Mohorovičić was a Croatian meteorologist and geophysicist who discovered the boundary between Earth’s crust......
Mohs hardness
Mohs hardness, rough measure of the resistance of a smooth surface to scratching or abrasion, expressed in terms......
molasse
molasse, thick association of continental and marine clastic sedimentary rocks that consists mainly of sandstones......
Mollisol
Mollisol, one of the 12 soil orders in the U.S. Soil Taxonomy. Mollisols are characterized by a significant accumulation......
molybdate and tungstate minerals
molybdate and tungstate minerals, naturally occurring inorganic compounds that are salts of molybdic acid, H2MoO4,......
molybdenite
molybdenite, the most important mineral source of molybdenum, molybdenum disulfide (MoS2). Molybdenite crystals......
moment magnitude
moment magnitude (MW), quantitative measure of an earthquake’s magnitude (or relative size), developed in the 1970s......
monazite
monazite, phosphate mineral, cerium and lanthanum phosphate, (Ce, La)PO4, that is the major commercial source of......
Monograptus
Monograptus, extinct genus of graptolites (small aquatic colonial animals related to primitive chordates) found......
Monsoon
Monsoon, a major wind system that seasonally reverses its direction—such as one that blows for approximately six......
montebrasite
montebrasite, phosphate mineral (LiAl(PO4)(OH,F)) similar to amblygonite...
monzonite
monzonite, intrusive igneous rock that contains abundant and approximately equal amounts of plagioclase and potash......
Moon
Moon, Earth’s sole natural satellite and nearest large celestial body. Known since prehistoric times, it is the......
Moore, Raymond Cecil
Raymond Cecil Moore was an American paleontologist known for his work on Paleozoic crinoids, bryozoans, and corals......
Morganucodon
Morganucodon, extinct genus of tiny mammals known from fossils dated to the Triassic-Jurassic boundary (approximately......
Morocco earthquake of 2023
Morocco earthquake of 2023, severe earthquake that struck near the town of Oukaïmedene in western Morocco on September......
Morocco earthquake of 2023: At a Glance
The Morocco earthquake of 2023 was a magnitude-6.8 temblor that struck central Morocco on September 8, 2023, at......
Moropus
Moropus, extinct genus of the chalicotheres, a group of very unusual perissodactyls (“odd-toed” ungulates) related......
moroxite
moroxite, clear blue variety of the mineral apatite...
morphogenetic region
morphogenetic region, theoretical area devised by geomorphologists to relate climate, geomorphic processes, and......
morphometric analysis
morphometric analysis, quantitative description and analysis of landforms as practiced in geomorphology that may......
Morrison Formation
Morrison Formation, series of sedimentary rocks deposited during the Jurassic Period in western North America,......
Morse, Jedidiah
Jedidiah Morse was an American Congregational minister and geographer, who was the author of the first textbook......
mosasaur
mosasaur, (family Mosasauridae), extinct group of aquatic lizards that attained a high degree of adaptation to......
Moschops
Moschops, extinct genus of mammal-like reptiles (Therapsida) found as fossils in rocks of Permian age (299 million......
mottramite
mottramite, vanadate mineral (PbCu(VO4)(OH)) similar to descloizite...
Mount Tambora 200 Years Later
April 5, 2015, marks 200 years since the beginning of the largest volcanic eruption in recorded history. The catastrophic......
Mucrospirifer
Mucrospirifer, genus of extinct brachiopods (lamp shells) found as fossils in Middle and Upper Devonian marine......
mud volcano
mud volcano, mound of mud heaved up through overlying sediments. The craters are usually shallow and may intermittently......
mudstone
mudstone, sedimentary rock composed primarily of clay- or silt-sized particles (less than 0.063 mm [0.0025 inch]......
multituberculate
multituberculate, any member of an extinct group of small, superficially rodentlike mammals that existed from about......
Munk, Walter
Walter Munk was an Austrian-born American oceanographer whose pioneering studies of ocean currents and wave propagation......
Murchison, Sir Roderick Impey
Sir Roderick Impey Murchison was a geologist who first established the geologic sequence of Early Paleozoic strata......
Murray, Sir John
Sir John Murray was a Scottish Canadian naturalist and one of the founders of oceanography, whose particular interests......
Myanmar earthquake of 2025
Myanmar earthquake of 2025, powerful magnitude-7.7 earthquake that struck Myanmar (Burma) on March 28, 2025. The......
Mylodon
Mylodon, extinct genus of ground sloth found as fossils in South American deposits of the Pleistocene Epoch (2.6......
Myophoria
Myophoria, genus of extinct clams found as fossils in Triassic rocks. It is readily identified by its distinctive......
myrmekite
myrmekite, irregular, wormy penetration by quartz in plagioclase feldspar; these wartlike, wormlike, or fingerlike......
Müller, Sophus Otto
Sophus Otto Müller was a Danish archaeologist who, during the late 19th century, discovered the first of the Neolithic......
Münster, Sebastian
Sebastian Münster was a German cartographer, cosmographer, and Hebrew scholar whose Cosmographia (1544; “Cosmography”)......
nahcolite
nahcolite (NaHCO3), colourless to white carbonate mineral, a naturally occurring sodium bicarbonate. (The name......
Nansen, Fridtjof
Fridtjof Nansen was a Norwegian explorer, oceanographer, statesman, and humanitarian who led a number of expeditions......
nappe
nappe, in geology, large body or sheet of rock that has been moved a distance of about 2 km (1.2 miles) or more......
National Geographic Magazine
National Geographic Magazine, monthly magazine of geography, archaeology, anthropology, and exploration, providing......
National Geographic Society
National Geographic Society, American scientific society founded (1888) in Washington, D.C., by a small group of......
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration (NOAA), U.S. governmental agency established in 1970 within the......
native element
native element, any of a number of chemical elements that may occur in nature uncombined with other elements. The......
Nazca Plate
Nazca Plate, major tectonic plate composed of oceanic crust underneath the Pacific Ocean adjacent to the western......
Neanderthal
Neanderthal, (Homo neanderthalensis, Homo sapiens neanderthalensis), member of a group of archaic humans who emerged......
neap tide
neap tide, tide of minimal range occurring near the time when the Moon and the Sun are in quadrature. This condition......
Neogene Period
Neogene Period, the second of three divisions of the Cenozoic Era. The Neogene Period encompasses the interval......
neoprioniodiform
neoprioniodiform, conodont, or small toothlike phosphatic fossil of uncertain affinity, that is characterized by......
Neospirifer
Neospirifer, genus of extinct brachiopods (lamp shells) found as fossils in Late Carboniferous to Permian marine......
Nepal earthquake of 2015
Nepal earthquake of 2015, severe earthquake that struck near the city of Kathmandu in central Nepal on April 25,......
nepheline syenite
nepheline syenite, medium- to coarse-grained intrusive igneous rock, a member of the alkali-syenite group (see......
nephelinite
nephelinite, silica-poor (mafic) lava that contains nepheline and pyroxene and is usually completely crystallized.......
nesosilicate
nesosilicate, compound with a structure in which independent silicate tetrahedrons (each consisting of a central......
New Madrid earthquakes of 1811–12
New Madrid earthquakes of 1811–12, series of three large earthquakes that occurred near New Madrid, Missouri, between......
New Madrid Seismic Zone
New Madrid Seismic Zone (NMSZ), region of poorly understood, deep-seated faults in Earth’s crust that zigzag southwest-northeast......
niccolite
niccolite, an ore mineral of nickel, nickel arsenide (NiAs). It is commonly found associated with other nickel......
nickel–iron
nickel–iron, very rare native alloy of nickel and iron that contains between 24 and 77 percent nickel. It occurs......
Nightglow
Nightglow, weak, steady light emanating from the whole night sky. See...
Niobrara Limestone
Niobrara Limestone, division of rocks in the central United States dating to the Late Cretaceous Period, which......
Nitisol
Nitisol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
nitrate and iodate minerals
nitrate and iodate minerals, small group of naturally occurring inorganic compounds that are practically confined......
Noctilucent cloud
Noctilucent cloud, rare cloud form, probably composed of ice crystals and dust from meteor smoke, that occurs at......
nodule
nodule, rounded mineral concretion that is distinct from, and may be separated from, the formation in which it......
normal fault
normal fault, type of fault in which lengthening, or extension, of a portion of Earth’s crust causes a block of......
North America
North America, third largest of the world’s continents, lying for the most part between the Arctic Circle and the......
- Introduction
- Geology, Plate Tectonics, Erosion
- Geology, Forests, Lakes
- Tectonics, Evolution, Geology
- Prehistoric, Geology, Plate Tectonics
- Late Mesozoic, Cenozoic, Geology
- Glaciation, Migration, Megafauna
- Marginal Mountains, Geology, Climate
- Lowlands, Plains, Coastlines
- Lakes, Rivers, Coastlines
- Grassland, Desert, Tundra
- Air Masses, Climate, Weather
- Climate, Geography, Wildlife
- Boreal Forest, Wildlife, Ecosystems
- Prairies, Steppes, Savannas
- Indigenous, Settlers, Immigration
- Dispossession, Indigenous, Colonization
- African Heritage, Culture, History
- Economy, Trade, Resources
- Coal Deposits, Mining, Geology
- Wildlife, Flora, Fauna
- Farming, Crops, Livestock
- Hydroelectricity, Rivers, Dams
- Trade, Resources, Markets
- Transportation, Infrastructure, Trade
North Pole
North Pole, the northern end of Earth’s axis, lying in the Arctic Ocean, about 450 miles (725 km) north of Greenland.......
Northern lights
Northern lights, luminous atmospheric display visible in the Northern Hemisphere. See...
Northridge earthquake of 1994
Northridge earthquake of 1994, earthquake that struck the densely populated San Fernando Valley in southern California,......
Notharctus
Notharctus, extinct genus of small primates (family Adapidae) that shares many similarities with modern lemurs,......