Earth Sciences, MEN-NOR
The Earth sciences are the fields of study concerned with the solid Earth, its waters, and the air that envelops it. Included are the geologic, hydrologic, and atmospheric sciences.
Earth Sciences Encyclopedia Articles By Title
Merapi, Mount
Mount Merapi, volcanic mountain peak located near the center of the island of Java, Indonesia. The volcano is about......
mercury
mercury (Hg), chemical element, liquid metal of Group 12 (IIb, or zinc group) of the periodic table. atomic number80......
meridian
meridian, imaginary north–south line on the Earth’s surface that connects both geographic poles; it is used to......
mesolite
mesolite, mineral of the zeolite family, similar to natrolite...
Mesosphere
Mesosphere, region of the upper atmosphere between about 50 and 80 km (30 and 50 miles) above the surface of the......
Messina earthquake and tsunami of 1908
Messina earthquake and tsunami of 1908, earthquake and subsequent tsunami that devastated southern Italy on Dec.......
Messinian Stage
Messinian Stage, uppermost division of Miocene rocks, representing all rocks deposited worldwide during the Messinian......
metacinnabar
metacinnabar, a mercury sulfide mineral that has the same chemical composition as cinnabar (HgS). Typical specimens......
metallogenic province
metallogenic province, geographic area characterized by a particular assemblage of mineral deposits, or by a distinctive......
metallography
metallography, study of the structure of metals and alloys, particularly using microscopic (optical and electron)......
metallurgy
metallurgy, art and science of extracting metals from their ores and modifying the metals for use. Metallurgy customarily......
- Introduction
- Copper Alloy, Zinc Alloy, Brass
- Iron, Steel, Alloy
- Aluminum, Magnesium, Titanium
- Extractive, Refining, Alloying
- Roasting, Smelting, Refining
- Matte Smelting, Refining, Alloying
- Refining, Alloying, Smelting
- Leaching, Extraction, Refining
- Alloying, Heat Treatment, Casting
- Electrical Properties
- Alloying, Refining, Smelting
- Casting, Alloying, Refining
- Metalworking, Alloying, Refining
- Forging, Heat Treatment, Alloying
- Powder, Process, Components
- Hardening, Treatments, Heat
- Corrosion Resistance, Alloying, Heat Treatment
- Nitriding, Alloying, Hardening
- Testing, Mechanical Properties
metamorphic rock
metamorphic rock, any of a class of rocks that result from the alteration of preexisting rocks in response to changing......
- Introduction
- Pressure, Temperature, & Deformation
- Pressure, Heat, Transformation
- Heat, Pressure, Reactions
- Isograds, Foliations, Textures
- Retrograde Metamorphism
- Foliated, Textures, Minerals
- Foliations, Textures, Deformations
- Facies, Pressure, Heat
- Pressure, Temperature, Time
- Regional, Foliated, Pressure
- Zeolite Facies, Minerals, Textures
- Foliated, Igneous, Sedimentary
- Foliated, Non-Foliated, Textures
metamorphism
metamorphism, mineralogical and structural adjustments of solid rocks to physical and chemical conditions differing......
metasomatic replacement
metasomatic replacement, the process of simultaneous solution and deposition whereby one mineral replaces another.......
Meteorology
Meteorology, Scientific study of atmospheric phenomena, particularly of the troposphere and lower stratosphere.......
Methane burp hypothesis
Methane burp hypothesis, in oceanography and climatology, an explanation of the sudden onset of the Paleocene-Eocene......
Mexico City earthquake of 1985
Mexico City earthquake of 1985, severe earthquake that occurred on September 19, 1985, off the coast of the Mexican......
mica
mica, any of a group of hydrous potassium, aluminum silicate minerals. It is a type of phyllosilicate, exhibiting......
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......
microcline
microcline, a common feldspar mineral, one form of potassium aluminosilicate (KAlSi3O8) that occurs in igneous......
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......
millerite
millerite, a nickel sulfide mineral (NiS) found in carbonate veins, as at Keokuk, Iowa, or as an alteration product......
mimetite
mimetite, arsenate mineral, lead chloride arsenate [Pb5(AsO4)3Cl], in the pyromorphite series of the apatite group......
Mindel Glacial Stage
Mindel Glacial Stage, major division of Pleistocene time and deposits in Alpine Europe (the Pleistocene Epoch began......
Mindel-Riss Interglacial Stage
Mindel-Riss Interglacial Stage, major division of Pleistocene time and deposits in Alpine Europe, part of the classical......
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,......
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......
Mistral
Mistral, cold and dry strong wind in southern France that blows down from the north along the lower Rhône River......
mofette
mofette, fumarole, or gaseous volcanic vent, that has a temperature well below the boiling point of water, though......
Moho
Moho, boundary between the Earth’s crust and its mantle. The Moho lies at a depth of about 22 mi (35 km) below......
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......
Monongahela Series
Monongahela Series, division of Pennsylvanian rocks in the eastern and southeastern United States. (The Pennsylvanian......
Monsoon
Monsoon, a major wind system that seasonally reverses its direction—such as one that blows for approximately six......
monticellite
monticellite, grayish silicate mineral in the olivine family, calcium and magnesium silicate (CaMgSiO4), that occurs......
montmorillonite
montmorillonite, any of a group of clay minerals and their chemical varieties that swell in water and possess high......
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......
moonstone
moonstone, gem-quality feldspar mineral, a mixed sodium and potassium aluminosilicate, (K,Na)AlSi3O8, that shows......
mordenite
mordenite, hydrated sodium, potassium, and calcium aluminosilicate mineral (Na2,K2,Ca) Al2Si10O24·7H2O, in the......
morganite
morganite, gem-quality beryl (q.v.) coloured pink or rose-lilac by the presence of cesium. It is often found with......
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......
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......
Moscovian Stage
Moscovian Stage, second of four internationally defined stages of the Pennsylvanian Subsystem of the Carboniferous......
moss agate
moss agate, grayish to milky-white agate (q.v.), a variety of the silica mineral quartz that contains opaque, dark-coloured......
Mount Marapi
Mount Marapi, an active volcano located in the Padang Highlands of western Sumatra, Indonesia. The mountain is......
Mount Tambora 200 Years Later
April 5, 2015, marks 200 years since the beginning of the largest volcanic eruption in recorded history. The catastrophic......
mud volcano
mud volcano, mound of mud heaved up through overlying sediments. The craters are usually shallow and may intermittently......
mudflow
mudflow, flow of water that contains large amounts of suspended particles and silt. It has a higher density and......
mudstone
mudstone, sedimentary rock composed primarily of clay- or silt-sized particles (less than 0.063 mm [0.0025 inch]......
Mullite
Mullite, any of a type of rare mineral consisting of aluminum silicate (3Al2O3·2SiO2). It is formed upon firing......
Murray Fracture Zone
Murray Fracture Zone, submarine fracture zone in the Earth’s surface, a long mountainous lineation on the North......
muscovite
muscovite, abundant silicate mineral that contains potassium and aluminum. Muscovite is the most common member......
Myanmar earthquake of 2025
Myanmar earthquake of 2025, powerful magnitude-7.7 earthquake that struck Myanmar (Burma) on March 28, 2025. The......
myrmekite
myrmekite, irregular, wormy penetration by quartz in plagioclase feldspar; these wartlike, wormlike, or fingerlike......
nahcolite
nahcolite (NaHCO3), colourless to white carbonate mineral, a naturally occurring sodium bicarbonate. (The name......
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......
natrolite
natrolite, hydrated sodium aluminosilicate mineral, Na2Al2Si3O10·2H2O, in the zeolite family. It has been found......
Nazca Plate
Nazca Plate, major tectonic plate composed of oceanic crust underneath the Pacific Ocean adjacent to the western......
neap tide
neap tide, tide of minimal range occurring near the time when the Moon and the Sun are in quadrature. This condition......
Nebraskan Glacial Stage
Nebraskan Glacial Stage, major division of Pleistocene time and deposits in North America (the Pleistocene Epoch......
Nepal earthquake of 2015
Nepal earthquake of 2015, severe earthquake that struck near the city of Kathmandu in central Nepal on April 25,......
nepheline
nepheline, the most common feldspathoid mineral, an aluminosilicate of sodium and potassium [(Na,K)AlSiO4]. It......
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.......
nephrite
nephrite, a gem-quality silicate mineral in the tremolite–actinolite series of amphiboles. It is the less prized......
nesosilicate
nesosilicate, compound with a structure in which independent silicate tetrahedrons (each consisting of a central......
Nevadan orogeny
Nevadan orogeny, mountain-building event in western North America that started in the Late Jurassic Epoch about......
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......
Norian Stage
Norian Stage, middle of three divisions in the Upper Triassic Series, representing those rocks deposited worldwide......
normal fault
normal fault, type of fault in which lengthening, or extension, of a portion of Earth’s crust causes a block of......