5,021 articles
Aljustrel mine
The Aljustrel mine is an underground copper, zinc, lead, and silver mine near Aljustrel in southern Portugal, owned by Almina and mined since Roman times as Vipasca.
Alkali basalt
Alkali basalt is a fine-grained volcanic rock of basaltic silica content that is undersaturated in silica, defined by nepheline in its CIPW norm and typical of ocean-island and intraplate volcanism.
Alkenone paleothermometry
Alkenone paleothermometry is a method for reconstructing past sea surface temperature from alkenone compounds produced by haptophyte algae, introduced in 1986 and applied worldwide to Quaternary and older sediments.
Alliance of Small Island States
The Alliance of Small Island States (AOSIS) is a coalition of small island and low-lying coastal developing states, formed in 1990 to amplify climate voices.
Alligator Lake
Alligator Lake volcanic complex, Yukon, Canada: a basaltic volcanic field 30 km southwest of Whitehorse with two cinder cones on a small shield volcano, 2,217 m summit, ~3 Ma age, no known Holocene eruptions.
Alluvial fan
An alluvial fan, also known as an alluvial cone, is a fan-shaped sediment body deposited where a stream leaves a mountain valley and spreads onto a plain.
Alluvial plain
An alluvial plain is a level or gently sloping surface built by river flood deposits, typically beside the river; examples include the Huang He plain, about 409,500 square kilometers.
Almandine
Almandine is an iron-aluminum garnet, the most common member of the garnet group, typically deep red and common in mica schists and gneisses from regional metamorphism.
Almolonga
Almolonga (Volcán de Almolonga, Cerro Quemado) is a 3,173 m Guatemalan stratovolcano with a late-Pleistocene caldera near Quezaltenango; last erupted 1818, VEI 2, with a fatal 1991 geothermal landslide.
Alney-Chashakondzha
Alney-Chashakondzha (Алней-Чашаконджa), volcano 300450, is a glacier-capped twin stratovolcano complex in Kamchatka's Sredinny Range: Alney 2,598 m and Chashakondzha 2,526 m on a Pliocene shield, Holocene-active, last eruption 1600 CE.
Alpine climate
Alpine climate, also called mountain or highland climate, is the climate above the tree line: low temperatures, a short growing season, and precipitation falling largely as snow.
Alpine Fault
The Alpine Fault is a major geological fault running about 600 km along the Southern Alps on New Zealand's South Island, forming the on-land boundary between the Pacific and Australian tectonic plates.
Alpine orogeny
The Alpine orogeny is the Mesozoic to Cenozoic mountain-building event that formed the Alps as the African and Eurasian plates converged and the Adriatic microplate collided with Europe.
Alternative stable states
Alternative stable states are distinct self-maintaining ecosystem configurations possible under identical environmental conditions, an idea from the 1960s with shallow lakes as the classic example.
Altocumulus cloud
Altocumulus is a mid-level cloud genus of white or gray patches of rounded cloudlets, one of ten WMO cloud genera, usually signaling settled weather but with castellanus forms preceding thunderstorms.
Altostratus cloud
Altostratus is one of the ten basic cloud genera, a mid-level gray or bluish sheet through which the sun appears dimly, sometimes producing virga or very light precipitation.
Aluminosilicate
An aluminosilicate is a compound containing aluminum, silicon, and oxygen, covering minerals such as feldspars, zeolites, clays, glasses, and synthetic gels used in catalysis and construction.
Amaruq
Amaruq is a gold mine in the Kivalliq region of Nunavut, Canada, owned by Agnico Eagle, whose open pit and underground operations supply ore to the nearby Meadowbank mill.
Amazon dieback
Amazon dieback is the projected large-scale conversion of Amazon rainforest to drier, savanna-like vegetation under climate change, deforestation, and fire, first modeled by the Hadley Centre's HadCM3LC in 2000.
Amazonian (Mars)
The Amazonian is the most recent of Mars' three geologic periods, spanning roughly 3 billion years to the present with slow erosion, low volcanism, and a cold, dry climate.
Amazonite
Amazonite, also called amazon stone, is a green to blue-green gem variety of potassium feldspar, named in 1847 for an area near the Amazon River, though no deposits exist there.
Amber
Amber, sometimes called resinite, is fossilized tree resin hardened over millions of years, prized as an ornament and for preserving insects, spiders, and plants in lifelike detail.
Ambient noise cross-correlation
Ambient noise cross-correlation is a seismology technique that estimates the Green's function between two stations by cross-correlating continuous recordings of background seismic noise, treating one as a virtual source.
Ambient noise tomography
Ambient noise tomography is a seismic imaging technique that cross-correlates continuous background noise recorded at station pairs to build 3D shear-wave velocity models of the crust.
American Association of Petroleum Geologists
The American Association of Petroleum Geologists is an international nonprofit professional society for petroleum and energy geoscientists, founded in 1917 and headquartered in Tulsa, Oklahoma.
American Meteorological Society
The American Meteorological Society (AMS) is a professional society founded in Boston in 1919 by Charles Franklin Brooks, publishing 12 journals and certifying weather broadcasters and consultants.
Amethyst
Amethyst is the purple gem variety of quartz, the February birthstone, whose color comes from iron and natural irradiation; it was once valued with ruby and sapphire.
AMIP (climate model experiment)
AMIP is a climate modeling experiment protocol in which an atmospheric model is run with observed sea surface temperatures and sea ice prescribed rather than an interactive ocean.
Ammolite
Ammolite, also sold as calcentine, is an iridescent organic gemstone made of aragonite from the fossilized shells of ammonites about 70 to 75 million years old, mined commercially only in southern Alberta, Canada.
Amosite
Amosite, commonly called brown asbestos, is the asbestiform variety of the amphibole mineral grunerite, one of the most important types of asbestos, mined chiefly in South Africa until 2001 and now banned there since 2008.