5,021 articles
Special flood hazard area
A special flood hazard area (SFHA) is land subject to the 1-percent-annual-chance base flood, designated by FEMA, where flood insurance is mandatory for federally backed mortgages.
Special Report on Emissions Scenarios
The Special Report on Emissions Scenarios (SRES) is a 2000 IPCC report presenting 40 scenarios of future greenhouse gas emissions to 2100, serving as standard inputs for climate projections until replaced by the RCPs.
Specific capacity
Specific capacity is a measure of water-well productivity defined as the pumping rate divided by the drawdown at a stated time after pumping began, used to compare wells and estimate aquifer transmissivity.
Specific storage
Specific storage measures the volume of water a unit volume of confined aquifer releases per unit decline in hydraulic head, expressed in units of inverse length.
Specific yield
Specific yield is the ratio of water a saturated rock or soil releases by gravity drainage to its total volume, fundamental for modeling unconfined aquifers.
Spectral decomposition (seismic)
Spectral decomposition in seismology is a family of time-frequency analysis methods that breaks a seismic trace into its frequency components, revealing bed thickness variations, discontinuities, and fluid effects.
Spectrum Range
Spectrum Range: a 2,430 m shield volcano in the Mount Edziza volcanic complex, Northern Cordilleran Volcanic Province, British Columbia, Canada; rhyolite domes over basaltic shield, vividly colored by solfataric alteration.
Spence (mine)
Spence is a large open-pit copper mine in the Atacama Desert of northern Chile, wholly owned and operated by BHP, producing copper cathode and concentrates since 2006.
Spessartine
Spessartine is a manganese aluminum silicate mineral of the garnet group, the manganese end-member of the garnet series, occurring in granite pegmatites and cut as an orange to red-orange gemstone.
Sphalerite
Sphalerite, also known as zinc blende or blackjack, is a zinc sulfide mineral, (Zn,Fe)S, and the world's principal ore of zinc, named from the Greek for treacherous.
Spherical Earth
Spherical Earth, also called the sphericity of the Earth, is the model of Earth's figure as a sphere, argued from antiquity and refined into an oblate spheroid.
Spheroidal carbonaceous particles
Spheroidal carbonaceous particles are carbon-rich fly-ash particles produced only by industrial coal and oil combustion, which accumulate in sediments as unambiguous markers of fossil-fuel pollution.
Spinel
Spinel, also known as Balas ruby, is a magnesium aluminum oxide gem mineral, historically mistaken for ruby; famous "rubies" in the English Crown Jewels are spinel.
Spodosol
A Spodosol is a soil order in USDA soil taxonomy, defined by a spodic horizon of accumulated organic matter and aluminum, known as Podzol in the World Reference Base.
Spodumene
Spodumene is a lithium aluminum silicate mineral of the pyroxene group and the principal hard-rock ore of lithium, first described in 1800 from Sweden's Utö mines.
Spokane area fires
The Spokane area fires, also known as the Spokane Complex fires, are the major wildfire disasters of Spokane County, Washington, from the Great Fire of 1889 to 2026.
Spotter Network
Spotter Network is an American non-profit online service, introduced in 2006, that connects storm spotters and chasers, feeding their reports and GPS positions to National Weather Service offices.
Spraberry
The Spraberry is a Permian oil-producing sandstone and siltstone formation in the Midland Basin of West Texas, first developed in 1949 as a major Permian Basin tight-oil target.
Spring tide
A spring tide is the larger-than-average tide at new and full moon, when Earth, Moon, and Sun align and tidal forces add, producing higher highs and lower lows.
Sprite (lightning)
A sprite, often called a red sprite, is a brief electrical discharge appearing 40 to 90 km above Earth, above intense thunderstorms, triggered by positive cloud-to-ground lightning.
Squall
A squall is a sudden, strong increase in wind lasting minutes, often with a shower or thunderstorm; in nautical use it names the whole local storm.
Squall line
A squall line, also called a quasi-linear convective system, is a continuous or broken line of thunderstorms whose leading gust front produces strong gusty winds and heavy rain.
Square array (electrical resistivity)
The square array is a four-electrode resistivity surveying configuration introduced by Habberjam and Watkins in 1967, used chiefly to detect the directional fabric of fractured bedrock.
SRV Dominator
The SRV Dominator, or Storm Research Vehicle, is a series of armored tornado intercept vehicles owned by meteorologist Reed Timmer and featured on Discovery Channel's Storm Chasers.
SSR Mining
SSR Mining is a Denver-based precious metals mining company producing gold and silver from four mines in the Americas, incorporated in Canada in 1946 as a silver company.
St. Elmo's fire
St. Elmo's fire, also called corposant, is a persistent blue or violet glow caused by electrical discharge on sharp conductors such as masts and aircraft during thunderstorms.
St. Lawrence River Divide
The St. Lawrence River Divide is a continental divide in central and eastern North America separating the Great Lakes–St. Lawrence basin from the Mississippi and Hudson Bay basins.
St. Louis tornado history
St. Louis, Missouri, has one of the most extensive tornado records of any major American city, including the deadly Great Cyclone of 1896 and a 2025 EF3 tornado.
Stalactite
A stalactite is an icicle-shaped mineral formation that hangs from a cave ceiling and grows as dripping water deposits calcite, usually beginning as a hollow soda straw.
Standard penetration test
The standard penetration test (SPT) is a widely used in-situ geotechnical test that records the hammer blows needed to drive a sampler into soil, giving the N-value.