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Skaergaard intrusion
The Skaergaard intrusion is a layered gabbro body on the coast of East Greenland, formed about 55 million years ago and a type example of closed-system differentiation, discovered by Lawrence Wager in 1931.
Skarn
Skarn is a coarse-grained metamorphic rock rich in garnet, pyroxene, and other calc-silicate minerals, formed where magma intrudes and alters carbonate rocks such as limestone.
Skouriotissa
Skouriotissa (Σκουριώτισσα) is a copper mine in the Solea Valley of Cyprus, worked since at least the ninth century BC and the island's only active copper mine today.
Skyquake
A skyquake is a loud boom or rumbling from the sky with no visible local cause and no felt earthquake, known regionally as Seneca Guns, mistpouffers, and Barisal guns.
Skywarn
Skywarn is a National Weather Service volunteer program of trained civilian spotters, numbering roughly 290,000, who report tornadoes, hail, damaging winds, and flooding to aid warning decisions.
Slab detachment
Slab detachment, also called slab break-off, is the separation of a dense subducted oceanic slab from lighter lithosphere during continental collision, after which the slab sinks into the mantle.
Slab pull
Slab pull is the force generated when the cold, dense edge of an oceanic plate sinks into the mantle at a subduction zone, and it is considered the main driving force of plate tectonics.
Slab rollback
Slab rollback is the seaward migration of the subduction hinge, driven by the negative buoyancy of the sinking slab, and is the leading model for back-arc basin formation.
Slack water
Slack water, also called slack tide, is when a tidal current's speed is near zero, occurring between the flood and ebb currents as the tide changes.
Slamet
Mount Slamet (Gunung Slamet) is a 3,428 m active basaltic stratovolcano in Central Java, Indonesia, on the Sunda Arc, with two overlapping edifices, about 35 flank cinder cones, a 2014 VEI 2 eruption, and Level II unrest since 2024.
Slate
Slate is a fine-grained metamorphic rock with slaty cleavage that splits into flat slabs, a principal roofing material in Europe and North America since Roman times.
Slide
Slide (geography): a landslide mechanism in which rock, debris, or earth moves downslope as a coherent mass along a distinct failure surface; rotational or translational; one of five slope-movement modes; GeoNames code SLID names the resulting landform.
SLOSH
SLOSH (Sea, Lake, and Overland Surges from Hurricanes) is a two-dimensional operational storm surge model developed by NOAA, used for decades in hurricane forecasting and US evacuation planning.
Slump
A slump is a type of landslide in which a coherent mass of soil or rock moves downslope by rotational sliding along a curved, spoon-shaped failure surface.
Smackover Formation
The Smackover Formation is an Upper Jurassic (Oxfordian) limestone of the Louark Group beneath the Gulf Coastal Plain and a major oil reservoir named after the Smackover field, Arkansas.
Small Baseline Subset
Small Baseline Subset (SBAS) is a differential InSAR time-series method, reported in 2002, that measures ground deformation from stacks of short-baseline SAR interferograms, producing velocity maps and displacement time series.
Small Island Developing States
Small Island Developing States (SIDS) are small island and low-lying coastal countries recognized by the United Nations since 1992, totaling 39 states with about 65 million people.
Smithsonite
Smithsonite is a zinc carbonate mineral, ZnCO₃, that forms in oxidized zinc deposits, serves as an ore of zinc, and was named in 1832 for James Smithson.
Smog
Smog is visible air pollution from smoke, gases, and chemical pollutants, harming health and visibility. The two main types are sulfurous coal-smoke smog and photochemical smog rich in ground-level ozone.
Smokehouse Creek Fire
The Smokehouse Creek Fire was a February 2024 wildfire that burned over 1 million acres in the Texas Panhandle and Oklahoma, the largest on record in Texas.
Snake River Plain
The Snake River Plain is a broad, arc-shaped lowland across southern Idaho, formed by late Cenozoic volcanism as the North American plate moved over the Yellowstone hotspot.
SNOTEL
SNOTEL (SNOwpack TELemetry) is a network of more than 900 automated stations measuring snowpack in the mountains of the western United States, operated by the USDA.
Snow
Snow, also called snow crystal, is precipitation of branched, hexagonal ice crystals formed from water vapor in clouds, often agglomerated into snowflakes that store water and reflect sunlight.
Snow course
A snow course is a permanent transect where snowpack depth and water content are measured at fixed points year after year to forecast seasonal water supply.
Snow cover decline
Snow cover decline is the shrinking area, water content, and duration of seasonal snow as the climate warms, with Arctic June snow cover halved since the 1960s.
Snow depth
Snow depth is the vertical distance from a snowpack's surface to the ground, measured in centimeters or inches and distinct from snowfall and snow water equivalent.
Snow drought
Snow drought is a period of abnormally little snowpack for the time of year, of two types: dry, from low precipitation, and warm, from warm temperatures.
Snow grain metamorphism
Snow grain metamorphism is the set of processes that change the size, shape, and bonding of snow grains after deposition, producing rounded grains, facets, and depth hoar.
Snow grains
Snow grains are a form of solid precipitation of very small, white, opaque ice particles under 1 mm across, the frozen counterpart of drizzle, falling from stratus or fog.
Snow in Australia
Snow in Australia falls mainly on the Australian Alps between Melbourne and Canberra and the highlands of Tasmania, with declining snow depths since the late 1950s.