Earth science

Shatsky Rise: Pacific oceanic plateau and the Tamu Massif Shatsky Rise Shatsky Rise is a large Mesozoic oceanic plateau southeast of Japan that includes Tamu Massif. Formed near a former three‑plate junction, it is important for studies of large igneo…

Shield Volcano: Form, Structure, Examples, and Planetary Occurrence Shield volcano Broad, gently sloping volcanoes built by low‑viscosity basaltic lava. Covers morphology, eruption style, tectonic settings, notable examples on Earth and other planets, hazards, an…

Shingle beach (pebble beach): characteristics, formation and examples Shingle beach Shingle beaches are coastal shores made of pebbles rather than sand. This article describes their composition, formation, distribution, ecological roles, coastal management relevan…

Shiprock: Volcanic Neck and Navajo Landmark in Northwestern New Mexico Shiprock Shiprock is an eroded volcanic neck in northwestern New Mexico, an Oligocene igneous remnant sacred to the Navajo Nation and a striking subject of geological study and cultural sig…

Siberian Traps: a Large Igneous Province and the End‑Permian Event Siberian Traps The Siberian Traps are one of Earth's largest flood basalt provinces. Formed around the Permian–Triassic boundary, they are linked to massive volcanic eruptions and dramatic enviro…

Siderian (Palaeoproterozoic): Early oxygenation and banded iron formations Siderian The Siderian (2.50–2.30 billion years ago) is the earliest Palaeoproterozoic period, notable for widespread banded iron formation deposition and the rise of atmospheric oxygen duri…

Silicate mineral Minerals built from silicon–oxygen units (SiO4 tetrahedra). Silicates form most rock-forming minerals — quartz, feldspars, clays — and dominate the Earth's crust and many industria…

Sill (geology): sheet-like igneous intrusions Sill (geology) A sill is a concordant, sheet-like igneous intrusion formed when magma intrudes between layers of older rock. This article explains formation, characteristics, examples, and how si…

Silt: fine sediment and soil particle type Silt Silt is a fine-grained soil or sediment between clay and sand in size. This article explains its properties, formation, agricultural impacts, and practical management.

Siltstone: a sedimentary mudrock dominated by silt-sized grains Siltstone Siltstone is a fine-grained sedimentary rock composed mainly of silt-sized particles. This article explains its properties, formation, common environments, uses, and how it differs…

Silurian Period — post-Ordovician recovery, early land plants and marine diversification Silurian Geologic period about 443–419 million years ago. Marked by recovery after a major extinction, widespread shallow seas and reefs, first vascular plants on land, diverse marine life,…

Sirius Passet: Cambrian Lagerstätte of northern Greenland Sirius Passet Sirius Passet is an Early Cambrian fossil lagerstätte in northern Greenland known for exceptionally preserved soft-bodied invertebrates, predating the Burgess Shale and providing k…

Skjaldbreiður: Icelandic Shield Volcano Skjaldbreiður Skjaldbreiður is a broad shield volcano in Iceland, reaching about 1,060 m with a crater near 300 m across. Formed by fluid basaltic flows, it is a prominent geological landmark an…

Slate (metamorphic rock) Slate Fine-grained metamorphic rock produced from shale under low-grade metamorphism; notable for slaty cleavage and widespread use in roofing, flooring, tablets and decorative stone.

Sleet (precipitation) Sleet Sleet: frozen precipitation with two common meanings—small ice pellets (North America) or a rain–snow mix (other English usages). Covers formation, differences from similar precipi…

Slope (mathematics, geometry, and applied contexts) Slope Slope is a measure of steepness or rate of change, defined in basic algebra as rise over run. It appears in geometry, calculus (derivative), statistics (regression), engineering (g…

Small shelly fossils (small shelly fauna) Small shelly fossils Small shelly fossils are tiny mineralized remains from the late Ediacaran to early Cambrian that record the first widespread appearance of hard parts in marine animals and illumina…

Smithsonite Smithsonite is a zinc carbonate mineral (ZnCO3) that occurs as a secondary ore of zinc. It is notable for its botryoidal habits, varied colors from impurities, and historical confu…

Smoky Hill Chalk: Late Cretaceous Fossil-Bearing Chalk of the Western Interior Smoky Hill Chalk A section of the Niobrara Chalk notable as an Upper Cretaceous conservation Lagerstätte, preserving diverse, exceptionally complete marine fossils including plesiosaurs, mosasaurs,…

Snow: formation, characteristics, uses and hazards Snow Snow is composed of ice crystals formed from atmospheric water vapor. This article explains how snow forms, its shapes and layers, common uses, hazards, and notable weather phenome…

Snowball Earth: global glaciation events and scientific debate Snowball Earth Summary of the Snowball Earth hypothesis, the geological evidence and mechanisms, competing views (including Slushball variants), and implications for Earth's climate and life.

Soapstone (steatite): composition, history, uses and properties Soapstone Soapstone, or steatite, is a talc-rich metamorphic rock known for softness, heat resistance and carvability. It has long use in sculpture, cookware, stoves, countertops and electri…

Soil: composition, formation, ecology and human significance Soil An encyclopedia overview of soil: its composition and horizons, formation processes, ecological roles, organisms, uses in agriculture and engineering, and human impacts and conserv…

Soil classification: systems, criteria and uses Soil classification Overview of soil classification: principles, common systems, key diagnostic properties, practical uses in agriculture, engineering and environmental management, and limitations.

Soil erosion: causes, types, impacts and prevention Soil erosion Soil erosion is the loss of fertile topsoil by water, wind or human activity. This article covers causes and types, historic examples, impacts on agriculture and infrastructure, mo…

Soil science: study, structure, formation and uses Soil science Soil science examines the natural body of soil: its formation, composition, classification, mapping, and roles in agriculture, engineering, ecology and water supply.

Solnhofen Limestone — Upper Jurassic fossil lagerstätte in Bavaria Solnhofen Limestone Upper Jurassic Solnhofen Limestone in Bavaria is a world-famous lagerstätte known for exquisitely preserved fossils, notably Archaeopteryx, and for historical quarrying and use as…

Soriatitan — Early Cretaceous sauropod from Spain Soriatitan Soriatitan is a genus of long-necked sauropod dinosaur from the Early Cretaceous of Spain, represented by the species S. golmayensis and known from fossil remains that illuminate E…

Soufrière Hills volcano (Montserrat) Soufrière Hills Active stratovolcano on Montserrat that reawakened in 1995; its eruptions destroyed the capital, created long-term exclusion zones and deadly pyroclastic flows, and reshaped the is…

South American Plate: structure, boundaries, and geological impact South American plate Major tectonic plate carrying the continent of South America and adjacent seafloor; its interactions (notably with the Nazca and African plates) shape the Andes, seismicity, and At…

South Atlantic tropical cyclone Rare tropical cyclones that form in the South Atlantic Ocean. Overview of why they are uncommon, their characteristics, notable occurrences, monitoring, impacts, and possible futur…

South Magnetic Pole The South Magnetic Pole is the location in the Southern Hemisphere where Earth's magnetic field points vertically upward; its position slowly shifts with changes in the planet's ma…

Sphalerite: the primary zinc sulfide mineral Sphalerite Sphalerite (Zn,Fe)S is the chief ore of zinc. This article covers its composition, appearance, structure, deposits, uses and notable properties that distinguish it from related sul…

Spring (water) A spring is where groundwater emerges at the Earth's surface. This article explains how springs form, their types, roles in ecosystems and human use, and basic water-quality and ma…

Stage (geology) A stage is a formal chronostratigraphic unit: the rock equivalent of a geologic age. It helps subdivide Earth's history by strata with shared characteristics and globally agreed bo…

Statherian Period (1.8–1.6 billion years ago) Statherian The Statherian (1.8–1.6 Ga) is the final period of the Palaeoproterozoic, notable for continental stabilization, assembly of the supercontinent Columbia, craton formation and wides…

Steam devil: small whirlwinds formed in steam, smoke, or fog Steam devil A steam devil is a short-lived, small vortex that becomes visible when spinning air mixes with steam, smoke or fog. They form near warm water, industrial exhaust, hot springs, dese…

Stenian Period — final Mesoproterozoic interval, 1.2–1.0 billion years ago Stenian The Stenian (1.2–1.0 Ga) is the last period of the Mesoproterozoic, notable for the early assembly of Rodinia, major igneous events such as the Keweenawan, and fossils interpreted…

Stone: natural rock, types, uses, and cultural significance Stone An overview of stone as a natural material: definitions, types, formation, historical use, common applications, physical properties, and distinctions from manufactured materials.

Storegga Slide: prehistoric submarine landslides and the resulting North Atlantic tsunami Storegga Slide The Storegga Slide refers to massive submarine landslides off Norway's continental shelf that generated a North Atlantic tsunami around 6100 BC, leaving sedimentary evidence across…

Storm (meteorological phenomenon) Storm A storm is a period of disturbed weather with strong winds, precipitation and often thunder or lightning. This article explains types, formation, hazards, forecasting and safety.

Meteorological history of Hurricane Wilma (October 2005) Storm history of Hurricane Wilma Detailed account of Hurricane Wilma’s development, explosive intensification to a record low pressure, landfalls in Mexico and Florida, and subsequent weakening and extratropical t…

Storm surge: coastal flooding caused by intense storms Storm surge A storm surge is the abnormal rise of seawater pushed ashore by a storm. This article explains causes, factors that influence surge height, impacts, forecasting, and ways to reduce…

Fossil Fuels, Future Generations, and Climate Risk: James Hansen's 2009 Call to Action Storms of My Grandchildren James Hansen's 2009 call to action links fossil fuel emissions to long-term climate risks, urging rapid CO2 reductions and policy shifts to protect future generations.

Strata: layers of rock and soil, formation, study and significance Strata Strata are layered deposits of rock or soil formed by sedimentation. This article explains how they form, how geologists study them, their uses, common modifications and notable fe…

Stratigraphic column A stratigraphic column is a graphic summary of rock layers at a location, showing relative order, lithology, age relationships and unconformities for correlation, interpretation, a…

Stratigraphy: Principles, History, and Applications Stratigraphy Stratigraphy studies rock layers (strata), their relationships and ages. It uses principles like superposition, fossil correlation, and radiometric dating and supports resource exp…

Stratosphere The stratosphere is the stable atmospheric layer above the troposphere where temperature increases with height, containing the ozone layer and influencing climate, aviation, and st…