Earth science

Stratovolcano: layered, steep volcanic mountain with explosive behavior Stratovolcano A stratovolcano is a steep, layered volcanic mountain built from alternating lava and fragmental deposits, noted for episodic explosive eruptions and significant hazards to nearby…

Stratus cloud Low, uniform gray cloud layer that forms a blanket-like cover. Stratus often produces drizzle or light rain, reduces visibility, forms from gentle uplift or cooling, and is common…

Stromatolite: microbial laminated rock formations and their significance Stromatolite Stromatolites are layered sedimentary structures created by microbial mats. They record early life, oxygen-producing photosynthesis, and remain important for geology, paleontology…

Structure of the Earth: layers, composition, dynamics and boundaries Structure of the Earth Overview of Earth's internal layers, their composition and physical state, how boundaries are detected, and why this structure matters for geology, earthquakes and the magnetic fie…

Subduction (plate tectonics) Subduction Subduction is the process by which one tectonic plate sinks beneath another into the mantle, driving volcanic arcs, deep earthquakes and recycling of crustal material.

Submarine volcanoes — undersea volcanic systems Submarine volcano Volcanoes that erupt below the ocean surface. Covers how they form, typical structures (seamounts and guyots), eruption behavior under pressure, hydrothermal vents, ecological impo…

Subtropical cyclone: hybrid low-pressure weather system Subtropical cyclone An explanation of subtropical cyclones: their structure, formation, differences from tropical and extratropical cyclones, impacts, and forecasting challenges.

Subtropical ridge (subtropical high-pressure belt) Subtropical ridge A persistent belt of high atmospheric pressure near 30° latitude in each hemisphere that shapes trade winds, westerlies, dry climates and tropical cyclone tracks.

Subtropical Storm Andrea (2007) — early-season subtropical cyclone Subtropical Storm Andrea (2007) Subtropical Storm Andrea formed off Florida in May 2007 as the first named and first subtropical cyclone of the Atlantic season. It produced dangerous surf, caused indirect fatalit…

Sudbury Basin Ancient impact structure in Ontario, Canada, known for its origin as a meteorite crater, shock-modified rocks, and large deposits of nickel, copper and platinum-group metals.

Suiko Seamount — extinct guyot of the Hawaiian–Emperor chain Suiko Seamount Suiko Seamount is an extinct, flat-topped submarine volcano in the Hawaiian–Emperor chain. Formed by hotspot volcanism about 60 million years ago, it illustrates volcanic island li…

Summer — the warm season and its causes, climates, and cultural impact Summer Summer is the warmest season, produced by Earth’s tilt and orbit. This article explains its astronomical cause, regional climate variations, typical months, activities, risks, and…

Sun angle (solar elevation and incidence) Sun angle Sun angle is the direction at which sunlight strikes a particular place and time on Earth; it affects heating, day length, seasons, and practical design choices like solar panels a…

Sundance Sea: Jurassic inland sea of western North America Sundance Sea An epeiric Jurassic sea that flooded parts of western North America. Its shallow marine deposits and fossils record transgressions and regressions before the rise of the Cordillera…

Supercontinent: formation, examples and geological significance Supercontinent A supercontinent is a very large landmass made of multiple continental cores. This article explains how they form, examples such as Pangaea and Gondwana, the supercontinent cycle,…

Supervolcano: giant eruptions, causes, effects, and notable examples Supervolcano Overview of supervolcanoes: definition, geological causes, eruption processes, impacts on landscapes and climate, monitoring, and notable prehistoric examples.

Surface mining: methods, machinery, impacts and reclamation Surface mining Surface mining is extraction of minerals from the earth by removing soil and rock at the surface. This article summarizes methods, equipment, history, environmental issues and recl…

Surface runoff (overland flow) Surface runoff Surface runoff is water that flows over land when rainfall or melt exceeds the soil's ability to absorb it; it shapes landscapes, delivers water to streams, and is a major source o…

Surveying: principles, history, tools, and applications Surveying Surveying is the practice and science of determining positions, distances and angles for mapping, construction, land boundaries and infrastructure projects.

Taal Volcano (Philippines) Taal Volcano Taal Volcano is a small but highly active complex volcano in the caldera of Taal Lake on Luzon, Philippines. It is notable for frequent eruptions, a central island, and significant…

Talc: properties, composition, uses, occurrence and safety Talc Talc is the softest mineral on the Mohs scale, a hydrated magnesium silicate used in powders, ceramics, plastics and more. This article covers its composition, occurrences, applica…

Tales from Earthsea: Ursula K. Le Guin's later stories from the Earthsea world Tales from Earthsea A concise guide to Ursula K. Le Guin's 2001 collection Tales from Earthsea: its place in the Earthsea cycle, themes, development, reception and adaptations.

Tanzanite: a blue‑purple zoisite from Tanzania Tanzanite Tanzanite is the trade name for a blue–violet variety of the mineral zoisite found only in northern Tanzania. Valued for its color and rarity, it is commonly heat‑treated and used…

Teapot Rock (Wyoming): sandstone landmark and namesake of Teapot Dome Teapot Rock Teapot Rock is an eroded sandstone outcrop in Natrona County, Wyoming, noted for its teapot-like silhouette, its place in regional petroleum history and its association with the Te…

Tectonics: structure, processes and significance of Earth's deforming crust Tectonics Study of the Earth's lithospheric structures and the forces that shape them: plate boundaries, mountain building, earthquakes, volcanism, resource distribution and landscape evolut…

Temperature record of the past 1,000 years Temperature record of the past 1000 years Summary of how scientists reconstruct temperatures over the last millennium using proxy records, key climate intervals, main causes of change, methods, uncertainties, and why the r…

Terraforming Mars: Concepts, Methods, and Challenges Terraforming of Mars Overview of proposals to alter Mars’ climate and surface to support Earth life: main approaches, technical and ethical challenges, history of the idea, and present-day alternatives…

Terrestrial — meanings across planets, land, animals and plants Terrestrial Terrestrial describes things of the land or Earth: rocky planets, land ecosystems, animals that live on land, and plants growing in soil. It contrasts with aquatic, aerial, epiphyt…

Terrestrial planet A terrestrial planet is a rocky world composed mainly of silicate rocks and metals. This article explains their structure, formation, examples in the Solar System, and how the term…

Tertiary (historical geological term) Tertiary Former geologic interval covering the early Cenozoic (about 66–2.6 million years ago). Once an official period, now replaced by the Palaeogene and Neogene in modern stratigraphy.

Tethys Ocean: Mesozoic seaway between Gondwana and Laurasia Tethys Ocean A broad shallow ocean that separated Gondwana and Laurasia during much of the Mesozoic; its shrinking and closure shaped modern Eurasian basins and mountain belts.

The Call of Earth The Call of Earth (1992) is the second novel in Orson Scott Card's Homecoming Saga, a science-fiction series that mixes artificial intelligence, religious allegory, and a human jou…

The Quiet Earth (1985) — New Zealand science fiction film The Quiet Earth (movie) 1985 New Zealand sci-fi film directed by Geoff Murphy, adapted from Craig Harrison's novel; a contemplative post-apocalyptic drama noted for its atmosphere, performances, and ambig…

Thecodontosaurus — Early sauropodomorph ("socket‑toothed" lizard) Thecodontosaurus Thecodontosaurus was an early sauropodomorph dinosaur first recognized from fossils in southwest England. This article summarizes its anatomy, discovery, environment, classificatio…

Theory of the Earth — James Hutton and the origins of modern geology Theory of the Earth Summary of James Hutton's Theory of the Earth: its principles, publication history, influence on geology and biological thought, and its legacy in modern Earth science.

Thermosphere — Earth's high-altitude, heat-absorbing atmospheric layer Thermosphere The thermosphere is the upper atmospheric layer above the mesosphere where solar X-rays and extreme ultraviolet heat and ionize sparse gases, forming the ionosphere and affecting s…

Thundersnow: Thunderstorms that Produce Snow Thundersnow Thundersnow is a winter thunderstorm whose precipitation falls as snow. It occurs where strong convection, cold air and lift combine, notably near lakes, mountains, and some coasta…

Thunderstorms: formation, structure, hazards, and occurrences Thunderstorm Thunderstorms are convective storms producing lightning, thunder, heavy rain, strong winds and sometimes hail. This article explains their formation, life cycle, types, hazards and…

Tide — the periodic rise and fall of Earth's ocean waters Tide Periodic rise and fall of the ocean caused mainly by the Moon's gravity, driving currents, shaping coasts and ecosystems, affecting navigation and offering renewable energy potenti…

Tipas (Cazadero / Cerro Walther Penck) — High Andes Volcano Tipas Tipas is a 6,670 m (21,880 ft) volcano in the Andes of Argentina, also called Cazadero or Cerro Walther Penck. It is ranked among the highest Andean summits and attracts scientific…

Tonian — first period of the Neoproterozoic Tonian Tonian (1000–720 million years ago): the opening period of the Neoproterozoic marked by continental rifting, the early breakup of Rodinia and a notable diversification of microfoss…

Topaz (mineral) Topaz Topaz is a silicate mineral used as a gemstone and collector specimen. This article summarizes its chemistry, physical properties, color causes, varieties, occurrence, treatments a…

Tor (rock outcrop) — formation, features, and examples Tor A tor is an exposed rock outcrop shaped by weathering and erosion, typically found on hills. This article explains how tors form, their characteristics, where they occur, and their…

Torridonian: Proterozoic red sandstones of northwest Scotland Torridonian Torridonian refers to thick Proterozoic red sandstones and related sediments in NW Scotland that overlie ancient Lewisian gneiss and form the Torridon Hills and parts of Skye.

Travertine: formation, properties, history and uses Travertine Travertine is a terrestrial carbonate rock formed by rapid precipitation of calcium carbonate from groundwater or hot springs. It has distinct porosity, historic architectural use,…

Triassic Period Triassic First period of the Mesozoic Era (251.9–201.3 Ma). Marked recovery after the greatest mass extinction, origin of dinosaurs, early mammals and marine reptiles, and the breakup of Pa…

Tropical climate Climate type found in the Earth's tropics with year‑round warm temperatures and distinct wet and dry patterns; includes rainforest, monsoon and savanna variants and important ecolo…

Tropical cyclogenesis Tropical cyclogenesis is the process by which a tropical cyclone forms and intensifies. It requires specific oceanic and atmospheric conditions and is studied to improve warning, f…