3,546 articles
Thermokarst
Thermokarst is the process in which thawing ice-rich permafrost or melting massive ground ice causes the land surface to collapse and subside, forming depressions, sinkholes, and especially thaw lakes across Arctic lowlands.
Thermopylae (Θερμοπύλαι)
Thermopylae (Θερμοπύλαι, "Hot Gates") is a narrow Greek coastal pass, site of the 480 BC battle where Leonidas' 300 Spartans and allied Greeks held Xerxes' Persian army before being flanked via the Anopaia path; also fought over in 279 BC, 191 BC, and 1941.
Thirteen Lives
Thirteen Lives (2022) is Ron Howard's survival drama, written by William Nicholson, dramatizing the 2018 Tham Luang cave rescue of the Wild Boars team, starring Viggo Mortensen, Colin Farrell, and Joel Edgerton on Prime Video.
Thordarhyrna
Thordarhyrna (Þórðarhyrna) is a subglacial stratovolcano beneath Vatnajökull, Iceland, the second central volcano of the Grímsvötn-Laki system, 20 km SW of Grímsvötn, 1,650 m high, last erupting in 1903–1904 (VEI 4).
Thousand Islands
The Thousand Islands are 1,864 islands in the St. Lawrence River on the Ontario-New York border, formed on the granite Frontenac Axis by glacial scouring and post-glacial flooding; home to Thousand Islands National Park (est. 1904) and the UNESCO Frontenac Arch Biosphere Reserve.
Thousand Islands (Indonesia)
Kepulauan Seribu (Thousand Islands) is Jakarta's island regency in the Java Sea: 113 islands, 11 inhabited, 29,008 residents (2022), a marine national park, and reefs under urban pressure.
Three Sisters (Oregon)
Three Sisters (Oregon): North, Middle, and South Sister, three aligned Cascade stratovolcanoes near Bend; South Sister is tallest at 3,157 m, with rhyolite eruptions about 2,000 years ago and ongoing uplift since the 1990s.
Three Slice Nunatak
Three Slice Nunatak (Chilean: Nunatak Tres Tajadas) is a c. 500 m nunatak marking the north point of Joerg Peninsula, Bowman Coast, Graham Land, Antarctica; surveyed by USAS in 1940 and named for its three vertical rock faces.
Thurston Island
Thurston Island, West Antarctica's third-largest island (about 220 km long), off the Eights Coast beside the Abbot Ice Shelf; determined an island by a 1940 Byrd flight; rocks record 349 Ma to 110–100 Ma Gondwana-margin magmatism.
Thwaites Glacier
Thwaites Glacier, the "Doomsday Glacier," is a Florida-sized West Antarctic ice stream losing ice rapidly; its main trunk retreats ~800 m/yr and it could raise sea level 65 cm if it collapsed.
Tian Shan (天山)
Tian Shan (天山), the Heavenly Mountains, is a ~2,500 km east-west Central Asian range across China, Kazakhstan, Kyrgyzstan, and Uzbekistan; highest peak Tomur (7,443 m), reactivated by the India-Eurasia collision, with rapidly retreating glaciers vital to regional water supply.
Tianmen Mountain (天门山)
Tianmen Mountain (天门山), 8 km south of Zhangjiajie, Hunan, is a 1,518.6 m karst table mountain with the Tianmen Cave arch, a 7,455 m cableway, 99-bend Tongtian Avenue, and over 5 million annual visitors.
Tiaojishan Formation
Tiaojishan Formation (髫髻山组), also called Lanqi Formation, a Middle-Late Jurassic andesitic volcanic and volcaniclastic unit in Beijing, Hebei, and Liaoning, China, about 165-153 Ma, hosting Yanliao Biota fossils including Anchiornis and Darwinopterus.
Tibesti Mountains
Tibesti Mountains (Tibesti Massif): volcanic range in the central Sahara, mostly northwestern Chad with extension into Libya and Niger; about 480 km long, 100,000 km2; Emi Koussi 3,415 m is the Sahara's highest point; Toubou homeland with ancient rock art.
Tibetan Plateau
Tibetan Plateau (青藏高原), the “Roof of the World” and “Third Pole”: Earth's highest, largest plateau (~2.5 million km², average ~4 km), formed by the India–Eurasia collision and headwaters of Asia's great rivers.
Tibidabo
Tibidabo: 512 m Barcelona hill, highest point of the Collserola range, home to the 1901 amusement park (second oldest in Europe) and the Sacred Heart basilica; name means "I shall give you".
Tidal flat
Tidal flat, also called mudflat or intertidal flat: a marsh, sandy, or muddy coastal flatland covered and uncovered by tides; at least 127,921 km² globally, rich in shorebirds, fisheries, and blue carbon.
Tidal island
Tidal island: land joined to the mainland or another island at low tide and cut off at high tide, via a bar, causeway, or road. Examples include Lindisfarne, St Michael's Mount, and Mont-Saint-Michel; Britain has 43 principal tidal islands.
Tierra del Fuego
Tierra del Fuego, the Land of Fire archipelago at South America's southern tip, split between Argentina and Chile since 1881, noted for its depauperate land fauna, Selk'nam and Yaghan peoples, and Ushuaia's Antarctic cruise hub.
Tihāmah
Tihāmah (Tihamah, تهامة), the "hot lands" coastal plain along Arabia's Red Sea coast in Saudi Arabia and Yemen, an arid wadi-irrigated agricultural belt with scanty pre-Islamic Sabaean remains and Himyarite, then Aksumite, control.
Tikopia
Tikopia is a small Polynesian outlier island in eastern Solomon Islands, home to a Polynesian-speaking people and famously documented by anthropologist Sir Raymond Firth from 1928.
Till
Till, also called glacial till, is unsorted, unstratified glacial sediment deposited directly by ice, a jumbled mix of clay to boulders, forming lodgement, melt-out, and traction tills and moraines.
Timor
Timor is the easternmost Lesser Sunda island, split between Indonesian West Timor and Timor-Leste (eastern half, plus Oecussi, Atauro, Jaco). Geologically a young Banda Arc collision; Timor-Leste joined ASEAN 2025 as oil revenues end.
Tinguiririca
Tinguiririca (Morro de Azufre) is a 4,280 m active stratovolcano in Chile's O'Higgins Andes, part of a NNE-aligned volcanic complex with a 1917 eruption, fumaroles, and a 57 km Late Pleistocene debris avalanche.
Tioga Pass
Tioga Pass, crossed by Tioga Road (Highway 120) in Yosemite National Park, is the highest auto pass in the Sierra Nevada. Seasonally open late May/June to November; built as the 1883 Great Sierra Wagon Road, reopened 1961.
Tipas
Tipas (Cerro Tipas, Walter Penk, Cazadero), a 6,658 m volcanic complex in Catamarca, Argentina, the world's third highest active volcano, SSW of Ojos del Salado, with no confirmed Holocene eruptions.
Tlayúa Formation
Tlayúa Formation, Tlayúa quarry, Cantera Tlayúa: Early Cretaceous (Albian, ~100 Ma) Konservat-Lagerstätte near Tepexi de Rodríguez, Puebla, Mexico, famed for exceptionally preserved fishes, reptiles, and invertebrates in laminated micritic limestones.
Tobago
Tobago, the smaller island of Trinidad and Tobago (also historically Bellaforma), lies 20 miles northeast of Trinidad, is dominated by the Main Ridge forest reserve, changed colonial hands repeatedly, and depends on tourism.
Tobira Jima
Tobira Jima (トビラ島) is a small 0.017 km² island off the Ichi settlement, Sumiyō-chō, Amami City, Kagoshima, Japan, at 28.2326°N 129.4456°E, known for a goddess legend and absence of habu snakes.
Tokachidake
Tokachidake (十勝岳) is an active 2,077 m basaltic-andesitic volcano group in central Hokkaido, Japan, site of the deadly 1926 Taisho Mudflow and eruptions in 1962 and 1988–89.