Earth Science, Geologic Time & Fossils, THE-VOL
Planet Earth has billions of years of history, from the time when it was an inhospitable ball of hot magma to when its surface stabilized into a variety of diverse zones capable of supporting many life-forms. Many are the species that lived through the various geologic eras and left a trace of their existence in the fossils that we study today. But Earth is never done settling, as we can see from the earthquakes, tsunamis, volcanic eruptions, and other phenomena manifested in Earth’s crust, oceans, and atmosphere.
Earth Science, Geologic Time & Fossils Encyclopedia Articles By Title
Theodossia
Theodossia, genus of extinct brachiopods (lamp shells) the fossils of which are restricted to Early Devonian marine......
theralite
theralite, any member of a group of intrusive igneous rocks that contain labradorite (basic plagioclase feldspar),......
therapsid
therapsid, any member of the Therapsida, a major clade of tetrapods that lived during Permian and Triassic time......
therizinosaur
therizinosaur, group of theropod dinosaurs that lived during the Late Cretaceous (roughly 100 million to 66 million......
thermocline
thermocline, oceanic water layer in which water temperature decreases rapidly with increasing depth. A widespread......
thermohaline circulation
thermohaline circulation (THC), the component of general oceanic circulation controlled by horizontal differences......
thermonatrite
thermonatrite, a carbonate mineral, hydrated sodium carbonate (Na2CO3·H2O), found near saline lakes as an evaporation......
Thermosphere
Thermosphere, region of increasing temperature in Earth’s atmosphere that is located above the mesosphere. The......
theropod
theropod, any member of the dinosaur subgroup Theropoda, which includes all the flesh-eating dinosaurs. Theropods......
Thompson, David
David Thompson was an English explorer, geographer, and fur trader in the western parts of what are now Canada......
thorite
thorite, thorium silicate, ThSiO4, one of the most important thorium minerals. Almost always altered by hydration,......
Thrinaxodon
Thrinaxodon, extinct genus of cynodont, a close mammal relative, found as fossils in continental deposits formed......
thunderstorm
thunderstorm, a violent short-lived weather disturbance that is almost always associated with lightning, thunder,......
tidal bore
tidal bore, body of water that, during exceptionally high sea tides, rushes up some rivers and estuaries near a......
tide
tide, any of the cyclic deformations of one astronomical body caused by the gravitational forces exerted by others.......
Tiktaalik roseae
Tiktaalik roseae, an extinct fishlike aquatic animal that lived about 380–385 million years ago (during the earliest......
tillite
tillite, sedimentary rock that consists of consolidated masses of unweathered blocks (large, angular, detached......
Timeline of Climate Change
This infographic presents a timeline of climate change. A detailed description of this infographic appears below.......
tin
tin (Sn), a chemical element belonging to the carbon family, Group 14 (IVa) of the periodic table. It is a soft,......
tincalconite
tincalconite, a borate mineral, hydrated sodium tetraborate (Na2B4O5(OH)4·3H2O), that is found in nature only as......
tinguaite
tinguaite, pale- to dark-green, very fine-grained igneous rock that may be considered the dike (tabular body injected......
TIROS
TIROS, any of a series of U.S. meteorological satellites, the first of which was launched on April 1, 1960. The......
Titan
Titan, the largest moon of Saturn and the only moon in the solar system known to have clouds and a dense atmosphere.......
titanite
titanite, titanium and calcium silicate mineral, CaTiSiO4(O,OH,F), that, in a crystallized or compact form, makes......
Titanoboa
Titanoboa, (Titanoboa cerrejonensis), extinct snake that lived during the Paleocene Epoch (66 million to 56 million......
titanosaur
titanosaur, (clade Titanosauria), diverse group of sauropod dinosaurs classified in the clade Titanosauria, which......
Titanosaurs: 8 of the World’s Biggest Dinosaurs
In terms of mass, Earth’s largest mammal is the blue whale (Balaenoptera musculus). Weighing approximately 136......
titanothere
titanothere, any member of an extinct group of large-hoofed mammals that originated in Asia or North America during......
Today in History—April 14: The Volcanic Eruption That Grounded a Continent
On this day in 2010, Iceland’s Eyjafjallajökull volcano erupted in earnest. Small earthquakes had been rumbling......
Today in History—August 24: A Buried City Keeps Surprising Us
We still have questions about the eruption of Mount Vesuvius that doomed Pompeii—even though the study of its site......
Today in History—December 18: Piltdown Man: The Missing Link That Wasn’t
At a meeting of the Geological Society of London on this day in 1912, respected paleontologist Arthur Smith Woodward......
Today in History—March 29: A Woman Discovers Earth’s Core
The Danish seismologist who discovered Earth’s inner core built her theory using cardboard oatmeal boxes filled......
Tokyo-Yokohama earthquake of 1923
Tokyo-Yokohama earthquake of 1923, earthquake with a magnitude of 7.9 that struck the Tokyo-Yokohama metropolitan......
topaz
topaz, silicate mineral that is valued as a gemstone. It is believed that the topaz of modern mineralogists was......
torbernite
torbernite, hydrated copper uranate phosphate mineral, Cu(UO2)2(PO4)2·8–12H2O, that is one of the principal uranium-bearing......
tornado
tornado, a small-diameter column of violently rotating air developed within a convective cloud and in contact with......
Tornoceras
Tornoceras, extinct genus of cephalopods, forms related to the modern pearly nautilus. Tornoceras is a form that......
tourmaline
tourmaline, borosilicate mineral of complex and variable composition. Three types of tourmaline, distinguished......
Toxodon
Toxodon, extinct genus of mammals of the late Pliocene and the Pleistocene Epoch (about 3.6 million to 11,700 years......
trachyte
trachyte, light-coloured, very fine-grained extrusive igneous rock that is composed chiefly of alkali feldspar......
transform fault
transform fault, in geology and oceanography, a type of fault in which two tectonic plates slide past one another.......
Trepostomata
Trepostomata, extinct order of bryozoans (moss animals) found as fossils in marine rocks of Ordovician to Triassic......
Triassic Period
Triassic Period, in geologic time, the first period of the Mesozoic Era. It began 252 million years ago, at the......
Triconodon
Triconodon, genus of extinct mammals found in European deposits of the late Jurassic Period (about 161 million–146......
trilobite
trilobite, any member of a group of extinct fossil arthropods easily recognized by their distinctive three-lobed,......
triphylite
triphylite, common phosphate mineral, lithium iron phosphate (LiFePO4), usually forming bluish or grayish, glassy......
triplite
triplite, phosphate mineral, consisting of manganese, iron, magnesium, and calcium phosphate [(Mn, Fe, Mg, Ca)2PO4(F,OH)].......
Triton
Triton, U.S. nuclear-powered submarine that was the first vessel to circumnavigate the globe underwater. The Triton......
tritylodont
tritylodont, any member of a genus (Tritylodon) of extinct cynodont therapsids (mammal relatives) found as fossils......
Trochonema
Trochonema, genus of extinct gastropods (snails) found as fossils in rocks dating from the Ordovician Period to......
troctolite
troctolite, coarse-grained, intrusive igneous rock that is composed almost entirely of olivine (often iron-rich)......
troilite
troilite, variety of the iron sulfide mineral pyrrhotite (q.v.) present in...
trona
trona, an evaporite mineral, hydrated sodium bicarbonate [Na3H(CO3)2·2H2O], occasionally encountered as a saline......
Tropical and subtropical desert climate
Tropical and subtropical desert climate, major climate type of the Köppen classification dominated in all months......
Tropical and subtropical steppe climate
Tropical and subtropical steppe climate, major climate type of the Köppen classification that occurs primarily......
tropical cyclone
tropical cyclone, an intense circular storm that originates over warm tropical oceans and is characterized by low......
Tropical monsoon and trade-wind littoral climate
Tropical monsoon and trade-wind littoral climate, major climate type of the Köppen classification characterized......
tropical storm
tropical storm, organized centre of low pressure that originates over warm tropical oceans. The maximum sustained......
Tropical wet-dry climate
Tropical wet-dry climate, major climate type of the Köppen classification characterized by distinct wet and dry......
Tropidoleptus
Tropidoleptus, genus of extinct brachiopods (lamp shells) found as fossils only in marine rocks of the Devonian......
Tropites
Tropites, genus of extinct cephalopods (animals similar to the modern squid and octopus but with an external shell)......
Troposphere
Troposphere, lowest region of the atmosphere, bounded by the Earth beneath and the stratosphere above, with its......
tsunami
tsunami, catastrophic ocean wave, usually caused by a submarine earthquake, an underwater or coastal landslide,......
tuff
tuff, a relatively soft, porous rock that is usually formed by the compaction and cementation of volcanic ash or......
Tundra climate
Tundra climate, major climate type of the Köppen classification characterized by sub-freezing mean annual temperatures,......
turquoise
turquoise, hydrated copper and aluminum phosphate [CuAl6(PO4)4(OH)8·4H2O] that is extensively used as a gemstone.......
Twenhofel, William Henry
William Henry Twenhofel was a geologist noted for his investigations of sedimentation processes. He taught at the......
Twilight glow
Twilight glow, weak, widespread, and relatively steady glow from the sky that is observed around twilight; it is......
Tyndall, John
John Tyndall was an Irish experimental physicist who, during his long residence in England, was an avid promoter......
tyuyamunite
tyuyamunite, radioactive, yellow, soft, and waxy uranium and vanadium oxide mineral, Ca(UO2)2(VO4)2·5–8H2O. It......
Törnebohm, Alfred Elis
Alfred Elis Törnebohm was a Swedish geologist and pioneer in the study and analysis of mountain structure. In 1888,......
Uintatherium
Uintatherium, extinct genus of large, hoofed mammals found as fossils in North America and Asia in terrestrial......
ulexite
ulexite, borate mineral, NaCaB5O6(ΟH)6·5H2O, that consists of hydrated sodium and calcium borate. Individual crystals......
Ultisol
Ultisol, one of the 12 soil orders in the U.S. Soil Taxonomy. Ultisols are reddish, clay-rich, acidic soils that......
umangite
umangite, a copper selenide (Cu3Se2) occurring only in small grains or fine granular aggregates with other copper......
Umbrisol
Umbrisol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
undertow
undertow, a strong seaward bottom current returning the water of broken waves back out to sea. There is in fact......
Ungava-Quebec Crater
Ungava-Quebec Crater, geologically young crater, produced by an impact event involving a meteorite, located in......
uniformitarianism
uniformitarianism, in geology, the doctrine suggesting that Earth’s geologic processes acted in the same manner......
Updraft and downdraftdowndraft
Updraft and downdraftdowndraft, in meteorology, upward-moving and downward-moving air currents, respectively, that......
uplift
uplift, in geology, an increase in the vertical elevation of Earth’s surface in response to natural causes. Broad,......
urban climate
urban climate, any set of climatic conditions that prevails in a large metropolitan area and that differs from......
vadose zone
vadose zone, region of aeration above the water table. This zone also includes the capillary fringe above the water......
Van Allen radiation belt
Van Allen radiation belt, doughnut-shaped zones of highly energetic charged particles trapped at high altitudes......
Van earthquake of 2011
Van earthquake of 2011, severe earthquake that struck near the cities of Erciş and Van in eastern Turkey on October......
vanadate mineral
vanadate mineral, any of the many naturally occurring compounds of vanadium (V), oxygen (O), and various metals;......
vanadinite
vanadinite, vanadium mineral in the pyromorphite series of the apatite group of phosphates, lead chloride vanadate,......
Varenius, Bernhardus
Bernhardus Varenius was a major figure in the revival of geographic learning in Europe, whose scholarly general......
variscite
variscite, phosphate mineral, hydrated aluminum phosphate (AlPO4·2H2O), which is valued as a semiprecious gemstone......
varved deposit
varved deposit, any form of repetitive sedimentary rock stratification, either bed or lamination, that was deposited......
Venezuelan earthquakes of 2026
Venezuelan earthquakes of 2026, a pair of severe earthquakes that struck northwestern Venezuela on June 24, 2026,......
Venyukovia
Venyukovia, genus of extinct mammallike reptiles (therapsids) that are found as fossils in Permian deposits in......
Vertisol
Vertisol, one of the 12 soil orders in the U.S. Soil Taxonomy. Vertisols are clay-rich soils that undergo significant......
Vertisol
Vertisol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
vesuvianite
vesuvianite, common silicate mineral that occurs in crystalline limestones near their contacts with igneous rocks,......
Vidal de La Blache, Paul
Paul Vidal de La Blache was a French geographer who had a profound influence on the development of modern geography.......
Vindija
Vindija, site of paleoanthropological excavations in the Hrvatsko Zagorje region of Croatia, known for Neanderthal......
vivianite
vivianite, phosphate mineral, hydrated iron phosphate [Fe3(PO4)2·8H2O], that occurs as colourless when freshly......
Vogt, Johan Herman Lie
Johan Herman Lie Vogt was a Norwegian geologist and petrologist who pioneered in the use of physical-chemical methods......
volcanic eruption
volcanic eruption, an eruption of molten rock, hot rock fragments, and hot gases through a volcano, which is a......