Earth Science, Geologic Time & Fossils, PSE-SAL

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.
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Earth Science, Geologic Time & Fossils Encyclopedia Articles By Title

pseudomorph
pseudomorph, mineral formed by chemical or structural change of another substance, though retaining its original......
Pseudoschwagerina
Pseudoschwagerina, extinct genus of fusulinid foraminiferans (single-celled animals with hard shells preservable......
psychrometer
psychrometer, a hygrometer composed of two similar thermometers. The bulb of one thermometer is kept wet (by means......
Pteranodon
Pteranodon, (genus Pteranodon), flying reptile (pterosaur) found as fossils in North American deposits dating from......
Pteraspis
Pteraspis, genus of extinct jawless fishlike vertebrates found as fossils in Early Devonian rocks (those 398 million......
pterodactyl
pterodactyl, informal term for a subgroup of flying reptiles (Pterosauria) known from the Late Jurassic through......
pterosaur
pterosaur, any of the flying reptiles that flourished during all periods (Triassic, Jurassic, and Cretaceous) of......
Ptilodus
Ptilodus, extinct genus of mammals found as fossils in deposits dated to the Paleocene Epoch (65.5–55.8 million......
Ptolemy
Ptolemy was an Egyptian astronomer, mathematician, and geographer of Greek descent who flourished in Alexandria......
pumice
pumice, a very porous, frothlike volcanic glass that has long been used as an abrasive in cleaning, polishing,......
Pumpelly, Raphael W.
Raphael W. Pumpelly was an American geologist and scientific explorer known for his studies and explorations of......
pycnocline
pycnocline, in oceanography, boundary separating two liquid layers of different densities. In oceans a large density......
Pycnodontiformes
Pycnodontiformes, order of extinct fishes of the class Actinopterygii, containing the genus Pycnodus, common in......
pyrargyrite
pyrargyrite, a sulfosalt mineral, a silver antimony sulfide (Ag3SbS3), that is an important source of silver, sometimes......
pyrite
pyrite, a naturally occurring iron disulfide mineral. The name comes from the Greek word pyr, “fire,” because pyrite......
pyrochlore
pyrochlore, a complex oxide mineral [(Na, Ca)2Nb2O6(OH,F)] composed of niobium, sodium, and calcium that forms......
pyroclastic flow
pyroclastic flow, in a volcanic eruption, a fluidized mixture of hot rock fragments, hot gases, and entrapped air......
pyroelectricity
pyroelectricity, development of opposite electrical charges on different parts of a crystal that is subjected to......
pyrolite
pyrolite, rock consisting of about three parts peridotite and one part basalt. The name was coined to explain the......
pyromorphite
pyromorphite, a phosphate mineral, lead chloride phosphate, [Pb5(PO4)3Cl], that is a minor ore of lead. It occurs......
pyrophyllite
pyrophyllite, very soft, pale-coloured silicate mineral, hydrated aluminum silicate, Al2(OH)2 Si4O10, that is the......
pyroxene
pyroxene, any of a group of important rock-forming silicate minerals of variable composition, among which calcium-,......
pyroxenite
pyroxenite, dark-coloured, intrusive igneous rock that consists chiefly of pyroxene. Pyroxenites are not abundant;......
pyrrhotite
pyrrhotite, iron sulfide mineral (Fe1–xS) in the niccolite group; in it, the ratio of iron to sulfur atoms is variable......
Pääbo, Svante
Svante Pääbo is a Swedish evolutionary geneticist who specialized in the study of DNA from ancient specimens and......
Qafzeh
Qafzeh, paleoanthropological site south of Nazareth, Israel, where some of the oldest remains of modern humans......
Qinghai earthquake of 2010
Qinghai earthquake of 2010, severe earthquake that occurred on April 14, 2010, in the isolated southern Yushu Tibetan......
quartz monzonite
quartz monzonite, intrusive igneous rock (solidified from a liquid state) that contains plagioclase feldspar, orthoclase......
quasi-biennial oscillation
quasi-biennial oscillation, layer of winds that encircle Earth’s lower stratosphere, at altitudes from 20 to 40......
Quaternary
Quaternary, in the geologic history of Earth, a unit of time within the Cenozoic Era, beginning 2,588,000 years......
Quenstedt, Friedrich August
Friedrich August Quenstedt was a German mineralogist and paleontologist. Quenstedt studied at the University of......
Quetzalcoatlus
Quetzalcoatlus, genus made up of two species of giant pterosaurs classified in the family Azhdarchidae, which contains......
quicksand
quicksand, state in which saturated sand loses its supporting capacity and acquires the character of a liquid.......
radiative forcing
radiative forcing, a measure, as defined by the Intergovernmental Panel on Climate Change (IPCC), of the influence......
radiosonde
radiosonde, balloon-borne instrument for making atmospheric measurements, such as temperature, pressure, and humidity,......
rain
rain, precipitation of liquid water drops with diameters greater than 0.5 mm (0.02 inch). When the drops are smaller,......
rainbow
rainbow, series of concentric coloured arcs that may be seen when light from a distant source—most commonly the......
rainmaking
rainmaking, any process of increasing the amount of precipitation discharged from a cloud. Primitive methods, such......
Ramapithecus
Ramapithecus, fossil primate dating from the Middle and Late Miocene epochs (about 16.6 million to 5.3 million......
Ramusio, Giovanni Battista
Giovanni Battista Ramusio was an Italian geographer who compiled an important collection of travel writings, Delle......
Ratzel, Friedrich
Friedrich Ratzel was a German geographer and ethnographer and a principal influence in the modern development of......
Read, Herbert Harold
Herbert Harold Read was a geologist known for his research on the origins of granite. A member of His Majesty’s......
realgar
realgar, an important ore of arsenic, a red or orange mineral containing both arsenic and sulfur. Typically it......
Reclus, Élisée
Élisée Reclus was a French geographer and anarchist who was awarded the gold medal of the Paris Geographical Society......
red snow
red snow, snow or ice surfaces, usually overlying soil on mountains, that are coloured by algae such as Chlamydomonas......
red soil
red soil, Any of a group of soils that develop in a warm, temperate, moist climate under deciduous or mixed forests......
reflection seismology
reflection seismology, analysis of vibrations caused by man-made explosions to determine Earth structures, generally......
regolith
regolith, a region of loose unconsolidated rock and dust that sits atop a layer of bedrock. On Earth, regolith......
Regosol
Regosol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
relative humidity
relative humidity, ratio of the actual vapour pressure of water in the air to that in air saturated with water......
remanent magnetism
remanent magnetism, the permanent magnetism in rocks, resulting from the orientation of the Earth’s magnetic field......
Rennell, James
James Rennell was the leading British geographer of his time. Rennell constructed the first nearly accurate map......
Rensselaeria
Rensselaeria, genus of extinct brachiopods (lamp shells) found as fossils in Lower Devonian marine rocks (387 to......
Resserella
Resserella, extinct genus of brachiopods (lamp shells) that occurs as fossils in marine rocks of Middle Ordovician......
Rhamphorhynchus
Rhamphorhynchus, (genus Rhamphorhynchus), flying reptile (pterosaurs) found as fossils from the Late Jurassic Period......
Rhipidistia
Rhipidistia, extinct group of lobe-finned bony fishes of the order Crossopterygii that included the ancestors of......
rhodochrosite
rhodochrosite, mineral, composed of manganese carbonate (MnCO3), that is a source of manganese for the ferromanganese......
Rhynchotrema
Rhynchotrema, extinct genus of brachiopods, or lamp shells, found as fossils in Middle and Late Ordovician rocks......
Rhynchotreta
Rhynchotreta, extinct genus of brachiopods (lamp shells) commonly found as fossils in Silurian marine rocks (between......
Rhynie plant
Rhynie plant, rootless, leafless, spore-bearing plant preserved in the Rhynie Chert, a mineral deposit that has......
rhyolite
rhyolite, extrusive igneous rock that is the volcanic equivalent of granite. Most rhyolites are porphyritic, indicating......
Richardson, Lewis Fry
Lewis Fry Richardson was a British physicist and psychologist who was the first to apply mathematical techniques......
Richter scale
Richter scale (ML), quantitative measure of an earthquake’s magnitude (size), devised in 1935 by American seismologists......
Richter, Charles F.
Charles F. Richter was an American physicist and seismologist who developed the Richter scale for measuring earthquake......
Richthofen, Ferdinand Paul Wilhelm, Freiherr von
Ferdinand Paul Wilhelm, baron von Richthofen was a German geographer and geologist who produced a major work on......
rickardite
rickardite, copper telluride mineral with the formula Cu7Te5, the purple-red masses of which resemble tarnished......
riebeckite
riebeckite, a sodium-iron silicate mineral [Na2Fe2+3Fe3+2Si8O22(OH)2] in the amphibole family. It forms part of......
rime
rime, white, opaque, granular deposit of ice crystals formed on objects that are at a temperature below the freezing......
Ring of Fire
Ring of Fire, long horseshoe-shaped seismically active belt of earthquake epicentres, volcanoes, and tectonic plate......
rip current
rip current, narrow jetlike stream of water that flows sporadically seaward for several minutes, in a direction......
ripple mark
ripple mark, one of a series of small marine, lake, or riverine topographic features, consisting of repeating wavelike......
Rittenhouse, David
David Rittenhouse was an American astronomer and inventor who was an early observer of the atmosphere of Venus.......
Ritter, Carl
Carl Ritter was a German geographer who was a cofounder, with Alexander von Humboldt, of modern geographical science.......
Riversleigh fossils
Riversleigh fossils, any of numerous assemblages of fossils found at Riversleigh Station, in northwestern Queensland,......
Robinson, Edward
Edward Robinson was an American biblical scholar, considered the father of biblical geography. Robinson graduated......
rock-forming mineral
rock-forming mineral, any mineral that forms igneous, sedimentary, or metamorphic rocks and that typically, or......
Rodinia
Rodinia, in geologic time, a supercontinent that incorporated almost all the landmasses on Earth for about 450......
Rogers, Henry Darwin
Henry Darwin Rogers was an American structural geologist who contributed much to the theory of mountain building......
rogue wave
rogue wave, a relatively unpredictable and unexpectedly high water wave arising at the water’s surface and formed......
romanechite
romanechite, barium and manganese oxide [(Ba, H2O)2(Mn4+, Mn3+)5O10], an important ore mineral of manganese. A......
Romer, Alfred Sherwood
Alfred Sherwood Romer was a U.S. paleontologist widely known for his concepts of evolutionary history of vertebrate......
Ronne Ice Shelf
Ronne Ice Shelf, large body of floating ice, lying at the head of the Weddell Sea, which is itself an indentation......
roof pendant
roof pendant, downward extension of the surrounding rock that protrudes into the upper surface of an igneous intrusive......
Rosenbusch, Karl Heinrich Ferdinand
Karl Heinrich Ferdinand Rosenbusch was a German geologist who laid the foundations of the science of microscopic......
Ross Ice Shelf
Ross Ice Shelf, world’s largest body of floating ice, lying at the head of Ross Sea, itself an enormous indentation......
Rossby, Carl-Gustaf Arvid
Carl-Gustaf Arvid Rossby was a Swedish American meteorologist whose innovations in the study of large-scale air......
Royal Geographical Society
Royal Geographical Society (RGS), British group founded as the Geographical Society of London in 1830. Its headquarters......
Rubey, William W.
William W. Rubey was a U.S. geologist known for his theory, proposed in 1951, of the origin of the Earth’s atmosphere,......
Ruffin, Edmund
Edmund Ruffin was known as the father of soil chemistry in the United States, who showed how to restore fertility......
Runcorn, Stanley Keith
Stanley Keith Runcorn was a British geophysicist whose pioneering studies of paleomagnetism provided early evidence......
runoff
runoff, in hydrology, quantity of water discharged in surface streams. Runoff includes not only the waters that......
Russell, Richard Joel
Richard Joel Russell was a geologist known for his studies of coastal morphology. He was a professor of geology......
Sabine, Edward
Edward Sabine was an Anglo-Irish astronomer and geodesist noted for his experiments in determining the shape of......
sabre-toothed cat
sabre-toothed cat, any of the extinct catlike carnivores belonging to either the extinct family Nimravidae or the......
Saccopastore skulls
Saccopastore skulls, two Neanderthal fossils found in 1929 and 1935 in a river deposit on the bank of a small tributary......
Saint Elmo’s fire
Saint Elmo’s fire, luminosity accompanying brushlike discharges of atmospheric electricity that sometimes appears......
Saint-Césaire
Saint-Césaire, paleoanthropological site in southwestern France where in 1979 the remains of a young adult male......
salinity
salinity, the amount of dissolved salts present in water. In natural bodies of water, salinity is most commonly......
salt dome
salt dome, largely subsurface geologic structure that consists of a vertical cylinder of salt (including halite......

Earth Science, Geologic Time & Fossils Encyclopedia Articles By Title