Earth Science, Geologic Time & Fossils, LA -MAR

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

La Niña
La Niña, cyclic counterpart to El Niño, consisting of a cooling of surface waters of the Pacific Ocean along the......
laccolith
laccolith, in geology, any of a type of igneous intrusion that has split apart two strata, resulting in a domelike......
Lacroix, Alfred
Alfred Lacroix was a French mineralogist whose Minéraux des roches (1888; “The Minerals of Rocks”), written with......
Lagar Velho
Lagar Velho, site near Leiria, central Portugal, where the buried skeleton of a four-year-old child, dating to......
lahar
lahar, mudflow of volcanic material. Lahars may carry all sizes of material from ash to large boulders and produce......
Lamont, Johann von
Johann von Lamont was a Scottish-born German astronomer noted for discovering that the magnetic field of the Earth......
lamprophyre
lamprophyre, any of a group of dark gray to black intrusive igneous rocks that generally occur as dikes (tabular......
Langley, Samuel Pierpont
Samuel Pierpont Langley was an American astrophysicist and aeronautical pioneer who developed new instruments with......
lapillus
lapillus, unconsolidated volcanic fragment with a diameter between 4 and 32 mm (0.16 and 1.26 inches) that was......
lapis lazuli
lapis lazuli, semiprecious stone valued for its deep blue colour. The source of the pigment ultramarine (q.v.),......
Lapworth, Charles
Charles Lapworth was an English geologist who proposed what came to be called the Ordovician Period (about 488......
Larsen Ice Shelf
Larsen Ice Shelf, ice shelf in the northwestern Weddell Sea, adjoining the east coast of the Antarctic Peninsula......
Lartet, Édouard
Édouard Lartet was a French geologist, archaeologist, and a principal founder of paleontology. He is credited chiefly......
last glacial maximum
last glacial maximum (LGM), the most recent geologic interval, which spanned 29,000 to 19,000 years ago, in which......
laterite
laterite, soil layer that is rich in iron oxide and derived from a wide variety of rocks weathering under strongly......
latite
latite, extrusive igneous rock very abundant in western North America. Usually coloured white, yellowish, pinkish,......
Laurasia
Laurasia, ancient continental mass in the Northern Hemisphere that included North America, Europe, and Asia (except......
lava
lava, magma (molten rock) emerging as a liquid onto Earth’s surface. The term lava is also used for the solidified......
lazulite
lazulite, phosphate mineral, a basic magnesium and aluminum phosphate [MgAl2 (PO4)2(OH)2], that often occurs as......
Le Moustier
Le Moustier, paleoanthropological and archaeological site in the Dordogne region of southwestern France that has......
leaching
leaching, in geology, loss of soluble substances and colloids from the top layer of soil by percolating precipitation.......
lead
lead (Pb), a soft, silvery white or grayish metal in Group 14 (IVa) of the periodic table. Lead is very malleable,......
Leake, William Martin
William Martin Leake was a British army officer, topographer, and antiquary whose surveys of ancient Greek sites......
Leakey, Louis
Louis Leakey was a Kenyan archaeologist and anthropologist, a member of the distinguished Leakey family of scholars......
Lebachia
Lebachia, a genus of extinct cone-bearing plants known from fossils of the Late Carboniferous and Early Permian......
lee cyclone
lee cyclone, small-scale cyclone that forms on the leeward, or downwind, side of mountain barriers as the general......
lee wave
lee wave, vertical undulation of airstreams on the lee side of a mountain. (The lee side is the side that is downstream......
Lehmann, Johann Gottlob
Johann Gottlob Lehmann was a German geologist who contributed to the development of stratigraphy, the scientific......
Leidy, Joseph
Joseph Leidy was a zoologist, one of the most distinguished and versatile scientists in the United States, who......
Lepidodendron
Lepidodendron, extinct genus of tree-sized lycopsid plants that lived during the Carboniferous Period (about 359......
Leptaena
Leptaena, genus of extinct brachiopods (lamp shells) commonly found as fossils in Ordovician to Lower Carboniferous......
Leptodesma
Leptodesma, extinct genus of pelecypods (clams) found as fossils in Silurian to Lower Carboniferous rocks (between......
Leptodus
Leptodus, extinct genus of articulate brachiopods, or lamp shells, of the Permian Period (299 million to 251 million......
Leptolepis
Leptolepis, genus of marine fishes very closely related to the first teleosts, the dominant group of fishes in......
Leptosol
Leptosol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
leucitite
leucitite, extrusive igneous rock, coloured ash gray to nearly black, that contains leucite and augite as large,......
Li Zhizao
Li Zhizao was a Chinese mathematician, astronomer, and geographer whose translations of European scientific books......
lightning
lightning, the visible discharge of electricity that occurs when a region of a cloud acquires an excess electrical......
limburgite
limburgite, dark-coloured volcanic rock that resembles basalt but normally contains no feldspar. It is associated......
limnology
limnology, subsystem of hydrology that deals with the scientific study of fresh waters, specifically those found......
Limnoscelis
Limnoscelis, extinct genus of tetrapod that appeared very close to the origin of amniotes (mammals, birds, or reptiles).......
Lindgren, Waldemar
Waldemar Lindgren was a Swedish-born American economic geologist noted for a system of ore classification that......
linnaeite
linnaeite, a cobalt sulfide mineral (Co3S4) or any member of a series of similar substances with the general formula......
Linoproductus
Linoproductus, genus of extinct articulate brachiopods (lamp shells) found throughout the midcontinent region of......
Lipalian interval
Lipalian interval, in geology, time span suggested in an attempt to explain the sudden appearance of abundant life......
Lisbon earthquake of 1755
Lisbon earthquake of 1755, series of earthquakes that occurred on the morning of Nov. 1, 1755, causing serious......
list of earthquakes
An earthquake is a sudden shaking of the ground caused by the passage of seismic waves through Earth’s rocks. Seismic......
litharge
litharge, one of two mineral forms of lead(II) oxide (PbO). It is found with the other form, massicot, as dull......
lithification
lithification, complex process whereby freshly deposited loose grains of sediment are converted into rock. Lithification......
lithiophilite
lithiophilite, common phosphate mineral [LiMnPO4] similar to triphylite...
lithosphere
lithosphere, rigid, rocky outer layer of Earth, consisting of the crust and the solid outermost layer of the upper......
litoptern
litoptern, (order Litopterna), any of various extinct hoofed mammals that first appeared in the Paleocene Epoch......
Little Ice Age
Little Ice Age (LIA), climate interval that occurred from the early 14th century through the mid-19th century,......
Lituites
Lituites, genus of extinct cephalopods (primitive animals related to the modern pearly nautilus) found as fossils......
Lixisol
Lixisol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
Llanocetus denticrenatus
Llanocetus denticrenatus, one of the earliest known baleen whales, sole member of the family Llanocetidae, suborder......
Lluc
Lluc, (Anoiapithecus brevirostris), nickname for the nearly complete upper and lower jaws and much of the associated......
loam
loam, Rich, friable (crumbly) soil with nearly equal parts of sand and silt, and somewhat less clay. The term is......
loellingite
loellingite, an iron arsenide mineral (FeAs2) that usually occurs with iron and copper sulfides in hydrothermal......
loess
loess, an unstratified, geologically recent deposit of silty or loamy material that is usually buff or yellowish......
Logan, Sir William Edmond
Sir William Edmond Logan was one of the foremost Canadian geologists of the 19th century. Logan was educated at......
Lonsdale, William
William Lonsdale was an English geologist and paleontologist whose studies of fossil corals suggested the existence......
lophophore hypothesis
lophophore hypothesis, viewpoint that conodonts, small toothlike structures found as fossils in marine rocks over......
Lophophyllum
Lophophyllum, extinct genus of solitary marine corals found as fossils especially characteristic of the Late Carboniferous......
Lophospira
Lophospira, genus of extinct gastropods (snails) found as fossils in marine rocks of Ordovician to Devonian age......
lopolith
lopolith, igneous intrusion associated with a structural basin, with contacts that are parallel to the bedding......
Lorelei
Lorelei, large rock on the bank at a narrows of the Rhine River near Sankt Goarshausen, Germany. The rock produces......
Lorenz, Edward
Edward Lorenz was an American meteorologist and discoverer of the underlying mechanism of deterministic chaos,......
Loxonema
Loxonema, genus of extinct gastropods (snails) found as fossils in rocks of Ordovician to Early Carboniferous age......
Lucy
Lucy, nickname for a remarkably complete (40 percent intact) hominin skeleton found by American paleoanthropologist......
Lugeon, Maurice
Maurice Lugeon was a Swiss geologist who provided the first comprehensive interpretation of the Alps as a whole.......
lustre
lustre, in mineralogy, the appearance of a mineral surface in terms of its light-reflective qualities. Lustre depends......
lutite
lutite, any fine-grained sedimentary rock consisting of clay- or silt-sized particles (less than 0.063 mm [0.0025......
Luvisol
Luvisol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO).......
Lyell, Charles
Charles Lyell was a Scottish geologist largely responsible for the general acceptance of the view that all features......
Lystrosaurus
Lystrosaurus, extinct genus of about seven species of medium-sized heavily built animals that lived from the middle......
L’Aquila earthquake of 2009
L’Aquila earthquake of 2009, severe earthquake that occurred on April 6, 2009, near the city of L’Aquila in the......
Mackinder, Halford
Halford Mackinder was a British political geographer noted for his work as an educator and for his geopolitical......
Maclurites
Maclurites, extinct genus of Ordovician gastropods (snails) found as fossils and useful for stratigraphic correlations......
Madden-Julian oscillation
Madden-Julian oscillation (MJO), intraseasonal fluctuation of atmospheric pressure over the equatorial Indian and......
mafic rock
mafic rock, in geology, igneous rock that is dominated by the silicates pyroxene, amphibole, olivine, and mica.......
Magellan, Ferdinand
Ferdinand Magellan was a Portuguese navigator and explorer who sailed under the flags of both Portugal (1505–13)......
maghemite
maghemite, an iron oxide mineral. It has a composition close to ferric oxide (Fe2O3) and exhibits strong magnetism......
magma
magma, molten or partially molten rock from which igneous rocks form. It usually consists of silicate liquid, although......
magnesite
magnesite, the mineral magnesium carbonate (MgCO3), a member of the calcite group of carbonate minerals that is......
magnetic survey
magnetic survey, one of the tools used by exploration geophysicists in their search for mineral-bearing ore bodies......
magnetosphere
magnetosphere, region in the atmosphere where magnetic phenomena and the high atmospheric conductivity caused by......
malachite
malachite, a minor ore but a widespread mineral of copper, basic copper carbonate, Cu2CO3(OH)2. Because of its......
Malte-Brun, Conrad
Conrad Malte-Brun was an author and coauthor of several geographies and a founder of the first modern geographic......
mammoth
mammoth, (genus Mammuthus), any member of an extinct group of elephants found as fossils in Pleistocene deposits......
Manabe Syukuro
Manabe Syukuro is a meteorologist who was awarded the Nobel Prize for Physics in 2021 for the foundational progress......
manganite
manganite, an ore mineral of manganese, basic manganese oxide [MnO(OH)] that forms dark gray to black crystal bundles......
mansfieldite
mansfieldite, arsenate mineral (AlAsO4·2H2O) similar to scorodite...
Mantell, Gideon Algernon
Gideon Algernon Mantell was a British physician, geologist, and paleontologist, who discovered four of the five......
Maqdisī, al-
al-Maqdisī was an Arab traveler, geographer, and author of a noted work based on personal observations of the populations,......
Marasuchus
Marasuchus, genus of archosaurian reptiles that inhabited part of present-day South America during the Ladinian......
marble
marble, granular limestone or dolomite (i.e., rock composed of calcium-magnesium carbonate) that has been recrystallized......
Marbut, Curtis Fletcher
Curtis Fletcher Marbut was an American geologist and authority on soils who worked closely with experts from many......
marcasite
marcasite, an iron sulfide mineral that forms pale bronze-yellow orthorhombic crystals, usually twinned to characteristic......

Earth Science, Geologic Time & Fossils Encyclopedia Articles By Title