Book Glossary Flashcards - Historical_Geology
The origin of life from nonliving matter.
Abiogenesis
A widespread succession of Pennsylvanian and Permian sedimentary rocks bounded above and below by unconformities; deposited during a transgressive–regressive cycle of the Absaroka Sea.
Absaroka Sequence
Assigning an age in years before the present to geologic events; absolute dates are determined by radioactive decay dating techniques.
Absolute dating
A Devonian episode of mountain building in the northern Appalachian mobile belt resulting from a collision of Baltica with Laurentia.
Acadian orogeny
Pennsylvanian to Permian mountain building in the Appalachian mobile belt from New York to Alabama.
Alleghenian orogeny
A variant form of a single gene.
Allele
Model for the origin of a new species from a small population that became isolated from its parent population.
Allopatric speciation
A cone-shaped accumulation of mostly sand and gravel where a stream flows from a mountain valley onto an adjacent lowland.
Alluvial fan
A linear zone of deformation extending from the Atlantic eastward across southern Europe and North Africa, through the Middle East and into Southeast Asia.
Alpine–Himalayan orogenic belt
A Late Mesozoic–Early Cenozoic episode of mountain building affecting southern Europe and North Africa.
Alpine orogeny
An egg in which an embryo develops in a liquid-filled cavity (the amnion); and a waste sac is present as well as a yolk sac for nourishment.
Amniote egg
Refers to organisms that do not depend on oxygen for respiration.
Anaerobic
Body part, such as wings of insects and birds, that serves the same function but differs in structure and development.
Analogous structure
Late Paleozoic uplift in the southwestern part of the North American craton.
Ancestral Rockies
Any member of the primate suborder Anthropoidea; includes New World and Old World monkeys, apes, and humans.
Anthropoid
A Late Devonian to Mississippian episode of mountain building that affected the Cordilleran mobile belt from Nevada to Alberta, Canada.
Antler orogeny
A long narrow region of tectonic activity along the eastern margin of the North American craton extending from Newfoundland to Georgia.
Appalachian mobile belt
The oldest positively identified fossil bird; it had feathers but retained many reptile characteristics; from Jurassic rocks in Germany.
Archaeopteryx
A term referring to the ruling reptiles—dinosaurs, pterosaurs, crocodiles, and birds.
Archosaur
The practice of selectively breeding plants and animals with desirable traits.
Artificial selection
The mammalian order whose members have two or four toes; the even-toed hoofed mammals such as deer, goats, sheep, antelope, bison, swine, and camels.
Artiodactyla
Part of the upper mantle over which the lithosphere moves; it behaves as a plastic and flows.
Asthenosphere
The broad, low relief area of eastern North America extending from the Appalachian Mountains to the Atlantic shoreline.
Atlantic Coastal Plain
The smallest unit of matter that retains the characteristics of an element.
Atom
The total number of protons and neutrons in an atom’s nucleus.
Atomic mass number
The number of protons in an atom’s nucleus.
Atomic number
A collective term for all species of the extinct genus Australopithecus that existed in South Africa during the Pliocene and Pleistocene.
Australopithecine
Describes organisms that synthesize their organic nutrients from inorganic raw materials; photosynthesizing bacteria and plants are autotrophs.
Autotrophic
A marine basin, such as the Sea of Japan, between a volcanic island arc and a continent; probably forms by back-arc spreading.
Back-arc marginal basin
One of six major Paleozoic continents; composed of Russia west of the Ural Mountains, Scandinavia, Poland, and northern Germany.
Baltica
Sedimentary rocks made up of alternating thin layers of chert and iron minerals, mostly the iron oxides hematite and magnetite.
Banded iron formation (BIF)
A long sand body more or less parallel with a shoreline but separated from it by a lagoon.
Barrier island
An area of Cenozoic block-faulting centered on Nevada but extending into adjacent states and northern Mexico.
Basin and Range Province
All bottom-dwelling marine organisms that live on the seafloor or within seafloor sediments.
Benthos
A theory for the evolution of the universe from a dense, hot state followed by expansion, cooling, and a less dense state.
Big Bang
Any feature such as tracks, trails, and burrows in sedimentary rocks produced by the activities of organisms.
Biogenic sedimentary structure
The churning of sediment by organisms that burrow through it.
Bioturbation
A unit of sedimentary rock defined solely by its fossil content.
Biostratigraphic unit
All biostratigraphic units such as range zones and concurrent range zones.
Biozone
Walking on two legs as a means of locomotion as in birds and humans.
Bipedal
A submarine hydrothermal vent that emits a plume of black water colored by dissolved minerals.
Black smoker
The shells, teeth, bones, or (rarely) the soft parts of organisms preserved in the fossil record.
Body fossil
The processes whereby atoms join with other atoms.
Bonding
Members of the class Osteichthyes that evolved during the Devonian; characterized by a bony internal skeleton; includes the ray-finned fishes and the lobe-finned fishes.
Bony fish
A stream with an intricate network of dividing and rejoining channels.
Braided stream
An animal that eats tender shoots, twigs, and leaves.
Browser
A Silurian–Devonian episode of mountain building that took place along the northwestern margin of Baltica, resulting from the collision of Baltica with Laurentia.
Caledonian orogeny
The Precambrian shield in North America; mostly in Canada but also exposed in Minnesota, Wisconsin, Michigan, and New York.
Canadian shield
An absolute dating technique relying on the ratio of C14 to C12 in organic substances; useful back to about 70,000 years ago.
Carbon 14 dating
Any mineral with the negatively charged carbonate ion (CO3)-2 (e.g., calcite [CaCO3] and dolomite [CaMg(CO3)2]).
Carbonate mineral
Any rock composed mostly of carbonate minerals (such as limestone and dolostone).
Carbonate rock
A pair of specialized shearing teeth in members of the mammal order Carnivora.
Carnassials
An order of mammals consisting of meat eaters such as dogs, cats, bears, weasels, and seals.
Carnivora
Any animal that eats other animals, living or dead, as a source of nutrients.
Carnivore-scavenger
Fish such as living sharks and their living and extinct relatives that have an internal skeleton of cartilage.
Cartilaginous fish
A mountain range made up of volcanic rock stretching from northern California through Oregon and Washington and into British Columbia, Canada.
Cascade Range
A replica of an object such as a shell or bone formed when a mold of that object is filled by sediment or minerals.
Cast
A concept proposed by Baron Georges Cuvier explaining Earth’s physical and biologic history by sudden, worldwide catastrophes; also holds that geologic processes acted with much greater intensity during the past.
Catastrophism
A Devonian clastic wedge deposited adjacent to the highlands that formed during the Acadian orogeny.
Catskill Delta
The mammal order that includes whales, porpoises, and dolphins.
Cetacea
Rock formed of minerals derived from materials dissolved during weathering.
Chemical sedimentary rock
One of six major Paleozoic continents; composed of all Southeast Asia, including China, Indochina, part of Thailand, and the Malay Peninsula.
China
Any member of the phylum Chordata, all of which have a notochord, dorsal hollow nerve cord, and gill slits at some time during their life cycle.
Chordate
Complex, double-stranded, helical molecule of deoxyribonucleic acid (DNA); specific segments of chromosome are genes.
Chromosome
One of two major Mesozoic-Cenozoic areas of large-scale deformation and the origin of mountains; includes orogens in South and Central America, the North American Cordillera, and the Aleutian, Japan, and Philippine arcs.
Circum-Pacific orogenic belt
A steep-walled, bowl-shaped depression formed on a mountainside by glacial erosion.
Cirque
A type of analysis of organisms in which they are grouped together on the basis of derived as opposed to primitive characteristics.
Cladistics
A diagram showing the relationships among members of a clade, including their most recent common ancestor.
Cladogram
An extensive accumulation of mostly detrital sedimentary rocks eroded from and deposited adjacent to an area of uplift, as in the Catskill Delta or Queenston Delta.
Clastic wedge
A vast upland area in Colorado, Utah, Arizona, and New Mexico with only slightly deformed Phanerozoic rocks, deep canyons, and volcanic mountains.
Colorado Plateau
A substance made up of different atoms bonded together (such as water [H2O] and quartz [SiO2]).
Compound
A biozone established by plotting the overlapping geologic ranges of fossils.
Concurrent range zone
Refers to a sequence of sedimentary rocks deposited one after the other with no or only minor discontinuities resulting from nondeposition or erosion.
Conformable
Metamorphism taking place adjacent to a body of magma (a pluton) or beneath a lava flow from heat and chemically active fluids.
Contact metamorphism
The process whereby continents grow by additions of Earth materials along their margins.
Continental accretion
A convergent plate boundary along which two continental lithospheric plates collide, such as the collision of India with Asia.
Continental–continental plate boundary
The theory proposed by Alfred Wegener that all continents were once joined into a single landmass that broke apart with the various fragments (continents) moving with respect to one another.
Continental drift
A glacier covering at least 50,000 km2 and unconfined by topography. Also called an ice sheet.
Continental glacier
An area in North America made up of the Great Plains and the Central Lowlands, bounded by the Rocky Mountains, the Canadian shield, the Appalachian Mountains, and parts of the Gulf Coastal Plain.
Continental interior
Red-colored rock, especially mudrock and sandstone, on the continents. Iron oxides account for their color.
Continental red bed
The gently sloping part of the seafloor lying between the base of the continental slope and the deep seafloor.
Continental rise
The area where the seafloor slopes gently seaward between a shoreline and the continental slope.
Continental shelf
The relatively steep part of the seafloor between the continental shelf and continental rise or an oceanic trench.
Continental slope
The origin of similar features in distantly related organisms as they adapt in comparable ways, such as ichthyosaurs and porpoises.
Convergent evolution
The boundary between two plates that move toward one another.
Convergent plate boundary
An area of extensive deformation in western North America bounded by the Pacific Ocean and the Great Plains; it extends north–south from Alaska into central Mexico.
Cordilleran mobile belt
A period of deformation affecting the western part of North America from Jurassic to Early Cenozoic time; divided into three phases known as the Nevadan, Sevier, and Laramide orogenies.
Cordilleran orogeny
The inner part of Earth from a depth of about 2900 km consisting of a liquid outer part and a solid inner part; probably composed mostly of iron and nickel.
Core
Demonstration of the physical continuity of stratigraphic units over an area; also matching up time-equivalent events in different areas.
Correlation
Name applied to a stable nucleus of a continent consisting of a Precambrian shield and a platform of buried ancient rocks.
Craton
A widespread association of sedimentary rocks bounded above and below by unconformities that were deposited during a transgressive–regressive cycle of an epeiric sea, such as the Sauk Sequence.
Cratonic sequence
A Late Cretaceous arm of the sea that effectively divided North America into two large landmasses.
Cretaceous Interior Seaway
A race of Homo sapiens that lived mostly in Europe from 35,000 to 10,000 years ago.
Cro-Magnon
A type of bedding in which individual layers are deposited at an angle to the surface on which they accumulate, as in sand dunes.
Cross-bedding
A specific type of lobe-finned fish that had lungs.
Crossopterygian
The upper part of Earth’s lithosphere, which is separated from the mantle by the Moho; consists of continental crust with an overall granitic composition and thinner, denser oceanic crust made up of basalt and gabbro.
Crust
A solid with its atoms arranged in a regular three-dimensional framework.
Crystalline solid
The temperature at which iron-bearing minerals in a cooling magma attain their magnetism.
Curie point
A sequence of cyclically repeated sedimentary rocks resulting from alternating periods of marine and nonmarine deposition; commonly contain a coal bed.
Cyclothem
A type of therapsid (advanced mammal-like reptile); ancestors of mammals are among the cynodonts.
Cynodont
A deposit of sediment where a stream or river enters a lake or the ocean.
Delta
The chemical substance of which chromosomes are composed.
Deoxyribonucleic acid (DNA)
Any area where sediment is deposited; a depositional site where physical, chemical, and biological processes operate to yield a distinctive kind of deposit.
Depositional environment
Rock made up of the solid particles derived from pre-existing rocks as in sandstone.
Detrital sedimentary rock
Any of the Mesozoic reptiles belonging to the orders Saurischia and Ornithischia.
Dinosaur
A type of unconformity above and below which the strata are parallel.
Disconformity
The diversification of a species into two or more descendant species.
Divergent evolution
The boundary between two plates that move apart; characterized by seismicity, volcanism, and the origin of new oceanic lithosphere.
Divergent plate boundary
A collective term for all sediment deposited by glacial activity; includes till deposited directly by ice, and outwash deposited by streams discharging from glaciers.
Drift
Metamorphism in fault zones where rocks are subjected to high differential pressure.
Dynamic metamorphism
Any of the cold-blooded vertebrates such as amphibians and reptiles; animals that depend on external heat
Ectotherm
Name for all Late Proterozoic faunas with animal fossils similar to those of the Ediacara fauna of Australia.
Ediacaran fauna
A substance composed of only one kind of atom (such as calcium [Ca] or silicon [Si]).
Element
A pile or ridge of rubble deposited at the terminus of a glacier.
End moraine
A type of mutually beneficial symbiosis in which one symbiont lives within the other.
Endosymbiosis
Any of the warm-blooded vertebrates such as birds and mammals who maintain their body temperature within narrow limits by internal processes.
Endotherm
A broad shallow sea that covers part of a continent; six epeiric seas were present in North America during the Phanerozoic Eon, such as the Sauk Sea.
Epeiric sea
A cell with an internal membrane-bounded nucleus containing chromosomes and other internal structures such as mitochondria that are not present in prokaryotic cells.
Eukaryotic cell
Sedimentary rock formed by inorganic chemical precipitation from evaporating water (for example, rock salt and rock gypsum).
Evaporite
An igneous rock that forms as lava cools and crystallizes or when pyroclastic materials are consolidated.
Extrusive igneous rock
A Late Mesozoic–Cenozoic oceanic plate that was largely subducted beneath North America; the Cocos and Juan de Fuca plates are remnants.
Farallon plate
The dating process in which small linear tracks (fission tracks) resulting from alpha decay are counted in mineral crystals.
Fission-track dating
Relating to streams and rivers and their deposits.
Fluvial
The basic lithostratigraphic unit; a mappable unit of strata with distinctive upper and lower boundaries.
Formation
Remains or traces of prehistoric organisms preserved in rocks.
Fossil
A specific segment of a chromosome constituting the basic unit of heredity.
Gene
A diagram showing a composite column of rocks arranged with the oldest at the bottom followed upward by progressively younger rocks.
Geologic column
The record of prehistoric physical and biologic events preserved in rocks.
Geologic record
A chart arranged so that the designation for the earliest part of geologic time appears at the bottom followed upward by progressively younger
time designations.
Geologic time scale
A time of extensive glaciation that occurred several times in North America during the Pleistocene.
Glacial stage
A mass of ice on land that moves by plastic flow and basal slip.
Glacier
A Late Paleozoic association of plants found only on the Southern Hemisphere continents and India; named after its best-known genus, Glossopteris.
Glossopteris flora
One of six major Paleozoic continents; composed of South America, Africa, Australia, India, and parts of Southern Europe, Arabia, and Florida.
Gondwana
A sediment layer in which grain size decreases from the bottom up.
Graded bedding
One of the two main rock associations found in areas of Archean rocks.
Granite-gneiss complex
An animal that eats low-growing vegetation, especially grasses. (See browser.)
Grazer
A linear or podlike association of rocks particularly common in Archaean terranes; typically synclinal and consists of lower and middle volcanic units and an upper sedimentary unit.
Greenstone belt
An episode of deformation that took place in the eastern United States and Canada during the Neoproterozoic.
Grenville orogeny
Any easily identified fossil with a wide geographic distribution and short geologic range; useful for determining relative ages of strata in different areas.
Guide fossil
The broad low-relief area along the Gulf Coast of the United States.
Gulf Coastal Plain
A flowerless, seed-bearing plant.
Gymnosperm
The time necessary for one-half of the original number of radioactive atoms of an element to decay to a stable daughter product; for example, the half-life of potassium 40 is 1.3 billion years.
Half-life
An animal dependent on vegetation as a source of nutrients.
Herbivore
Pennsylvanian to Permian deformation in the Hercynian mobile belt of southern Europe.
Hercynian orogeny
Organism such as an animal that depends on preformed organic molecules from its environment for nutrients.
Heterotrophic
Abbreviated term for Hominidae, the family that includes bipedal primates such as Australopithecus and Homo.
Hominid
Abbreviated term for Hominoidea, the superfamily that includes apes and humans. (See hominid.)
Hominoid
The genus of hominids consisting of Homo sapiens and their ancestors Homo erectus and Homo habilis.
Homo
Body part in different organisms with a similar structure, similar relationships to other organs, and similar development but does not necessarily serve the same function; such as forelimbs in whales, bats, and dogs. (See analogous structure.)
Homologous structure
Localized zone of melting below the lithosphere; detected by volcanism at the surface.
Hot spot
A provisional explanation for observations that is subject to continual testing and modification if necessary. If well supported by evidence, hypotheses may become theories.
Hypothesis
A small Early Eocene mammal that was ancestral to today’s horses.
Hyracotherium
A Paleozoic ocean between North America and Europe; it eventually closed as North America and Europe moved toward one another and collided during the Late Paleozoic.
Iapetus Ocean
A dome-shaped mass of glacial ice covering less than 50,000 km2.
Ice cap
An area eroded by glaciers resulting in low-relief, extensive bedrock exposures with glacial polish and striations, and little soil.
Ice-scoured plain
Any of the porpoise-like, Mesozoic marine reptiles.
Ichthyosaur
Rock formed when magma or lava cools and crystallizes and when pyroclastic materials become consolidated.
Igneous rock
Jean-Baptiste de Lamarck’s mechanism for evolution; holds that characteristics acquired during an individual’s lifetime can be inherited by descendants.
Inheritance of acquired characteristics
A time of warmer temperatures between episodes of widespread glaciation.
Interglacial stage
Igneous rock that cools and crystallizes from magma intruded into or formed within the crust. (See plutonic rock.)
Intrusive igneous rock
The occurrence of a higher-than-usual concentration of the element iridium at the Cretaceous-Paleogene boundary.
Iridium anomaly
The concept of Earth’s crust “floating” on the more dense underlying mantle. As a result of isostasy, thicker, less dense continental crust stands higher than oceanic crust.
Isostasy
The phenomenon in which unloading of the crust causes it to rise, as when extensive glaciers melt, until it attains equilibrium.
Isostatic rebound
Any planet with a low mean density that resembles Jupiter (Jupiter, Saturn, Uranus, and Neptune); the Jovian planets, or gas giants, are composed largely of hydrogen, helium, and frozen compounds such as methane and ammonia. (See terrestrial planet.)
Jovian planet
A widespread association of Devonian and Mississippian sedimentary rocks bounded above and below by unconformities; deposited during a transgressive–regressive cycle of the Kaskaskia Sea.
Kaskaskia Sequence
One of six major Paleozoic continents; a triangular-shaped continent centered on Kazakhstan.
Kazakhstania
Any of the Devonian to Triassic amphibians characterized by complex folding in the enamel of their teeth.
labyrinthodont
Late Cretaceous to Early Paleogene phase of the Cordilleran orogeny; responsible for many of the structural features in the present-day Rocky Mountains.
Laramide orogeny
A Late Paleozoic, Northern Hemisphere continent made up of North America, Greenland, Europe, and Asia.
Laurasia
A Proterozoic continent composed mostly of North America and Greenland, parts of Scotland, and perhaps parts of the Baltic shield of Scandinavia.
Laurentia
Magma that reaches the surface.
lava
The process of converting sediment into sedimentary rock.
lithification
The outer, rigid part of Earth consisting of the upper mantle, oceanic crust, and continental crust; lies above the asthenosphere.
lithosphere
A body of sedimentary rock, such as a formation, defined solely by its physical attributes.
lithostratigraphic unit
An interval from about 1500 to the mid- to late-1800s during which glaciers expanded to their greatest historic extent.
Little Ice Age
An existing organism that has descended from ancient ancestors with little apparent change.
living fossil
Fish with limbs containing a fleshy shaft and a series of articulating bones; one of the two main groups of bony fish.
lobe-finned fish
Evolutionary changes that account for the origin of new species, genera, orders, and so on. (See microevolution.)
macroevolution
Molten rock material below the surface.
magma
Any change, such as the average strength, in Earth’s magnetic field.
magnetic anomaly
The phenomenon involving the complete reversal of the north and south magnetic poles.
magnetic reversal
The inner part of Earth surrounding the core, accounting for about 85% of the planet’s volume; probably composed of peridotite.
mantle
Withdrawal of the sea from a continent or coastal area resulting from emergence of the land with a resulting seaward migration of the shoreline.
marine regression
Invasion of a coastal area or much of a continent by the sea as sea level rises resulting in a landward migration of the shoreline.
marine transgression
The pouched mammals such as wombats and kangaroos that give birth to young in a very immature state.
marsupial mammal
Greatly accelerated extinction rates resulting in marked decrease in biodiversity, such as the mass extinction at the end of the Cretaceous.
mass extinction
A stream with a single, sinuous channel with broadly looping curves.
meandering stream
Cell division yielding sex cells, sperm and eggs in animals, and pollen and ovules in plants, in which the number of chromosomes is reduced by half. (See mitosis.)
meiosis
Any rock altered in the solid state from preexisting rocks by any combination of heat, pressure, and chemically active fluids.
metamorphic rock
Evolutionary changes within a species. (See macroevolution.)
microevolution
A Mesoproterozoic intracontinental rift in Laurentia in which volcanic and sedimentary rocks accumulated.
Midcontinent rift
A theory that explains cyclic variations in climate and the onset of glacial episodes triggered by irregularities in Earth’s rotation and orbit.
Milankovitch theory
Naturally occurring, inorganic, crystalline solid, having characteristic physical properties and a narrowly defined chemical composition.
mineral
Cell division resulting in two cells with the same number of chromosomes as the parent cell; takes place in all cells except sex cells. (See meiosis.)
mitosis
Elongated area of deformation generally at the margins of a craton, such as the Appalachian mobile belt.
mobile belt
A combination of ideas of various scientists yielding a view of evolution that includes the chromosome theory of inheritance, mutations as a source of variation, and gradualism. It also rejects inheritance of acquired characteristics.
modern synthesis
Any of a mammal’s teeth that are used for grinding and chewing.
molar
An evolutionary trend in hoofed mammals in which the premolars become more like molars, giving the animals a continuous series of grinding teeth.
molarization
A cavity or impression of some kind of organic remains such as a bone or shell in sediment or sedimentary rock. (See cast.)
mold
A comparatively simple organic molecule, such as an amino acid, that can link with other monomers to form more complex polymers such as proteins. (See polymer.)
monomer
The egg-laying mammals; includes only the platypus and spiny anteater of the Australian region.
monotreme
A ridge or mound of unsorted, unstratified debris deposited by a glacier.
moraine
The concept holding that not all parts of an organism evolve at the same rate, thus yielding organisms with features retained from the ancestral condition as well as more recently evolved features.
mosaic evolution
A term referring to a group of Mesozoic marine lizards.
mosasaur
A crack in clay-rich sediment that forms in response to drying and shrinkage.
mud crack
Organism made up of many cells as opposed to a single cell; possesses cells specialized to perform specific functions.
multicellular organism
Any change in the genes of organisms; yields some of the variation on which natural selection acts.
mutation
A mechanism accounting for differential survival and reproduction among members of a species; the mechanism proposed by Charles Darwin and Alfred Wallace to account for evolution.
Natural selection
A type of human that inhabited the Near East and Europe from 200,000 to 30,000 years ago; may be a subspecies (Homo sapiens neanderthalensis) of Homo or a separate species (Homo neanderthalensis).
Neanderthal
Actively swimming organisms, such as fish, whales, and squid. (See plankton.)
nekton
An episode in Earth history from about 6000 years ago until the mid to late 1800s during which three periods of glacial expansion took place.
neoglaciation
The discarded concept held by Abraham Gottlob Werner and others that all rocks formed in a specific order by precipitation from a worldwide ocean.
neptunism
Late Jurassic to Cretaceous phase of the Cordilleran orogeny; most strongly affected the western part of the Cordilleran mobile belt.
Nevadan orogeny
An unconformity in which stratified sedimentary rocks overlie an erosion surface cut into igneous or metamorphic rocks. (See angular unconformity, disconformity, and unconformity.)
nonconformity
A complex mountainous region in western North America extending from Alaska into central Mexico.
North American Cordillera
A convergent plate boundary along which oceanic and continental lithosphere collide; characterized by subduction of the oceanic plate, seismicity, and volcanism.
oceanic–continental plate boundary
A convergent plate boundary along which oceanic lithosphere collides with oceanic lithosphere; characterized by subduction of one of the oceanic plates, seismicity, and volcanism. (See continental–continental plate boundary, convergent plate boundary, and oceanic–continental plate boundary.)
oceanic–oceanic plate boundary
See theory of evolution.
organic evolution
A wave-resistant limestone structure with a framework of animal skeletons, such as a coral reef or stromatoporoid reef.
organic reef
One of the two orders of dinosaurs; characterized by a birdlike pelvis; includes ornithopods, stegosaurs, ankylosaurs, pachycephalosaurs, and ceratopsians. (See Saurischia.)
Ornithischia
A linear part of Earth’s crust that was or is being deformed during an orogeny; part of an orogenic belt.
orogen
An episode of mountain building involving deformation, usually accompanied by igneous activity, metamorphism, and crustal thickening.
orogeny
The “bony-skinned” fish characterized by bony armor but no jaws or teeth; appeared during the Late Cambrian, making them the oldest known vertebrates.
ostracoderm
An area of deformation along the southern margin of the North American craton; probably continuous to the northeast with the Appalachian mobile belt.
Ouachita mobile belt
A period of mountain building that took place in the Ouachita mobile belt during the Pennsylvanian Period.
Ouachita orogeny
The process whereby gases released from Earth’s interior by volcanism formed an atmosphere.
outgassing
All sediment deposited by streams that issue from glaciers.
outwash
A spreading ridge that was located off the coast of western North America during part of the Cenozoic Era.
Pacific–Farallon ridge
A warming trend that began abruptly about 55 million years ago.
Paleocene–Eocene Thermal Maximum
The study of Earth’s ancient geography on a regional as well as a local scale.
paleogeography
The study of the direction and strength of Earth’s past magnetic field from remanent magnetism in rocks.
paleomagnetism
The use of fossils to study life history and relationships among organisms.
paleontology
Alfred Wegener’s name for a Late Paleozoic supercontinent made up of most of Earth’s landmasses.
Pangaea
A supercontinent that existed during the Neoproterozoic.
Pannotia
A Late Paleozoic ocean that surrounded Pangaea.
Panthalassa
Evolution of similar features in two separate but closely related lines of descent as a result of comparable adaptations. (See convergent evolution.)
parallel evolution
Pennsylvanian to Permian reptile, many species with large fins on the back, that possessed some mammal characteristics.
pelycosaur
The fundamental unit in the hierarchy of time units; part of geologic time during which the rocks of a system were deposited.
period
The order of odd-toed hoofed mammals; consists of present-day horses, tapirs, and rhinoceroses.
Perissodactyla
A process whereby water molecules in the upper atmosphere are disrupted by ultraviolet radiation, yielding oxygen (O2) and hydrogen (H).
photochemical dissociation
The metabolic process in which organic molecules are synthesized from water and carbon dioxide (CO2), using the radiant energy of the Sun captured by chlorophyll-containing cells.
photosynthesis
The concept that a species evolves gradually and continuously as it gives rise to new species. (See punctuated equilibrium.)
phyletic gradualism
All mammals with a placenta to nourish the developing embryo, as opposed to egg-laying mammals (monotremes) and pouched mammals (marsupials).
placental mammal
Late Silurian through Permian “plate-skinned” fish with jaws and bony armor, especially in the head-shoulder region.
placoderm
Animals and plants that float passively, such as phytoplankton and zooplankton. (See nekton.)
plankton
A segment of Earth’s crust and upper mantle (lithosphere) varying from 50 to 250 km thick.
plate
Theory holding that lithospheric plates move with respect to one another at divergent, convergent, and transform plate boundaries.
plate tectonic theory
The buried extension of a Precambrian shield, which together with a shield makes up a craton.
platform
A temporary lake in an arid region.
playa lake
A type of Mesozoic marine reptile; short-necked and long-necked plesiosaurs existed.
plesiosaur
Igneous rock that cools and crystallizes from magma intruded into or formed within the crust. (See igneous rock.)
plutonic rock
Any lake that formed in non-glaciated areas during the Pleistocene as a result of increased precipitation and reduced evaporation rates during that time.
pluvial lake
Identification and statistical analysis of pollen from sedimentary rocks; provides information about ancient floras and climates.
pollen analysis
A comparatively complex organic molecule, such as nucleic acids and proteins, formed by monomers linking together. (See monomer.)
polymer
An area in which a continent’s ancient craton is exposed, as in the Canadian shield.
Precambrian shield
Any of a mammal’s teeth between the canines and the molars; premolars and molars together are a mammal’s chewing teeth.
premolar
Organism in a food chain, such as bacteria and green plants, that manufacture their own organic molecules, and on which all other members of the food chain depend for sustenance. (See autotrophic.)
primary producer
The order of mammals that includes prosimians (lemurs and tarsiers), monkeys, apes, and humans.
Primates
A principle holding that an igneous intrusion or fault must be younger than the rocks it intrudes or cuts across.
principle of cross-cutting relationships
A principle holding that fossils, especially groups or assemblages of fossils, succeed one another through time in a regular and determinable order.
principle of fossil succession
A principle holding that inclusions or fragments in a rock unit are older than the rock itself, such as granite inclusions in sandstone are older than the sandstone.
principle of inclusions
A principle holding that rock layers extend outward in all directions until they terminate.
principle of lateral continuity
According to this principle, sediments are deposited in horizontal or nearly horizontal layers.
principle of original horizontality
A principle holding that sedimentary rocks in a vertical sequence formed one on top of the other so that the oldest layer is at the bottom of the sequence whereas the youngest is at the top.
principle of superposition
A principle holding that we can interpret past events by understanding present-day processes, based on the idea that natural processes have always operated as they do now.
principle of uniformitarianism
The order of mammals that includes elephants and their extinct relatives.
Proboscidea
A lake formed of meltwater accumulating along the margin of a glacier.
proglacial lake
The seaward (or lakeward) migration of a shoreline as a result of nearshore sedimentation.
progradation
A cell lacking a nucleus and organelles such as mitochondria and plastids; the cells of bacteria and archaea. (See eukaryotic cell.)
prokaryotic cell
Any of the so-called lower primates, such as tree shrews, lemurs, lorises, and tarsiers.
prosimian
A loosely grouped category of small, lizardlike reptiles.
protorothyrid
Any of the Mesozoic flying reptiles that had a long finger to support a wing.
pterosaur
A concept holding that new species evolve rapidly, in perhaps a few thousands of years, then remain much the same during its several million years of existence. (See phyletic gradualism.)
punctuated equilibrium
Fragmental materials such as ash explosively erupted from volcanoes.
pyroclastic materials
A term referring to locomotion on all four limbs as in dogs and horses. (See bipedal.)
quadrupedal
A clastic wedge resulting from deposition of sediment eroded from the highland formed during the Taconic orogeny.
Queenston Delta
The spontaneous change in an atom by emission of a particle from its nucleus (alpha and beta decay) or by electron capture, thus changing the atom to a different element.
radioactive decay
A biostratigraphic unit defined by the occurrence of a single type of organism such as a species or a genus.
range zone
Metamorphism taking place over a large but usually elongate area resulting from heat, pressure, and chemically active fluids.
regional metamorphism
The process of placing geologic events in their proper chronological order with no regard to when the events took place in number of years ago. (See absolute dating.)
relative dating
When it was first established, the geologic time scale as deduced from the geologic column showed only relative time; that is, Silurian rocks are younger than those of the Ordovician but older than those designated Devonian.
relative geological time scale
A linear depression made up of several interconnected basins extending from Colorado into Mexico.
Rio Grande rift
Wavelike structure on a bedding plane, especially in sand, formed by unidirectional flow of air or water currents, or by oscillating currents as in waves.
ripple mark
An aggregate of one or more minerals as in granite (feldspars and quartz) and limestone (calcite), but also includes rocklike materials such as natural glass (obsidian) and altered organic material (coal).
rock
A sequence of processes through which Earth materials may pass as they are transformed from one rock type to another.
rock cycle
Any of about two dozen minerals common enough in rocks to be important for their identification and classification.
rock-forming mineral
The name of a Neoproterozoic supercontinent.
Rodinia
The process involving abrasion of sedimentary particles during transport so that their sharp edges and corners are smoothed off.
rounding
Any cud-chewing placental mammal with a complex three- or four-chambered stomach, such as deer, cattle, antelope, and camels.
ruminant
A major transform fault extending from the Gulf of Mexico through part of California to its termination in the Pacific Ocean off the north coast of California. (See transform fault.)
San Andreas transform fault
A ridge or mound of wind-deposited sand.
sand dune
An association of sedimentary rocks typically found on passive continental margins.
sandstone-carbonate-shale assemblage
A widespread association of sedimentary rocks bounded above and below by unconformities that was deposited during a Neoproterozoic to Early Ordovician transgressive–regressive cycle of the Sauk Sea.
Sauk Sequence
An order of dinosaurs; characterized by a lizardlike pelvis; includes theropods, prosauropods, and sauropods. (See Ornithischia.)
Saurischia
A logical, orderly approach involving data gathering, formulating and testing hypotheses, and proposing theories.
scientific method
The phenomenon involving the origin of new oceanic crust at spreading ridges that then moves away from ridges and is eventually consumed at subduction zones.
seafloor spreading
Any aspect of sediment or sedimentary rocks that make them recognizably different from adjacent rocks of about the same age, such as a sandstone facies.
sedimentary facies
Any rock composed of (1) particles of preexisting rocks, (2) or made up of minerals derived from solution by inorganic chemical processes or by the activities of organisms, and (3) masses of altered organic matter as in coal.
sedimentary rock
All features in sedimentary rocks such as ripple marks, cross-beds, and burrows that formed as a result of physical or biological processes that operated in a depositional environment.
sedimentary structure
Animal that ingests sediment and extracts nutrients from it.
sediment-desposit feeder
Plant with specialized tissues for transporting fluids and nutrients that reproduces by spores rather than seeds, such as ferns and horsetail rushes.
seedless vascular plant
The study of rock relationships within a time-stratigraphic framework of related facies bounded by widespread unconformities.
sequence stratigraphy
Cretaceous phase of the Cordilleran orogeny that affected the continental shelf and slope areas of the Cordilleran mobile belt.
Sevier orogeny
One of six major Paleozoic continents; composed of Russia east of the Ural Mountains, and Asia north of Kazakhstan and south of Mongolia.
Siberia
A mineral containing silica, a combination of silicon and oxygen, and usually one or more other elements.
silicate
An explanation for the origin and evolution of the solar system from a rotating cloud of gases.
solar nebula theory
A Permian–Triassic orogeny caused by the collision of an island arc with the southwestern margin of North America.
Sonoma orogeny
The process whereby sedimentary particles are selected by size during transport; deposits are poorly sorted to well sorted depending on the range of particle sizes present.
sorting
A population of similar individuals that in nature can interbreed and produce fertile offspring.
species
The branch of geology concerned with the composition, origin, areal extent, and age relationships of stratified (layered) rocks; concerned with all rock types but especially sediments and sedimentary rocks.
stratigraphy
The layering in sedimentary rocks; layers less than 1 cm thick are laminations, whereas beds are thicker.
stratification (bedding)
A biogenic sedimentary structure, especially in limestone, produced by entrapment of sediment grains on sticky mats of photosynthesizing bacteria.
stromatolite
A crack or fissure in the seafloor through which superheated water issues. (See black smoker.)
submarine hydrothermal vent
A wide seaway that existed in western North America during the Middle Jurassic Period.
Sundance Sea
A landmass consisting of most of Earth’s continents (such as Pangaea).
supercontinent
Animal that consumes microscopic plants and animals or dissolved nutrients from water.
suspension feeder
The fundamental unit in the hierarchy of time-stratigraphic units, such as the Devonian System; also a combination of related parts that interact in an organized manner.
system
An Ordovician episode of mountain building resulting in deformation of the Appalachian mobile belt.
Taconic orogeny
A Cenozoic sea largely restricted to the Gulf and Atlantic Coastal Plains, coastal California, and the Mississippi Valley.
Tejas epeiric sea
A small lithospheric block with characteristics quite different from those of surrounding rocks; terranes probably consist of seamounts, oceanic rises, and other seafloor features accreted to continents during orogenies.
terrane
Any of the four, small inner planets (Mercury, Venus, Earth, and Mars) similar to Earth (Terra); all have high mean densities, indicating they are composed of rock. (See Jovian planet.)
terrestrial planet
An explanation for some natural phenomenon with a large body of supporting evidence; theories must be testable by experiments and/or observations, such as plate tectonic theory.
theory
The theory holding that all living things are related and that they descended with modification from organisms that lived during the past.
theory of evolution
Permian to Triassic mammal-like reptiles; the ancestors of mammals are among one group of therapsids known as cynodonts.
therapsid
A type of circulation of material in the asthenosphere during which hot material rises, moves laterally, cools and sinks, and is reheated and continues the cycle.
thermal convection cell
A broad, extensive area along a coastline that is alternately water-covered at high tide and exposed at low tide.
tidal flat
Sediment deposited directly by glacial ice, as in an end moraine.
till
A body of strata that was deposited during a specific interval of geological time; for example, the Devonian System, a time-stratigraphic unit, was deposited during that part of geological time designated the Devonian Period.
time-stratigraphic unit
Any of the units such as eon, era, period, epoch, and age referring to specific intervals of geologic time.
time unit
A widespread body of sedimentary rocks bounded above and below by unconformities; deposited during an Ordovician to Early Devonian transgressive-regressive cycle of the Tippecanoe Sea.
Tippecanoe Sequence
Any indication of prehistoric organic activity such as tracks, trails, burrows, and nests. (See biogenic sedimentary structure, body fossil, and fossil.)
trace fossil
Area extending from Minnesota to New Mexico that stood above sea level as several large islands during the Cambrian transgression of the Sauk Sea.
Transcontinental Arch
A type of fault that changes one kind of motion between plates into another type of motion; recognized on land as a strike-slip fault. (See San Andreas transform fault.)
transform fault
Plate boundary along which adjacent plates slide past one another and crust is neither produced nor destroyed.
transform plate boundary
The process of determining the age of a tree or wood in a structure by counting the number of annual growth rings.
tree-ring dating
A break or gap in the geologic record resulting from erosion or nondeposition or both. Also the surface separating younger from older rocks where a break in the geologic record is present. (See angular unconformity, nonconformity, and disconformity.)
unconformity
An informal term referring to a variety of mammals but especially the hoofed mammals of the orders Artiodactyla and Perissodactyla.
ungulate
A valley with steep or nearly vertical walls and a broad, concave, or rather flat floor; formed by movement of a glacier through a stream valley.
U-shaped glacial trough
A glacier confined to a mountain valley.
valley glacier
A dark-light couplet of sedimentary laminations representing an annual deposit in a glacial lake.
varve
A plant with specialized tissues for transporting fluids in land plants.
vascular plant
Any animal possessing a segmented vertebral column as in fish, amphibians, reptiles, birds, and mammals; members of the subphylum Vertebrata.
vertebrate
In an organism, any structure that no longer serves any or only a limited function, or a different function, such as dewclaws in dogs, wisdom teeth in humans, and middle ear bones in mammals.
vestigial structure
An igneous rock that forms as lava cools and crystallizes or when pyroclastic materials are consolidated. (See extrusive igneous rock.)
volcanic rock
A concept holding that the facies in a conformable vertical sequence will be found laterally to one another.
Walther’s law
The relationship between mountain building (orogeny) and the opening and closing of ocean basins.
Wilson cycle
A widespread sea present in North America mostly during the Cretaceous, but it persisted into the Paleogene.
Zuni epeiric sea
