escarpment a cliff.
esker a winding ridge of stratified glacial deposits, stretching from a few meters to as long as 160 kilometers.
eustatic change worldwide change of sea level produced by an increase or decrease in amount of ocean water.
evaporite any salt deposit left behind when seawa- ter evaporates.
extrusive rock rock solidified from magma that has flowed out of the earth and onto the surface.
fault a fracture in strata or, on a larger scale, the Earth's crust.
floodplain an area bordering a stream that periodically floods.
fold bend or wrinkle in rock formed when rock was in a plastic state.
fold mountain a mountain consisting of sedimentary rocks that have been folded over and elevated.
fossil fuels underground deposits of hydrocarbons, including petroleum, methane, coal, and natural gas, formed from the fossilized remains of millions of tons of prehistoric plants and animals, with phy- toplanktons and zooplanktons transforming largely into petroleum and terrestrial plants and organisms transforming largely into coal.
frost action erosional process caused by the expansion of water through repeated cycles of freezing and thawing.
geocentric pertaining to the center of the Earth.
geochronology the history of the Earth as marked by geological events.
geodesy the science of the measuring of Earth's size, shape, and weight.
geomorphology the study of land forms.
geosyncline a basin in which thousands of meters of sediments have accumulated and which may ultimately become compressed into a mountain system.
Gondwanaland hypothetical Southern Hemisphere continent thought to have broken up in the Mesozoic era and now the continents of Africa, India, Australia, South America, and Antarctica.
guyot flat-topped mountain under the sea.
igneous rock rock formed from the cooling and solidification of magma.
inselberg a vestigial mountain reduced by erosion to a rocky nubbin or isolated "island," found in ancient desert areas.
intrusive rock rock that has solidified from magma after intruding into or between other rocks.
island-arc deeps deep sea trenches bordering some continents; some reach depths of 9,000 meters.
kame a steep hill of stratified glacial drift.
karst topography an area characterized by numerous sinkholes and caverns, due to limestone erosion.
Kerguelen-Gaussberg Ridge a mountain range under the Indian Ocean between India and Antarctica.
kettle a depression in a large accumulation of glacial drift caused by an ice block melting and later forming a lake.
koppie pile of boulders formed by the weathering and breakdown of inselbergs.
lava extruded from a volcano, any molten rock or molten rock that has cooled and hardened.
lithosphere the outermost layer of the Earth, comprising the crust and the upper mantle.
loess an accumulation of loose silt, deposited by wind as dust.
lowland any land at or slightly above sea level.
magma molten rock beneath the surface of the Earth.
magnetic reversal a complete shift of Earth's magnetic field, which, if occurring today, would make a compass needle point south instead of north. Such reversals have taken place several times throughout the Earth's history.
magnetostratigraphy the study of magnetized rocks to determine magnetic reversals in the Earth's past.
mantle the layer of Earth between the crust and the core.
marl forming in a water environment, a loose deposit of clay and calcium carbonate.
melange different types of rocks grouped together.
metamorphic rock rock that has changed or "metamorphosed" into other rock through heat, pressure, or chemical processes.
metamorphism the process by which a rock is altered through heat and pressure.
microfossil a tiny fossil, often requiring study through a microscope.
mid-ocean ridge a long, elevated rise in the sea- floor, caused by the eruption of basalt and formation of new crust.
mineralization the process by which minerals infiltrate a dead organism and turn it into a fossil.
Mohorovicic discontinuity (Moho) the base of the Earth's crust, ranging from about 13 kilometers under the oceans to about 40 kilometers under the continents.
mold an impression of an organism, left behind to fossilize in rock.
monolith slender, eroded butte that eventually topples over.
monument a butte.
moraine a large accumulation of glacial till or drift.
oceanic trench an elongated trough on the ocean floor, caused by subduction activity.
orogeny the process by which mountains are formed.
outcrop any bedrock that has become exposed from the surrounding soil.
paleogeography the geography of a land as it was in the geologic past.
paleomagnetism Earth's magnetic field as it was in the geologic past.
Pangaea the huge, hypothetical ancient superconti- nent from which all of today's continents are thought to have split off.
Panthalassa the huge, hypothetical universal ocean surrounding the supercontinent Pangaea before it divided.
peat a deposit of decomposed plant remains from a swamp or marsh.
peneplain a flat or nearly flat land surface resulting from an advanced stage of erosion.
pingo a mound or hill, sometimes more than 100 meters high, formed by expanding permafrost, found frequently in arctic regions.
plate any one of the seven major lithospheric plates, consisting of either heavy basaltic ocean crust or lighter granitic continental crust, that cover the Earth and float on the plastic upper mantle.
plate tectonics the interaction and subsequent effects of the Earth's lithospheric plates colliding and scraping against one another.
pluton any mass of igneous rock formed beneath the Earth by the hardening of magma.
regression a recession in sea level, exposing new land.
rift a long crack in the Earth's crust.
rift valley a valley formed by faulting.
salt dome a dome formed in sedimentary rock by the upward flow of a large mass of salt.
seafloor spreading the expanding of the seafloor along mid-ocean ridges, forming new crust.
seamount a mountain under the sea.
sedimentary rock rock formed by the accumulation and bedding of silt, gravel, rocks, and organic matter, easily identified by its distinctive layering or strata.
seismic prospecting a technique of determining the nature of an underground rock structure by setting off explosive charges and measuring the time the shock waves take to travel varying underground paths.
seismograph an instrument that records vibrations of the Earth, particularly during an earthquake.
seismology the study of earthquakes.
sinkhole an area of ground, usually consisting of limestone or some other soluble material, that collapses due to water erosion.