oce test one vocab

hypothesis

initial explanation of data that is based on well-established physical or chemical laws

theory

tested, reliable, and precise statement of the relationships among reproducible observations, may be used to predict the existence of phenomena or relationships not previously recognized

galaxy

huge aggregate of stars held together my mutual gravitation

light-year

distance that light travels in one year. A light-year is equal to 9.46 × 1012 km, or 5.87 × 1012 mi.

cluster

a group of galaxies, may contain thousands of galaxies

nebula

large, dense cloud of gas and dust in space

radiometric dating

determining ages of geologic samples by measuring the relative abundance of radioactive isotopes and comparing isotopic systems

isotope

atoms of the same element having different numbers of neutrons

half-life

time required for half of an initial quantity of a radioactive isotope to decay

vertebrates

animals with backbones or a spinal column

tropics of cancer and capricorn

latitudes 23½°N and 23½°S, respectively, marking the maximum angular distance of the Sun from the equator during the summer and winter solstices

Arctic and Antarctic Circles

latitudes 66½°N and 66½°S, respectively, marking the boundaries of light and darkness during the summer and winter solstices

equinox

the two moments in the year when the Sun is exactly above the Equator and day and night are of equal length

lunar month

time required for the Moon to pass from one new Moon to another new Moon (approximately twenty-nine days)

solar day

time period determined by one rotation of Earth relative to the Sun; the mean solar day is twenty-four hours

sidereal day

time period determined by one rotation of Earth relative to a far-distant star, about four minutes shorter than the mean solar day

latitude

distance north or south of the equator. Latitude is the angle between the equatorial plane and a line drawn outward from the center of Earth to a point on the surface of Earth. Latitude varies from 0° to +90° north of the equator and 0° to –90° south of the equator. Together with longitude, it specifies the location of a point on the surface of Earth

longitude

distance east or west of the prime meridian. Longitude is the angle in the equatorial plane between the prime meridian and a second meridian that passes through a point on the surface of Earth whose location is being specified. Longitude may be specified in one of two ways: either from 0° to 360° east of the prime meridian, or 0° to 180° east and 0° to 180° west. Together with latitude, it specifies the location of a point on the surface of Earth

parallel

circle on the surface of Earth parallel to the plane of the equator and connecting all points of equal latitude; a line of latitude

equator

0° latitude, determined by a plane that is perpendicular to Earth’s axis and is everywhere equidistant from the North and South Poles

meridian

circle of longitude passing through the poles and any given point on Earth’s surface

prime meridian

meridian of 0° longitude, used as the origin for measurements of longitude; internationally accepted as the meridian of the Royal Naval Observatory, Greenwich, England

international date line

imaginary line through the Pacific Ocean roughly corresponding to 180° longitude, to the east of which, by international agreement, the calendar date is one day earlier than to the west

great circle

intersection of a plane passing through the center of Earth with the surface of Earth. Great circles are formed by the equator and any two meridians of longitude 180° apart

nautical mile

unit of length equal to 1852 m, or 1.15 land miles, or 1 minute of latitude

polaris

also known as the North Star; located less than 1° from the celestial pole, a line corresponding to the extension of Earth’s axis of rotation into the sky from the north geographic pole. The angular elevation of Polaris above the horizon corresponds to the latitude of an observer in the Northern Hemisphere

zenith

point in the sky that is immediately overhead

Greenwich Mean Time (GMT)

solar time along the prime meridian passing through Greenwich, England; also known as Universal Time or ZULU Time

universal time

solar time along the prime meridian passing through Greenwich, England; also known as Greenwich Mean Time (GMT) or ZULU Time

zulu time

solar time along the prime meridian passing through Greenwich, England; also known as Greenwich Mean Time (GMT) or Universal Time

Global Positioning System (GPS)

worldwide radio-navigation system consisting of twenty-four navigational satellites and five ground-based monitoring stations. GPS uses this system of satellites as reference points for calculating accurate positions on the surface of Earth with readily available GPS receivers.

reservoir

source or place of temporary residence for water, such as the oceans or atmosphere.

hydrologic cycle

movement of water among the land, oceans, and atmosphere due to vertical and horizontal transport, evaporation, and precipitation.

transpiration

the loss of water through evaporation

sublimation

transition of a substance from its solid state to its gaseous state without becoming a liquid.

residence time

mean time that a substance remains in a given area before being replaced, calculated by dividing the amount of a substance by its rate of addition or subtraction.

hypsographic curve

graph of land elevation and ocean depth versus area

seismic waves

elastic disturbances, or vibrations, generated by earthquakes

surface wave

seismic wave that travels on Earth’s surface

body wave

seismic wave that travels beneath Earth’s surface

refract

change in direction, or bending, of a wave

P-wave (primary wave)

type of seismic wave in which material is alternately compressed and stretched in the direction of propagation of the wave

S-wave (secondary wave)

type of seismic wave in which material is sheared from side to side, perpendicular to the direction of propagation of the wave

crust

outer shell of the solid Earth; the lower limit is usually considered to be the Mohorovičić discontinuity.

continental crust

crust forming the continental land blocks; mainly granite and its derivatives

granite

crystalline, coarse-grained, igneous rock composed mainly of quartz and feldspar.

oceanic crust

crust below the deep-ocean sediments; mainly basalt

basalt

fine-grained, dark igneous rock, rich in iron and magnesium, characteristic of oceanic crust.

mantle

main bulk of Earth between the crust and the core; increasing pressure and temperature with depth divide the mantle into concentric layers.

Mohorovičić discontinuity (Moho)

boundary between crust and mantle, marked by a rapid increase in seismic wave speed.

core

vertical, cylindric sample of bottom sediments, from which the nature of the bottom can be determined; also the central zone of Earth, thought to be liquid or molten on the outside and solid on the inside.

lithosphere

outer, rigid portion of Earth; includes the continental and oceanic crusts and the upper part of the mantle.

asthenosphere

upper, deformable portion of Earth’s mantle, the layer below the lithosphere; probably partially molten; may be site of convection cells.

mesosphere

either the layer of the atmosphere above the stratosphere extending from about 50–90 km or the region of the mantle beneath the asthenosphere.

outer core

region surrounding the inner core; it is liquid and consists primarily of iron with minor amounts of other elements that likely include nickel, sulfur, and oxygen.

inner core

innermost region of Earth. It is solid and consists primarily of iron with minor amounts of other elements that likely include nickel, sulfur, and oxygen.

isostasy

mechanism by which areas of Earth’s crust rise or subside until their masses are in balance, “floating” on the mantle.

Gondwanaland

ancient landmass that fragmented to produce Africa, South America, Antarctica, Australia, and India.

continental drift

movement of continents; the name of Alfred Wegener’s theory, preceding plate tectonics.

Pangaea

ancient landmass that consisted of all of the present-day continents; it fragmented into Laurasia and Gondwanaland.

Panthalassa

single, great ocean that existed when all of the landmasses were combined in the ancient continent Pangaea.

Laurasia

ancient landmass that fragmented to produce North America and Eurasia

convection cell

circulation in a fluid, or fluid-like material, caused by heating from below. Heating the base of a fluid lowers its density, causing it to rise. The rising fluid cools, becomes denser, and sinks, creating circulation.

seafloor spreading

movement of crustal plates away from the mid-ocean ridges; process that creates new crustal material at the mid-ocean ridges.

spreading center

region along which new crustal material is produced

subduction zone

plane descending away from a trench and defined by its seismic activity, interpreted as the convergence zone between a sinking plate and an overriding plate.

epicenter

point on Earth’s surface directly above an earthquake location, specified by identifying the latitude and longitude of the earthquake. See also focus, hypocenter.

focus

location of an earthquake within Earth. Focus is specified by identifying latitude, longitude, and depth of the earthquake. See also epicenter.

hypocenter

location of an earthquake within Earth. Focus is specified by identifying latitude, longitude, and depth of the earthquake.

dipole

magnetic field like Earth’s, with two opposite poles.

Curie temperature

temperature at which the magnetic signature is frozen into an igneous rock during cooling.

paleomagnetism

study of ancient magnetism recorded in rocks; includes study of changes in location of Earth’s magnetic poles through time and reversals in Earth’s magnetic field.

polar reversal

periodic reversal of Earth’s magnetic field where the north magnetic pole becomes the south magnetic pole and vice versa.

plate tectonics

theory and study of Earth’s lithospheric plates, their formation, movement, interaction, and destruction; the attempts to explain Earth’s crustal changes in terms of plate movements.

divergent plate boundary

boundary between two plates that are diverging, or moving apart from one another.

convergent plate boundary

boundary between two plates that are converging or colliding with one another.

transform boundary

boundary between two plates that are sliding past one another. This boundary is marked by a transform fault.

transform fault

fault with horizontal displacement connecting the ends of an offset in a mid-ocean ridge. Some plates slide past each other along a transform fault.

rift zone

region where the lithosphere splits and separates, allowing new crustal material to intrude into the crack or rift.

graben

portion of Earth’s crust that has moved downward and is bounded by steep faults; a rift

pillow basalt

a volcanic igneous rock that forms when lava of basaltic compositionis erupted underwater

escarpment

nearly continuous line of cliffs or steep slopes caused by erosion or faulting.

fracture zone

long, linear zone of irregular bathymetry of the sea floor, characterized by asymmetric ridges and troughs; commonly associated with fault zones.

ocean-ocean convergence

one of the plates (oceanic crust and lithospheric mantle) is pushed, or subducted , under the other

Wadati-Benioff zone

dipping patterns of earthquake activity that descend into the mantle along convergent plate boundaries.

island arc

chain of volcanic islands formed above the sinking plate at a subduction zone

ocean-continent convergence

occur when a tectonic plate primarily composed of oceanic lithosphere collides with a plate with continental lithosphere

andesite

volcanic rock intermediate in composition between basalt and granite; associated with subduction zones.

continent-continent convergence

describes the collision of two tectonic plates composed of continental lithosphere

suture zone

area where two continental plates have joined together through continental collision. Suture zones are often marked by high mountain ranges, such as the Himalayas and the Alps.

passive/trailing margin

continental margin closest to the mid-ocean ridge

active/leading margin

edge of the overriding plate at a trench or subduction zone

convection

transmission of heat by the movement of a heated gas or liquid; vertical circulation resulting from changes in density of a fluid.

ridge-push/slab-pull

slab pull: the force due to the weight of the cold, dense sinking tectonic plate. ridge push: the force due to the buoyancy of the hot mantle rising to the surface beneath the ridge

spreading rate

rate at which two plates move apart. Spreading rates are generally about between 2 and 10 cm (0.8 and 4 in) per year.

hotspot

surface expression of a persistent rising plum of hot mantle material

guyot

submerged, flat-topped seamount; also known as a tablemount.

transverse/aseismic ridge

ridge running at nearly right angles to the main, or principal, ridge.

Tethys Sea

ocean between the continents of Gondwana and Laurasia before the opening of the Indian and Atlantic Oceans.

Rodinia

supercontinent that formed approximately 1.11 billion years ago.