Oceanography

Front 1

density, 52

Back 1

property of a substance defined as mass per unit volume and usually expressed in grams per cubic centimeter or kilograms per cubic meter

Front 2

seismic wave, 52

Back 2

elestic disturbances, or vibrations, that are generated by earthquakes

Front 3

P-wave, 53

Back 3

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

Front 4

S-wave, 53

Back 4

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

Front 5

refract, 54

Back 5

change in direction, or bending, of a wave

Front 6

inner core, 54

Back 6

the 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

Front 7

outer core, 54

Back 7

a 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

Front 8

mantle, 55

Back 8

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

Front 9

seismic tomography, 55

Back 9

the use of seismic data to produce computerized, detailed, three-dimensional maps of the boundaries between earth's layers

Front 10

Moho discontinuity, 55

Back 10

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

Front 11

Laurasia, 58

Back 11

an ancient landmass that fragmented to produce north america and eurasia

Front 12

granite, 55

Back 12

crustalline, coarse grained, igneous rock composed mainly of quartz and feldspar

Front 13

basalt, 55

Back 13

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

Front 14

lithosphere, 56

Back 14

outer, rigid portion of earth; includes the continental and oceanic cursts and the upper part of the mantle

Front 15

asthenosphere, 56

Back 15

upper, deformable portion of earths mantle, the layer below the lithosphere; probalby partially moltenl may be site of convection cells

Front 16

mesophere, 56

Back 16

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

Front 17

isostasy, 56

Back 17

mechanism by which areas of earths crust rise or subside until their masses are in balance, "floating" on the mantle

Front 18

Gondwanaland, 58

Back 18

an ancient land mass that fragmented to produce africa, south america, antartica, australia, and india

Front 19

continental drift, 58

Back 19

the movement of continenets; the name of Alfred Wegeners theory, preceding plate tectonics

Front 20

Pangaea, 58

Back 20

an ancient landmass that consisted of all of the present day continents; it fragmented into laurasia and gondwanaland

Front 21

ridge, 59

Back 21

long, narrow elevation of the sea floor, with steep sides and irregular topography

Front 22

rise, 59

Back 22

long, broad elecation that rises gently and genereally smoothly from the sea floor

Front 23

rift valley, 59

Back 23

trough formed by fualting along a zone in which plates move apart and new crust is created, such as along the crest of a ridge system

Front 24

trench

Back 24

long, deep, and narrow depression of the sea floor with relatively steep sides, associated with a subduction zone

Front 25

convection cell

Back 25

circulation in a fluid, or fluidlike 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

Front 26

seafloor spreading

Back 26

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

Front 27

spreading center

Back 27

region along which new crustal material is produced

Front 28

subduction zone

Back 28

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.

Front 29

epicenter

Back 29

point on earths surface directly above an earthquake location, specified by indentifying the latitude and longitude of the earthquake

Front 30

focus

Back 30

the location of an earthquake within earth. focus is specified by indentifying latitude, longitude, and depth of the earthquake

Front 31

sediment

Back 31

particulate organic and inorganic matter that accumulates in loose, unconsolidated form.

Front 32

core

Back 32

verticle, cyclindrical 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

Front 33

diple

Back 33

a magnetic field like earths, with two opposite poles

Front 34

curie temperature

Back 34

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

Front 35

paleomagnetism

Back 35

study of ancient magnetism recorded in rocks; includes study of changes in location of earths magnetic poles through time and reversals in earths magnetic field

Front 36

polar reversal

Back 36

the periodic reversal of earths magnetic field where the north magnetic pole becomes the south magnetic pole and vice versa

Front 37

polar wandering curve

Back 37

a plot of the apparent location of earths north magnetic pole as a function of geologic time.

Front 38

inertia

Back 38

the property of matter that causes it to resist any change in its motion

Front 39

rift zone

Back 39

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

Front 40

graben

Back 40

a portion of earths crust that has been moved downward and is bounded by steep faults; a rift

Front 41

wadati-benioff zone

Back 41

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

Front 42

escarpment

Back 42

nearly continuos line of cliffs or steep slopes caused by erosion or faulting

Front 43

fracture zone

Back 43

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

Front 44

craton

Back 44

large peices of earths crust that form the centers of continents

Front 45

island arc

Back 45

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

Front 46

terrane

Back 46

fragments of earths crust bounded by faults, each fragment with a history distinct from each other fragment

Front 47

spreading rate

Back 47

the rate at which two plates move apart. spreading rates are generally between about 2 and 10 cm a year

Front 48

hotspot

Back 48

surface expression of a persistent rising plume of hot mantle material

Front 49

guyot

Back 49

submerged, flat top seamount

Front 50

hydrothermal vent

Back 50

seafloor outlet for high temperature groundwater and associated mineral deposits; a hot spring