Earth's Structure And Change Over Time

Front 1

absolute age

Back 1

the age of a rock given as the number of years since the rock formed

Front 2

asthenosphere

Back 2

the soft layer of the mantle on which the lithosphere floats

Front 3

atmosphere

Back 3

the relatively thin layer of gases that form Earth's outermost layer

Front 4

biosphere

Back 4

the parts of Earth that contain living organisms

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compression

Back 5

the stress that squeezes rock until it folds or brakes

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conduction

Back 6

the transfer of thermal energy from one particle of matter to another

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continent

Back 7

any of Earth's seven large land masses

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continental drift

Back 8

the hypothesis that the continents slowly move across Earth's surface

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convection

Back 9

the transfer of thermal energy by the movement of a fluid

Front 10

convection current

Back 10

the movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another

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convergent boundary

Back 11

a plate boundary where two plates move toward each other

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crust

Back 12

the layer of rock that forms Earth's outer surface

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deep-ocean trench

Back 13

a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle

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density

Back 14

the ratio of the mass of a substance to its volume (mass divided by volume)

Front 15

displacement

Back 15

the moving of something from its place or position; the occupation by a submerged body or part of a body of a volume that would otherwise be occupied by a fluid

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divergent boundary

Back 16

a plate boundary where two plates move away from each other

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earthquake

Back 17

the shaking that results from the movement of rock beneath Earth's surface

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energy

Back 18

the ability to do work or cause change

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epicenter

Back 19

the point on Earth's surface directly above an earthquake's focus

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era

Back 20

one of three long units of geologic time between the Precambrian and the present

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evolution

Back 21

change over time; the process by which modern organisms have descended from ancient organisms

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extinct

Back 22

condition in which there are no more living members of a species

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extrusion

Back 23

an igneous rock layer formed when lava flows onto Earth's surface and hardens

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fault

Back 24

a break in Earth's crust along which rocks move

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flood

Back 25

an overflowing of a large amount of water beyond its normal borders, especially over what is normally dry land

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focus

Back 26

the point beneath Earth's surface where rock first breaks under stress and causes an earthquake

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formations

Back 27

the geological features of the earth (ridge, mountain ranges, shore line, etc.)

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fossil

Back 28

the preserved remains or traces of an organism that lived in the past

Front 29

fracture zones

Back 29

a long, narrow rift on the ocean floor, separating areas of differing depth: where such a zone crosses a mid-ocean ridge, it displaces the ridge by faulting.

Front 30

frequency

Back 30

the rate at which something occurs or is repeated over a particular period of time or in a given sample

Front 31

geologic time scale

Back 31

a record of the geologic events and life forms in Earth's history

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geology

Back 32

the study of Earth's structure, composition, forces, history, and future

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geosphere

Back 33

the densest parts of Earth that include the crust mantle, and core

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half-life

Back 34

the time it takes for half of the atoms of a radioactive element to decay

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hydrosphere

Back 35

the portion of Earth that consists of water in any of its forms, including oceans, glaciers, rivers, lakes, groundwater and water vapor

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igneous rock

Back 36

formed through the cooling and solidification of magma or lava

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index fossil

Back 37

fossils of widely distributed organisms that lived during a geologically short period

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inner core

Back 38

a dense sphere of solid iron and nickel at the center of Earth

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intrusion

Back 39

an igneous rock layer formed when magma hardens beneath Earth's surface

Front 40

landslide

Back 40

form of erosion in which a large amount of the land surface suddenly moves downhill

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law of crosscutting relationships

Back 41

igneous intrusion is always younger than the rock it cuts across

Front 42

law of superposition

Back 42

geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it

Front 43

lithosphere

Back 43

a rigid layer made up of the uppermost part of the mantle and the crust

Front 44

magma

Back 44

the molten mixture of rock-forming substances, gases, and water from the mantle

Front 45

magnitude

Back 45

the measurement of an earthquake's strength based on seismic was and movement along faults

Front 46

mantle

Back 46

the layer of hot, solid material between Earth's crust and core

Front 47

mid-ocean ridge

Back 47

an undersea mountain chain where new ocean floor is produced; a divergent plate boundary

Front 48

outer core

Back 48

a layer of molten iron and nickel that surround the inner core of Earth

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paleontology

Back 49

scientific study of life in the geologic past, especially through the study of animal and plant fossils

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Pangaea

Back 50

the name of the single landmass that began to break apart 200 million years ago and gave rise to today's continents

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period

Back 51

one of the units of geologic time into which geologists divide eras

Front 52

plate

Back 52

a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust

Front 53

plate tectonics

Back 53

the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle

Front 54

p-wave

Back 54

a type of seismic wave that compresses and expands the ground

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radiation

Back 55

the transfer of energy by electromagnetic waves

Front 56

relative age

Back 56

method of describing the age of one object or event compared to another object or event

Front 57

Richter Scale

Back 57

a scale that rates an earthquake's magnitude based on the size of its seismic waves

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rift valley

Back 58

a deep valley that forms where two plates move apart

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Ring of Fire

Back 59

a major belt of volcanoes that rims the Pacific Ocean

Front 60

sea-floor spreading

Back 60

the process by which molten material adds new oceanic crust to the ocean floor

Front 61

seismic wave

Back 61

vibrations that travel through Earth carrying the energy released during an earthquake

Front 62

seismogram

Back 62

the record of an earthquake's seismic waves produced by a seismograph

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seismograph

Back 63

a device that records ground movements caused by seismic waves as they move through Earth

Front 64

stress

Back 64

a force that acts on rock to change its shape or volume

Front 65

subduction

Back 65

the process by which more dense crust sinks beneath less dense crust and back into the mantle at a convergent plate boundary

Front 66

surface wave

Back 66

a type of seismic wave that forms when P-waves and S-waves reach Earth's surface

Front 67

s-wave

Back 67

a type of seismic wave in which the shaking is perpendicular to the direction of the wave

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system

Back 68

a group of parts that work together as a whole

Front 69

tectonic plates

Back 69

(also called lithospheric plate) a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere

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tension

Back 70

stress that stretches rock so that it becomes thinner in the middle

Front 71

transform boundary

Back 71

a plate boundary where two plates move past each other in opposite directions

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unconformity

Back 72

a gap in the geologic record that shows where rock layers have been lost due to erosion

Front 73

volcano

Back 73

a weak spot in the crust where magma has come to the surface