11. Earth History, Earth Interior

Question 1

anthropocene

Answer 1

age of human transformation of earth’s physical systems; generally seen as starting in 1800

Question 2

crust

Answer 2

rigid outermost portion of earth’s surface

Question 3

volcano

Answer 3

mountain or hill formed by eruptions of lava and rock fragments

Question 4

cyanobacteria

Answer 4

photosynthetic bacteria that were among the first known forms of life to evolve about 3.5 billion years ago

Question 5

uniformitarianism

Answer 5

principle that the same imperceptible gradual processes are operating now and have operated in the past

Question 6

relative age

Answer 6

age of one object or event in relation to the age of another without regard to how old either is

Question 7

absolute age

Answer 7

an age that is specified in years before the present

Question 8

superposition

Answer 8

the principle that in a sequence of rock layers, the oldest rocks are always at the bottom and the youngest at the top

Question 9

radiometric dating

Answer 9

a method of assigning absolute ages to earth materials based on the radioactive decay of unstable elements in those materials

Question 10

seismic wave

Answer 10

energy released by an earthquake that travels through earth’s interior as a wave

Question 11

earthquake

Answer 11

a sudden shaking of the ground caused by movements of earth’s crust

Question 12

inner core

Answer 12

the innermost layer of earth, composed of solid iron and nickel

Question 13

outer core

Answer 13

the second innermost layer of earth, composed of a liquid alloy of iron and nickel, which generates earth’s magnetic field

Question 14

mantle

Answer 14

the layer of heated and slowly deforming solid rock between the base of the crust and the outer core

Question 15

asthenosphere

Answer 15

the layer of the mantle, which deforms and flows, found between about 100 and 200 km in depth

Question 16

lithosphere

Answer 16

the layer of earth that consists of the rigid crust and the rigid lithosphere mantle beneath it, extending to a depth of about 100km on average

Question 17

continental crust

Answer 17

the crust that makes up the continents, composed mainly of granite

Question 18

granite

Answer 18

a silica-rich rock composed of coarse grains

Question 19

oceanic crust

Answer 19

the crust beneath the oceans, composed mainly of basalt

Question 20

basalt

Answer 20

a dark, heavy, fine-grained volcanic rock that constitutes oceanic crust

Question 21

magma

Answer 21

melted rock that is below the surface of earth’s crust

Question 22

lava

Answer 22

hot molten rock that spills onto the surface of earth’s crust

Question 23

moho

Answer 23

the boundary that separates the crust from the lithospheric mantle, which lies about 35km deep on average

Question 24

magnetosphere

Answer 24

the outer edge of the magnetic field that surrounds earth and shields it from the solar wind