earth's internal structure (12)

Question 1

earth’s average density

Answer 1

about 5.5gm/cm

Question 2

what mineral makes up the average composition of the upper continental crust?

Answer 2

granodiorite (felsic rock)

Question 3

what mineral is in the upper mantel and crust?

Answer 3

xenolith

Question 4

xenolith

Answer 4

an inclusion of unmelted country rock in an igneous pluton

Question 5

what mineral is the main composition of the upper mantle?

Answer 5

peridotite

Question 6

peridotite

Answer 6

an igneous rock of ultramafic composition thought to be abundant in the upper mantle

Question 7

what minerals make up peridotite?

Answer 7

60% olivine

25% pyroxene

Question 8

meteorite

Answer 8

any portion of a meteoroid that survives its traverse through earth’s atmosphere and strikes the surface

Question 9

what materials are in stony meteorites?

Answer 9

olivine and pyroxene

Question 10

what materials are in iron meteorites?

Answer 10

alloys of iron with lesser amounts of nickel

Question 11

what types of minerals make up oceanic crust?

Answer 11

rock basalt, gabbro

Question 12

what types of minerals make up continental crust?

Answer 12

granodiorite

Question 13

lower mantle

Answer 13

part of the mantle that extends form the core-mantle boundary to a depth of 660 kilometers

Question 14

what minerals make up the lower mantle?

Answer 14

olivine and pyroxene (perovskite or bridgemanite)

Question 15

D” layer

Answer 15

a region in roughly the lowermost 200 kilometers of the mantle where p waves experience a sharp decrease in velocity

Question 16

moho

Answer 16

the boundary separating the crust and the mantle, discernible by an increase in seismic velocity

Question 17

shadow zone

Answer 17

the zone between 105 and 140 degrees from an earthquake epicenter. direct waves do not penetrate the shadow zone because of refraction by earth’s core

Question 18

convection

Answer 18

the transfer of heat by the mass movement or circulation of a substance

Question 19

conduction

Answer 19

the transfer of heat through matter by molecular activity

Question 20

mantle plume

Answer 20

a mass of hotter-than-typical mantle material that ascends toward the surface, where it may lead to igneous activity

Question 21

geothermal gradient

Answer 21

the gradual increase in temperature with depth in the crust

Question 22

gravity anomaly

Answer 22

a gravitational force that deviates from the average

Question 23

earth’s magnetic field

Answer 23

a phenomenon occurring around a magnet or an electric charge, characterized by a magnetic force at every point in the region

Question 24

geodynamo

Answer 24

the generation and maintenance of earth’s magnetic field by the raising of iron-rich fluid in the outer core

Question 25

declination

Answer 25

measures the direction to the magnetic North Pole with respect to the geographic north pole

Question 26

inclination

Answer 26

measures the downward tilt of the magnetic lines of force at any location

Question 27

magnetic reversal

Answer 27

a change in earth’s magnetic field from normal to reverse or vise versa

Question 28

seismic tomography

Answer 28

a technique in which seismic signals collected from many earthquakes are used to make images that map locations within earth where seismic waves travel slower or faster