Quiz 4- Ch 13

Question 1

P Waves

Answer 1

compressional waves that can travel through solid, liquid, or gaseous material and arrive first on a seismograph

Question 2

S Waves

Answer 2

shear waves than can only travel through solids

Question 3

shadow zone

Answer 3

(1) A zone beyond 105° from the focus of an earthquake where S waves are not recorded because they are not transmitted through Earth’s liquid outer core. (2) A zone at angular distances of 105° to 142° from the focus of an earthquake where P waves are not recorded because they are refracted downward into the core and emerge at greater distances after the delay caused by their detour through the core.

Question 4

seismic profiling

Answer 4

used to locate oil deposits, measure the thickness of glaciers, depth of oceans and thickness of sediments on the seafloor

Question 5

geotherm

Answer 5

the curve that describes how earth’s temperature increases with depth

Question 6

low-velocity zone

Answer 6

layer just below the lithosphere (~100km) where S-waves take a sudden decrease in velocity indicating the ductile athenosphere

Question 7

phase change

Answer 7

a change in rock’s crystal structure (not chemical composition) by changing temp and pressure. signaled by a change is S wave velocity at the upper mantle (olivine)

Question 8

lower mantle

Answer 8

more than 2000km thick and relatively homogenous

Question 9

transition zone

Answer 9

between 400-700 km thick contains two major phase changes

Question 10

seismic tomography

Answer 10

technique that uses differences in travel time of seismic waves to form a three-dimensional model of earth