Chapter 2: Plate Tectonics

Question 1

plate tectonics

Answer 1

the grand unifying theory of geology which says that the Earth’s crust is made up of about 20 plates/pieces that slowly move relative to one another

Question 2

continental drift

Answer 2

the theory that the continents broke apart and moved away from each other into the positions we know today

Question 3

evidence of continental drift

Answer 3

• glacial striations and till deposits
• distribution of climate belts
• distribution of fossils
• matching geologic units

Question 4

mid-ocean ridges

Answer 4

sub-marine mountain ranges in the middle of an abyssal plain that are roughly symmetrical on either side of the ridge axis

Question 5

deep sea trenches

Answer 5

bordering volcanic arcs, trenches are elongate, deep troughs in the ocean

Question 6

fracture zones

Answer 6

lie at right angles to mid-ocean ridges and interrupt the continuity of the ridge axis

Question 7

seamount chains

Answer 7

where numerous, formerly volcanic mounts of basalt poke up from the ocean floor

Question 8

how does thickness of the ocean sediment layer vary further away from a mid-ocean ridge?

Answer 8

the ocean sediment layer become thicker further away from the mid-ocean ridge due to uplift of the oceanic crust in that part of the ocean and new crust forming around the mid-ocean ridge

Question 9

seafloor spreading

Answer 9

the theory that says that at mid-ocean ridges, the basalt formed at the ridge moves away from the ridge axis, widening the ocean basin

Question 10

paleomagnetism

Answer 10

the study of rocks that can preserve a record of the Earth’s magnetic field in the past.

Question 11

what does paleomagnetism mean

Answer 11

in rocks that have magnetic field, ancient rocks may not have the same oriented dipole as the Earth today because of how the Earth’s poles switch periodically

Question 12

apparent polar-wander path

Answer 12

successive position of dated paleo-poles trace out a curving line that shows how the continents moved relative to the Earth’s poles

Question 13

normal and reverse polarity

Answer 13

normal: the polarity we have today
reverse: the opposite polarity of what we have today

Question 14

active margins

Answer 14

continental boundaries that are also a plate boundaries

Question 15

passive margins

Answer 15

continental margins that are not a plate boundaries

Question 16

divergent boundary

Answer 16

a spreading boundary

Question 17

convergent boundary

Answer 17

two plates, at least one of which is oceanic, move toward one another, but rather than butt against each other, one oceanic plate bends and sinks down into the asthenosphere

Question 18

subduction

Answer 18

the sinking process of one plate submerging into the asthenosphere

Question 19

transform boundary

Answer 19

the actively slipping segment of a fracture zone