Chapter 6

Question 1

What happens to Earth’s magnetic field over time?

Answer 1

It changes direction.

Question 2

Why does seafloor spreading happen?

Answer 2

magma pushes the seafloor away from the ridges in both directions

Question 3

Why was continental drift theory not well received by other scientists?

Answer 3

There was no scientific explanation for the force responsible for moving the continents

Question 4

How can two lithospheric plates move relative to each other?

Answer 4

They can collide, pull apart, or slide against each other.

Question 5

Which of the following is correct about mountain ranges located on both sides of the Atlantic Ocean?

Answer 5

have the same rock types, structures, and ages

Question 6

At the end of the continental slope, the ocean floor flattens into what feature?

HINT: very flat areas that make up most of the ocean floor.

Answer 6

abyssal plain

very flat areas that make up most of the ocean floor.

Question 7

What is transform plate boundary?

Answer 7

where two plates slide past one another.

Question 8

What do the crust and the uppermost mantle make up?

Answer 8

lithosphere

Convection in the mantle drives the movement of the plates of the lithosphere over the Earth’s surface.

Question 9

What theory did Alfred Wegner propose?

Answer 9

continental drift

the hypothesis developed in the early 20th century that states that the continents move about on the surface.

Question 10

Where is new oceanic crust created?

Answer 10

at mid-ocean ridges

Question 11

How do plates move at a divergent boundary?

Answer 11

The plates move apart

Question 12

What was used to map the ocean floor using the speed of sound through water?

Answer 12

echo sounders

Question 13

What explanation did Wegener give for why Mesosaurus fossils were found on both Africa and South America?

Answer 13

Africa and South America were joined when Mesosaurus lived and then moved apart

Question 14

Which plate tectonic process creates a deep ocean trench?

Answer 14

subduction

Question 15

Where are the thickest sediments in the ocean basins found?

Answer 15

the furthest distance from the mid-ocean ridge axis.

Question 16

Complete the sentence. The Hawaiian Islands formed at a _________.

Answer 16

hotspot

Question 17

Which is true about the oldest oceanic crust?

Answer 17

It is less than 180 million years old.

Question 18

What is the driving force for plate tectonics?

Answer 18

mantle convection

Mantle convection is responsible for a variety of geological phenomena, including plate tectonics, earthquakes, and the formation of volcanic features. The movement of the Earth’s plates at the surface is influenced by the flow of the mantle beneath them, leading to the creation and destruction of tectonic plates at plate boundaries. This dynamic process contributes to the Earth’s overall thermal and geological evolution.

Question 19

Which of the following features are evidence that many continents were at one time near Earth’s south pole?

Answer 19

glacial deposits

Glacial deposits indicate a continent was once in a colder climate.

Question 20

Which plate tectonic process creates a deep ocean trench?

Answer 20

Convergent

a location where two lithospheric plates come together.

Question 21

What evidence in rocks supports the theory of seafloor spreading?

Answer 21

magnetic reversals

refer to the periodic change in the Earth’s magnetic field where the magnetic north and south poles switch places. This natural phenomenon is recorded in rocks and provides important insights into the Earth’s geological history.

Question 22

Where does most geologic activity take place?

Answer 22

at plate boundaries

a location where two plates interact.

Question 23

What is the name of the supercontinent that consisted of all the present continents?

Answer 23

Pangea