Science Chapter 1/section 4 and 5

Question 1

what is the mid ocean ridge

Answer 1

the longest chain of mountains in the world. It was mapped in the mid-1900s by scientists using sonar. It extends into all of the earth’s oceans and is mostly hidden underwater

Question 2

what is sonar

Answer 2

a device that bounces sound waves off underwater objects and then records the echos of these sound waves. It maps the ocean floor

Question 3

What happens to rock along the mid-ocean ridge when new molten material erupts

Answer 3

molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge.

Question 4

what is sea floor spreading

Answer 4

A term used by Harry Hess. It is when the molten material from the mantle erupts and pushes older rock to the side which causes new rock to form on the ocean floor.

Question 5

What evidence support’s theory of sea floor spreading

Answer 5

evidence from molten material, evidence from magnetic stripes and evidence from drilling samples

Question 6

what is the evidence from molten material that supports sea floor spreading

Answer 6

Using a submarine (called the Alvin) scientists saw rocks shaped like pillows that could only be formed when molten material hardens quickly after erupting underwater.

Question 7

what evidence from magnetic stripes supports sea floor spreading

Answer 7

the rocks that makes up the ocean floor lie in patterns of magnetized stripes. They hold record of the reversals in the Earth’s magnetic field. The rocks contain iron which would line up with the magnetic pole. Some point north and some point south

Question 8

what evidence from drilling supports sea floor spreading

Answer 8

Rock samples drilled into the ocean floor were brought up through pipes. The scientists found that the further away from the ridge the rock samples were taken- the older the rocks were. The youngest rocks were always in the center of the ridges.

Question 9

How can the ocean floor keep getting wider

Answer 9

the ocean floor plunges into deep underwater canyons called deep ocean trenches. the trenches form where the oceanic crust bends downward.

Question 10

what is subduction

Answer 10

the process by which the ocean floor sinks beneath a deep ocean trench and back into the mantle

Question 11

Is new oceanic crust hot or cold

Answer 11

hot but as it moves away from the mid-ocean ridge, it cools and becomes more dense

Question 12

How long does it take subduction to allow deep ocean trenches to sink back down into the mantle

Answer 12

tens of millions of years. the ocean floor is renewed every 200 million years

Question 13

What is happening with subduction in the Pacific Ocean.

Answer 13

the mid-ocean ridge does not add new crust fast enough before it is swallowed by the deep ocean trenches- so the ocean floor is SHRINKING

Question 14

What is happening with subduction in the Atlantic Ocean

Answer 14

the ocean floor is EXPANDING. The ocean floor has only a few short trenches so the spreading ocean floor has no where to go and the ocean floor is spreading which will cause the ocean to become wider

Question 15

What is plate tectonics

Answer 15

A geological theory that states pieces of the Earth’s Lithosphere are in constant, slow motion, driven by convection currents.

Question 15

What are plates

Answer 15

A section of the Lithosphere that slowly moves.

Question 16

What are plate boundaries

Answer 16

The edges of different pieces of the Lithosphere

Question 18

What are plate boundaries

Answer 18

They divide the lithosphere into large plates.

It is where the edges of different plates meet at lines.

Question 19

What are faults

Answer 19

A break in Earth’s crust where rocks have slipped past each other- form along plate boundaries

Question 20

What are convergent boundaries

Answer 20

Where two boundaries collide

Question 21

What are divergent boundaries

Answer 21

A plate boundary where two plates move apart- or away from each other. They usually occur in the ocean ridge. They can occur on land- causing a deep valley (a rift valley)

Question 22

What are convergent boundaries

Answer 22

Where two boundaries come together or converge- it is a collision. It can form a mountain range.

Question 22

What are convergent boundaries

Answer 22

Where two boundaries come together or converge- it is a collision.

Question 23

What are 3 types of plate boundaries

Answer 23

transform boundaries
divergent boundaries
convergent boundaries

Question 24

What is the continents’ slow dance

Answer 24

The fact that the continents are moving slowly. They move about 1-10 cm per year.

Question 25

When 2 plates collide, what determines which one comes out on top

Answer 25

The density of the plates- the less dense (or lighter) plate comes out on top

Question 26

what does subduction mean

Answer 26

The process where oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary

Question 27

What happens when 2 plates carrying continental crust collide

Answer 27

subduction DOES NOT happen because both plates are low density.

Question 28

What happens when 2 plates- one oceanic crust and one continental crust- collide

Answer 28

oceanic crust is more dense and goes under the continental crust- so the oceanic crust is subducted.

Question 29

What major event in Earth’s history began about 225 million years ago? explain.

Answer 29

Pangea began to break apart and the continents began to form. Plate movements caused the land mass to split apart.