Seafloor Spreading

A divergent boundary occurs where plates ....

• Pull apart

• Come together

• Slide past each other

• subducting

How is it possible for new crust to be formed without increasing the surface area of the Earth?

• Crust is recycled in subduction zones at the same time it is created at mid-ocean ridges

• New crust is underwater where it sinks

• New crust breaks more easily than old crust

• The oldest crust just breaks apart as the plates move

The average density of continental crust is 2.8 g/cm³ and the average density of oceanic crusts is 3.2 g/cm³. If these two plates came together, what would happen?

• The two plates would push apart and form a rift zone.

• The oceanic plate would rise up over the continental plate.

• The oceanic plate would sink under the continental plate.

• The two plates would meet head on and rise up to form mountains.

Which of the following objects best represents the movement that occurs during sea-floor spreading?

• Elevator
• Conveyor belt
• Rollercoaster
• Hot air balloon

Scientists use ______ to map the ocean floor

• radar

• pulsar

• lidar

• sonar

At its oldest, ocean crust is about __________ years old

• 300-350 million

• 180-200 million

• 3.5 billion

• 10-20 million

The OLDEST seafloor is located

• closest to the mid-ocean ridge.

• farthest from the mid-ocean ridge.

• east of Hawaii

• west of California

Which of the following supports the theory of seafloor spreading?

• Correlation of rock layers

• Crustal slab pull

• Magnetic reversals recorded in rocks

• Continuous mountain chains

Seafloor spreading...

• creates new oceanic crust

• destroys or recycles crust

• creates new continental crust

• creates old crust

Rock at the mid ocean ridges...

• is the oldest rock on the earth.

• is older than continental rock.

• is younger than continental rock.