Sea Floor Spreading and Plate Tectonics

Magma, or molten material, __________ and hardens

• cools
• warms
• shrinks

The oceanic crust is pushed aside on both sides of the 

• Continent's edge
• Deep-ocean trench
• Mid-ocean ridge

The process by which the ocean floor sinks beneath a deep-ocean trench back into the mantle is known as...

• sea-floor spreading
• adding material to the ocean floor
• subduction
• continental drift

The land feature that happens when there is subduction is called a...

• mid-ocean ridge
• deep-ocean trench
• asthenosphere

New crust is always formed at the...

• mid-ocean ridge
• deep-ocean trench
• asthenosphere

Older crust is found towards the...

• Mid-ocean ridge
• Deep-ocean trench
• Asthenosphere

If there are MORE mid-ocean ridges than subduction zones, what happens to the ocean?

• It gets larger
• It gets smaller
• It sinks

If there are more subduction zones than mid-ocean ridges, what happens to the ocean?

• It gets bigger
• It gets smaller
• It sinks and rises

Which is NOT evidence of sea-floor spreading?

• Molten magma constantly erupting
• Drilling samples of rock
• Magnetic stripes
• Fossil evidence

Sea-floor spreading begins at the 

• Deep ocean trench
• Mid-ocean ridge
• Continent's edge