Sea Floor Spreading

The theory of continental drift stated that

• the continents were once moving but have now stopped

• the continents are slabs of rock that move and interact with each other

• there is no evidence of sea floor spreading

• the continents have always looked the way they do today

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What did Tharp and Hezzen use to create the first bathymetric map?

• line dropping

• photography

• sonar

• meter sticks

What does the ocean floor actually look like?

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How did Tharp and Hezzen's map help support Wegener's Theory of Continental Drift?

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At a divergent plate boundary,

• Two plates are pushed together by convection currents

• Magma rises and covers the ocean floor

• Magma rises and helps push the plates apart

• Magma is pushed below the ocean floor

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As you move away from the ridge, the rock on the seafloor gets

• older

• younger

• darker

• lighter

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As you get closer to the ridge, the sediment layer becomes

• thicker

• lighter

• thinner

• heavier

Why did the navy first look for magnetism in the ocean? What were they looking for?

The Earth is a gigantic magnet because

• the water in the ocean causes the rocks to rub against each other and become magnetic

• the inner core is made of liquid iron which is magnetic

• there are many metal ships on the ocean floor that attract magnets

• the magma in the outer core is always moving and creates magnetism