Harper seafloor spreading

1. The youngest rocks on the ocean floor are located ____.

• near continents

• far from mid-ocean ridges

• at mid-ocean ridges

• near Asia

2. Scientists have observed that the continents move apart or come together at speeds of a few centimeters per ____

• century

• day

• year

• decade

3. The alignment of iron minerals in rocks when they are formed reflects the fact that Earth's ____ has reversed itself several times in the past.

• core

• magnetic field

• asthenosphere

• gravity

4. Seafloor spreading occurs because ____.

• new material is being added to the asthenosphere

• earthquakes break apart the ocean floor

• sediments accumulate at the area of spreading

• molten material beneath Earth's crust rises to the surface

5. While studying the ocean floor, scientists found ____ bands of magnetism.

• alternating

• plastic

• no

• sediment

6. Wegener believed that the continents were assembled as part of a supercontinent about ____ years ago.

• 250 million

• 400 million

• 300 million

• 500 million

7. Many early mapmakers thought Earth’s continents had moved based on ____.

• plate boundary locations

• climatic data

• matching coastlines

• fossil evidence

8. The magnetic pattern of ocean-floor rocks on one side of an ocean ridge is ____.

• younger than on the other side

• much different from the magnetic pattern found in rocks on land

• at right angles to the ocean ridge

• a mirror image of that of the other side

9. A vast, underwater mountain chain is called a(n) _________.

• Mid -ocean ridge

• deep-sea trench

• oceanic crust

• ocean floor sediment

10. Wegener’s hypothesis of _________________________ stated that Earth’s continents had once been joined as a single landmass.