G6 Plate Tectonics

What was the most complete hypothesis that Alfred Wegener made?

• All the continents would slowly drift together over millions of years.

• All the continents would fit together like a giant world jigsaw puzzle.

• All the continents were once grouped together and had drifted apart over time.

• All the continents were slowly rotating around the world in continental drift.

Why is the Atlantic Ocean growing larger while the Pacific Ocean is growing smaller?

• The Atlantic Ocean has more mid-ocean ridges than the Pacific Ocean, so that keeps it growing larger.

• The Atlantic Ocean is building more islands than the Pacific Ocean, so the continents are pushed apart more.

• The Atlantic Ocean has more subduction areas, whereas the Pacific Ocean has more mid-ocean ridges.

• The Atlantic Ocean has a spreading mid-ocean, while the Pacific Ocean is subducting faster than the mid-ocean ridges can make new land.

What type of crust is thin and dense?

• oceanic

• continental

• water

• geosphere

What type of crust is thick and less dense?

• oceanic

• continental

• water

• geosphere

What is the name for the area between the two diverging plates in this picture?

• transform boundary

• ocean trench

• rift valley

• subduction zone

How do tsunamis differ from waves caused by strong winds?

• Larger amounts of water are displaced by waves caused by the wind than by tsunamis.

• Tsunamis involve both deep water and surface water, but waves caused by wind involve only surface water.

• Tsunamis involve only surface water, but waves caused by wind involve both deep water and surface water.

• Waves caused by wind carry more energy and are more destructive than tsunamis.

How did fossils show that the continents were once joined together?

• Animal fossils such as the mesosaurus were found on one continent.

• Scientists found examples of different kinds of fossils on some continents.

• Plant fossils of the same kind of fern like plants were found on five continents.

• Freshwater animal fossils were found in the nearby oceans.

Which of the following statements is NOT true about sea-floor spreading?

• Magma flows through cracks in Earth's crust and hardens.

• Continental crust is formed by the ridges as they grow.

• Mid-ocean ridges are the sources of the spreading.

• Older rock is farther away from the mid-ocean ridges.

The sinking of ocean crust back into the mantle when it meets continental crust is ____ , and this occurs at ____ .

• sea-floor spreading / ocean trench

• sea-floor spreading / mid-ocean ridge

• subduction / ocean trench

• subduction / mid-ocean ridge

How do convection currents drive the motion of Earth’s plates?

• Ocean water rises as it warms and falls as it cools to move the plates.

• Hot melted rock rises and cooler rock sinks in the mantle, forming currents that move the plates.

• Melted rock rises and falls, and the currents move the mantle while the crust remains in place.

• The crust moves in a current to drive the motion of the water in the oceans.