Seafloor Spreading

What did Harry Hess discover about the Pacific Ocean floor during World War II?

• It was a flat, featureless plain covered in sediment.

• It contained vast mountain ranges, canyons, and trenches, similar to land formations.

• It was home to an ancient, sunken city.

• It was completely devoid of any geological features.

What significant geological feature was discovered in the Atlantic Ocean in 1953?

• A deep, narrow trench.

• A vast, flat abyssal plain.

• A 12,000-mile long mountain range of underwater volcanoes.

• A large, inactive volcanic island.

What was Harry Hess's theory of "seafloor spreading"?

• The ocean floor was slowly sinking into the Earth's mantle.

• Molten rock was forced up from inside the Earth at mid-ocean ridges, forming new crust and pushing older crust away.

• Ocean currents were causing the seafloor to expand and contract.

• Sediment accumulation was causing the ocean floor to grow in size.

What is the process called where the Earth's crust is recycled back into the Earth's interior?

• Continental drift.

• Seafloor spreading.

• Subduction.

• Volcanic eruption.