Quiz Chapter #13 The Ocean Floor

Select the correct description of a passive continental margin and the correct description of an active continental margin. Select one for each.

A passive continental margin is tectonically inactive and features a continental shelf, a continental slope, and a continental rise (from land toward the sea); An active continental margin is located along a convergent plate boundary, has a deep-ocean trench where subduction takes place, and may have evidence of an accretionary wedge or of subduction erosion.

How are active continental margins related to plate tectonics?

Active continental margins are located along convergent plate boundaries, where oceanic lithosphere subducts beneath the edge of the continent.

Excluding the Southern Ocean, name the four main ocean basins from the smallest surface area to the largest surface area.

Arctic Ocean, Indian Ocean, Atlantic Ocean, Pacific Ocean

How are deep-ocean trenches related to plate boundaries?

Deep-ocean trenches are sites of plate convergence where an oceanic plate subducts under another plate.

Contrast the distribution of land and water in the Northern Hemisphere and the Southern Hemisphere.

In the Northern Hemisphere, 61 percent of the surface is water whereas 39 percent of the surface is land. In contrast, the surface of the Southern Hemisphere is 81 percent water and 19 percent land.

How do oceanic ridges differ from continental mountain ranges?

Most mountain ranges form through the collision of two continents, whereas oceanic ridges form when material upwells from the mantle and generates new oceanic crust.

How does the area of Earth's surface covered by oceans compare with the area covered by land?

Nearly 71 percent of Earth's surface is covered by global oceans, whereas roughly 29 percent of Earth's surface is covered by land.

How does a guyot form?

Over time, guyots lose their original shapes and sizes through the process of weathering, after moving away from their original locations over hot spots.

The lowest point on earth is in the ________ Ocean.

Pacific

Describe the three basic types of seafloor sediments, with one example of each. Select all that apply.

Terrigenous sediments, which are derived from land, include weathered grains from rocks.; Hydrogenous sediments, which are derived from water, include manganese nodules.; Biogenous sediments, which are derived from organisms, include calcareous ooze.

How does the average depth of the oceans compare to the average elevation of the continents?

The average depth of the oceans is nearly four and a half times the average elevation of continents above sea level.

What is the primary reason for the elevated position of the oceanic ridge system?

The oceanic lithosphere at the ridge is hotter than the older lithosphere that is farther from the ridge. Because the hotter lithosphere at the ridge is less dense than the cooler lithosphere farther away, the lithosphere is more elevated at the ridge, sinking as it cools as it moves away from the ridge.

How can satellites orbiting Earth determine features on the seafloor without being able to directly observe them beneath several kilometers of seawater?

The satellite measures the variation in the sea-surface elevation by bouncing microwaves off the water's surface, which mimics the shape of the seafloor.

Why are seafloor sediments useful in studying past climates?

These sediments are composed of organisms that once lived near the surface of the sea. Because the number and types of these organisms change as the climate changes, the sea sediments they create provide a history of changes in climate.

Why are abyssal plains more extensive on the floor of the Atlantic than on the floor of the Pacific?

Unlike the floor of the Pacific Ocean, the floor of the Atlantic Ocean has very few trenches to act as traps for sediment carried down the continental slope.

Which of the following is associated with ocean ridges?

all of these

Where do some rift valleys form along the oceanic ridge system?

along the axis of the oceanic ridge system, such as the Mid-Atlantic Ridge

The continental rise is located ________.

between an abyssal plain and continental slope

What are gas hydrates?

compact chemical structures made of water and natural gas

What are the three major topographic provinces of the ocean floor?

continental margins; deep-ocean basins; oceanic ridges

Which choices below correctly describe the three major features of a passive continental margin? Select all that apply.

continental slope; continental rise; continental shelf

What features on the ocean floor most resemble flood basalts on the continents?

oceanic plateaus

In the present day, what is the most valuable non-living commodity obtained from sea floor?

oil and gas

Which type of seafloor resource is presently most valuable?

oil and natural gas

Ocean floor topography can be estimated from space using ________.

radar pulses that bounce off the ocean surface

What non-energy seafloor resource is most valuable?

sand and gravel

Which ocean is almost entirely within the Southern hemisphere?

the Indian Ocean

What is bathymetry?

the topography of the ocean floor and the measurement of ocean depths

Deep sea trenches are important features for plate tectonic studies because ________.

they are sites where the oceanic lithosphere is consumed into the mantle

Which process creates most submarine canyons?

turbidity currents