Chapter 9

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

• The ocean floors are an average of about four times deeper below sea level than the average elevation of the continents above sea level.

• The continents stick up above sea level by about the same vertical distance that the ocean floor is below sea level.

• The oceans are hundreds of times deeper on average than the continents' average elevation.

• The ocean floors are higher in elevation than the continents' average distance below sea level.

Ocean covers approximately ________ percent of Earth's surface

• 71

• 11

• 51

• 91

What are the two most abundant elements dissolved in seawater? What is produced when these elements combine?

• The two most abundant elements dissolved in seawater are chlorine and sodium, which combine to form sodium chloride.

• The two most abundant elements dissolved in seawater are chlorine and calcium, which combine to form calcium chloride.

• The two most abundant elements dissolved in seawater are bromine and calcium, which combine to form calcium bromide.

• The two most abundant elements dissolved in seawater are chlorine and potassium, which combine to form potassium chloride.

• The two most abundant elements dissolved in seawater are bromine and sodium, which combine to form sodium bromide.

Identify the feature indicated by the letter C in the image above.

• continental rise

• continental margin

• deep-sea fan

• continental slope

• abyssal plain

What are turbidity currents?

• dense mixtures of sand, mud, and other debris that  move at high speeds up submarine canyons

• dense mixtures of sand, mud, and other debris that move at low speeds down submarine canyons

• dense mixtures of sand, mud, and other debris that move at high speeds down submarine canyons

• dense mixtures of sand, mud, and other debris that  move at low speeds up submarine canyons

How are active continental margins related to plate tectonics?

• Active continental margins are associated with divergent boundaries, where new lithosphere is created and added both to the continental crust and the seafloor.

• Active continental boundaries are the starting points of the creation of new ocean basins.

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

• Active continental margins commonly have submarine canyons where oceanic lithosphere subducts.

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

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

• Although both the Atlantic Ocean and the Pacific Ocean have the same number of ridges, the ridges in the Pacific Ocean consume sediment and lithosphere at a much quicker rate than those in the Atlantic Ocean.

• Although both the Atlantic Ocean and the Pacific Ocean have the same number of trenches, the trenches in the Pacific Ocean consume sediment and lithosphere at a much quicker rate than those in the Atlantic Ocean.

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

• 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.

• Less sediment is provided to the Pacific Ocean than the Atlantic Ocean; thus, fewer abyssal planes are produced in the Pacific Ocean.

Which of the following is associated with oceanic ridges?

• rift zones

• volcanoes

• elevated topography

• all of the above