Biology chapter 13

Which of the following materials or features are not found at mid-ocean ridges?

Deep submarine trenches

Volcanic island arcs are found near which features on the seafloor?

Deep-ocean trenches

What is the average thickness of the oceanic crust?

7 km

Which of the following is associated with a passive continental margin?

No tectonic boundaries nearby

Which region is surrounded by an active continental margin?

Pacific Ocean

Which of the following is a failed rift that formed in North America over 1 billion years ago?

A Mid-Continent Rift in the Upper Midwest region

Why do mantle plumes tend to concentrate beneath supercontinents such as Pangaea?

A large landmass acts as an insulating blanket to trap heat in the mantle.

What happened when the spreading center that generated the Farallon plate collided with the North American plate?

A transform boundary was created.

On the HMS Challenger what was used to measure ocean depths?

A weighted overline

Which of the following locations displays a triple junction that resulted from a rising mantle plume? A) Eastern Africa/Arabian Peninsula B) East Pacific Rise C) Japan/East Asia D)Mid-Atlantic Ridge

A) Eastern Africa/Arabian Peninsula

The oceanic crust is composed almost entirely of ________ rocks that are underlain by ________ rocks, which makes up the lithospheric mantle.

mafic; ultramafic

Submarine volcanoes, called ________ may rise hundreds of meters above the surrounding seafloor.

seamounts

What is the speed of sound waves in water?

1,500 m/sec

Which of the following choices represents a rate of seafloor spreading commonly associated with a ridge such as the Mid-Atlantic Ridge A) 1-5 mm/yr B) 1-5 cm/yr C) 1-5 m/yr D) 1-5 km/yr

1-5 cm/yr

The Challenger Deep has previously been measured to have a depth of 10,994 meters. You have been sent to the part of the Pacific Ocean to verify this depth with an echo sounder. Assuming that Depth = 1/2 (1,500 m/sec*echo travel time), approximately how many seconds should it take for the sound wave to leave your ship, strike the bottom of the Challenger Deep, and return if the depth is correct?

14.66 seconds

The sheeted dike complex is layer ________ of the ocean floor.

3

The HMS Challenger expedition took about ________ years.

3 and a half

Where do rift valleys form along the oceanic ridge system?

Along the axis of some ridge segments where the rift is down-faulted

The deep diving submersible ________ can reach 4000 m, and is 7.6 meters long

Alvin

Which of the following is not an example of a continental rift?

Appalachia, United States

What generates the magma necessary for seafloor spreading?

Decompression melting

Approximately what percentage of the Earth's surface consists of deep-ocean basins?

B) 30%

What rock would you expect to find associated with a mid-ocean ridge?

Basalt As found in the nether in minecraft

Where is the deepest place on Earth?

Challenger Deep

Which of the following is not a possible mechanism contributing to continental rifting?

Changes in gravitational attraction of the moon

Which of the following scenarios would likely result in the development of a passive continental margin?

Continental blocks rifting apart and becoming separated by seafloor spreading

Which of the following groups contains all three major topographic provinces oceanographers use to define the seafloor?

Continental margins, mid-ocean ridges, and deep-ocean basins

Which part of a passive continental margin is built up by repeated deposition from turbidity currents?

Continental rise

This is the flattest portion of the continental margin.

Continental shelf

Along which tectonic boundary are deep-ocean trenches found?

Convergent

Which of the following is associated with an active continental margin?

Convergent boundaries

T/F Deep-ocean basins comprise about 20% of Earth's surface.

FALSE

T/F Abyssal plains refer to flat areas of the ocean floor that are riddled with hundreds of seamounts.

FLASE

T/F An active continental margin is located hundreds of miles away from the nearest tectonic boundary.

FLASE

T/F Because massive submarine structures such as seamounts and ridges exert stronger than average gravitational attraction, they produce depressed areas on the ocean's surface.

FLASE

T/F Black smokers can be found along subduction zones.

FLASE

T/F Oceanic ridges form as a result of compressional stress.

FLASE

Which of the following is an example of a mid-ocean ridge?

Mid-Indian Ridge

The continental shelf is composed of which material(s)?

Granitic crust covered with sedimentary rocks

1) Which ship was involved in the first global, comprehensive study of the Earth's oceans starting in 1872?

H.M.S. Challenger

How do researchers today routinely determine the depth of the water to the seafloor?

High-resolution multibeam instruments

Which process, common near black smokers, uses hot water circulating through the crust to alter olivine and pyroxene into chlorite and serpentine?

Hydrothermal metamorphism

Which of the following locations is an example of spontaneous subduction? Mariana Trench B) Peru-Chile Trench C) East African Rift D) Cascadia Trench

Mariana Trench

What are the two types of continental margins?

Passive and active

What is the name of the supercontinent that preceded Pangaea?

Rodinia

What is the definition of subduction erosion?

Sediment and rock are scraped off the bottom of an overriding plate and transported into the mantle by a descending plate.

What tool is often used to measure the topography of the seafloor today?

Sonar

What kind of subduction occurs when old, dense lithosphere sinks into the mantle by its own weight rather than by compressional force?

Spontaneous subduction

How do deep-ocean trenches form?

Subducting lithosphere descends into the mantle.

What is the definition of turbidity current?

Submarine landslide

T/F Based on its fast rate of spreading, the East Pacific Rise has a gradual profile with gently sloping sides.

TRUE

T/F Continental shelves are valuable locations that support important fishing grounds.

TRUE

T/F Continental shelves on passive margins are larger and broader than those on active margins.

TRUE

T/F The Challenger Deep of the Mariana Trench is named for the H.M.S Challenger, the ship that first measured it.

TRUE

T/F The continental rise sediments are deposited by turbidity currents that flow down the continental slope.

TRUE

Which of the following will mark the furthest extent of a continent?

The lowest part of the continental slope

Although many areas of the continental shelves are relatively featureless, there are some locations on the shelves that have received extensive glacial deposits and significant dissection by streams. How would this have been possible?

The sea level dropped during the last glacial episode because water was stored in large ice sheets, exposing the shelves.

A(n) ________ forms when sediments from the ocean floor and pieces of oceanic crust are scraped from a subducting oceanic plate and adhere to an overriding tectonic plate.

accretionary wedge

The measurement of ocean depth and the topography of the ocean floor are known as ________.

bathymetry

Thermal springs known as ________ are often associated with oceanic ridges, where hot water containing dissolved minerals gushes from the seafloor.

black smokers

Submarine canyons found cutting into the continental shelf and slope are believed to have been created ________.

by rivers during the ice age

A ________ forms when a rising mantle plume causes the overlying crust to dome and separate into three rifts.

divergent boundary

Since the oceanic lithosphere in the Peru-Chile area is too buoyant to subduct spontaneously, it ________.

is forced under the overlying plate by compression

Volcanic islands such as the Hawaiian Islands form as a result of ________.

mantle plumes