Geology Exam 3: Chapter 13

tablemount

A seamount that grew above sea level, experienced wave erosion, and is now inactive.

accretionary wedge

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.

ophiolite complex

A(n) ________ is a sequence of layers composing the oceanic crust that includes sheeted dikes, basalts, and gabbro.

Convergent

Along which tectonic boundary are deep-ocean trenches found?

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

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?

Seamount

An active volcano that occurs along the crest of the mid-ocean ridge.

pacific

Baja Mexico and the city of Los Angeles are both located on the ____________ plate.

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

How are active continental margins related to plate tectonics?

Due to gravity, ocean water is attracted to areas of high topography and away from areas of low topography on the sea floor, causing bulges and depressions on the ocean surface. Satellite radar can detect these changes in elevation.

How are satellites able to map the ocean floor?

Subducting lithosphere descends into the mantle.

How do deep-ocean trenches form?

An accretionary wedge forms at an active continental margin when the subducting oceanic slab scrapes pieces of itself onto the more buoyant continental slab.

How does an accretionary wedge form?

Farallon plate

It was an oceanic plate that used to exist between the Pacific and North American Plates.

-continental volcanic arcs -volcanic island arcs

Melt from the subducting plate rises to the surface, erupts through the crust on the overriding plate and forms _____________________ on continents, or _______________________ in the ocean.

crustal upwarp, rift valley, linear sea, ocean

Name the correct order of rifting events.

mid-ocean ridges

Oceanic crust spreads at _________________, creating new crust and slowly enlarging the ocean basin.

a right lateral sense of motion

Strike-slip faulting of the Queen Charlotte and San Andreas fault systems shows __________.

Ring of Fire

Subduction zones surrounding the Pacific Ocean give rise to volcanoes. This area surrounding the Pacific Ocean is called the ____________________.

by rivers during the ice age

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

True

T/F: A passive continental margin is located hundreds of miles away from the nearest tectonic boundary.

True

T/F:Abyssal plains are flat areas of the ocean floor that are likely the most level places on Earth.

14.66 seconds

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?

linear sea

The Gulf of Aden represents which part of the rifting sequence?

-Mid-Atlantic -East Pacific

The _________________Ridge is spreading at a much slower rate than the ________________Rise.

Granitic crust covered with sedimentary rocks

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

Gabbro

The lowest layer of an ophiolite complex of the oceanic crust is ______.

bathymetry

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

convergent; transform

The plate boundary in the U.S. Pacific Northwest is _____, while most of the California coast is characterized by a _____ plate boundary.

Mariana's Trench

The steepest angle of subduction of oceanic plates can be found at _______.

flood basalt formation

The timing of __________ and continental breakup strongly correlate.

black smokers

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

mantle plumes

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

a relatively smooth swell with gentle slopes

What are the features associated with a divergent boundary that is spreading quickly?

passive and active

What are the two types of continental margins?

decompression of rock

What causes melting of material under divergent plate boundaries?

mantle peridotite, gabbro, sheeted dike complex, pillow lavas, deep-sea sediments

What contains the entire ophiolite suite, in order from the mantle to the seafloor?

seamount chains

What feature connects the South American Paraná and African Entedeka flood basalts?

Decompression melting

What generates the magma necessary for seafloor spreading?

The San Andreas and Queen Charlotte Faults were established where it was subducted beneath the North American plate.

What happened to the Farallon Plate approximately 20 million years ago?

New oceanic crust and lithospheric mantle are generated by the cooling of molten rock upwelling from the mantle.

What happens as plates diverge at an oceanic ridge?

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

What is bathymetry? -the composition of the seafloor -the total volume of water within a given ocean -the topography of the ocean floor and the measurement of ocean depths -a continuous record of plants and animals that live in the sea and have been fossilized in the seafloor the salinity of ocean water

4500 meters

What is the correct water depth for an echo travel time of 6 seconds? (For the purposes of this exercise, assume pressure and temperature effects on sound wave velocity are negligible.)

Submarine landslide

What is the definition of a turbidity current?

Barrier reefs surround an inactive volcano emerging above sea level, while atolls surround the previous location of a submerged volcano.

What is the difference between a barrier reef and an atoll?

1,500 m/sec

What is the speed of sound waves in water?

Basalt

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

volcanic rocks, clastic sedimentary rocks, deep sea sedimentary rocks

What sequence of rocks would you expect rift valley evolution to produce, from oldest to youngest?

pillow lavas and gabbro

What two layers of the ophiolite sequence are compositionally similar, but formed in different areas with respect to the crust?

when a continent is broken apart by a divergent boundary

When do new oceans form?

at mid-ocean ridges

Where are most modern divergent plate boundaries found?

In tropical latitudes

Where do coral reefs exist with sea mounts?

within continents

Where do most divergent boundaries originate?

Challenger Deep

Where is the deepest place on Earth?

-continental slope -continental rise

Which is a feature of a passive continental margin? -continental slope -continental rise -accretionary wedge -trench -hot spot

Fringing reef, barrier reef, atoll

Which is the correct order of coral reef development near seamounts?

magnetometer

Which method is not a technique currently used by ocean scientists to map the topography of the ocean floor?

-continental slope -continental shelf -continental rise

Which of the below choice(s) correctly describe(s) the three major features of a passive continental margin? -continental slope -deep-ocean trench -continental shelf -continental rise -accretionary wedge

1-5 cm/yr

Which of the following choices represents a rate of seafloor spreading commonly associated with a ridge such as the Mid-Atlantic Ridge?

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

Which of the following groups contains all three major topographic provinces oceanographers use to define the seafloor? -Mid-ocean ridges, continental shelves, and divergent boundaries -Deep-ocean basins, active margins, and passive margins -Continental margins, mid-ocean ridges, and deep-ocean basins -Submarine trenches, mid-ocean ridges, and turbidity currents

No tectonic boundaries nearby

Which of the following is associated with a passive continental margin? -Divergent boundaries -Convergent boundaries -No tectonic boundaries nearby -Transform boundaries

convergent boundaries

Which of the following is associated with an active continental margin? -No tectonic boundaries nearby -Convergent boundaries -Divergent boundaries -Transform boundaries

Coral reefs at the ocean surface grow away from seamounts over time.

Which of the following statements about coral reefs and seamounts is most accurate? -Coral reefs at the ocean surface grow towards seamounts over time. -Seamounts at the ocean surface grow towards coral reefs over time. -Coral reefs at the ocean surface grow away from seamounts over time. -Seamounts at the ocean surface grow away from coral reefs over time.

Continental rises

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

Pacific ocean

Which region is surrounded by an active continental margin?

Satellites with radar altimeter

Which seafloor mapping method can map the largest extent of seafloor in the shortest amount of time?

normal faulting

Which type of faulting is associated with the development of new ocean floor?

Seamounts subside as tectonic plates move. Coral reefs grow away from the seamount in order to stay near the sunlight.

Why do coral reefs at the ocean surface grow away from seamounts over time?

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

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

The rate of seafloor spreading at the East Pacific Rise is very fast.

Why does the East Pacific Rise lack a rift valley?

Thermal contraction

________ accounts for greater ocean depths moving away from the oceanic ridge toward the deep ocean basin.

-submarine canyons -turbidity currents

_____________________ are deep valleys at passive continental boundaries. They are likely carved out by _________________ , which occur when sediment-laden water rapidly moves down slope

continental slope

a steep incline that marks the boundary between the continental crust and the oceanic crust.

abyssal plain

flat seafloor in the deep ocean.

continental shelf

gently sloping, submerged extension of the continent.

submarine trench

narrow creases in the seafloor that result from subduction.

Continental rise

wedge of sediments deposited by turbidity currents that formed at the base of the slope.