OCE 1001 Ch. 3

Satellites are used to map the ocean floor because ________.

the shape of the ocean surface reflects large features on the seafloor

Rocks like the ones shown in the photo most likely formed at which of the following tectonic settings?

divergent plate boundary

Along the margins of the Pacific are found most of Earth's:

oceanic trenches

New lithosphere is produced in association with:

oceanic ridges

Which of the following feature(s) is/are associated with the mid-ocean ridge? Choose all that apply.

-basalt volcanism and pillow lavas -a central rift valley -volcanoes -hydrothermal vents

Which of the following techniques used to determine ocean bathymetry is illustrated in the image?

Side-scan sonar

Extending from the base of the continental rises into the deep-ocean basins are flat depositional surfaces called:

abyssal plains.

The reason the deposit on the bottom forms the way it does is a result of

settling velocity

What percent of Earth's volcanic activity, each year, takes place on the seafloor?

85%

To which planet is NASA sending the spacecraft InSight to study crustal movements similar to earthquakes?

Mars

Why is the average depth of the ocean much greater than the average height of land?

Oceanic crust is more dense than continental crust.

Which of the following is the predominant process that forms the thick blanket of sediment on abyssal plains the deep-ocean floor?

Suspension settling

What common item is used in this video to demonstrate a turbidity current?

a large jar filled with water and sediment

Of the following items, which is/are associated with a passive continental margin? Choose all that apply.

- a wide continental shelf - a continental rise

In the figure above, which shows a portion of the hypsographic curve. Which area(s) represent(s) the middle of tectonic plates? Choose all that apply.

-B -D

In the figure above, which shows a portion of the hypsographic curve. Which area(s) represent(s) the abyssal plains?

-D

Of the following statements about Earth's hypsographic curve, which is/are true? Choose all that apply.

-The hypsographic curve shows the percentage of Earth's surface area that is covered by ocean waters. -The hypsographic curve shows that a majority of the exposed land is below 1 kilometer in elevation. -The hypsographic curve shows that a majority of the ocean floor is more than 4 kilometers deep. -The hypsographic curve shows that the average depth of the ocean is about four times the average height of the continents.

Review the accompanying topographic map of the eastern United States and the figure of a typical continental margin in this region. Label the different features shown. Note that not all labels will be used. Drag the appropriate labels to their respective targets. You do not need to use all labels.

1. Continental Shelf 2. Shelf Break 3. Continental Slope 4. Continental Rise 5. (bottom) Passive Continental Margin

Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. Note that some terms will remain unused.

1. Oceanic crust spreads at "mid-ocean ridges," creating new crust and slowly enlarging the ocean basin. 2. "Submarine canyons" are deep valleys at passive continental boundaries. They are likely carved out by "turbidity currents," which occur when sediment-laden water rapidly moves down slope. 3. Melt from the subducting plate rises to the surface, erupts through the crust on the overriding plate and forms "continental volcanic arcs" on continents, or "volcanic island arcs" in the ocean. 4. Subduction zones surrounding the Pacific Ocean give rise to volcanoes. This area surrounding the Pacific Ocean is called the "Ring of Fire."

The greatest proportion of Earth's surface lies in this elevation/depth interval.

4,000 - 5,000 m below sea level

A ship's fathometer (an echo sounder) transmits a sound pulse and records the return of an echo 7.4 seconds later. If the speed of sound in water is 1,500 m/second, what is the water depth in meters?

5,550 meters

Compare continental margins and ocean basins of the Atlantic and Pacific oceans using the map below. Deep ocean trenches are delineated with red lines, which indicates the margin is active. Label these features correctly for margin type and ocean basin dynamics.

Active Continental Margins: -Continental margin D -Continental margin E Passive Continental Margins: -Continental margin A -Continental margin B -Continental margin C Shrinking Ocean Basin: -Pacific Ocean Basin Expanding Ocean Basin: -Atlantic Ocean Basin

Match the term with the appropriate phrase. Drag the terms on the left to the appropriate blanks on the right

Bathymetry− measurement of ocean depth and seafloor topography Hypsographic curve− cumulative plot of the frequency of depth or elevation Multi-beam sonar− a method of mapping the topography of the ocean floor along a strip up to 60 km wide Seismic reflection profile− used to determine ocean structure beneath the sea floor Precision-depth recorder (PDR)− uses high frequency sound waves to measure ocean depth

Characteristics of passive continental margins include which of the following?

Broad continental shelves

Where does the deep-ocean basin begin along a passive continental margin?

Continental slope

Which of the following is a difference between passive and active continental margins?

Convergent active margins will have a steep continental slope, whereas passive margins will have a more gradual slope.

Can you explain why atolls extend from the surface of the ocean down to great depths into the sea? Corals, which make up these ring-shaped structures, can only live where water is warmed and illuminated by sunlight, no more than approximately 45 meters deep. How do you explain an atoll that extends thousands of meters deep?

The coral reef once formed around an active volcano. The reef became a barrier reef, with hard skeletons of previous colonies acting as the scaffolding for new ones on top. The volcano gradually sank into sea, moving with the plate it rested on, as the coral continued to grow upward, leaving the atoll as a ring structure at the top.

What effect do turbidity currents have on the continental slope? Hints

Turbidity currents are erosive to the continental slope and, as a result, carve out submarine canyons.

Which of the following best describes turbidity currents?

Underwater avalanches of muddy water mixed with rocks and other debris

Satellites use microwave beams to measure sea level to an accuracy of four ________.

centimeters

Volcanic peaks that are below sea level but rise more than 1 kilometer above the deep-ocean floor and have a flattened top are called ________.

guyots

The direction of motion along a seafloor transform fault is:

in the same direction as the plates are spreading.

The island of Java is an example of a volcanic island associated with volcanic activity at a ________.

island arc

With respect to mid-ocean ridges, transform faults are:

perpendicular to the ridge axis

Most large ocean floor features owe their origins to _________.

plate tectonic processes

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Choose the one option that does not fit the pattern.

rift velley metal sulfide deposits pillow basalts seamounts (trenches)

In comparison with other ocean basins, major sedimentary features such as continental rises and abyssal plains are relatively rare in the Pacific. The primary reason for their scarcity in the Pacific is that __________.

sediment is trapped within the trenches of the convergent plate boundaries ringing the Pacific

The correct order of seafloor features from the coast to the mid-ocean ridge is:

shelf, slope, rise, abyssal plain

The method that is used most frequently to investigate sediment and rock layers of the sea floor is:

sound waves (specifically seismic reflecting profiling)

Older lithosphere is destroyed in association with:

deep-sea trenches.

What is a linear sea floor feature that is seismically inactive, occurs beyond offset mid-ocean ridge segments, and the relative movement between two points on either side of the feature is in the same direction?

fracture zone

What is the characteristic layering of an individual turbidity current deposit called?

graded bedding

All true oceanic islands are ________ in origin.

volcanic

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Choose the one option that does not fit the pattern.

Rift valley

The first recorded attempt to measure the ocean's depth was conducted using which of the following techniques?

Sounding

Volcanic features on the ocean floor that are less than 1,000 meters (0.6 miles) tall are called:

abyssal hills or seaknolls.

The distinctive type of sedimentary layering that has largest particles on the bottom and smallest particles on the top, with intermediate sized particles in the middle, is called which of the following?

graded bedding

On a deep-sea voyage in the North Pacific, near the Aleutian Islands of Alaska, you begin to explore a deep, long, narrow region in the ocean floor. You begin to discuss what this is with a partner and come up with the following theories. Determine whether each statement presents a likely scenario. Select the three that apply.

-It is most likely a deep-ocean trench because they are common along the active continental margins. -It is most likely a deep-ocean trench because they are common along the margins of the Pacific Ocean. -The feature was most likely caused by one oceanic crust subducting under a leading edge of a continent.

Of the following statements about mapping the ocean floor, which is/are true? Choose all that apply.

-Measurements of sea surface elevation by satellites are used to produce maps of the sea floor. -Only about 20% of the sea floor has been accurately mapped in detail. -Multibeam surveys from ships produce very detailed maps of the sea floor.

Which of the following statements accurately describe(s) the depth and height of Earth's surface as shown on the hypsographic curve? Choose all that apply.

-The percentage of Earth's surface above sea level is 29.2%. -More people have been to the top of the tallest mountain on Earth than have been to the bottom of the deepest trench. -The average depth of the ocean is much greater than the average height of land.

What processes influence the shape and features of continental shelves? Choose all that apply.

-large fluctuations in sea level over geologic time -trench formation at convergent boundaries -tectonic activity produced by offshore faults -major climate changes, such as ice ages

Judge the following sentence according to the criteria given below: Multibeam SONAR systems have resolution limitations in deep water BECAUSE beams of sound spread out with depth.

The assertion and the reason are both correct, and the reason is valid.

Judge the following sentence according to the criteria given below: Few abyssal plains are located in the Pacific Ocean BECAUSE turbidity currents only occur along passive continental margins.

The assertion is correct, but the reason is incorrect.

The measurement of ocean depth and the charting of seafloor topography is called __________.

bathymetry

Of the following techniques, which one(s) can be used to map the sea floor? Choose all that apply.

-recording many depths using a long cable -using satellites to measure the sea surface -sending sound through water (sonar) -direct visitation of the sea floor

The majority of ocean trenches are associated with ___________. Choose all that apply.

-very deep ocean water depths -the Pacific Ring of Fire -volcanic arcs and active continental margins -subduction zones and associated faults -narrow or no continental shelves

Which of the following is an example of an active continental margin? Choose all that apply.

-west coast of Chile -west coast of the United States

On the cross-section shown below, correctly identify the following features.

1. A- Magma (heat source) 2. C- Metal sulfide deposits 3. B- Black smoker

The image below shows a perspective view of a mature ocean basin. Match the letters with the correct marine provinces or features listed below.

1. B-Continental Margin 2. A-Mid-ocean ridge 3. C- Ocean Basin

Review the figure, and label the different features shown. Drag the appropriate labels to their respective targets. Note that not all labels will be used.

Left to right: turbidite deposits, graded bed, fine-grained particles, coarse-grained particles, type of sediment that settled last during a turbidity, type of sediment that settles first during a turbidity.

Judge the following sentence according to the criteria given below: The Pacific Ring of Fire is home to the majority of Earth's active volcanoes and large earthquakes BECAUSE of the prevalence of divergent plate boundaries along the Pacific Rim.

The assertion is correct, but the reason is incorrect.

What features are associated with a passive continental margin? Choose all that apply.

-continental rise -Flat coastal terrain

The image below shows a close-up view of a mid-ocean ridge that is offset by a linear fault/fracture. Match the letters with the correct features.

1. A: Rift valley of a mid-ocean ridge 2. E: Lithosphere 3. C: Asthenosphere 4. B: Fracture zone 5. D: Transform fault

On the diagram of a passive continental margin shown below, match the letters with the correct features.

1. C- Turbidity Current 2. B- Deep-Sea Fans 3. D- Submarine Canyons 4. A- Graded Bedding

Which part of Earth's cumulative hypsographic curve includes the mid-ocean ridges?

The shallowest slope below sea level

Volcanic peaks on the deep-ocean floor with conical tops are called:

seamounts

What is turbidity?

suspended sediment

Seamounts and abyssal hills are ________ in origin.

volcanic

Warm water (From 30°C to 350°C) hydrothermal vents form:

white smokers

On this perspective view of a passive continental margin, match the following letters with the correct features.

1. E- Oceanic Crust 2. D- Continental Slope 3. F- Continental Rise 4. A- Continental Shelf 5. C- Continental Crust 6. B- Abyssal Plain 7. G- Shelf Break

Refer to the figure above. Where would you expect to find a rift valley?

B

Passive margins are usually produced over geologic time by which of the following?

Continental rifting and continued sea floor spreading

In the figure above, darker blue areas indicate deep water, and lighter blue areas indicate shallow water. Land is shown in shades of brown and green. Which area in the figure is on a continental margin?

D

Active continental margins are characterized by which of the following?

Deep-sea trenches

Which of the following features is related to transform faults along mid-ocean ridges?

Fracture zone

Which of the following techniques used to determine ocean bathymetry is illustrated in the image?

Multibeam Sonar

Tamu Massif, the largest single volcano on Earth occurs in which of the following oceans?

Pacific Ocean

The average slope of the continental shelf is approx. ________.

a tenth of a degree