Deck 3: The Ocean Floor

Question 1

The apron of accumulated sediment at the base of the continental slope is known as the .

A) continental rise
B) abyssal hills
C) abyssal plains
D) mid-ocean mountains

Answer 1

A

Question 2

The deep-ocean basin includes which of the following features?

A) continental shelf
B) coral reefs
C) abyssal plains
D) the shelf break

Answer 2

C

Question 3

Ocean trenches .

A) have submerged erosional features
B) are arc-shaped depressions in the oceanic crust that occur at subduction zones
C) consist of glacial troughs dating back to the Ice Age
D) are erosional canyons cut by turbidity currents

Answer 3

B

Question 4

Flat-topped seamounts that once rose near or above sea level are called .

A) ridges
B) island arcs
C) guyots
D) abyssal hills

Question 5

Hydrothermal vents are located near .

A) passive continental margins
B) zones of rapid seafloor spreading
C) the edges of the deep sea trenches
D) the margins of the Hawai'ian chain

Question 6

The islands bordering deep-sea trenches are .

A) also referred to as "black smokers"
B) accumulations of sediments on the margins of the trenches
C) formed from the activities of coral and other organisms
D) eruptive volcanoes called island arcs

Question 7

The Pacific coast of South America has many volcanic mountains and a narrow continental shelf. This is an example of .

A) an oceanic ridge system
B) a hotspot
C) a passive margin
D) an active margin

Question 8

How can a satellite sense the contours of the ocean bottom from space?

A) by shining a laser through the ocean to see the bottom
B) by using radar to sense the height of the sea surface over submerged features
C) by using sonar to measure ocean bottom contours directly
D) by sensing changes in gravity as it flies over trenches and mountain ranges

Question 9

The origin of submarine canyons is not well understood but is most likely to be .

A) erosional, caused by a combination of stream erosion and turbidity currents
B) tectonic, representing down-folds of rock within the continental shelf
C) organic, resulting from the activities of burrowing organisms
D) glacial, through the process of depositing rock debris from melted ice on the shelf

Question 10

The submerged outer edge of a continent is called the .

A) abyssal plain
B) continental margin
C) ocean basin
D) continental convergence zone

Question 11

The deepest places in Earth's crust are .

A) continental slopes
B) abyssal plains
C) submarine canyons
D) ocean trenches

Question 12

The transition between the shelf and the deep seafloor is the .

A) littoral zone
B) continental slope and rise
C) abyssal plain
D) mid-ocean ridge

Question 13

Which statement accurately describes active continental margins?

A) They are regions of great geological stability.
B) They are characteristic of the margins along the Atlantic Basin.
C) They are areas of frequent earthquakes and volcanoes.
D) They are areas where lithospheric plates are actively moving apart.

Question 14

The discovery and study of ocean floor contours is called .

A) bathymetry
B) marine science
C) stratigraphy
D) paleoceanography

Question 15

Where is the widest continental shelf located?

A) The Arctic Sea north of Siberia
B) The western edge of South America
C) The margin surrounding the Hawai'ian  Islands
D) The Emperor Seamounts

Question 16

The deepest location in the ocean is the .

A) Peru-Chile Trench
B) Mid-Atlantic Ridge
C) Mariana Trench
D) Abyssal plains

Question 17

Which statement accurately describes a turbidity current?

A) a fast, dense current of water and sediment that runs down slopes
B) the result of mid-ocean trenches spreading at a fast rate
C) a phenomenon associated with violent atmospheric storms at sea
D) an event that always occurs at river mouths in shallow water, but does not extend into water more than 50 meters (165 feet) deep

Question 18

Which statement most accurately describes how the continental rise is formed?

A) from the convergence of oceanic plates at active continental margins
B) from  volcanic activity at active continental margins
C) from  the accumulation of sediments at the base of the continental slope
D) from  sedimentation surrounding spreading centers

Question 19

Active continental margins are located .

A) along the east coast of the United States
B) along the east coast of South America
C) on the west coasts of both North and South America
D) all around Africa

Question 20

Submarine canyons .

A) always run parallel to the coastline
B) are typically small in size
C) are never located just offshore of the mouth of a river
D) cut into the continental shelf and slope, often terminating on the deep seafloor

Question 21

Guyots are often formed near spreading centers.

Question 22

s ediments are found on the deep-ocean floor are mostly   in origin .

A) Pelagic, biogenous
B) Pelagic, terrigenous
C) Neritic, biogenous
D) Neritic, terrigenous

Question 23

What methods do scientists use to determine the bathymetry of the ocean floor, and how do they work?

Question 24

A seamount is a volcanic projection that does not rise above the surface.

Question 25

Hydrothermal vents such as black smokers are found at spreading centers.

Question 26

The Challenger expedition used multibeam echo sounders to contour the seafloor.

Question 27

Abyssal plains and abyssal hills cover about 25% of the surface of Earth. What are the characteristics of each of these features?

Question 28

The mid-ocean mountains, such as the ridges and rises, are .

A) similar in origin to the Alps, the Rockies, and the Appalachians
B) composed of folded and faulted marine sedimentary rocks
C) constructed of volcanic basalt
D) similar in size and features to most continental mountains

Question 29

Abyssal plains and abyssal hills cover a quarter of Earth's surface.

Question 30

Abyssal hills are small extinct volcanoes commonly associated with .

A) seafloor spreading
B) convergent zones
C) active continental margins
D) continental shelves

Question 31

A depression along the boundary of a seamount where sediment has built-up is a(n) .

A) scour moat
B) guyot
C) island arc
D) abyssal plain

Question 32

Which type of sediment is most abundant in neritic deposits?

A) terrigenous sediments
B) biogenous sediments
C) hydrogenous (or authigenic) sediments
D) cosmogenous sediments

Question 33

Scientists think that turbidity currents contribute to the formation of submarine canyons.

Question 34

Continental shelves can be made of granitic crust, basaltic crust, or both.

Question 35

What is the deepest feature in the ocean? Where is this feature located, and how did it form? Is this feature, and others like it, tectonically stable or tectonically active?

Question 36

What are submarine canyons and how are they formed?

Question 37

Which of the following are hydrogenous sediments?

A) quartz sand
B) phosphorite deposits
C) siliceous oozes
D) tektite spheres

Question 38

Which type of sediment is generated in place, on the spot where we find them?

A) terrigenous sediments
B) biogenous sediments
C) hydrogenous (or authigenic) sediments
D) cosmogenous sediments

Question 39

Distinguish between active and passive continental margins.

Question 40

Passive continental margins are sometimes referred to Atlantic-type margins.

Question 41

Manganese nodules .

A) are a type of cosmogenous sediment
B) are almost exclusively found on continental shelves
C) "grow" very slowly, at an average rate of 1 to 10 millimeters per million years
D) are inexpensive to collect and are, therefore, widely exploited

Question 42

The analysis of layered sedimentary deposits in the ocean is known as .

A) stratigraphy
B) oceanography
C) marine biology
D) ecology

Question 43

Aside from manganese, what is the other primary component of manganese nodules?

A) iron oxide
B) uranium
C) silver
D) gold

Question 44

What type of information can scientists derive from observing deep-ocean cores?

A) how much light penetrates the ocean
B) information about historical changes in Earth's climate
C) historical changes in tidal cycles
D) direct measurements of salinity over time

Question 45

An example of terrigenous sediment is the manganese nodule.

Question 46

Carbonate sediments are rare in deep sea sediments because the .

A) organisms providing shells do not live in the deep sea
B) abundance of muds and clays cover the carbonate shells
C) carbonate shells are dissolved in deep water
D) organisms do not live beyond the edge of the continental shelf

Question 47

Which type of sediment is of organic origin, that is, made by organisms?

A) terrigenous sediments
B) biogenous sediments
C) hydrogenous (or authigenic) sediments
D) cosmogenous sediments

Question 48

Which sediments would be considered oozes?

A) terrigenous sediments
B) biogenous sediments
C) hydrogenous (or authigenic) sediments
D) cosmogenous sediments

Question 49

Which of the following is a major source of terrigenous sediments?

A) weathering and erosion of rocks
B) dissolved organic material
C) dissolved nutrients
D) precipitation over the open ocean

Question 50

Neritic sediments are found on the .

A) deep-ocean floor, mostly in the Atlantic Ocean
B) continental shelf
C) continental rise
D) abyssal plains

Question 51

The oozes on the seafloor mostly consist of .

A) boulders and cobbles from glaciers oozing off the land
B) bones and teeth of bottom-dwelling fishes
C) fine muds washed down the continental slope to the seafloor
D) microscopic hard parts of single-celled living organisms

Question 52

What term refers to the depth in the ocean where the rate at which calcareous sediments supplied to the seabed equals the rate at which those sediments dissolve?

A) calcium carbonate compensation depth
B) calcium dissolution depth
C) calcium carbonate pressure point
D) carbonate equalization depth

Question 53

Sediments are organic or inorganic materials that accumulate on the seafloor.

Question 54

Large volumes of bottom sediments may be transported long distances by .

A) storm waves
B) icebergs
C) tidal action
D) turbidity currents

Question 55

Over millions of years, natural gas and oil can be formed from .

A) erosion
B) volcanic ash
C) biogenous sediments
D) terrigenous sediments

Question 56

Radiolarians and diatoms are both examples of .

A) organisms that are only found in tropical parts of the ocean
B) multi-celled animals
C) creatures whose shells form siliceous oozes
D) calcareous oozes in the deepest parts of the ocean

Question 57

The study of the ocean's past is referred to as .

A) stratigraphy
B) geology
C) paleogeochemistry
D) paleoceanography

Question 58

In the process of lithification , sediments .

A) are subducted into the mantle at a deep trench
B) are converted into solid rock
C) slip into the center of the mid-ocean ridges and become new seafloor
D) are uplifted to form the edges of continents

Question 59

Which sediments arrive in the ocean from continents via wind and water?

A) terrigenous sediments
B) biogenous sediments
C) hydrogenous (or authigenic) sediments
D) cosmogenous sediments

Question 60

One area in the ocean that has an extreme abundance of sediment deposition is the .

A) shallow waters around Alaska
B) waters around the tip of Africa
C) deep-ocean floor in the middle of the Pacific Ocean
D) waters near the Gulf Coast of North America

Question 61

Paleoceanography is the study of past processes and past events that have occurred in the ocean. What types of questions do paleoceanographers ask and what are the methods they use to obtain information about the ocean's past?

Question 62

Stratigraphy is the study of the deposition and layering of sediments over time.

Question 63

An example of a siliceous ooze are those formed from radiolarian shells.

Question 64

The white cliffs of Dover are chalk-like deposits of coccolithophores that are around 100 million years old.

Question 65

What is the calcium carbonate compensation depth? Briefly explain why calcareous oozes are not found below this depth.

Question 66

What is sediment and what are the four classifications of marine sediments based on their origin?

Question 67

What are the main sources of terrigenous sediments?

Question 68

Scientists use ocean sediments to obtain information about ocean processes throughout the history of the ocean.

Question 69

Describe neritic sediments and explain what you would expect in the composition of a typical neritic sample.

Question 70

The only way in which calcium carbonate sediment can form is by evaporation.