Deck 15: Ocean Basins

Question 1

Beyond the Mid-Oceanic Ridge system are flat, level, featureless submarine surfaces known as the _______________.

Answer 1

abyssal plain

Question 2

A ____ is an open-mouthed steel net dragged along the seafloor behind a research ship to collect samples of rock.

A) core barrel
B) magnetometer
C) piston core
D) rock dredge

Answer 2

D

Question 3

Oceanic crust is mostly composed of _______________.

Answer 3

basalt

Question 4

The continental rise and continental slope are found between the deep ocean floor and the _______________.

Question 5

Where two plates converge and one dives beneath the other, a(n) _______________ zone is formed.

Question 6

There is very little tectonic activity at _______________ continental margins.

Question 7

Mid-Ocean Ridges are examples of _______________ plate boundaries.

Question 8

A circular coral reef that forms a ring of islands around a central lagoon is a(n) _______________.

Question 9

A chain of volcanic islands that form along a subduction zone is called a(n) _______________.

Question 10

A flat-topped seamount is called a(n) _______________.

Question 11

The Mid-Oceanic Ridge rises high above the surrounding sea floor because new lithosphere forming at the ridge axis is ____ and of relatively ____ density.

A) hot; low
B) hot; high
C) cool; high
D) cool; low

Question 12

Techniques that do not require direct physical contact with the ocean floor, such as ship-based echo sounders or satellite-based microwave radar, are called _______________ methods.

Question 13

Erupting lava on the seafloor quickly cools in contact with seawater, forming bulbous spheroids called ____.

A) pelagics
B) gabbro
C) pillow basalt
D) accreted terranes

Question 14

Silt- and clay-sized particles transported by wind as dust derived from continental weathering and the remains of tiny plankton make up _______________ sediment.

Question 15

_______________ is a mixture of silt- and clay-sized particles transported by wind from continents and the remains of tiny organisms that lived in the surface waters of the oceans.

Question 16

The Hawaiian Islands have formed as the Pacific plate passes over a(n) _______________ that fuels each of the volcanoes.

Question 17

Oceans cover about ____ percent of Earth's surface.

A) 31
B) 51
C) 71
D) 81

Question 18

Oceanic crust is ____ than continental crust and therefore ____ isostatically.

A) denser; sinks
B) denser; rises
C) lighter; sinks
D) lighter; rises

Question 19

Strike-slip faults between two offset segments of a mid-ocean ridge are called _______________ faults.

Question 20

A submarine mountain that rises 1 kilometer or more above the surrounding seafloor but does not rise above sea level is called a(n) _______________.

Question 21

The abyssal plains of the ocean are covered with ____ sediment.

A) pelagic
B) terrigenous
C) fluvial
D) pillow

Question 22

Most of the water that fills Earth's oceans came from ____.

A) the outer regions of the Solar System
B) the collision with a Mars-sized object that formed the Moon
C) volcanoes
D) a gigantic flood

Question 23

When two oceanic plates converge, the sinking plate pulls the sea floor down to create ____.

A) a black smoker
B) a rift valley
C) accreted terranes
D) an oceanic trench

Question 24

____ are a form of sediment gravity flows in which a turbulent mixture of sediment and seawater, which is more dense than seawater alone, flows downslope along the seafloor.

A) Turbidity currents
B) Rock dredges
C) Mudslides
D) Submarine fans

Question 25

What is a large piece of space debris, such as an asteroid or comet, that crashes into a planet?

A) nebula
B) volatile
C) geoid
D) bolide

Question 26

The lowermost layer of oceanic crust is composed of ____.

A) pelagic sediment
B) pillow basalt
C) gabbro
D) terrigenous sediment

Question 27

Island arcs grow from ____.

A) atolls
B) passive continental margins
C) submarine volcanoes near a subduction zone
D) abyssal fans

Question 28

The age of the oldest ocean floor is about ____ million years.

A) 50
B) 200
C) 500
D) 800

Question 29

Rift valleys can be found at ____ plate boundaries.

A) convergent
B) divergent
C) transform
D) passive

Question 30

How do atolls form?

A) A fringing reef around a volcanic island grows upward as the island sinks.
B) A caldera on a volcanic island fills with water.
C) The central portion of a reef sinks below sea level, leaving a ring around the outer edge.
D) Organisms on the outer edge of a reef grow more quickly than organisms in the center.

Question 31

Active continental margins where an oceanic plate sinks into the mantle are called ____ zones.

A) divergent
B) transform
C) terrigenous
D) subduction

Question 32

If the Earth is around 4.6 billion years old, why is the oldest oceanic crust no older than 200 million years?

A) Earth was molten when it formed and took a very long time to cool.
B) Oceanic crust is recycled into Earth's interior at subduction zones.
C) Older oceanic crust was destroyed during the extinction of the dinosaurs.
D) The continents are made of all the old oceanic crust.

Question 33

How could the Mid-Ocean Ridge system have caused sea level to rise in the past?

A) By bringing water up from the mantle
B) By spreading rapidly, creating a broader mid-ocean ridge that displaces seawater
C) By causing tsunamis during earthquakes
D) By heating the ocean until polar sea ice melts

Question 34

If a series of island arcs collide with a continent over a long period of time, they add to a continent as ____.

A) accreted terranes
B) mid-oceanic ridges
C) guyots
D) high plains

Question 35

Sediment gravity flows can erode steep-sided valleys in the seafloor called ____.

A) guyots
B) submarine canyons
C) rift valleys
D) subduction trenches

Question 36

What led to the discovery of mid-ocean ridges?

A) The sinking of the Titanic
B) Underwater testing of atomic bombs
C) Military maps of the seafloor created during World War II
D) Measurements of ocean depth performed by scientists in the 1920s

Question 37

Samples of sediment can be collected from the seafloor using ____.

A) coring devices
B) echo sounders
C) seismic profilers
D) remote sensing

Question 38

Sand, silt, and clay that erodes from the continents and is carried to the deep seafloor is called ____.

A) zooplankton
B) terrigenous sediment
C) pelagic sediment
D) pillow basalt

Question 39

Thick, extensive accumulations of limestone on the seafloor are called ____.

A) abyssal plains
B) carbonate platforms
C) submarine fans
D) terrigenous drifts

Question 40

At seafloor vents, bacteria produce energy from hydrogen sulfide in a process called ____.

A) seafloor spreading
B) photosynthesis
C) subduction
D) chemosynthesis

Question 41

There is no volcanic activity along subduction zones.

Question 42

Granite is more dense than basalt.

Question 43

Trenches along subduction zones form because the two plates are spreading apart.

Question 44

Piston coring devices use the inertia of a falling, weighted core barrel to penetrate into seafloor sediment and retrieve a core sample.

Question 45

Which of these is commonly found extending from the lower end of a submarine canyon?

A) fringing reef
B) pelagic wedge
C) guyot
D) submarine fan

Question 46

An oceanic island ____.

A) rises isostatically as it becomes older
B) is a seamount that rises above sea level
C) forms because continental crust is less dense than oceanic crust
D) is composed entirely of terrigenous sediment

Question 47

The west coast of South America is a passive continental margin.

Question 48

During the formation of the solar system, the solar wind pulled volatile compounds toward the inner planets.

Question 49

The base of the food chain at seafloor hydrothermal vents relies on chemical energy rather than energy from the Sun.

Question 50

Oceanic crust is thicker than continental crust.

Question 51

The Mid-Oceanic Ridge system is Earth's largest mountain chain.

Question 52

The Atlantic Ocean opened as the supercontinent Pangaea rifted apart about 250 million years ago.

Question 53

Atolls are volcanic peaks on the ocean floor.

Question 54

Seismic reflection profilers work by emitting a high-energy signal that penetrates and reflects from layers of sediment and rock below the seafloor.

Question 55

Oceans are commonly warmer than adjacent land in the winter and cooler in the summer.

Question 56

Island arcs form ____.

A) along convergent boundaries between two continental plates
B) along transform faults
C) along subduction zones between two colliding oceanic plates
D) near mid-ocean ridges

Question 57

Magnetometers can be used to ____.

A) study the past behavior of seafloor spreading along mid-ocean ridges
B) measure the depth of water beneath a ship
C) collect samples of sediment and rock from the seafloor
D) detect earthquakes

Question 58

An echo sounder determines water depth by measuring the time it takes a sound signal to bounce off the seafloor and travel back to the instrument.

Question 59

Hot seawater dissolves metals as it circulates through oceanic crust beneath hydrothermal vents such as black smokers.

Question 60

Compared to active continental margins, continental shelves along passive continental margins tend to be ____.

A) wider
B) thinner
C) composed of different types of sediment
D) steeper

Question 61

What is a magnetometer?

Question 62

What is an atoll, how big are they?

Question 63

Compare and contrast passive continental margins and active continental margins.

Question 64

What is the composition and density of the continental crust and oceanic crust?

Question 65

What is an advantage of the multibeam system?

Question 66

What is a turbidity current?

Question 67

What is an echo sounder?

Question 68

Describe the length and width of the Mid-Ocean Ridge system.

Question 69

What are submarine canyons and submarine fans?

Question 70

What is a rock dredge?

Question 71

What are the four spheres on Earth?

Question 72

Compare and contrast seamounts and long island chains.

Question 73

Explain a comet's nucleus and the other compounds that exist in comets.

Question 74

Discuss the three factors that contribute to sinking after a volcanic island forms.

Question 75

Describe the age of the Earth and the age of the seafloor.

Question 76

What are carbonate platforms and where are modern-day examples found?

Question 77

Explain how heat is being transported by ocean currents.

Question 78

Where do active continental margins form?

Question 79

What is a rift valley?

Question 80

What are the two types of sediment in the uppermost layer of the oceanic crust and where are they found?