Oceanography Chapter 2

Which of the following statements about tectonic plates is true?
Few tectonic plates contain both oceanic and continental lithosphere.
Most tectonic plates contain both oceanic and continental lithosphere.
All tectonic plates contain both oceanic and continental lithosphere.
No tectonic plates contain both oceanic and continental lithosphere.

Most tectonic plates contain both oceanic and continental lithosphere.

What is the relationship between continent edges and plate boundaries?

Very few plate boundaries follow the edges of continents.

What was Panthalassa?

the single ocean that existed after the Pangaean supercontinent formed

What was the Tethys Sea?

a piece of the Panthalassa Ocean that existed after the Pangaean supercontinent formed

What was Pangaea?

a supercontinent that began to break apart about 200 million years ago

What were the names of the two smaller super continents that formed when Pangaea broke apart?

Laurasia and Gondwanaland

Which supercontinent contained Africa and South America?

Gondwanaland

What caused the formation of the Himalayas?

the collision of India with Asia

Which type of plate boundary is most closely associated with the formation of new ocean floor?

divergent

Which of the following statements about Earth’s magnetic field is most accurate?

Earth’s magnetic field switches polarity at irregular time intervals.

How often does the Earth’s magnetic field switch polarity?

every 100,000 to several million years

How are normal polarity and reverse polarity of Earth’s magnetic field different?

A compass points toward the North Pole during normal polarity and to the South Pole during reverse polarity.

In general, what is our best evidence that the orientation of Earth’s magnetic field has changed over time?

A record of Earth’s magnetic field is recorded in oceanic rocks, which show a clear pattern of changes in Earth’s magnetic polarity.

Where would you expect to see alternating bands of rock with different magnetic polarities?

on both sides of the mid-ocean ridge

What is the relationship between the crust and lithosphere?

The crust is part of the lithosphere.

Complete this statement: Divergence is to moving away as convergence is to _______

moving toward

Plates move apart at __________ boundaries, move together at __________ boundaries, and move side-by-side at __________ boundaries.

divergent/convergent/transform

Which geologic features are associated with divergent boundaries?

mid-ocean ridges and continental rift valleys

Which geologic features are associated with convergent boundaries?

ocean trenches and volcanoes

Where is the youngest ocean floor found?

along the crest of mid-ocean ridges

What would happen to Earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?

The Earth would increase in volume.

What is a volcanic arc?

a row of volcanoes that forms on the overriding plate near a subduction zone

Which of the following mountain ranges are examples of continental arcs?

andes and cascades

When will magma rise to Earth’s surface?

when the magma is less dense than adjacent rock

In general, when will melted rock in the mantle rise?

almost always

How are felsic magmas formed?

Heat from the mantle melts part of the lower crust.

In general, why does Earth’s crust sit on top of the mantle?

Earth’s crust is less dense than the mantle.

How do mafic volcanic rocks get to Earth’s surface?

Pressure from overlying crust forces mantle magmas through cracks to Earth’s surface. These magmas erupt out of volcanoes, cool, and solidify into rock.

What is a fault?

fractures along which rocks move

What are rocks below and above a fault called?

the footwall below and the hanging wall above

Which type of force is responsible for normal fault formation?

tensional force

Which type of force is responsible for reverse fault formation?

compressional force

Which type of force is responsible for normal strike-slip formation?

shear force

Which type of fault has no vertical motion of rocks associated with it?

strike-slip fault

What is the relationship between the crust and the lithosphere?

All of the crust is contained within a larger layer called the lithosphere

What is the relationship between the mantle and the lithosphere?

Some of the mantle is contained within a smaller layer called the lithosphere.

What is the relationship between the mantle and the asthenosphere?

All of the asthenosphere is contained within a larger layer called the mantle.

What surface feature provides evidence for the location of hot spots?

volcanoes within tectonic plates

When will a hot spot volcano become extinct?

when the volcano is carried away from the hot spot by the tectonic plate

What surface feature would you expect to form if both a hot spot and a tectonic plate are stationary?

a single volcano

What is a seamount?

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

What is a tablemount?

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

Where do coral reefs exist with sea mounts

in tropical latitudes

Which of the following statements about coral reefs and seamounts is most accurate?

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

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

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

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

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

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

Fringing reef, barrier reef, atoll

Fossils of ancient tropical plants are currently found near the poles because the:

plants lived in the tropics, but landmasses have drifted to current locations.

Climate distribution on Earth is primarily controlled by:

latitude.

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Please identify the word and/or phrase that does NOT fit the pattern. Enter only the letter of the answer (caps, no period, and not the full entry) in the field below.

A. Gondwanaland
B. Panamerica
C. Pangaea
D. Panthalassa
E. Tethys Sea

B

Sea floor spreading along the axis of an oceanic ridge results in symmetrical patterns of all of the following EXCEPT ______________.

the location of subduction zones

Which of the following is the main reason that Earth has a magnetic field?

Convection in the liquid iron-nickel outer core generates a magnetic field.

Of the following statements about Earth’s magnetic field, which is/are true?
The magnetic field is oriented vertical relative to Earth’s surface at the south magnetic pole.
The magnetic field is oriented vertical relative to Earth’s surface at the north magnetic pole.
Earth’s magnetic field has varying dips around the world that range from vertical to horizontal, depending on latitude.
The locations of Earth’s magnetic poles have moved through time and have even reversed in polarity.
The magnetic field is oriented horizontal (parallel) to Earth’s surface at the magnetic equator.

ALL

Of the following statements about ocean crust, which is/are true?
Ocean crust is destroyed at transform faults.
Ocean crust is destroyed at deep sea trenches.
Ocean crust is created at transform faults.
Ocean crust is destroyed at the mid-ocean ridge.
Ocean crust is created at deep sea trenches.
Ocean crust is created at the mid-ocean ridge.

2 and 6

Earthquakes can occur only in the __________.

lithosphere

The magnetic north pole has remained very close to the geographic North Pole throughout all of geologic time.

False

New crust is formed at trenches and older crust is subducted at oceanic ridges.

False

The magnetic field of the Earth reverses itself each time that magma erupts at a mid-ocean ridge.

False

The book The History of Ocean Basins, which contained the idea of seafloor spreading, was written by geologist:

Harry Hess.

The seafloor magnetic pattern is best described as:

parallel to and symmetric about mid-ocean ridges.

Tectonic plates are pieces of the ________ that float on the more fluid ________ below.

lithosphere; asthenosphere

What do all plate boundaries have in common? Select only one answer.

They are all associated with zones of earthquakes.

Of the following statements about nemataths and volcanic arcs, which is/are true?
A volcanic arc is associated with a convergent plate boundary.
In a volcanic arc, any of the volcanoes can be active at any time.
Nemataths and volcanic arcs are both the result of volcanic activity.
In a nematath, the age of the volcanoes progressively decreases as you move closer to the volcanic source.
A nematath is created by a hotspot.

ALL

Nematath

chain of extinct volcanoes that is progressively older as one travels away from a hotspot

Match the term with the appropriate phrase.
seafloor magnetic stripes

spreading center

Match the term with the appropriate phrase.
trench

subduction zones

Deep-sea trenches are found at convergent plate boundaries.

True

Water depth decreases as you move away from the mid-ocean ridge.

False

Convergent plate boundaries occur when tectonic plates move away from each other.

False

The Mid-Atlantic Ridge is an example of a:

divergent plate boundary

Which of the following is characteristic of oceanic-continental convergent plate boundaries?

Andesitic volcanoes

Andesitic volcanoes

type of volcanic rock in the andes

Which of the following is characteristic of continental-continental convergent plate boundaries?

uplifted mountain ranges

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Please identify the word and/or phrase that does NOT fit the pattern. Enter only the letter of the answer (caps, no period, and not the full entry) in the field below.

A. divergent plate boundary
B. oceanic-continental convergence
C. oceanic-oceanic convergence
D. transform plate boundary
E. hot spot

E

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Please identify the word and/or phrase that does NOT fit the pattern. Enter only the letter of the answer (caps, no period, and not the full entry) in the field below.

A. hydrothermal vents
B. island arcs
C. tall, folded mountain belts
D. oceanic trenches
E. large volcanoes caused by subduction

A

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Please identify the word and/or phrase that does NOT fit the pattern. Enter only the letter of the answer (caps, no period, and not the full entry) in the field below.

A. transform fault
B. San Andreas Fault
C. oceanic transform fault
D. Mendocino Fracture Zone
E. Mariana Trench

E

Which hypothesis best explains the continuous bend in the Hawaiian Islands-Emperor Seamount chain?

The direction of plate motion shifted over time over a stationary mantle plume (hot spot).

Iceland is located on what type of plate boundary?

Divergent

Areas of intense volcanic activity that remain in more or less the same location over long periods of geologic time and are unrelated to plate boundaries are called hotspots.

True

The majority of the world’s hotspots are associated with plate boundaries.

False

Charles Darwin was the first person to propose a hypothesis on the origin of coral reefs.

True

The Hawaiian Islands are located where the Pacific plate is:

moving over a hot spot or mantle plume.

volcanoes on the seafloor that are flat-topped because of wave erosion are called:

tablemounts

The first scientist to propose the origin of coral reefs based upon subsidence (sinking) of volcanic islands was:

Darwin

Examine the five words and/or phrases and determine the relationship among the majority of words/phrases. Please identify the word and/or phrase that does NOT fit the pattern. Enter only the letter of the answer (caps, no period, and not the full entry) in the field below.

A. Aleutian Islands
B. Canary Islands
C. Galapagos Islands
D. Hawaiian Islands
E. Iceland

A

The study of historical changes of continental shapes and positions is called:

paleogeography.

The following set of observations describes an actual body of water. Evaluate these statements and determine the evolutionary stage of an ocean basin based upon the following characteristics:
Lacks a mid-ocean ridge
Deep ocean basin is present
Early signs of mountain formation
Volcanic island arc and trench absent

terminal

Loihi is __________.

the newest Hawaiian volcano

A researcher interested in the vertical zonation of oceanic lithosphere would want to study __________.

ophiolites

Ophiolites

pieces of oceanic crust thrusted onto continental crust

Match the term with the appropriate phrase.
supercontinent 250 million years ago

Pangaea

Match the term with the appropriate phrase.
study of magnetism over geologic time

paleomagnetism

Match the term with the appropriate phrase.
island arc

subduction zone

The Wilson Cycle uses plate tectonic processes to show the life cycles of ocean basins during their growth, formation, and destruction over geologic time.

True