OCE1001 ch 2

A(n)____ occurs where two plates converge, and the denser plate is subducted
Oceanic-continental convergence

A(n) ____ occurs where two plates of the same composition converge, resulting in the older, denser plate being subducted
Oceanic-oceanic convergence

A(n) ____ occurs where two plates of the same composition converge, resulting in neither plate being subducted
Continental-continental convergence

India seperated from Antartica _____
120 mya

The North Atlantic Ocean opened _____
180 mya

The continents came together as Pangaea ______
300 mya

North America lay on the equator ________
540 mya

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 magentic 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 towards the North Pole during normal polarity and the South Pole during reverse polarity

In general, what is our best evidence that the orientation of Earth’s magentic field has changed over time?
A record of Earth’s magnetic field is recorded in oceanic rocks, which shows a clear pattern of changes in Earth’s magnetic field

Where would you expect to see alternating bands of rock with different magnetic polarities
on both sounds of the mid-ocean ridge

The slowly increasing distance between South America and Africa is due to
Seafloor spreading

Old Faithful Geyser at Yellowstone National Park in the United States acquires its energy from a
hot spot

Layered ____ exposed by erosion can be seen when looking at the Grand Caynon in the United States
sedimentary rock

Australia is composed of relatively old and thick
continental crust

The extremely deep ocean Mariana’s Trench is a result of
subduction

____ found in the Atlantic Ocean between North America and Europe is composed of dense and relatively young rock
Seafloor crust

The earthquakes that occur in Southern California generally occur above a
fault

Evidence for continental drift includes:
The distribution of organisms, matching sequences of rocks and mountain chains, past glacial activity, and the fit of the continents

Fossils of ancient polar plants are currently found near the equator because the:
plants lived near the poles, but landmases have drifted to current locations

Climate distribution on Earth is primarily controlled by
latitude

Regarding glacial ages, why is it unlikely that the entire world was covered by ice 300 mya?
Coal deposits from the same geological age are now present in North America and Europe, which formed the remains of vast tropical swamps

Earthquakes can only occur in the ______
lithosphere

The seafloor magnetic pattern is best described as
parallel to and symetric about mid ocean ridges

Tectonic plates are pieces of the ________ that float on the more fluid ________ below
lithosphere; asthenosphere

Describe seafloor spreading and why it is an important piece of evidence in support of plate tectonics
Captain Hess suggested that new ocean crust was created at the mid-oceanic ridges and dispearred back into deep Earth at the trenches near the edge of ocean basins. This was an important piece of evidence in support of plate tectonics because it provided a mechanism for continental and oceanic plate motion

When will magnma rise to the 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 solidy into rock1

Where are tectonic plates located?
At Earth’s surface

What are the three types of plate boundaries?
Divergent, convergent and transform

Which of the following statements about earthquakes with magnitude greater than 4.0 is most accurate?
Earthquake with a magnitude greater than a 4.0 occur in a pattern that correlates closely with plate boundaries

Which plate boundary is NOT associated with volcanic eruptions?
Transform

Which phenomenon can explain the presence of volcanoes in the middle of the Pacific Ocean?
hotspots

Which type of plate boundary is most closely associated with uplifting continental regions and mountain building?
Convergent boundaries

What is convection
A cycle of moving material formed by the rise of less-dense material and sinking of denser material

What is responsible for most tectonic plate action?
Forces at subduction zones

What is the relationship between temperature and denisty?
In general, warmer materials are less dense and colder materials are denser

Which of the following best characterizes upwelling in the asthenosphere
diffuse

What is a plume
a zone of upwelling material originating at the outer-core mantle boundary

What features at the surfaces provide evidence of plumes?
Hot spots

Which of the following are types of volcanoes?
Cinder cone, shield volcano, composite volcano

What information do geologists use to classify volcanoes?
shape and type of deposits

Cinder cones are made of________.
Pyroclastic deposits

In general, how often do most cinder cones erupt?
once

What are shield volcanoes generally made of?
Basalt flows

What is the range of shield volcano height?
300 to 10000 m

What are composite volcanoes made of?
Basalt flows, pryroclastic volcanos

Why are shield volcanoes wider than composite volcanoes?
The lava that flows out of shield volcanoes is more fluid than the lava that flows out of composite volcanoes.

What type of volcanoes are the highest?
Shield volcanoes

What is the range of dome complex height?
500 to 2000 m

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

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

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 in opposite directions.
False

Do most lithospheric plates contain both oceanic- and continental-type crust?
Yes, most contain both oceanic and contintenal type crust

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 coarl reefs exist within seamounts
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 seamouts overtime

Why do coral reefs grow away from seamounts over time?
Seamounts subside as tectonic plates move. Coral reefs grow away from the seamounts 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

Iceland is located on what type of plate boundaray
Divergent

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:
Charles Darwin

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

How is the age distribution pattern of the Hawaiian Islands-Emperor Seamount chain explained by the position of the Hawaiian hot spot
The volcanoes here get progessively odler as one heads NW from Hawaii. These age relationships suggest that the Pacific plate has been steadily moving NW, while underlying mantle plume has remained relatively stationary

How can plate tectonics be used to help explain the difference between a seamount and a tablemount?
A seamount is a volcano with a cone-shaped top, whereas a tablemount is a volcano with a flattened top. Though both of these features originate at the crest (and topographic high) of the mid-ocean ridge, a tablemount has been subject to wave erosion when it rises above sea level. When the crust containing the tablemount is pushed away from the crest (and therefore onto a topographically lower position), or is moved away from a hot spot, it is re-submerged with its flat top

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

Loihi is
the neweste Hawaiian volcano

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

The wilson cycle uses plate tectonic processes to show the life cycle of ocean basins during their growth, formation, and destruction over gelogical time
True

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

Of the following statements about ocean crust, which is/are true
Ocean crust is destroyed at deep sea trenches

What do all plate boundaries have in common?
They are all associated with zones of Earthquakes

Of the following statements about nemataths and volcanic arcs, which is/are true?
In a volcanic arc, any of the volcanoes can be active at any time

What was the main reason scientists objected to Alfred Wegners idea of continental drift?
Wegener’s proposed mechanism for movement was thought to violate the laws of physics

As a tool, the modern evidence from paleomagnetism has helped support plate tectonics by showing that
magnetic sea floor “stripes” are symmetric with respect to the mid ocean ridge

The East Pacific ridge is associated with what type of boundary?
Divergent

How is it that the Ocean floor is much younger than the ocean itself
The ocean floor keeps regenerating itself

plate boundaries where new oceanic crust is being added are called
divergent boundaries

The faster the rate of spreading at the mid ocean ridge or rise, the ____ the underwater volcanic range
broader (wider)

Most lithospheric plates contain both oceanic and continental crust
True

The Hawaiian islands are associated with which type of plate boundary
they are not associated with any type of plate boundary

In general, where would the youngest ocean floor be found
at the mid ocean ridge

What happens when an oceanic and continental plate converge>
The oceanic plate will be subducted

What happens when two continental plates conver
Neither subducts; instead a mntn range forms

Your job is to locate the worlds plate boundaries. To do this you may use only one map. The best map to choose for this job is a map that shows the worldwide locations of
earthquakes

Which of the following is associated with a subduction zone
a volcanic arc

How much wider is the Atlantic Ocean today than when Christopher Columbus sailed? Assume that the Atlantic Ocean is getting wider at a rate of 3 centimeters per year (about 1 inch). (Round off the dates to the nearest century to make the calculation simpler.)
15 m (49 ft)

An ocean trench is what type of boundary
convergent

The San Andreas Fault is associated with which type of plate boundary?
transform

Where would you not expect to find significant volcano activity
continental collision zones

Which of the following tropical islands would likely be the youngest?
Tropical island with a fringing reef

What best describes the tectonic setting of the Cascade mtns of the Pacific NW
subduction zone

Overall the Atlantic Ocean is ____ and the Pacific is _____
growing; shrinking

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