GEOL 215 Test One

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Who proposed the theory of continental drift?

Alfred Wegener

Which of the following concepts was developed earliest?

continental drift
How old are the fossils of the reptile Mesosaurus found in Africa and South America
that suggest the two continents were once together?

about 300 million years old

When was the theory of plate tectonics developed?
1960s

Where is new lithosphere created?

divergent plate boundaries

Where does volcanism occur?
convergent plate boundaries and divergent plate boundaries

Where are the world's highest mountain ranges created?
Convergent plate boundries

Which type(s) of plate boundaries indicate(s) the direction of relative plate motions
transform fault boundries

New lithosphere is created ____________.

at mid-ocean ridges

What type of plate boundary is shown in the diagram?

a subduction zone

Which of the following locations could be represented by the diagram?

the west coast of South America

In which ocean are most of the world's convergent plate margins located?

Pacific Ocean

The east coast of North America is __________.

not a plate boundary

Which of the following is associated with a divergent plate boundary?
earthquakes volcanism rifting
all of the above

Which of the following is a divergent plate boundary?

the Mid-Atlantic Ridge

At what type of plate boundary do the deepest earthquakes occur?
convergent

Approximately how deep (below sea level) are the deepest deep-sea trenches?
10 km

Which of the following is not associated with convergent plate boundaries?
spreading centers

Which of the following is a type of convergent plate boundary?
subduction zone
Which of the following mountain ranges formed as a result of ocean-continent
convergence?
the Andes
When a deep-sea trench is located next to a continent, where would you expect to find
active volcanoes?
on the continent side of the trench
What plate is subducting beneath southwestern Canada and the northwestern United
States?
the Juan de Fuca Plate

The west coast of South America is __________.
a convergent plate boundary

Which of the following is an example of a transform plate boundary?
the San Andreas Fault

What type of plate boundary is parallel to the direction of plate movement?
transform plate boundary
Which of the following mountain ranges is the product of continent-continent
convergence?
the Himalayas

The North American Plate is bounded by ______ plate boundaries.
convergent, divergent and transform
Which of the following can be used to determine the rates of plate motion? ( ) astronomical positioning seafloor magnetic anomalies global positioning system
D) all of the above
The questions refer to this cross section, which depicts magnetized oceanic crust at a spreading center. The “+” symbol indicates positive (normal) magnetic anomalies; the “–” symbol
indicates negative (reverse d) magnetic anomalies.
How fast are points C and D spreading apart from each other?
about 100 millimeters/year
The questions refer to this cross section, which depicts magnetized oceanic crust at a spreading center. The “+” symbol indicates positive (normal) magnetic anomalies; the “–” symbol
indicates negative (reverse d) magnetic anomalies.
“Normal” magnetized crust at the spreading center formed during the ________ epoch.
Brunhes

Modern seafloor spreading rates range from _________.
2 to 15 centimeters per year
What two scientists related the positive and negative magnetic bands on the seafloor to
seafloor spreading?
F.J. Vine and D.H. Mathews
Which of the following is commonly used to determine the age of seafloor samples
recovered by the deep-sea drilling project?

foraminifera fossils

Which of the following plates is moving the fastest?
the Pacific Plate
On a map of the seafloor, the boundaries between normally magnetized oceanic crust
and reversely magnetized oceanic crust are called __________.
isochrons

When was the supercontinent of Pangaea assembled?
approximately 250 million years ago

How old are the oldest rocks on the ocean floor?
about 200 million years old

The oldest continental rocks are __________ than the oldest oceanic rocks.
much older
Isochrons on the seafloor are roughly __________ the ridge axis along which they were
created.
parallel to and symmetic about
Why are isochrons on the Pacific seafloor more widely spaced than isochrons on the
Atlantic seafloor?
the pacific seafloor formed at a faster spreading rate than the Atlantic seafloor
What ocean used to lie between Africa and Eurasia and was the ancestor to today's
Mediterranean Sea?
Tethys

When did the supercontinent Pangaea begin to break apart?
about 200 million years ago
Pangaea split into two continents: Laurasia, made up of the northern continents, and
______, made up of the southern continents.
Gondwana

When did India begin to collide with Asia to form the Himalayas?
about 50 million years ago
Compared to slower moving plates, faster moving plates are bounded by a greater
proportion of __________.
subduction zones

What drives plate tectonics?
mantle convection

Which of the following forces is important in driving plate tectonics?
A) the pulling force of a sinking lithospheric slab B) the pushing force of a plate sliding off a mid-ocean ridge C) the suction force of a retreating subduction zone
D) all of the above

How deep are plates subducted?
2900 km
Regions of intense localized volcanism such as Hawaii form above plumes of fast-rising
material that originate in the __________.
deep mantle

The Hawaiian volcanoes are __________.
not located at a plate boundary

The Earth's lithosphere is broken up into approximately _____ large plates.
12

New oceanic crust is created at ________.
mid-ocean ridges

Shallow focus earthquakes are associated with which type of plate boundary?
A) divergent B) convergent C) transform
D) all of the above

Mid-ocean ridges are also referred to as _________.
spreading centers

An island arc forms when there is __________ convergence
ocean-ocean
The convergence of the North American Plate with the Juan de Fuca Plate forms the
______ subduction zone.
Cascadia

Mount St. Helens is part of the ____________.
Cascade Range

The Great Rift Valley of East Africa is an early-stage _________.
divergent boundary

The Appalachian Mountains formed from an ancient ____________ plate boundary.
convergent
Oceanic crust that records negative magnetic anomalies formed when the Earth's
magnetic field was ___________.
reversed from what it is today

Astronomical positioning measures points on the Earth's surface relative to ________.
the position of fixed stars
If the position between antennas on two plates moving away from each other changes by
5 mm/yr, then each plate is moving at approximately ______.
2.5 mm/yr

Rhodinia is a supercontinent that formed __________.
before Pangea
Fifty million years in the future geoscientists predict the east coast of North America
will be _____________.
a convergent plate boundary

The main type of plate boundaries are (proper names only): __________.
convergent, transform, divergent
What kind of plate boundary defines the eastern edge of the plate we live on here in the
United States?
mid-ocean rift

How do we determine absolute direction of plate movement over millions of years?
with seafloor isochrons

__________ are the most extensive mountain ranges on Earth today.
mid-oceanic ridges

Who first described world tectonics in terms of rigid plates?
Tuzo Wilson

Who first proposed the three different kinds of plate boundaries widely accepted today
Tuzo Wilson

Which of the following locations is least likely to have active volcanoes?
transform fault

How many major plates cover the Earth's surface?
12

Which of the following plates is the largest?
A) Cocos Plate B) Indian Plate C) North American Plate
D) Pacific Plate

Which of the following plates contains only oceanic crust?
Nazca Plate

Who first suggested that the Earth's surface might be a fragile shell resting on fluid?

Alfred Wegener