OCE1001 ch 2
A(n)____ occurs where two plates converge, and the denser plate is subducted
A(n) ____ occurs where two plates of the same composition converge, resulting in the older, denser plate being subducted
A(n) ____ occurs where two plates of the same composition converge, resulting in neither plate being subducted
India seperated from Antartica _____
The North Atlantic Ocean opened _____
The continents came together as Pangaea ______
North America lay on the equator ________
Which type of plate boundary is most closely associated with the formation of new ocean floor?
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
Old Faithful Geyser at Yellowstone National Park in the United States acquires its energy from a
Layered ____ exposed by erosion can be seen when looking at the Grand Caynon in the United States
Australia is composed of relatively old and thick
The extremely deep ocean Mariana’s Trench is a result of
____ found in the Atlantic Ocean between North America and Europe is composed of dense and relatively young rock
The earthquakes that occur in Southern California generally occur above a
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
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 ______
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
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?
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?
Which phenomenon can explain the presence of volcanoes in the middle of the Pacific Ocean?
Which type of plate boundary is most closely associated with uplifting continental regions and mountain building?
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
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?
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________.
In general, how often do most cinder cones erupt?
What are shield volcanoes generally made of?
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?
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?
Which of the following is characteristic of continental-continental convergent plate boundaries?
uplifted mountain ranges
Deep-sea trenches are found at convergent plate boundaries
Water depth decreases as you move away from the mid ocean ridge
Convergent plate boundaries occur when tectonic plates move in opposite directions.
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
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:
The first scientist to propose the origin of coral reefs based upon subsidence (sinking) of volcanic islands was:
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.
The majority of the world’s hotspots are associated with plate boundaries.
Charles Darwin was the first person to propose a hypothesis on the origin of coral reefs.
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
the neweste Hawaiian volcano
A researcher interested in the vertical zonation of oceanic lithosphere would want to study __________.
The wilson cycle uses plate tectonic processes to show the life cycle of ocean basins during their growth, formation, and destruction over gelogical time
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?
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
The faster the rate of spreading at the mid ocean ridge or rise, the ____ the underwater volcanic range
Most lithospheric plates contain both oceanic and continental crust
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
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
The San Andreas Fault is associated with which type of plate boundary?
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
Overall the Atlantic Ocean is ____ and the Pacific is _____