Oceanography Chapter 2: Plate Tectonics Quiz

Questions and Answers

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

Convergent

Transform

Divergent (correct)

None of the above

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

It remains constant over time.

It cannot be measured.

It switches polarity at irregular time intervals. (correct)

It is not affected by tectonic activities.

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. Signup and view all the answers

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. Signup and view all the answers

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

On both sides of the mid-ocean ridge. Signup and view all the answers

Where do mantle plumes originate?

Deep in the mantle, near the core. Signup and view all the answers

Why do hotspots result in chains of volcanoes instead of a single volcanic peak?

Because the plate is moving over the hotspot. Signup and view all the answers

Which geographic example below was created by a hotspot?

Hawaii. Signup and view all the answers

What happens when an oceanic plate converges with a continental plate?

The oceanic plate is subducted. Signup and view all the answers

What happens when an oceanic plate meets another oceanic plate?

The older, colder oceanic plate is subducted. Signup and view all the answers

What happens when a continental plate meets another continental plate?

The two plates are forced upward, and a large mountain range is formed. Signup and view all the answers

Which of the following features are found at an oceanic-continental convergent plate boundary?

All of the above Signup and view all the answers

Which geographic examples result from ocean-ocean convergence?

All of the above Signup and view all the answers

Transform boundaries are classified under what type of fault?

Strike-slip. Signup and view all the answers

What role do transform boundaries play?

Transform boundaries connect other segments of plate boundaries. Signup and view all the answers

Do fracture zones near transform boundaries play a role in plate motion?

False Signup and view all the answers

What is the relationship between transform boundaries and mid-ocean ridges?

Transform boundaries connect segments of mid-ocean ridges. Signup and view all the answers

What is the relationship between the crust and the lithosphere?

The crust is part of the lithosphere. Signup and view all the answers

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

Moving toward. Signup and view all the answers

Plates move apart at boundaries, move together at boundaries, and move side by side at __ boundaries.

Divergent/Convergent/Transform. Signup and view all the answers

Which geologic features are associated with divergent boundaries?

Mid-ocean ridges and continental rift valleys. Signup and view all the answers

Which geologic features are associated with convergent boundaries?

Ocean trenches and volcanoes. Signup and view all the answers

Where is the youngest ocean floor found?

Along the crest of mid-ocean ridges. Signup and view all the answers

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

Earth would increase in volume. Signup and view all the answers

What is a volcanic arc?

A row of volcanoes that forms on the overriding plate near a subduction zone. Signup and view all the answers

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

Both A and B Signup and view all the answers

What did Pangaea (All Earth) split into 200 MYA?

Two major landmasses: Laurasia and Gondwana. Signup and view all the answers

What is evidence for continental drift?

<ol> <li>Fit of coastlines of South America and Africa; 2. Similarities of fossils found across separated continents; 3. Mountains line up in Northern Hemisphere; 4. Ancient glacier.</li> </ol> Signup and view all the answers

What are supporting evidences for plate tectonics?

<ol> <li>Locations of earthquakes ('Ring of Fire'); 2. Age structure of the seafloor and continents; 3. Seafloor spreading; 4. Paleomagnetism; 5. Hotspot tracks.</li> </ol> Signup and view all the answers

What are the components that liquid iron in the outer core conducts?

Electricity and convective flow. Signup and view all the answers

When flow reverses, polarity of magnetic field __________.

Reverses. Signup and view all the answers

What is paleomagnetism?

Earth's 'fossil' magnetic field. Signup and view all the answers

What are magnetic stripes?

Creation of new ocean crust over geologic time. Signup and view all the answers

What does plate movements tracked by hotspots indicate?

Mid-plate volcanoes ('hot spots') are produced as they move over continuous upwelling from the hot mantle. Signup and view all the answers

Where else are plumes found besides mid-ocean areas?

In continental areas too. Signup and view all the answers

Study Notes

Plate Boundaries and Ocean Formation

Divergent Boundaries: Associated with the formation of new ocean floor as plates move apart.
Convergent Boundaries: Oceanic plates subduct beneath continental plates, forming trenches and volcanoes.
Transform Boundaries: Plates slide horizontally past one another, creating strike-slip faults.

Earth's Magnetic Field

Polarity switches occur at irregular intervals, every 100,000 to several million years.
Normal polarity indicates a compass points to the North Pole; reverse polarity points to the South Pole.
Oceanic rocks record changes in magnetic polarity, revealing a history of Earth’s magnetic field.

Geological Features

Mid-Ocean Ridge: Long, underwater mountain ranges with alternating bands of rock displaying different magnetic polarities.
Ocean Trenches: Formed at oceanic-continental and oceanic-oceanic convergent boundaries, indicating subduction zones.

Volcano Formation

Hotspots: Chains of volcanoes form as tectonic plates move over stationary mantle plumes. Example: The Hawaiian Islands.
Volcanic Arcs: Rows of volcanoes develop on overriding plates in subduction zones, exemplified by the Andes and Cascades mountains.

Continental Drift Evidence

Continental coastlines, such as South America and Africa, fit together like puzzle pieces.
Similar fossils across separated continents support the theory of continental drift.
Glacial deposits align in the Northern Hemisphere evidencing past connections.

Plate Movements and Rates

Tectonic plates move at a rate of approximately 5 cm per year, driven by mantle convection.
Divergence creates new oceanic crust, while convergence leads to subduction and recycling of crust.

Rock and Crust Characteristics

Youngest ocean floor is found along mid-ocean ridges, indicating ongoing formation.
Ocean crust formed at divergent margins is dense and subducts when colliding with continental crust.

Supporting Evidence for Plate Tectonics

Earthquake locations primarily clustered along plate boundaries, known as the "Ring of Fire".
Age differences in seafloor and continental geology support tectonic activity.
Paleomagnetism reflects historical changes in Earth’s magnetic field recorded in rocks.

Transform Faults

Transform faults connect segments of mid-ocean ridges and exhibit a discontinuous pattern due to perpendicular fracture zones.
The San Andreas Fault is a notable continental transform fault, exhibiting significant tectonic activity.

Additional Notes

Liquid outer core is responsible for conducting electricity and convective flow, influencing Earth’s magnetic field.
Magnetic stripes in ocean crust provide evidence of seafloor spreading and historical plate movements.
Hotspot volcanism indicates the presence of stationary plumes of hot mantle material rising to create island chains.

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Description

Test your knowledge on plate tectonics and the ocean floor with this quiz based on Chapter 2 of Oceanography. Explore concepts such as divergent boundaries and the Earth's magnetic field behavior. Perfect for students looking to master oceanography fundamentals.