Chapter 5 - The Tectonic Cycle Flashcards
Along what type of plate boundary does subduction occur?
A. transform
B. divergent
C. convergent
C. convergent
The volcanic mountain range of the Andes is defined as a:
a. continental volcanic arc
b. Himalaya-like mountain zone
c. volcanic island arc
d. mini supercontinent
a. Continental volcanic arc
Since Pangaea, the lithosphere has broken into nine major plates and a large number of smaller plates
true or false
True
Large mountain ranges are characterized by significant negative gravity anomalies because of their deep, low-density routes
true or false
True
What type of plate margin is the majority of the rim surrounding the Pacific Ocean?
a. Active
b. passive
A. Active
When both plates of a converging pair are by low-density continental crust, neither plate will undergo subduction
true or false
False
As the plates of a transform fault grind past one another their edges may grab and lock, forcing the rocks on both sides to flex and bend
true or false
True
The highest temperature at which magnetic material can retain permanent magnetization is called the:
a. Newton point
b. centigrade scale
c. Fahrenheit proximity
d. Curie point
d. Curie point
Where is active sea-floor spreading occurring today?
a. Lake Michigan
b. the great Salt Lake
c. the Mississippi River
d. the Athabasca River
e. the Red Sea
f. saline Creek
e. The Red Sea
How does plate tectonics influence the composition of ocean water?
a. material from the core seeps into the ocean via submarine volcanoes
b. none of the choices
c. all of the choices
d. oceanic trenches from subduction zones trap salts and minerals thereby changing the overall ocean water composition
e. submarine volcanoes along mid-ocean ridges lead to chemical reactions between the ocean water in the hot rocks of the seafloor
e. submarine volcanoes along mid-ocean ridges lead to chemical reactions between the ocean water in the hot rocks of the seafloor
When a plate capped by a continental crust converges with a plate capped by an oceanic crust, the continental plate will undergo subduction
true or false
False
What type of plate boundary created Iceland?
a. transform
b. convergent
c. divergent
c. Divergent
Assume there is a mountain range with a deep root of low-density continental rock extending into the underlying asthenosphere. Would this produce a negative or positive gravity anomaly?
a. Negative
b. need more information answer this question
c. positive
a. Negative
Subduction zones are marked by deep trenches where ocean Lithosphere sinks into the asthenosphere.
true or false
True
Measuring the speed and direction of movement of lithospheric plates requires a fixed frame of reference, such as distant stars
true or false
True
How does hotspots and plate tectonics account for the islands of the Hawaiian island chain varying in age?
a. the volcanic hotspot in the middle of the Pacific Ocean is due to the divergence of the East Pacific rise
b. as molten material continually seeped from the hotspot, an island(s) would form. As the Pacific Plate continued to move the island locked to the Pacific Plate would move as well. A new island with then form from the hotspot.
c. hotspots and plate tectonics cannot for the age variability
b. as molten material continually seeped from the hotspot, an island(s) would form. As the Pacific Plate continued to move the island locked to the Pacific Plate would move as well. A new island with then form from the hotspot.
What was the first evidence that led Alfred Waggoner to suspect the continents were once connected?
a. the continents simply looked like they fit together, especially Africa and South America
b. the clock like ebb and flow of the tides
c. Alfred Wegener discovered marine sediments in the Himalaya Mountains
d. the direction that the currents moved
a. the continents simply looked like they fit together, especially Africa and South America
Apparent polar wandering is best explained by:
a. the movement of earth’s axis of rotation
b. The movements of continents
c. magnetic reversals
d. in truth, the magnetic poles wander significantly
b. The movements of continents
Where are the youngest seafloor rocks found?
a. nearest to the rift valleys of the midocean ridges
b. within the deep-sea trenches
c. nearest the continental margins
d. evenly distributed over the ocean basins
a. nearest to the rift valleys of the midocean ridges
A typical rate of seafloor spreading along the mid-Atlantic Ridge is
a. 2 to 4 feet per year
b. 2 to 4 cm per year
c. 2 to 4 inches per year
d. 2 to 4 m per year
b. 2 to 4 cm per year
What is the source of Earth’s magnetic field?
a. the sun
b. the moon
c. the moving electric field within the liquid outer core
d. the lithosphere
c. The moving electric field within the liquid outer core
Explanation: as a result of the Earth’s rotation, the molten iron of the outer core is continually flowing around the solid inner core. The flowing stream of molten iron causes an electrical current to flow in the outer core, and the electrical current, in turn, generates the magnetic field
How does lava carry a record of Earth’s changing magnetic field?
a. the magnetite in the magma, when the temperature exceeds 580°C, will align in the direction of an external magnetic field
b. the magnetite in the magma, when the temperature drops below 580°C, will align in the direction of an external magnetic field
b. the magnetite in the magma, when the temperature drops below 580°C, will align in the direction of an external magnetic field
Explanation: Above the Curie Point this thermal agitation of atoms is such that permanent magnetism is impossible. The Curie point for the mineral magnetite is 580°C; above 580°C, the atomic magnets within the magnetite are randomly oriented. If the magnetite cools to below 580°C, however, the tiny atomic magnets begin to align to whatever magnetic field is influencing them. Eventually they are pinned within the crystal structure, and will not change in future
The magnetic greens in oceanic crust, when solidified, are frozen in the direction of the magnetic field. Changing directions of magnetic inclination as seen around spreading centres indicates changes in the magnetic pole position over time
true or false
True
Explanation: As long as the volcanic rocks are not destroyed by weathering, metamorphism, or melting, they carry their paleomagnetism, or ancient magnetism, providing a record of Earth’s magnetic field long ago
Absolute speed refers to the movement of the plate in comparison to a neighbouring plate
true or false
False
Explanation: absolute speed requires a fixed or stationary frame of reference
If plate A is moving east at a rate of 5 cm per year, and plate B is moving west at a rate of 3 cm per year, to an observer standing on plate B what is the relative speed of plate A (assume that the margin between the two plates is a transform boundary)?
a. 2 cm per year towards the east
b. 8 cm per year towards the east
c. 2 cm per year towards the West
d. 8 cm per year towards the West
b. 8 cm per year towards the east
Which of the following locations are moving the fastest?
a. Mid-Atlantic Ridge
b. South-East Indian rise
c. East-Pacific Rise
d. San Andreas Fault (transform boundary)
c. East-Pacific Rise
What is the Earth’s surface separated into?
The Earth’s surface is separated into huge plates of lithosphere that float on the underlying mantle
To all of Earth’s major topographic features on earth’s surface arise from?
As a direct result of the motion and interactions of lithospheric plates
What did Alfred Wegener hypothesize?
Wegner hypothesized the continental drift hypothesis. it included that the supercontinent, Pangaea, consisted of a northern landmass called Lauraisia and a southern landmass called Gondwana.
As Pangaea broke up, the various continents moved to theirpresent-dayy locations
What was the problem with Wagner’s hypothesis?
Wegner could provide no mechanism to explain how the continents moved
What is some of the most compelling evidence for continental drift?
Fossil evidence
What are striations?
- Scratches or grooves on bedrock surface
- by rocks moving in base of glacier ice
- orientation shows direction of ice movement
- especially useful for continental glaciers, where valleys did not control ice flow direction
What revived the Continental Drift Hypothesis?
Polar wandering
Although it did not not provide a mechanism explaining the movement.
What is seafloor spreading?
Where the ocean crust moving laterally, splitting along the oceanic ridges
How were the continents able to move?
Confirmation of the hypothesis of seafloor spreading explained that continents are carried passively along atop the fragments of lithosphere that carry seafloor crust away from the oceanic ridges.
What is an example of a slow moving plate? Why does it move slowly?
An example of a slow-moving plate is the African plate. It moves slowly due to carrying a lot of continental crust
What is an example of a rapidly moving plate? Why does it move rapidly?
The Pacific plate is an example of a rapidly moving plate. It moves rapidly due to no continental crust
What is a hotspot? And what is an example of a hotspot?
A hot spot is where a source of magma is rooted in place. the Hawaiian Islands are an example of a hotspot, as plates move across the hotspot, new islands are formed one after another.
What are the three basic types of plate boundaries?
The three basic types of plate boundaries are divergent, convergent, and transform.
What are convergent plate margins?
- Where two plates move toward each other
- destructive margins
- occur between plates carrying either oceanic crust, continental crust or both
Describe an ocean-ocean convergent margin.
- One plate will undergo subduction into the mantle beneath the other plate
- this is called a subduction zone
- which of the two converging oceanic plates will be subducted seems dependent upon the velocity and the angle of approach
Describe an ocean-continent convergent margin.
- Continental crust is much less dense than oceanic crust
- continental crust will ride up and over while the oceanic crust gets subducted beneath
- also called subduction zone
Describe a continent-continent convergent margin.
- Both plates are low-density and cannot undergo subduction, so they collide
- form a continental collision zone
- marks the final disappearance of an ocean basin, form spectacular mountain ranges
describe a transform fault plate margin
- Where two plates slide past each other in a horizontal or strike-slip motion
- can occur in oceanic or continental crust
- conservative margins, where crust is neither created nor destroyed
- the most famous example of such a boundary is the San Andreas Fault
What type of boundary is the San Andreas Fault?
It is a transform fault plate margin
Will provide explanations for the major topographic and geologic features we see on earth surface?
Plate tectonics provides explanations for both ocean basins and for continents
What are the 5 major topographic features of ocean basins?
- Mid Ocean Ridge
- continental shelf
- continental slope
- continental rise
- abyssal plains
What formed the Himalayas?
Continent collision zones that form massive mountain chains
