Chapter 2 Flashcards
What did Alfred Wegener proposed?
- He proposed the “continental drift” hypothesis in 1912
- Pangaea (270-200 ma)
- Panthalassa
The evidence for continental drift included:
- the puzzle-like fit of the continents
- fossils
- Mountain Ranges
- Glacial Striations and Till
Why was continental drift rejected?
- because Wegener’s proposed mechanism of continental movement didn’t work
- lacked explanation for the cost of continental drift.
- Wegener believed that continental drift was the result of centrifugal force and tidal attraction, but the scientific community found the argument weak.
What were the results of seafloor mapping and drilling after WWII?
- Seafloor Spreading hypothesis.
- Mid-Ocean Ridges (MORs)
- symmetrical patterns of magnetism in seafloor rocks
- symmetrical patterns of rock ages on the seafloor
- increasing thickness of seafloor sediments
- Hot Spot Volcanoes
The ___________ says the earth’s surface is divided into large, puzzle-like pieces called________.
- Theory of Plate Tectonics
- Tectonic Plates
What are plates made of?
- Oceanic Crust
- Continental Crust
- Upper Mantle (lithosphere)
- Granite
- Basalt
- Peridotite
Where do plates “float” and “move”
Asthenosphere
Plate movement is related to _______ and _________.
- Mantle Convection
- Slab-Pull
Where are earthquakes and volcanoes located?
Plate Boundaries
What are the three types of Plate Boundaries?
- Divergent Plate Boundaries- result of seafloor spreading and form Mid-Ocean Ridges and Rift Valleys
- Transform Plate Boundaries - transform faults that cut across divergent plate boundaries. San Andreas Fault
- Convergent Plate Boundaries - Subduction, Trenches, Volcanic Arcs, or Complex Mountain Ranges
Ocean to Continent Convergence
Produces “Continental Volcanic Arcs”
Ocean to Ocean Convergence
Produces “Volcanic Island Arcs” (Japan)
Continent to Continent Convergence
Produces “Complex Mountain Chains”
The supercontinent ______ existed between 750 million and 1.1 Billion years ago
Rodinia
_____ could occur within the next 250 million years
Pangaea Ultima
also called Pangaea Proxima, Neopangaea, and Pangaea II
1) Which of the following was not used as evidence for continental drift?
a. The fit of the continents
b. Matching sequences of rocks
c. Past glacial activity
d. The distribution of organisms
e. Paleomagnetic Reversals
Paleomagnetic reversals
2) All continents fit together with the least number of overlaps and gaps when the continents are matched along\_\_\_\_\_\_. A) edges at around 2,000 meters depth B) current shorelines C) the edge of the continental shelf D) edges of the deep sea floor E) oceanic trenches in subduction zones
Edges at around 2,000 meters depth
3) The seafloor magnetic pattern is best described as ________.
A) not related to the location of mid-ocean ridges
B) parallel to and symmetric about mid-ocean ridges
C) parallel to, but not symmetric about mid-ocean ridges
D) perpendicular to and symmetric about mid-ocean ridges
E) perpendicular to, but not symmetric about mid-ocean ridges
Parallel to and symmetric about mid-ocean ridges
4) Which of the following fossils was used as data to help reconstruct Pangea because it was a reptile found in South America and Africa? A) Lepidodendron B) Archaeopteris C) Glossopteris D) Mesosauras E) All of the above
Mesosauras
5) Tectonic plates move about as fast as \_\_\_\_\_\_\_\_. A) a child crawls B) a river flows C) a snail crawls D) grass grows in the summer E) your fingernails grow
Your fingernails grow
6) Which of the following is the most convincing piece of evidence set forth to support the concept of sea floor spreading?
A) The correlation of rocks found in adjacent positions on matching continents.
B) The mid-ocean ridge is entirely volcanic in origin.
C) The mid-ocean ridge rises more than 2.5 kilometers above the surrounding deep-ocean floor.
D) The oceanic pattern of alternating reversals of Earth’s magnetic field.
E) None of the above
???????The oceanic pattern of alternating reversals of Earth’s magnetic field.
7) Based on the Theory of Plate Tectonics, you would expect to find \_\_\_\_\_\_\_\_ heat flow at the mid-ocean ridge and \_\_\_\_\_\_\_\_ heat flow at subduction zones when compared to other parts of the crust. A) decreased; decreased B) decreased; increased C) increased; decreased D) increased; increased E) None of the above are correct
Increased; Decreased
8) The Gulf of California is an example of \_\_\_\_\_\_\_\_ plate boundary. A) a continental-continental convergent B) a continental-continental divergent C) an oceanic-continental convergent D) an oceanic-oceanic convergent E) an oceanic-oceanic divergent
A continental-continental divergent
9) The Mariana Trench is an example of \_\_\_\_\_\_\_\_ plate boundary. A) a continental transform B) an oceanic transform C) an oceanic-continental convergent D) an oceanic-oceanic convergent E) an oceanic-oceanic divergent
An oceanic oceanic convergent
Students sometimes ask…What changes to Earth’s environment would occur when the magnetic poles reverse?
- incorrect directions and difficulty navigating
- fish, birds, and mammals, that sense magnetic field during migrations
- reduce protections that for life-forms against cosmic rays and particles coming from the sun
- Disrupts low-Earth-orbiting satellites as well as some communication and power grid systems.
- Aurora Borealis (Northern lights) and counterpart Aurora Australis (Southern lights) which are natural light display, might be visible at lower latitude
- Earth has successfully survived previous magnetic reversals.
Students sometimes ask…When will California fall off into the ocean?
- Earthquakes occur as the Pacific Plate continues to move to the northwest past the North American Plate, at a rate of about 5 centimeters (2 inches) a year.
- Los Angeles will be adjacent to San Francisco in just over 12 million years.
- CALIFORNIA WILL NEVER FALL INTO THE OCEAN
- people living near this fault should be very aware they are likely to experience a large earthquake within their lifetime.
Students sometimes ask…How long has plate tectonics been operating on Earth? Will it ever stop?
- Plate tectonics has been operating for at least the past 3.8 billion years of Earth History.
- active and continuous process w/ new seafloor constantly being formed while old sea floor is being destroyed.
- plates may move, then slow down or event stop and start up again. The reason for this intermittent plate motion appear to be related to plate distribution and changes in the amount of heat released form Earth.
- forces that drive plates will likely decrease until plates no longer move.
- powered by heat released from within Earth (which is of a finite amount.
