Unit 4 Plate Tectonics Flashcards
(45 cards)
Who created the theory of continental drift?
Alfred Wegener
In what year did Alfred Wegener propose the idea of continental drift?
1912
What makes the plates move?
Two forces move the plates whic are gravity and energy generated from convection cells.
What is the definition of convection?
The transfer if heat energy caused by differences in density.
Convection is only possible for which states of matter.
Liquid and Gas
Hot air or liquid is less ____ so it will ____ then be replaced by cold air and liquid.
Dense
rise
Read for a lecture on how convection works.
Convection is a method of thermal energy transfer where the transfer of heat occurs via fluid motion. This fluid motion is caused by the difference in density between hotter regions of the fluid and cooler regions. These motions are called convection currents, and the convective movement of fluid continues as long as there is a temperature difference between regions.
Mantle convection was belived to be the only mechanism of _____
Continental Drift
Was Mantle convection completly accepted and convection currents were moving the enormous tectonic plates?
No
If convection currents weren’t moving the plates then what was?
The other most important force was gravity which is slab pull–>Pull of gravity on a plate that is being subducted.
How did the theory of continental drift begin?
About 400 years ago when maps were being created people started to notice similarities in the coastlines in some of the continents. It looked like a massive jigsaw puzzle in some places.
Was the theory of continental drift accepted at first by other scientists. If not why?
The theory of continental drift was considered to be a bizzare idea and it was laughed at due to the lack of evidence and the inability to explain how.
What is an example of the giant jigsaw puzzle?
The east coastline of South America seemed to fit perfectly with the west coast of Africa.
Alfred Wegener proposed the idea of ____
kontinentalverschieburg or continental drift.
How did fossil evidence support the claim/theory of continental drift?
Wegener knew that if the continents were once joined then fossils of plants and animals were be found as evidence. He knew that there was unlikely a land bridge.
What fossils were found that supported Wegener’s claim?
Fossil remains of the triassic land repitile Cynognathus, and the remains if the Lystrosaurus. There were fossil remains of the fern Glossopteris and the freshwater repitile Mesosaurus.
What are some examples of geologic evidence that Wegener found?
Some types of evidence that Wegener found was that mountain chains that ended in one continent seemed to continuie on another. Ages and types of rock also matched closely.
What are the three types of evidence that supported Wegener’s claim?
Climatic, Rock/ Geologic, and fossil evidence.
What is an example of climatic evidence.
There are 2 examples of which are glacial striations and glacial erratics. Glacial striations are claw marks left by the glacier. Glacial erractics is a glacier that carries a massive boulder of rock not native to the area it is in.
Why did the continents move?(remember that this was why his continental drift hypothesis was rejected since he couldm’t explain how the continents move)
Spreading of the seafloor.
Who created the hypothesis that a valley at the center of the ridge was a craft or ridge.
Harry Hess created the hypothesis in the late 1950’s.
Which scientist was the first to form a hypothesis that a valley at the center of the mid-ocean ridges was a crack, or rift and contributed to seafloor spreading?
Harry Hess
The theory of plate tectonics states that _________________________________________________________________________
The crust of the earth is composed of many tectonic plates that move/slide around the hot slushy mantle known as the astherosphere.
What is a divergent boundary.
A divergent boundary occurs when two plates are moving or sliding away from each other. An example of this is seaflpoor spreding. Some effects of this are: New Crust, Mountain Building, and Mid-Ocean ridges.
Types of crust associated are Ocean vs Ocean and Continent vs Continent.
