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Plate Tectonics Chapter Challenge
Transcript of Plate Tectonics Chapter Challenge
A Little Bit About Plate Tectonics
A plate boundary refers to the border between 2 adjacent lithospheric plates, there are 3 kinds of plate boundaries: Convergent, Divergent, and transform plate boundaries.
Conservation of Matter
Flow of Energy
2 features of the Earth were the topic of study during the 1800s - the discovery of similar fossils on continents that are now seperated by oceans, and the origin of mountain ranges.
How Convection Works
The crust is the thin, outermost layer of the Earth. There are two types of crust: continental crust and oceanic crust. The oceanic crust consists mainly of less dense rocks, like granite. The oceanic crust is thought to be about 200 million years old, whereas the continental crust is about 4 billion years old.
By Hannah Edwards & Zoe Jonker
Convergent Plate Boundaries
As you can see from this simple diagram, convergent boundaries are when two plates slide towards each other
Sometimes when two plates collide a subduction zone is formed.
A subduction zone is where two plates collide and one of them dips down beneath the surface of the other plate.
Divergent Plate Boundaries
Divergent plate boundaries happen when two plates move away from each other.
Sometimes when two plates begin to move away from each other a ridge can form. This happens most often in the ocean. We will talk about how this occurs exactly in a separate slide.
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Transform plate boundaries happen when two plates move against each other in opposite directions.
This picture gives evidence of Transform boundaries. This happened at the last Hayward Earthquake in 1868
The lithosphere is the rigid outer layer of the Earth, that includes the crust and upper mantle.
The upper layer of the Earths mantle, below the lithosphere, where the flow of convection is thought to occur
The mantle is a term used to refer to the Earth between the crust and the core
Austrian geologist, Eduard Suess, (late 1800) addressed question
"How do mountain ranges form"?
Suess stated that as the Earth cooled from a molten state, the more dense materials contracted and sank toward the center, and the least dense materials floated and cooled to form a crust.
Suess speculation=Mountain ranges formed from the contraction and cooling of the Earth.
Suess claimed that certain parts of the ocean floor and continents could rise and sink as they adjusted to changes in the cooling Earth. This led him to propose the idea of land bridges between continents now separated by great oceans and seas. Land bridges were cited as allowing various kinds of organisms to move between continents now divided by oceans. According to Suess and many others, the land bridges sank into the ocean long ago and no longer exist as they used to.
1831 - 1914
1880 - 1930
German geologist, Alfred Wegner, first brought up the idea of continental drift.
Wegner strongly disagreed with Suess's ideas about land bridges and how mountain ranges were thought to have formed through the contracting of the Earth. One of the reasons Wegner had against the contraction process was the discovery of radioactive heat.
Wegner's big idea was that 200 million years ago there was a huge supercontinent called Pangea that over time broke up into separate continents and moved far apart. Wegner claimed that the compression at the edge of the moving continent led to the formation of mountains. This would also explain the variety of ages of different mountain belts. He thought that the timing of of the breakup was erratic, with some parts of Pangea seperating later then others.
Wegner's evidence also included the puzzle of fossils found on different continents in the present day.
Pangea began to break up about 200 million years ago as a result of the movement of the Earth's tectonic plates and mantle convection. Just as Pangea was formed by being pushed together due to the movement of the Earth's plates away at rift zones, a rift of new material caused it to separate. Scientists believe that the new rift began due to a weakness in the Earth's crust. At that weak area, magma began to push through and create a volcanic rift zone. Eventually the rift zone grew so large that it formed a basin and Pangea began to separate.
The principle that in any closed system subjected to no external forces, the mass is constant regardless of its changes inform the principle that matter cannot be created or destroyed
The movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink, which results in the transfer of heat
When two plates join together from pressure of heat
Lithosphere = 3.4 - 4.4
Athensosphere = 4.4 - 5.6
Crust = 2.2 - 3.0
Mantle = 3.3 - 6.0
Fossils can be used to see how continents used to fit together years ago. They form a kind of "trail" form one continent to another.
Core samples are handy because it shows on the ocean floor the age of rock increase from the crest of a ridge, and gives evidence to divergent plate boundaries
The study of the remanent magnetization in rocks
Thank You So Much For Listening To Our Presentation!
-Hannah & Zoe-
After WWII, lots more evidence was discovered that supported the theory of plate tectonics. In the 1960’s seismometers were installed to monitor nuclear testing. But these instruments revealed something knew. They showed that earthquakes, volcanoes, and other active geologic features (on land and in water) for the most part were along distinct belts all around the world, and those belts showed the edges of tectonic plates.
Also, further paleomagnetic studies showed a striped pattern of magnetic reversals in the crust of ocean basins.
Basalt contains a fair amount of magnetite (magnetic minerals) these minerals line up with the North pole. The Earth has went through a couple of magnetic reversals in the past, in which north and south poles are “switched” for a period of time. When scientists discovered that the ocean crust recorded these reversals, it gave even more proof that the lithosphere had to be in motion.
Rocks that were formed at different places on the Earth's surface have different magnetizations. Using this information, when rock layers were uncovered with a magnetization that did not agree with it's position on the Earth.
It might be a little hard to believe that all the continents we live on are moving. But believe it or not, they are. There is lots of evidence to support the idea of plate tectonics.