Three Different Theory's

By: Allie Green

Continental Drift

There are four different ways that can help the theory of continental drift. These four things are animal fossils, plants fossils, climate and different rock structures.


Animal fossils-

  • Some people found the same species of animals on different continent This would not be possible because the continent are separated by salt water and they were fresh water animals.

Plant fossils-

  • The same type of plant fossils was found on five different continents in polar and tropical regions. This means that they would have had the same climate at one point.

Climate-

  • There were tropical plants on arctic continents so that means that those continents would have been tropical at one time.
  • Also there are glacial deposits on tropical continents that wouldn't have had glaciers.

Rock Structures-

  • There was the same rock layers were the continents would have been connected.
  • Also some of the same rock structures were found on different continents.


We learned the Alfred Wegner thought that the continents were once all connected at one point in time because they fit together like a puzzle and that they moved apart by the spin of the Earth. Not many people believe that theory because they believe another theory which is convection currents.

Continental Drift SUmmary

I don believe this theory because we don't have enough evidence to show that the continents were connected. I think the Earth was made just as is is to this day but since the plates move underneath them it causes them to move that 2 cm a year.

Seafloor Spreading

The theory of seafloor spreading was made by Harry Hess. This theory states that when hot, less dense material below the earths crust it would flow sideways and carry the seafloor away from each other. Then magma would flow through the cracks and create mountains when it cooled. When the floor of the sea cools then it starts to sink which creates trenches.

This animation shows what happens over time when the magma comes up from the mid ocean ridges. I thought this was the best animation out of four different ones because it shows what can happen over time and what direction everything is going. It also has good labeling that you can turn on or off.

Seafloor Spreading Summmary

I believe that this theory is right because we actually have proof that this stuff is happening. For example we know that there is different magnetic poles every time that new rock is created from the magma. We also have found that there are mid ocean ridges that the magma is coming from. Lastly we have taken rock samples of different rocks ( ones that are closer to land and farther out ) and they have showed the ones closer to land are old then the ones farther from land.

Plate Tectonics

There are three different types of plates on our Earth. They are Convergent, Divergent and Transform.


Convergent-

  • These plates move together
  • Continental vs. Continental= mountain(s)(ranges), collide/crumbling/folding
  • Oceanic vs. Continental= subduction zone, volcanoes, mountains, magma, trench
  • Oceanic vs. Oceanic= subduction zone, trench

Divergent-

  • These plates move apart
  • Continental vs. Continental= valley (rift valley)
  • Oceanic vs. Continental= none
  • Oceanic vs. Oceanic= seafloor spreading, ridges, new rock, pole reversals, mountains, volcanoes
Transform-

  • These plates slide past each other
  • Rock catching, rock layers catching, tension/ pressure, rock breaks, earthquakes.

The arrows on the plate show which boundary ( convergent, divergent and transform) is by those two plates. The picture shows which plates or under each continent. It also tells what the name of each plate boundary is.

Plate Tectonic Summary

I believe that this theory is true because the things that could happen from them ( mountains, earthquakes etc.) have happened from the plates. Plus when the plates move suddenly it creates major cracks in the earth and earthquakes.