There are a total of 7 major tectonic plates that encompass the earth. The plates are constantly moving around and are a main reason that we are able to have life here on earth. Land sits on top of these plates and when they move around they create many different geological features such as mountains, and volcanoes and are responsible for earthquakes.

Now, how do we even know that these things exist? If I told you we are basically floating on a boat in the middle of a giant ocean you would say no way, we have to be standing on solid ground, but this isn't the case. We are on top of a giant plate that is constantly moving around and heres how we know. The first way is by mapping, we managed to map the sea floor, and you can see things like trenches and underwater mountains, because of the trenches you can see sea floor spreading and if you were to map it out you could see the outline of our plates. A second reason that we are aware that the plates exist is do to fossils " Finding identical or similar fossils in areas separated by vast distances were some of the first clues that scientists used to reconstruct past plate movement." (California Academy of Sciences). The other thing they used to find out was seismographs, these helped show that our earth had a liquid core and not a solid one, which helped complete the theory and answer the final question of "how are these plates moving?"

In my opinion, one of the most important aspects of plate tectonics, and their are many parts that are all important, is convection currents. So, what is a convection current? A convection current is a sort of process where liquid magma will hit the core of our Earth, and it will heat up and rise back to the surface. "Tremendous heat and pressure within the earth cause the hot magma to flow in convection currents." (Exploring Our Fluid Earth). Often times it will go through an opening between plates in the seafloor and cause what is known as sea spreading. When it hits the ocean, it immediately cools down, a portion of it solidifies and the rest cools down and heads back down through the mantle to restart the process. When it hits the ocean floor, it causes the plates to move away from each other, and we see one of the first processes of plate tectonics and how they are always on the move. Another way that convection currents move the plates is by one moving clockwise and the other moving counterclockwise to push the plates into each other.

Plate Tectonics have a long history, and I think the best way to summarize that history is by mentioning two people that played a major part in the discovery of Plate Tectonics. The first person we are going to talk about is Alfred Wegener. Wegener was the first person to realize that these plates existed and that all continents were interconnected at one point and formed a supercontinent that he called Pangea. "Wegener proposed that the continents plowed through crust of ocean basins, which would explain why the outlines of many coastlines (like South America and Africa) look like they fit together like a puzzle." (History of Plate Tectonics). The biggest problem that Wegener ran into was that, he was a meteorologist and a lot of people called his bluff because even though he had enough evidence for his theory to hold some ground, people said he was not qualified. The second problem was that Wegener didn't have any idea why the plates moved, and so just said that these giant land masses were moving and didn't know why which was a very bold claim. The second person that I think is very important in the history of plate tectonics is Marie Tharp. The reason that Marie is so important is that scientists started sending down sonar to put together a map of the ocean floor and she was in charge of drawing that map. While she was drawing it, she discovered that Wegener was right, you could see in the drawing that there were certain areas that were very obviously plate boundaries. She decided to start telling people about this and everyone pretty much told her she was wrong and foolish and said that she didn't know what she was talking about and none of this stuff like mountain ranges and giant trenches existed under the ocean. One man, Jacques Cousteau, even went as far to say that it was just girl talk, and told everyone he would prove it by going down in a submarine and taking a look around. When he came back up he had to face everyone and tell them, that he was wrong and that all of that stuff was down there.

So, we've covered that these plates exist and that they move around, but what happens when they interact with each other? Well, when the plates interact with each other, they form certain things called boundaries, and there are three types: divergent, convergent, and transform. We'll start things off by talking about divergent plate boundaries. A divergent plate boundary is a boundary in which two plates are moving away from each other. So, what does this mean? Well if this happens between oceanic crust, sea floor spreading occurs, and magma rises to the top. However, the real juicy stuff is when continental crust begans to split, in this case, the nearest body of water begins filling in the gap in the land inbetween the diverging plates and eventually a new waterway will appear. The second type of boundary is a convergent boundary. Convergent is a bit more complicated. With a convergent boundary, it means that the plates are converging on each other and this leads to three potential outcomes. The first is that oceanic-oceanic crust runs into each other, the older crust begins to go down and go underneath, this creates a trench, and will also create a volcano because the oceanic crust that went under hits the magma and melts and rises to the top. The second type of thing that can happen is that oceanic crust can hit contiental crust. In this case, the oceanic crust will go underneath the continental crust, and create a trench at the border while also causing volcanos like Mt. St. Helens. The final thing that can happen is when continental crust hits continental. Continental crust will never sink, so the crusts hit each other and form giant mountain ranges such as the Rocky Mountain Range. The final type of boundary is a transform boundary, and this one is kind of dull. In a transform boundary, two plates just run side by side and that's it, they usually don't touch each other. "One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater." (NOAA)

The last thing I want to talk about is a bit of an anomaly. There are things in the middle of plates that are called hot spots. Hot spots have no rhyme or reason and seem to appear random. In hot spots there is usually excess magma and heat in the middle of a plate, and in the case of the Hawaiian islands, this can lead to islands if it's in the middle of the ocean because, magma rises up from the bottom and begins to make new formations which eventually lead to islands."While the hot spot stays in one place, rooted to its deep source of heat, the tectonic plate is slowly moving above it." (American Museum of Natural History) Or the other case could be on land like Yellowstone National Park which is also a hot spot, where you can see geothermic activity such as hot springs and geysers.

In regards to earthquakes and plate tectonics, each different type of plate boundary is going to cause a different type of earthquake in intensity, depth, and magnitude. "Earthquakes occur along fault lines, cracks in Earth's crust where tectonic plates meet." (American Mueseum of Natural History) The first type that I want to look at is earthquakes that occur near transform boundaries. Because transform boundaries move at different rates, they may run in to each other at times and cause what is called a slip-strike. The next type is at convergent boundaries, When earthquakes happen at convergent plates, multiple things can happen. If subduction is occuring, we are going to be see larger magnitude earthquakes, and we are also going to be seeing them deeper in the ground. However if an earthquake occurs in a place like the Himalayas where continental crust is converging, we won't see subduction and there will be more surface level earthquakes. The final boundary type that earthquakes can occur at is divergent boundaries. Here, earthquakes are common and when they happen can begin to develop new fault lines, however they are mostly seen underwater by places like the mid atlantic ridge line.

American Museum Of Natural History. “Power of Plate Tectonics.” American Museum of Natural History, https://www.amnh.org/explore/ology/earth/power-of-plate-tectonics/hot-spots.

American Museum of Natural History. “Power of Plate Tectonics: Earthquake.” American Museum of Natural History, https://www.amnh.org/explore/ology/earth/power-of-plate-tectonics/earthquakes.

“Evidence of Plate Tectonics.” California Academy of Sciences, https://www.calacademy.org/explore-science/evidence-of-plate-tectonics.

“Exploring Our Fluid Earth.” Continental Movement by Plate Tectonics | Manoa.hawaii.edu/ExploringOurFluidEarth, https://manoa.hawaii.edu/exploringourfluidearth/node/1348.

Glasscoe, Maggi. History of Plate Tectonics, 1998, http://scecinfo.usc.edu/education/k12/learn/plate2.htm.

“What Are the Different Types of Plate Tectonic Boundaries?” What Are the Different Types of Plate Tectonic Boundaries?: Exploration Facts: NOAA Office of Ocean Exploration and Research, https://oceanexplorer.noaa.gov/facts/plate-boundaries.html.