Plate Tectonics

Hannah Krueger's Project

Layers of the Earth

There are three layers of the Earth; core, mantle, and the crust.

There are actually two called the inner and the outer core. The inner core is composed of nickel & iron and is completely solid. The outer core however is liquid and is composed of molten nickel and iron and spins creating the Earth's magnetic field!

  • The mantle is the thick layer of hot, solid rock between the earths crust and the molten iron core, although it still flows around the outer core. It makes up the bulk of the Earth, accounting for two-thirds of the planet's mass. In this layer of the earth, convection currents occur which is a very important factor for tectonics plates.
  • Lastly, the crust is the rocky thinnest layer of the three that is known as the Earth's surface. It is also the layer that we live on! The bottom of the crust and the upper mantle is considered another sub-layer. It is known as the lithosphere. This layer is significant because it consists of the essential resources of todays worlds such as natural gas, coal, and some minerals.

  • See model below ⤵

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    Plate tectonics & continental drift

    Plate tectonics is the theory that the outer rigid layer of the earth (the lithosphere) is divided into a couple of dozen "plates" that move around across the earth's surface relative to each other. In 1915, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift on top of the mantle. This theory has been proved by the "fossil record". This was a finding of two identical fossils on two different continents hundreds of miles apart, which can only mean that at one point they were not so far apart, but one piece of land. Another piece of proof is that all of todays separate continents fit together like one huge jigsaw puzzle! This one huge "mega continent" is known as Pangea.

    Plate Movement & Convection current

    In the mantle of our earth there is this cool thing that occurs called convection. Whether you know it or not, it happens all around you. Have you ever wondered why it feels so much warmer on a top bunk compared to a bottom bunk? Or why you are supposed to drop to the ground if your in a burning building? Its all because of Convection! This simply means that warm air rises and cool air sinks. This is exactly what happens in the mantle. The magma closest to the inner core heats up so it rises and allows the cooler magma to sink. Then as the, once cool magma, heats up from being close to the inner core the, once hot magma, is now cool and the cycle repeats! How does this have anything to do with plate tectonics? It actually has a very large impact on them. It is what makes them move! As the warm air rises and cool air sinks, it is creating a circular motion which allows the plates floating on top of them begin to float around and move in the direction that the convection currents are moving.

    Refer to diagram below⤵

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    Plate Boindries

    Because of all of this plate movement, the different plates tend to come across each other! They basically have 3 options: to collide, separate from each other going in opposite directions, or slide by each other. when they collide it is called a convergent boundary. There are two kinds of convergent boundaries; just plain convergent which creates folding mountain ranges, or subduction which creates trenches and volcanoes. There is a special place, the Andes Mountains were created by convergent by subduction which is not usual. It has also created something which is known as the ring of fire.

    The Ring of Fire is an area where a large number of earthquakes and volcanic eruptions occur. The ring of fire is located all around the pacific tectonic plate. When the two plates go in opposite directions it is called a divergent boundary. Divergent boundary's cause volcanoes, earthquakes, and mid Atlantic ridges (seafloor spreading) if they are two oceanic plates or else rift valleys if they are two continental plates. The last one is called a transform boundary which is when the two tectonic plates just slide right passed each other. As these two plates grind along one another they create major earthquakes, falt lines, and tsunamis which are underwater earthquakes.

    the three diferent types of plate boundries:

    Seafloor Spreading

    Mentioned earlier was sea floor spreading. This is an effect of a divergent boundary discovered by Harry Hess. When two oceanic tectonics plates pull away from each other there becomes a gap, but magma soon explodes out of that gap. It then immediately cool creating new rocks and material. Scientist have proven and carried out tests confirming that rock on the east and went of an ocean were old material but in the middle there was new material. This can only be explained by sea floor spreading. This also proves the theory of continental drift! For all of this to occur there has to be a divergent boundary which would confirm the theory of continental drift!

    The Natural History Museum

    Here is a great Museum where you can learn more about this subject and many more!