Difference between revisions of "Plate Tectonics"

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Latest revision as of 21:13, 11 June 2019

Plate tectonics is a scientific theory that explains and builds on the idea of continental drift. Continental drift was first put forward in 1596 as a theory that the continents were 'drifting' across the ocean floor. Later, it became accepted that 7 large tectonic plates and a larger number of smaller ones make up the outer-most shell of the Earth and that movement of these plates is what causes the continental drift. The boundaries between the plates are called faults and movement between them cause different phenomena. These include earthquakes, volcanic activity, mountain-building, and ocean trench formation. The movement of the plates is slow and ranges from 0 to 100 mm per year.

Movement[edit]

There are two layers to the Earth's crust - the lithosphere and asthenosphere. The lithosphere consists of the tectonic plates and is cooler and more rigid. The asthenosphere is hotter and flows more easily. The tectonic plates of the lithosphere ride on the fluid-like asthenosphere and move about as quickly as your hair or fingernails grow.

Plate Boundaries[edit]

  1. Transform boundaries (conservative) are when two plates move past one another along transform faults. Earthquakes can occur along these faults, such as the San Andreas fault in California.
  2. Divergent boundaries (constructive) are when two plates slide apart from one another. Seafloor spreading is an example of this and forms a new ocean basin. As they plates move away from one another, many small earthquakes or volcanic eruptions may occur. Ocean then fills in the gap between the plates, such as the Red Sea.
  3. Convergent boundaries (destructive) are when two plates slide toward one another to form either a subduction or a continental collision. Subduction is when one plate moves under and lifts it up, creating a mountain range as in the Andes Mountains. Continental collision is less common and results in two continents becoming melded together.

Driving Forces[edit]

  • Mantle dynamics is one of the driving forces behind the movement of tectonic plates. The asthenosphere is the upper part of the Earth's mantle, the fluid-like part of the Earth that is between the outer crust and the inner core. This mantle is hot and has convection currents that move it around as different parts heat and cool. The tectonic plates of the lithosphere then ride around on top of it as it moves underneath.
  • Gravity plays a part in moving the tectonic plates as well. As they get pushed around and away from the hotter core, they cool down and become denser. The denser they get, the more gravity acts upon them and they slide back into the mantle, toward the Earth's core.
  • The Earth's rotation has some effect on tectonic movement. As the Earth rotates and wobbles, the plates are affected. The moon's gravity also has some effect on plate movement.