Tectonic Theory - Physical Geography

• What is the process of convection currents?

  1. Heat form the inner core convects through the mantle into asthenosphere.

  2. Hot magma rises because it becomes less dense with heat (as particles are spread out).

  3. Magma is cooler at the top as it further away from the heat source. It becomes more dense and sinks back down to bottom.

  4. Cooler magma is reheated and begins to rise again, creating a loop called a convection current.
• What is the crust?

  Also known as the lithosphere. The uppermost layer of the Earth which is the thinnest, least dense, and lightest. Oceanic crust is only 7km thick, whereas the continental crust can be up to 70km thick.
• What is the mantle?

  May also be called the asthenosphere. Largely composed of the silicate rocks, rich in iron and magnesium. The mantle is semi-molten and a temperature gradient generates convection currents. This causes the circulation of the mantle and may contribute to the lithosphere's plate tectonic movement. The mantle is at a depth from 700km to 2890km below the crust.
• What is the outer core?

  It is dense, semi-molten rocks containing iron and nickel alloys. At a depth of 2890km to 5150km below the Earth's surface.
• What is the inner core?


  Similar composition to the outer core. It's over 5150km below the Earth's crust. The inner core is solid due to the extreme pressures it experiences. The core's high tempreture is a result of primordial heat left over from the earth's formation and the radiogenic heat produced from radioactive decay.