Plate Tectonics

The Earth is chemically divided into layers.

Day 21.1

The Earth’s innermost layer is the inner core. The inner core consists mainly of iron, nickel, silicon and sulfur. The inner core is solid although it is under extreme heat and pressure. The inner core counts for about 31.5% of the Earth’s total mass.

The outer core is a dense, viscous liquid that surround the inner core.

The mantle is the layer just beneath the crust of the earth. The mantle is a highly viscous liquid that lies between 30 and 2900km below the surface. The mantle makes up about 68% of the Earth’s mass.

The outermost layer of the Earth is the crust. The crust is a thin, relatively lightweight solid. This crust is also known as the lithosphere. It only accounts for approximately 0.4% of the Earth’s total mass.

Slabs of the Earth’s crust and upper mantle float over the hot mantle below. The heat from the mantle causes convection currents which contributes to the movement of the Earth’s continental plates, also known as continental drift. This also suggests the reasons for the breakup of Pangea over 200 million years ago.

The earth’s crust is broken up into ten major plates.

  1. African
  2. Antarctic
  3. Australian
  4. Eurasian
  5. North American
  6. South American
  7. Pacific
  8. Cocos
  9. Nazca
  10. Indian plates.

Day 21.2

These plates interact with each other at three types of boundaries: convergent, divergent and transform.

Convergent boundaries:  two plates come together and push against one another.

The boundary between the South American plate and the Nacza plate is a convergent boundary. As the South American plate moves eastward, the lithosphere rides up over the lithosphere of the Nazca plate at the subduction zone.

Divergent boundaries: two plates move away from each other creating a gap of magma to form new crust between the two.

The Mid-Atlantic ridge is a divergent boundary. The formation of the Atlantic basin was caused by the formation of new sea floor between the South American and African plate.

Transform boundaries: two plates slide past one another.

The boundary between the Pacific plate and the North American plate is an example of a transform boundary. Strong earthquakes occur at these boundaries, but sea floor is neither created nor lost.