Origins

We're done!

Well, sort of.

Origins of Plate Tectonics

Currently, our planet has a three-layered structure, with a crust, a mantle, and a core.  The outermost layer, the crust, is broken up into plates that move about our planet through the processes of subduction and sea-floor spreading.  New research suggests that these processes began about 3.2 billion years ago. 

Back then, our planet was much hotter than it is now.  The crust was just beginning to form but it was much hotter and weaker.  Small plates began to form but were immediately submerged back into the mantle.  As the mantle cooled, mantle plumes – superheated areas of the mantle that transfers heat from the core out to the crust – began to form. 

The mantle continued to cool and fewer mantle plumes formed.  This led to more stable convection cells.  Hot mantle material rises to the surface, cools, then sinks down, only to become heated again.  This allowed the crust to cool enough to stick around longer.  Plates bumped into one another, and one side would be pushed down, forming subduction zones, while upwelling formed spreading centers. 

Slowly, over time, plate tectonics formed.  You'll learn more about plate tectonics in the next module.

Something to think about  . . .

We've only investigated a small part of the Universe.  Watch this video, Comparison of planets and stars.  As you do, note the following:

• The video goes in order of size, not by distance from the sun.
• How big is our sun verses the largest known star?
• What do you think the possibility of an even larger star exists, and we just haven't found it yet?
• Did you know that stars can emit light not in the visible light spectrum?