The Story of Pangaea & Plate Tectonics

Leslie ProhaskaFlorida State University

SCE 5943Field Lab Internship

Dr. Alejandro GallardSeptember 14, 2009

Most people thought that the continents had always been and would always be in the same place

A puzzle?

But some people noticed that the continents fit together somewhat like a jigsaw puzzle

Try this puzzle for fun….

Click on Continents map below and you will be taken to the JigZone site. Choose the continents map when the page opens and then see how quickly you can solve the puzzle.

Continents map

Look at the western side of Africa and the eastern side of South America

If you turn South America, and then slide it over

It fits right in….

Some early ideas

• In 1858, an American, A. Snider published an article on the origin of the Americas

• He thought that South America and Africa were once together

• Snider believed this was the case at the time of Noah’s flood

• Snider proposed that a huge volcanic event caused the landmass to split

Half a century later… this idea continued as continental drift

• In 1910, an American, F.B. Taylor, discussed the origin of mountains

• He explained that continental movements that ended in collisions would cause the formation of mountains

More scientists joined in…

• German scientist, Alfred Wegener published The Origin of Continents and Oceans

• He proposed that the continents had once been joined together in a supercontinent he called Pangaea

• The continents then pulled apart through a mechanism called continental drift

What’s in a name?

• The word Pangea, or Pangaea, is Greek for “all land”

• Why do you think he chose this name for the supercontinent?

• What would you name it? Why?

• Most of his colleagues didn’t agree with him

• He couldn’t explain why the continents did not seem to be moving now

• He couldn’t explain how such huge landmasses moved

Wegener’s Evidence

• Fossils of a particular species of lizard and species of plant were found

• The same fossils were found in Africa and South America directly across the ocean from each other

• These species could not have crossed between the continents by swimming

More evidence finally came

• This idea of continental drift was not really excepted until the 1960’s

• Scientists found evidence that the sea floor was spreading

• Magnetic stripes found on the sea floor help lead to further development of the theory of plate tectonics

So…what happened to Pangaea?

• About 200 million years ago Pangaea existed

• Dinosaurs roamed all over the land

Tethys Sea

• About 180 million years ago, rifting along an ancient body of water called Tethys Sea broke the supercontinent into a northern land mass called Laurasia and a southern land mass called Gondwanaland

Tethys Sea

More splitting…

• Then plate movements split Laurasia into North America, Europe, and Asia

• And Gondwanaland split into South America, Africa, peninsular India and later Australia and Antarctica

• This also formed the Atlantic Ocean

Plate Tectonic Theory

• Not as simple as core, mantle, & crust

• Remember, there is a – A solid inner core composed mainly of iron

alloy– An outer core that is hot, liquid, iron– A solid mantle that is so hot that all but the

uppermost portion of it flows– An outer crust which is solid

New model

• Two new divisions– Asthenosphere –

molten, plastic layer of the mantle

– Lithosphere – upper part of mantle and crust

• The solid lithosphere moves over the flowing asthenosphere

The Broken Pieces of the Lithosphere

The lithosphere is divided into several very large plates which can be divided into smaller plates

Boundaries – where the plates meet

• Divergent, Mid-Atlantic Ridge

• Convergent, mountain building– Subduction Zones

• Transform Faults

San Andreas Fault,

lots of earthquakes

Our plates are still moving…

Where do you think we will be in 100 million more years?

650-million-years-in-1-min-20-sec

References650 Million Years in 1:20 Minutes. In Numaga.com. Retrieved

July 28, 2009, from http://www.numaga.com/index.php/hd/numaga-videos/630-650-million-years-in-120-min

Harcourt science grade 6 teacher's edition. (2005). Orlando, FL: Harcourt School Publishers.

Inside the earth. Retrieved September 12, 2009, from http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml

Prohaska, L. (2009, September 12). Retrieved September 12, 2009, from http://www.jigzone.com/gallery/B72509B7BA.77F4672?z=0

Spencer, E. W. (2003). Earth science understanding environmental systems. New York: McGraw-Hill.

The End

Or is it ...