Continental Drift

Text Book page numbers 92 - 96

Warm Up• 1. What is the thickest layer of the Earth? • 2. What is the thinnest layer of the Earth?• 3. What happens to temperature as the

depth within the Earth increases? • 4. What happens to the density as the

depth within the Earth increases? • 5. When you put your marshmallow into

the candle flame, what type of heat transfer were you modeling?

Would someone believe the Asthenosphere is

made of Jell-O?

It makes sense right?

• We know the Asthenosphere is a “plastic solid” or a solid that can move and flow….just like Jell-O!

• So why does it sound so crazy?

Alfred Wegener (Vegner) got the same response for his theory.

http://education-portal.com/academy/lesson/alfred-wegeners-theory-of-continental-drift.html#lesson

https://www.youtube.com/watch?v=MEh4B1Pv8YE

Wegener’s Theory of Continental Drift:

• What is Continental Drift?

It is the idea or Theory ……..that the continents slowly

move over Earth’s surface.

• All continents had once been joined together in a single land mass (PANGAEA) and later began to drift apart.

• Wegener was not alone in thinking that the continents appeared to fit together like puzzle pieces.

• He, however, came up with a theory to suggest that the continents were once joined together and drifted apart.

Sit very still!

• Can you feel the North American plate moving?

• It was a pretty radical idea at Wegener’s time to say the continents were moving.

• Most scientists were skeptical.

• However, Wegener had evidence…..

Wegener’s 3 main pieces of evidence:1. Landforms- Shapes of the Continents – They appeared to ‘fit’ South America and Africa.

Coal Fields - In North America and Europe match up when pieced together (also ‘fit’ as well)

Mountains and Rock Layers – In North America and Europe match up when the continents are pieced together (similar rocks)

2. Fossil Evidence - Fossils of the same animals were found on many different continents, now separated by oceans:

Glossopteris = plant

Cynognathus = land reptile

Lystrosaurus = land reptile

Mesosaurus = freshwater

reptile

These organisms had no way to travel across such oceans that exists today!

Wegener’s 3 main pieces of evidence:

• Also, fossils of the Glossopteris (a fern) have been found in rocks of Africa, South America, Australia, India, and Antarctica!

• Finding these fossils on such widely separated landmasses, convinced Wegener that the continents had once been united.

3. Climate Evidence – Tropical Plants - Found in areas that are considered Arctic (frozen) today.

Glaciers - Evidence of glaciers found in areas that have temperatures far too mild to have glaciers.

Evidence shows that climate must have been much different in the past

Wegener’s 3 main pieces of evidence:

So why didn’t Wegener’s fellow scientists accept his theory?

• He was missing one key point to support his theory?

• Can you guess what evidence the other scientists wanted to hear?

They wanted to know ….. HOW continental drift happened?

• Wegener could not provide an explanation for the force that pushes or pulls the continents.

Case closed, not enough evidence!

• Most scientists believed that the Earth was cooling and shrinking, which created Earth’s mountain ranges. (like the dried up, wrinkled skin of an apple)

• Wegener said that if this was true, Mountains should be found all over Earth, but they usually occur in bands along the edges of continents.

• Unfortunately, Wegener died before his theory was ever accepted.

• He went on a Meteorological expedition to Greenland one winter, and got lost in a bad snow storm.

continental drift animation link

http://www.phschool.com/webcodes10/index.cfm?wcprefix=cfp&wcsuffix=1015&fuseaction=home.gotoWebCode&x=0&y=0

https://www.youtube.com/watch?v=JmC-vjQGSNM

Sea-Floor Spreading