Transcript The Asthenosphere is made of Jello!

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/alfredwegeners-theory-of-continental-drift.html#lesson
https://www.youtube.com/watch?v=MEh4B
1Pv8YE
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. LandformsShapes 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)
Wegener’s 3 main pieces of evidence:
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!
• 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.
Wegener’s 3 main pieces of evidence:
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
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&f
useaction=home.gotoWebCode&x=0&y=0
https://www.youtube.com/watch?v=JmC-vjQGSNM