Continental Drift
We know the
Asthenosphere is a solid
that can move and
flow….also called a Non
Newtonian fluid
Who came up with the Theory of continental
drift?
• Alfred Wegener (Vegner) was a German
scientist.
• He gave the theory that Earth’s continents have
moved.
• It is the idea or Theory
•
that all the continents were once joined
together in a single landmass and have since
drifted (moved) apart slowly.
.
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:
• All continents had once been joined
together in a single land mass
(supercontinent - PANGAEA) and later
began to drift apart.
• Pangaea - The name of the single landmass that
broke apart 200 million years ago and gave rise to
today’s continents.
Pangaea (Supercontinent)
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?
• Wegener could not provide an explanation for
the force that pushes or pulls the continents.