Aim: How do Continents Drift?
Do Now:
- Take the “Continental Drift Theory”
reading from the back of the room.
- After reading the short article, answer
the questions on the back.
- You will have 5 minutes for this task.
The Continental Drift Theory
1. Wegener believed the landmasses could all fit together.
2. Wegener did not have enough hard evidence or proof to
support his ideas.
3. It took until the 1960’s for new evidence to emerge.
4. Fossils of Glossopteris (a fern plant) are found on many
continents. Scientists think the seeds were too large to be carried
by wind, and therefore, could not explain how it traveled the great
distances between the continents today. This indicates the
continents must have been closer.
5. Fossils of Lystrosaurus (swamp-dwelling hippo-like creature)
are found on many continents. Scientists do not believe this
creature could have swam the great distances between the
continents today. This indicates the continents must have been
closer.
I. The Continental Drift Theory
- proposed by Alfred Wegener
- theorized that the continents
floated around the planet and
moved through the oceans.
* ~ 300 mya the continents were
all together forming what was
called Pangaea = “All Land”
Formation of Pangaea (~300mya)
II. Evidence for Continental Drift
1. The Continental Puzzle
continents fit
together like a
giant puzzle
2. Matching Fossils
- Fossils of the same organisms (plants and
animals) are found on different continents.
3. Rock Types and Structures
- different mountain ranges across the
ocean have the same rock composition and
age.
Present (2013)
250 Million Years ago
Pangaea
After hearing about this theory and
III. Rejecting a Hypothesis
seeing compelling evidence, what
- Most
scientists
Wegener’s
questions
do rejected
you have
about
hypothesisContinental
because he could
explain
Wegner’s
Driftnot
Theory?
how the continents moved.
But all the
evidence
existed and is
true!
IV. A New Theory Emerges
Theory of Plate Tectonics suggests that the
Earth’s surface is composed of rigid plates
that move, carrying the continents. (uses
Wegner’s evidence)
Closure
Will the continents
come together
and form a single
landmass?
- YES – but not for a
very long time
(about 300 million
years).
Plate Tectonics