|
|
 |
Investing
Plate Tectonics
|
| |
Let’s
go on a fossil-collecting expedition to the continents
of South America, Africa, Australia, Antarctica, and
the sub-continent of India. In South America you will
collect fossils in Brazil. You will explore the coal
fields of Gondwana in southern India. Some of your
African rocks are in a gorge near Capetown. In Australia
you’ll look at rocks on the southern coast. Your fossils
of Antarctica occur mostly beneath glacial ice in the
mountains on the western shores. Since each continent
is now separated from the others by oceans and seas,
you must travel between them by plane and by boat.
You will look for fossils in sedimentary rocks of three
ages.
Imagine
that the five continents are each represented by a stack
of sedimentary rocks on five tables around the room.
The continents are in their natural geographical shape
and their sizes are proportional. The blue, top layer
represents modern times; and the pictures of the modern
animals you see are native to the continent. The three
lower layers depict sedimentary rocks of three past
ages:
| Green Rocks |
Late in the Age of Dinosaurs |
100 mya* |
| Yellow Rocks |
Early in the Age of Reptiles |
200 mya* |
| Red Rocks |
The Coal Age |
300 mya* |
*mya = million years
ago
Fossils
can be seen in sedimentary rocks of each past age.
These are some of the important organisms that lived
on the continents at those times. To identify and learn
more about each fossil, refer to the FOSSIL
CATALOG.
Record
on your data sheet the names of the fossils you find
in the rocks of each continent for the past ages. Also
record the names of the animals now living in the present
day continents.
DATA
SHEET
Fossils
and living animals found on the five continents of Gondwanaland
|
CONTINENT
|
|
Time
|
South
America
|
Africa
|
India
|
Australia
|
Antarctica
|
|
Present
day (blue)
|
|
|
|
|
|
|
100
million years ago (green)
|
|
|
|
|
|
|
200
million years ago (yellow)
|
|
|
|
|
|
|
300
million years ago (red)
|
|
|
|
|
|
ANALYSIS
Now that the expedition
is over, what sense can you make of your data?
1.
On the
basis of what you found in the red rocks,
a)
which
continents had similar fossils?
b)
from
this fossil evidence, which continents seem to have
been connected 300 million years ago?
2.
On the
basis of what you found in the yellow rocks,
a)
which
continents had similar fossils?
b)
from this fossil evidence,
what can you tell about the connections of the five
continents about 200 million years ago?
3.
On the
basis of what you found in the green rocks,
a)
which
continents had similar fossils?
b)
from
this fossil evidence, which continents seem to have
been connected 100 million years ago?
4.
a) Arrange cutouts
of the continents from according to where you think they
were situated during each of the three past ages. Arrange
them also as they appear in the present.
Southern Hemisphere
- 300 million
years ago
- 200 million
years ago
- 100 million
years ago
- Present
4.
b) Explain
your reasons for putting the continents together as
you did for each time period:
- 300 million
years ago
- 200 million
years ago
- 100 million
years ago
5.
Look at the black arrows on the red rocks
of the continents. The arrows represent grooves in
the rock. The grooves were carved by advancing continental
glaciers about 300 million years ago. The arrows point
in the direction the glaciers were moving.
a)
Suppose you were
the first person to have found the glacial grooves in
the south-eastern South America. From where would it
seem the glacier came? Could the glacier have come
from the ocean? Explain your answerb)
Why would the geologist who first found the glacial
grooves in India be puzzled by the discovery?
c)
How
might the idea of continental drift explain 300 million
year old glacial grooves on four separate southern
continents?
d)
Where was the
probable spreading center of the glaciers? Make an
“X” to mark the location on the map above. Where
on the surface of the earth was the probable location
of the “X” 300 million years ago? (Remember that
a continental glacier tends to move out and away from
its center, the North or South Pole - like a spreading
mass of bread dough)
e)
Where would you
look for glacial grooves in the 300 million year old
rock of Antarctica? Draw arrows where you would expect
to find glacial grooves in Antarctica on the map above.
6.
Two species of living earthworms in the
soils of southern South America and Africa were found
to be very closely related (members of the same genus).
Also, two species of living earthworms in soils of
southern India an southern Australia were found to be
very closely related (members of the same genus).
How
was the theory of continental drift strengthened by
discoveries of closely related earthworms on widely
separated continents?
7.
Examine the mammals pictured on the continents
of South America, Africa, India, and Australia. These
living animals are native on their continents. Each
eats insects, and is a major ant/termite eater among
all the mammals there. Each species belongs to a different
order of mammals. These four mammals are very distantly
related, even though each is highly specialized for
eating ants and/or termites.
Explain in
terms of continental drift and evolution how four very
different kinds of ant/termite eaters could occur in
India, Africa, South America, and Australia (Remember,
the Age of Mammals began on earth AFTER Dinosaurs become
instinct about 65 million years ago).
Conclusion
8a) List as many pieces
of evidence as you can to support the theory of continental
drift
8b) Why do you think
it is so difficult for some people to accept the idea
of continental drift?
