SHIFTING CONTINENTS HOMEWORK
READ pages 18-22 in your textbook and the narrative below…
If you look at a
globe, you can see
that some of the
continents look like
pieces of a big
jigsaw puzzle.
Geologists (earth
scientists) think that
millions of years ago
all the continents
were connected to
make one big supercontinent called
Pangaea.
For a long time, no one was able to explain how the continents had split apart, if they had
once really been connected. Then a man named Alfred Wegener developed a theory called
Continental Drift to explain why there are now seven continents instead of one. He used
evidence from fossils, mountain formations, climate evidence and glacial scarring on
different continents to try to convince others that what are now different continents were
once a single continent. What he did not know at the time and what would not be discovered
until after he died, was that the inside of the earth is composed of magma, a thick liquid
made up of melted rock. The top, or crust, of the earth is made up of large plates that float on
top of the magma. That new information, combined with Wegener’s evidence, is why
scientists now believe that at one time the plates carrying the continents were joined together
into a huge land mass called Pangaea. The rest of the world was one great ocean. But some
of the magma rose up through cracks in the ocean floor and formed some new crust. This
caused pressure on the huge land mass and broke it into two pieces. One piece was made up
of the continents of what are now Europe, Asia, and North America. The other piece
included present-day Africa, South America, Australia, and Antarctica. As more magma rose
up around the earth, the two large pieces of land gradually broke up again into the continents
we know today. The movement of the magma inside the earth carried the continents away
from each other, much as a current in a river pushes a boat along.
What kind of evidence do geologists have that the continents were once connected? Certain
rock structures in Africa and South America are so much alike that they must once have been
part of the same formation. Also, scientists have found fossils of the same plants and animals
on continents that are now far apart. But the best proof of the continental drift theory is that it
is still happening today. Scientists say that fifty million years from now, the Mediterranean
Sea will almost disappear, and North and South America will not be connected to each other
at all!
Think About It: Why is the Continental Drift theory important?
Main Idea
Choose another title for this story.
The Earth’s Crust
The Earth-A big Jigsaw Puzzle
The Continental Drift Theory
Sequencing
Number the events below in the order
that they happened.
The two large pieces gradually broke up into the continents of today.
Movement of magma carried the continents away from each other.
The continents were joined into a huge land mass.
Pangaea broke into two pieces.
Magma rose up through the ocean and formed new crust.
Reading for Details
Scan the story to answer these questions.
Who developed the Continental Drift theory?
What evidence is there that the continents were once connected?
When do geologists think that all continents were connected?
What continents made up one of the two pieces of broken Pangaea?
When do geologists predict that the Atlantic Ocean will be wider than it is today?
Reading for Understanding
Place the correct letter in the blank.
Pangaea
Continental Drift
a. theory explaining why there are seven continents
instead of one
b. ancient remains of plants and animals
Fossils
c. name of huge land mass formed by all the continents
Crust
d. thick liquid of melted rock
Magma
e. scientists who study the earth
Geologists
f. top layer of the earth