Continental Drift
Scientists believe that millions of years ago, Earth was very different from the way it is
today. There was only one supercontinent that had water all around it. Over time, the continent
began to break apart. Pieces of it slowly drifted apart and then came together again.
Eventually, those pieces became today’s seven continents.
The theory that the seven modern continents split apart one or more times from a single
landmass was suggested by German scientist Alfred Wegener in 1915. He called this theory
continental drift. He named the giant landmass Pangea, meaning “all lands.” Others added to
his theory that Pangea had separated into two landmasses. These masses broke apart to form
the seven modern continents.
To support his theory, Wegener showed how
the continents could fit together. If you look at the
coastlines of South America and Africa, they seem
to fit together like a jigsaw puzzle. Other places can
be found that might once have fit together as well.
The coastline shapes were only one of many
clues Wegener used to support his theory of
continental drift. Fossils of once living organisms
also provided support for Wegener’s theory.
Identical fossils have been found in South America
and Africa. Fossils of a specific type of plant and an
aquatic reptile found on two landmasses so far
apart were difficult to explain. Wegener suggested
that these organisms once lived on a single
landmass that split.
When pieces of a jigsaw puzzle are put
together, the shape of the pieces must match, but
the pictures must match too. When you bring the
continents together the land features of the
mountain ranges form a continuous chain of
mountains. Wegener also identified similar rock formations on both sides of the Atlantic Ocean.
Wegener also recognized that glacial features found in South America, Africa, India,
Australia, and Antarctica were formed at the same time. As glaciers move, they deposit sand
and scratch underlying rock. This indicates that these continents were connected at the time
the glaciers were present.
Scientists discussed continental drift for about two decades, but eventually interest in
the theory declined. They argued that the cause was not explained. They argued that although
his evidence was intriguing, it could not identify the force causing the continents to move. It
took many scientific studies to discover the cause of the drifting of the continents.
Complete the following in your notebook.
1. In your own words explain continental drift.
2. List and explain four pieces of evidence that support Wegener’s theory.