For scientists, making big discoveries and

Question

sharing them with the public can be a big
deal. Often, their discoveries come after years
of hard work, and they finally get to see the
results of what they’ve done. In some cases,
their work is welcomed by other scientists,
and can even make them celebrities! However,
this is not what happened to Alfred Wegener
(1880–1930). Wegener (VAY-geh-ner) was
the German scientist who first argued that
continents on the Earth’s surface had moved
over long periods of time. During Wegener’s
lifetime, other scientists thought his claim
was too strange to be true. They also said that
Wegener did not have convincing evidence
to support his ideas. At the time, many
scientists mocked Wegener’s claims. It wasn’t
until many years after his death that other
scientists came to accept his argument.
In 1915, Wegener shocked other scientists
when he made the claim that the continents
Alfred Wegener argued that the continents had changed their positions on Earth, but his claim wasn’t
accepted by other scientists until many years later.

A Continental Puzzle

2 A Continental Puzzle

A Continental Puzzle © 2018 The Regents of the University of California. All rights reserved. Permission granted to purchaser to photocopy for classroom use. Image Credit: Wikimedia/Public Domain

on Earth might have been like. To support
his claim, Wegener turned to evidence from
Earth itself, just as scientists do today.
Wegener was interested in what Earth’s
climate was like before humans existed. His
study of ancient climate led him to think
about how the continents might have been
arranged millions of years in the past.
One type of evidence Wegener considered as
he developed his ideas was the shapes of the
continents and the landforms that appeared
on them. He noticed that the edges of the
continents matched, as if they had once fit
together like puzzle pieces. Wegener wasn’t
the first to notice how similar the edges of
the continents were, but he was the first to
publicly argue that the way they appeared to
fit together was evidence that they had once
been connected. At the same time, he found
that some identical landforms could be found
on more than one continent. For instance,
mountain ranges and areas made of certain

types of rock that were found on the continent
of South America could also be found on the
continent of Africa. When scientists compared
these similar mountain ranges and rocks on the
two separate continents, they matched. Not
only that: when people placed the matching
rocks and mountains together, they appeared
to fit perfectly, like two puzzle pieces.
Another source of evidence Wegener used to
support his claim—and a type of evidence still
used by scientists today—was the study of
similar fossils found on different continents.
Fossils are the remains and impressions of
living things preserved in rock. They can tell us
about life on Earth millions or even billions of
years ago. By studying fossils and where they’re
found, scientists can tell when the organisms
that formed the fossils lived and what conditions
were like at the time. The oldest fossils on
Earth are found in the hard, solid rock on land,
because the plate material that makes up land
is older than plate material that makes up the
Alfred Wegener argued that the continents had once been joined together in a supercontinent called
Pangea. This map shows how Pangea may have looked hundreds of millions of years ago.

A Continental Puzzle 3

A Continental Puzzle © 2018 The Regents of the University of California. All rights reserved. Permission granted to purchaser to photocopy for classroom use. Image Credit: Getty Images; Shutterstock.
ocean floor. The plate material that makes
up the ocean floor is much younger because
the plates of the ocean floor are always being
destroyed at convergent boundaries, while
new plate material is being created at divergent
boundaries. In fact, the oldest plate material
on the ocean floor is only 180 million years old!
That may sound like it’s been around for a long
time, but plate material on land can be much
older: up to four billion years old! Fossils are
an important source of evidence as scientists
support ideas about where the continents were
located hundreds of millions of years ago.
In Wegener’s case, he noticed that the same
types of fossils were sometimes found in very
different parts of the world. The fossils were
sometimes thousands of miles apart or in
places where the organism that formed the
fossil wouldn’t be able to survive. For example,
Wegener studied fossils of tropical plants that
had been found in Antarctica, where the cold
climate would have killed the warm-weather
plants. This evidence led Wegener to the claim
that the entire continent where the fossils
were found had once been located somewhere
warmer. He concluded it had traveled to its
current position over millions of years.

Fossils, like these trilobites, are one source of
evidence that is still used today as scientists
support ideas about Earth’s history.
Wegener noticed that the edges of some continents seem to match up like puzzle pieces.

Wegener’s Legacy
Wegener found evidence that the Earth’s
continents had moved apart over time, but he
didn’t explain how that motion happened—
that’s one important reason why the scientific
community didn’t accept his claims. Over the
years other scientists collected additional
evidence and made hypotheses, or claims,
about how the continents moved apart. The
evidence didn’t support all of the claims,

A Continental Puzzle 4

A Continental Puzzle © 2018 The Regents of the University of California. All rights reserved. Permission granted to purchaser to photocopy for classroom use.
but those claims that were supported by
the evidence became part of the accepted
explanation. The work of many scientists,
including Wegener, and a lot of evidence
led to what we now call the “theory of plate
tectonics.” Scientific theories are explanations
for an observable phenomenon that have a
lot of evidence gathered over time. Although
he didn’t get credit for his research during
his lifetime, Wegener is now famous for his
contribution to the theory of plate tectonics.After slowly reading through, A Continental Puzzle, answer the following investigation question citing multiple pieces of evidence from the article:

What evidence do we have of past plate motion?

Please use complete sentences. You must have at least 3 sentences for each question to receive full credit. Answer the questions using your own words!
answer like a 14 year old would

Answer 1

One piece of evidence we have for past plate motion is the way the continents' edges seem to fit together like puzzle pieces. Alfred Wegener noticed this when he studied the shapes of continents, particularly how the coastlines of South America and Africa matched up. This led him to believe that these continents were once connected before they drifted apart.

Another important piece of evidence involves the mountain ranges and rock types found on different continents. For instance, Wegener found similar mountain ranges in both South America and Africa, which suggests that these continents were once joined because the same types of rocks are found in both places. When scientists compared these formations, they fit together perfectly, which supports Wegener's idea of continental movement.

Lastly, the discovery of similar fossils on widely separated continents provides strong evidence for past plate motion. Wegener pointed out that fossils of tropical plants were found in Antarctica, indicating that the continent must have been in a warmer location in the past. This suggests that continents have moved over millions of years, as the organisms couldn’t survive in their current climates, further supporting the idea of continental drift.