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Plate Tectonics Theory and Pangaea
Plate Tectonics
The plate tectonics theory came about in the 1960s and 1970s as new information was obtained
about the nature of the ocean floor, the distribution of volcanoes and earthquakes, the flow of heat from
Earth's interior, and the worldwide distribution of plant and animal fossils. The theory states that Earth's
outermost layer, the lithosphere, is broken into 7 large, rigid pieces called plates: the African, North
American, South American, Eurasian, Australian, Antarctic, and Pacific plates. Several minor plates also
exist, including the Arabian, Nazca, and Philippines plates.
The plates are all moving in different directions and at different speeds (from 2 cm to 10 cm per
year--about the speed at which your fingernails grow) in relationship to each other. The plates are
moving around like cars in a demolition derby, which means they sometimes crash together, pull apart,
or “sideswipe” each other. The place where the two plates meet is called a plate boundary. Boundaries
have different names depending on how the two plates are moving in relationship to each other.
Pangaea
Pangaea was a
supercontinent that existed
on the Earth millions of years
ago, and covered about onethird of its surface. A
supercontinent is a very large
landmass that is made up of
more than one continent. In
the case of Pangaea nearly all
of the Earth's continents were
connected into one large
landmass. It is believed that
Pangaea began forming about
300 million years ago, was
fully together by 270 million
years ago and began to
separate around 200 million
years ago.
Break-Up of Pangaea
Pangaea began to break up about 200 million years ago. Just as Pangaea was formed by being pushed
together due to the movement of the Earth's plates at rift zones, a rift of new material is what caused it to
separate. Scientists believe that the new rift began due to a weakness in the Earth's crust. At that weak
area, magma began to push through and create a volcanic rift zone. Eventually the rift zone grew so large
that it formed a basin and Pangaea began to separate.
In the areas where Pangaea began to separate, new oceans formed, such as the Atlantic Ocean. 80 million
years ago, North America and Europe separated, Australia and Antarctica separated and India and
Madagascar separated, which led to the birth of the oceans we have today. Over millions more years, the
continents slowly moved to their current positions.
Evidence for Pangaea
Earth's continents seem to fit together like a jigsaw puzzle in many areas around the globe. This is the
significant evidence for the existence of Pangaea millions of years ago. The most prominent place where
this is visible is the northwestern coast of Africa and the eastern coast of South America. In that location
the two continents look like they were once connected, which they in fact were during Pangaea.
Other evidence for Pangaea includes fossil distribution. For example matching reptile fossils have been
found in Africa and South America indicating that these species at one time lived very close to each other,
as it is not possible to them to have crossed the Atlantic Ocean.