How Variables Cause Change

HOW VARIABLES CAUSE CHANGE

Variables That Change the Earth

Puzzling Plates

5T2U2A01

Continental Drift?

Have your ever noticed how South America and Africa seem to fit together like pieces of a jigsaw puzzle? If your have, you are not alone. Sir Francis Bacon first noticed their peculiarity in the 17th century. Then about 100 years ago, a German scientist named Alfred Wegener was the first person to propose the theory of continental drift. In his book, he calculated that 200 million years ago the continents were originally joined together forming a large super continent. He named this super continent Pangaea, meaning “All earth.”

Wegener suggested:

·  The continents were once part of a single chunk of land that split apart millions of years ago.

·  Over millions of years, the continents moved to their present locations.

·  He used the fit of the continents, the distribution of fossils, a similar sequence of rocks at numerous locations, ancient climates, and the apparent wandering of the Earth’s Polar Regions to support his theory.

·  Wegener’s Continental Drift theory was not readily accepted by the science community of his day. It was difficult to imagine large land masses plowing through the sea floor to move to new locations.

Other scientists have found evidence to support the idea that the continents moved.

§  Rocks found on the east coast of South America are the same as rocks found on the west coast of Africa.

§  These rocks are different from rocks found in other places on Earth.

§  The Earth’s surface is constantly moving and reforming, but so slowly that you can’t observe it.

More evidence came from fossils.

·  Fossils of an animal that could not live in ocean water were found in both South America and Africa.

·  Scientists reasoned that these animals must have walked between South America and Africa when the two continents were joined.

All the evidence supported the idea that continents had moved, but no one could figure out how they moved.

·  The discovery of Earth's moving plates solved the mystery. The continents are part of the plates, and they move with them.

·  Some scientists studying the movement of plates suspect that the Earth has had several super continents throughout time.

·  Some scientists say that perhaps 200 million years in the future, people in North America won’t need to cross the Pacific Ocean to reach Asia.

Why should continental drift matter to us?

Scientists can predict about the features of the Earth existing today. In several million years:

§  The Atlantic Ocean will continue to expand, while the Pacific Ocean will shrink.

§  The Mediterranean Sea will disappear and connect Africa with Europe.

§  India will continue to push into the southern Asian continent, pushing the Himalayan Mountains higher.

§  The city of Los Angeles will continue to move north to join with the city of San Francisco.