CHAPTER 1

At the Bottom of the World

Did you know that the ground underneath your feet is always moving? The outer layer of Earth’s crust is made up of large areas called tectonic plates. They are separated from each other and they are always shifting, but at a very, very slow pace. As the plates move, they come together, drift apart, or slide past each other.

The movement of the plates has been occurring for millions of years and accounts for why Earth’s seven continents are where they are configured now. Three hundred million years ago, however, all the continents were joined together. They formed a supercontinent called Pangaea (say: pan-JEE-uh). An ocean called Panthalassa (say: PAN-thuh-LASS-uh) surrounded Pangaea. Many scientists believe that the interior area of Pangaea was a huge desert.

Around 200 million years ago, during the Triassic period, Pangaea began to break up as the plates moved apart. Two landmasses, called Laurasia (say: lor-AY-zhuh) and Gondwana (say: gon-DWAH-nuh), were formed. Laurasia was made up of what are now North America, Europe, and Asia. Gondwana was made up of what are now Africa, South America, Australia, India, and Antarctica.

During this time, Earth’s climate was much warmer than it is now. There was no ice on Antarctica, and plants and animals thrived there.

About 100 million years ago, during the Cretaceous period, Laurasia and Gondwana started breaking apart, and around 85 million years ago, Antarctica and Australia began to split apart.

Ankylosaurs (armored dinosaurs) made their way through forests of conifer trees and ferns, and plesiosaurs swam in the surrounding oceans.

Earth’s plates continued to move and change the appearance of the planet’s surface. By about 30 million years ago, Antarctica and Australia had completely separated.

After that, Antarctica drifted to the south and Australia drifted northward. During this time, Earth’s climate began to cool, and Antarctica started to freeze over. The tectonic plates continued to move and the continents drifted to their current positions. Antarctica ended up at the bottom of the world. And ice has covered it for several million years. A place that had once been warm and was home to many plants and animals became frigid and frozen.

Continental Drift

Frank B. Taylor

If you look at a map of the world, you see that the east coast of South America and the west coast of Africa look like two pieces of a jigsaw puzzle that fit together. Scientists had noticed this once fairly accurate maps of the entire Earth were created. But they could not explain how the two continents would have been connected and then split apart.

An American geologist named Frank B. Taylor first proposed the theory of “continental drift” in 1908. But the paper he wrote about his theory was ignored and forgotten.

Over the next several decades, because of new scientific equipment, scientists were able to study the ocean floor. They saw that there were cracks in the seabed that could be edges of the sections that make up Earth’s surface. So Taylor had been right. By the mid-1960s, the theory of continental drift, or plate tectonics as it came to be known, was recognized as one of the most important theories about the formation of Earth’s surface.