Continental Drift

• Alfred Wegener proposed that the earth's continents were once joined together forming a single supercontinent called Pangaea.
• Approximately 200 million years ago, the earth's crust fractured very slowly, forming tectonic plates.
• These tectonic plates hold the continents.
• They drifted across the earth's surface to the positions they occupy today- hence the name, continental drift.

• Pangaea initially split into two continents: Gondwanaland and Laurasia

• Gondwanaland then broke apart forming Africa, Antarctica, South America and the Indian Subcontinent.

• Laurasia split into Eurasia and North America. He based his theory on four observations:

• Continental fit: The outer shape of the Earth's continents allows them to fit together like pieces of a jigsaw puzzle. This is especially evident when the continental shelves of the east coast of South America and the west coast of Africa are aligned.

• Fossil similarity: Fossil remains of ancient freshwater reptiles like Mesosaurus have been found on both the African and South American continents. This species could not have lived in or swum across the Atlantic Ocean. Its presence on both continents suggests that these areas were once part of a single habitat of rivers and lakes when the continents were joined together.
• Areas that are warm today were once covered by ice sheets: Places such as India, Australia, and South Africa, which are currently near the equator and too warm to support an Ice Age, were once covered by ice sheets. The presence of these ice sheets suggests that these regions existed at different latitudes before being moved by continental drift.

• Matching rocks and mountain ranges: The mountain ranges of the east coast of the USA (e.g., Appalachian Mountains) and north-western Europe (i.e., Connacht, Ulster, Scotland, and Scandinavia) have similar features and are likely related.

At first, the theory was rejected by many as Wegener could not explain how continents could move. This was later explained by the theory of sea-floor spreading.