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How did seafloor spreading show that Pangea broke apart in stages?
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Pangea
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins near the end of the Permian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The theory of plate tectonics explains that Pangea did not fragment all at once but rather broke apart in distinct stages, a process evidenced by the patterns of seafloor spreading.1
Seafloor spreading occurs as molten material from the mantle rises at mid-ocean ridges, cools, and pushes the existing oceanic crust laterally away. By analyzing the age of marine sediments and magnetic anomalies within the seafloor, scientists have reconstructed the timeline of Pangea’s breakup:234
- ~180 million years ago: The central Atlantic Ocean began to open between northwestern Africa and North America, while the southwestern Indian Ocean formed between Africa and Antarctica.1
- ~140 million years ago: The South Atlantic opened as Africa separated from South America, and India began to rift away from Antarctica and Australia.1
- ~80 million years ago: North America separated from Europe, Australia continued to rift from Antarctica, and India broke away from Madagascar.1
These spreading patterns provide a chronological record of how the supercontinent fragmented into the modern continents.21