Is this Earth?
The existence of Wegener’s supercontinent Pangaea is completely accepted by geologists today. The movements of continents explain so much about the geological activity we see. But did it all begin with Pangaea? Or were there other supercontinents that came before? What does the future of the continents hold?
Wegener had lots of evidence for his continental drift hypothesis. One line of evidence was the similarity of the mountains on the west and east sides of the Atlantic. Those mountains rose at convergent plate boundaries. The continents on both sides of the ocean (where the Atlantic is now) smashed together to create Pangaea. The proto-Atlantic ocean shrank as the Pacific Ocean grew.
The Appalachian mountains of eastern North America formed at this convergent plate boundary (Figure below). About 200 million years ago, they were probably as high as the Himalayas.
The Appalachian Mountains in New Hampshire.
Pangaea has been breaking apart since about 250 million years ago. Divergent plate boundaries formed within the continents to cause them to rift apart. The continents are still moving apart. The Pacific is shrinking as the Atlantic is growing. The Appalachians (Figure below) are now on a passive margin. The mighty mountains have weathered and eroded to what they are today.
The Appalachians along the eastern U.S. These mountains began when North America and Eurasia collided as Pangaea came together.
The Supercontinent Cycle
Back before Pangaea, there were earlier supercontinents. Rodinia existed 750 million to 1.1 billion years ago. Columbia existed 1.5 to 1.8 billion years ago. If the continents continue in their current directions, they will come together to create a supercontinent on the other side of the planet in around 200 million years.
This is known as the supercontinent cycle. The continents smash together on opposite side of the planet around every 500 million years. The creation of supercontinents is responsible for most of the geologic features that we see. It is responsible for many features that are long gone.
This animation shows the movement of continents over the past 600 million years, beginning with the breakup of Rodinia: http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_plate_reconstruction_blakey.html.
supercontinent cycle: Cycle in which supercontinents are created and then destroyed.
- Pangaea came together as a set of continent-continent convergent plate boundaries.
- Pangaea is still breaking up as the continents move apart. The Atlantic Ocean is getting bigger, and the Pacific Ocean is getting smaller.
- The continents come together and break apart about every 500 million years. This is called the supercontinent cycle.
Use the resource below to answer the questions that follow.
- How did the continents form?
- When did the continents get their current shape?
- Describe how North America will look 100 million years from now.
- What will happen to Africa in the future?
- Describe the plate tectonics processes that brought Pangaea together.
- Describe the plate tectonics processes that split Pangaea up.
- Why do scientists think that there will be another supercontinent in the future?