By the start of the Permian Period, about 299 million years ago, much of the supercontinent of Pangaea was assembled. Gondwana and Laurasia (North America plus Europe) were attached along the long complex Ouachita- Allegheney-Variscan Orogenic Belt, but as I described yesterday, there was a huge bay called the Tethys Ocean between the eastern part of Gondwana and much of Asia. Siberia plus Kazakhstan were still impinging on eastern Baltica, and there were plenty of isolated microcontinents floating around, things that would become parts of China, Central Asia, and Indochina.
|Globe map 300 million years ago by Ron Blakey, under CC-BY-SA & GFDL, from Wikimedia commons.|
So Pangaea, which means “all earth,” wasn’t really quite all of the earth. But certainly most of it.
You should not think of the assembly of Pangaea as simply a convergence of everything. Before the end of the Permian, various slices were rifting off the supercontinent, although for most of the next 100 million years it did remain mostly intact. In fact much of it has remained more or less intact to this day – Eurasia and Africa do have some intervening breaks between them, but they’re still pretty close together.
|Pangaea (Tethys at right center)|
The idea of Pangaea goes all the way back to Alfred Wegener’s idea of continental drift published in 1915. Wegener suggested that if the continents had drifted apart, they must have started in some unified state. He used the name Pangaea once in a later edition of his book on the Origin of Continents and Oceans, and it was used by European and South African geologists thereafter. As Colleen Elliott and I discussed back in January, the concept of continental drift was largely rejected in the United States until the 1960s because there was no evident mechanism to make it happen.
During the course of this month we’ll talk about some of the various lines of evidence from the Permian that support the concept of Pangaea. With a few exceptions that we’ll discuss later this month, it’s fair to think of most of the Permian as a time when the supercontinent of Pangaea stayed intact.
—Richard I. Gibson
Globe map 300 million years ago by Ron Blakey, under CC-BY-SA & GFDL, from Wikimedia commons.
Pangaea outline map by Kieff, under Creative Commons license