What was the Tethys Ocean?
A sea held in the crook of a C-shaped continent — and the only ocean on this site whose ending is written down. It closed when India arrived, and the mountains that came up instead of it are still going up.
Where it was
“The open part of the letter cupped the Tethys Ocean.”
U.S. National Park Service, “Permian Period—298.9 to 251.9 MYA”. Courtesy of the National Park Service. The letter is the shape the same page gives the single continent.
Unpacked: picture the world’s land as one enormous letter C, with the open side facing east. The sea sitting in the gap of the C is the Tethys. It was not the big ocean — the big ocean was Panthalassa, wrapped round the outside.
What it separated
“the Tethys Ocean, the body of water between Gondwana and Laurasia”
U.S. National Park Service, “Triassic Period—251.9 to 201.3 MYA”. Courtesy of the National Park Service.
Unpacked: as the single continent came apart it split into a northern half and a southern half, and Tethys is the water between them. Gondwana is the southern half, Laurasia the northern one. Those are names for pieces of land, not for countries.
How it ended
“The rifting also caused the Tethys Ocean to close, though the final closing did not occur until about 35 million years ago when India collided with Asia, forming the Himalayan orogeny.”
U.S. National Park Service, “Triassic Period—251.9 to 201.3 MYA”. Courtesy of the National Park Service.
Unpacked: an ocean can be squeezed out of existence. India was a separate piece of land drifting north; when it ran into Asia there was nowhere left for the water between them to go, and the ground crumpled upwards instead. The crumpling is the Himalayas, and “orogeny” is the word for a mountain range being built.
This is the only ocean on this site with a date on its ending. It is worth noticing how the source words it: “about” 35 million years ago. Not 35 exactly. The people who study this write their uncertainty into the sentence, and so does this page.
The same world, twice
Two maps from the same set of maps. The first is the world while the continent was still one piece. The second is the world at the age the quotation above names, when the sea between India and Asia had run out of room.
The world about 250 million years ago. The source calls this map the Permo-Triassic Boundary.
Yellow is land, mid-blue is shallow sea, dark blue is deep ocean. The map is drawn flat, so places near the poles look wider than they really are.
This is one model’s answer, not a photograph. It shows the world about 250 million years ago — the age of the map itself, which is the closest the source gets to the ages on this site.
Map data: Scotese, C. R., & Wright, N. M. (2018). PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5460860 Licensed CC BY 4.0. Grid 360×180 at 1° — about 111 km per cell at the equator, so nothing the size of a town can be read from it.
The world about 35 million years ago. The source calls this map the Late Eocene.
Yellow is land, mid-blue is shallow sea, dark blue is deep ocean. The map is drawn flat, so places near the poles look wider than they really are.
This is one model’s answer, not a photograph. It shows the world about 35 million years ago — the age of the map itself, which is the closest the source gets to the ages on this site.
Map data: Scotese, C. R., & Wright, N. M. (2018). PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5460860 Licensed CC BY 4.0. Grid 361×181 at 1° — about 111 km per cell at the equator, so nothing the size of a town can be read from it.
Below sea level: 68.6% on the older map and 63.9% on the younger one. Those are two measurements, and the difference between them is arithmetic — not an explanation. This site does not say why the number moved, because no source it holds says why.
Neither map is labelled. The people who made them drew where sea was and never wrote down which sea it was, so no ocean name appears on either picture. Look at the second map on the right-hand side, though, and India is no longer out on its own.
Is the Mediterranean what is left of it?
You will read that in a lot of places. This site is not going to tell you either way, because no source it holds says so, and a sentence that sounds right is not a sentence that has been checked.
What this site does hold is the quotation above, which names one collision and one date. Everything past that would be us filling in the gap, and filling in the gap is exactly the habit this whole site is built to avoid.
Where this comes from
- The name and the dates
- U.S. National Park Service, “Permian Period—298.9 to 251.9 MYA” and “Triassic Period—251.9 to 201.3 MYA”, both last updated April 28, 2023, read . Material created by the National Park Service is in the public domain. Every quotation here is checked against the page it came from, word for word, each time this site is built.
- How sure is this?
- Both world maps are reconstructions — estimates, not photographs — from a different model than the one this site uses for individual places, and the two are never combined. The date for the closing is the source’s own, hedged with “about”, and this page keeps the hedge.