The Amazing and Compelling Story of the Tethys Sea [Greg Laden's Blog]
I remember finding out about the Tethys Sea and being really excited. I was just beginning my studies of Old World prehistory, Africa, and Human Evolution. What I learned about was the remnant sea separating Africa and Eurasia called Tethys, though it is much more than that (see below). Imagine a Eurasia with no Alps, no Caucasus, and no Arabian Peninsula. Much of southern Europe and huge swaths of North Africa are underwater, and Africa is so far away from Eurasia that all the classic seas of the region don’t exist simply because they are part of the ocean. If you were in the western Mediterranean, you would be able to travel across what is now the Black Sea to the Caspian Sea or the Persian Gulf and into the Indian Ocean, where you would not find India any where near it is today. That was all the Tethys. It allowed the world’s oceans to communicate not too far from the equator across the old world, instead of having the Indian and Atlantic oceans separated by Africa. Virtually everything about the modern climate system depends on tropical or subtropical closure of the major oceans. The fact that the Indian Ocean is on the equator and cut off from the North Atlantic determines and explains almost everything about Northern Hemisphere weather. The rest is explained by the Isthmus of Panama. Had Africa (and India) not moved north to close this sea and create the modern puddles known as the Caspian, Black and Aral seas, and the Persian Gulf, etc. there might well be no Atlantic Hurricanes, England would be rather cold, Canada might look much more like Greenland all year round, and if we add India moving north into Asia into the mix, and the formation of the great mountain ranges of Europe and Central Asia, we also get the present configuration of grasslands in Africa, and in fact, the evolution of grass itself. Prior to the closure of the Tethys, there was an oceanic habitat in Northern Africa and what is now Pakistan and Afghanistan in which evolved hippos, manatees, whales, and elephants. Probably. The sea was enormously influential and it’s demise equally so.
You know the story of Renaissance era scholars noticing sea shells made of lime stone high in the alps. Go look at the alps. Well, the geology there is pretty complicate, but the short version is that many of the fossil bearing (and other) sediments that the alps are made of were party of the western extent of the Tethys, during times when the Atlantic Ocean didn’t happen to exist, so if you were in a boat in that part of the Tethys you would not only be near Geneva (which didn’t exist yet) but also near Libya, Spain and Labrador. When the Tethys was finally pinched out the Alps, Caucuses, and other mountain ranges in the region were pushed up and those sediments exposed.
I’ve had close friends and colleagues who worked on a number of paleontological finds, and in some cases, I worked on them as well, that owe their existence to these dynamic changes. The hominoids of Pashalar were buried in sediments caused by landslides caused by uplift as Turkey became a place; The Siwalics, where all those amazing Asian pre-orang fossils were found, were once lowlands just risen from the sea, and later became the mountains of Pakistan. We will not speak of the Sahavi expedition, other than to say what is now among the driest deserts was once a sea in which it is possible, but highly unlikely, that early human ancestors rode on the back of dolphins swimming among hungry sharks. Well, the dolphins were swimming around among the sharks, anyway.
My own musings about this one thing … the sea that separated Africa from Eurasia, then went away as lands rose up and mountains formed, only addressed the latest period of the Tethys Ocean’s life. Like we have, mainly, the Atlantic and the Pacific today, in the very ver old days, even as life was just beginning to get complicated (and I don’t mean as in too many errands to run before Christmas, so much as I mean having more than one cell and organelles and stuff) it was the Tethys Ocean and the Panthalassic Ocean, the former to the east of, the latter to the west of, Pangea and the various daughter continents of Pangea as they formed over hundreds of millions of years.
It was in the Tethys that the Black Shales formed, during several (but many a few during a certain time period) in which a very large percentage of our oil was to be found, in many cases raised to dry land were it was easy (too easy, as it turns out) to get at. So, the Tethys sea gave us whales, and we used those for a while, but it also gave us Arabian Oil (and lots and lots of other oil around the world) which we are just now running out of.
So, given all this you can imagine how excited I was to see a book written just about the Tethys sea by an expert on it, who helped a great deal in developing our knowledge of it. Vanished Ocean: How Tethys Reshaped the World by Dorrik Stow is the story of the Tethys, told from the very beginning which is about a third of the way back to the very beginning of time itself, it’s fascinating disappearance. Stow is professor of Geoscience at Heriot Watt University, Edinburgh, and has a long history of research in oil geology and interpretation of deep sea cores. He was on some of the key deep sea coring projects that led not only to our understanding of the Tethys, but also, climate change.
To me, one of the most unsatisfying things one can do is to go to a place with interesting geology, stop in at the visitors center with the cute little museum, and see the same exact thing every time: “This region was once covered by a vast inland sea, bla bla bla” because those interpretive exhibits NEVER tell the most interesting aspects of the story. Like, the nearest shore off in that direction, even though you are currently in Michigan, was Norway and you could see if from here. Or, the rock formed by the reblown sand left behind when the sea receded is the same rock that outcrops at the other national park you visited five years ago and a thousand miles away. Or the wavy lines in this rock are from actual waves at the top of the water that were influenced by a wind that blew down from a mountain ridge that is now a low spot on a different continent, and when that was happening the only life on earth was … well there wasn’t any! (That sort of thing.) Vanished Ocean actually undoes that frustration by placing a huge amount of what you will ever encounter in your life as a person interested in the Earth and its History in a single unified processual context. Not all, but a lot of it.