Tethys Ocean

The Tethys Ocean (Greek: Τηθύς) was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.

Modern theory

During the Jurassic Period (150 Ma), Cimmeria finally collided with Laurasia. There it stalled, the ocean floor behind it buckling under, forming the Tethyan Trench. Water levels rose and the western Tethys came to shallowly cover significant portions of Europe, forming the (first) Tethys Sea. Around the same time, Laurasia and Gondwana began drifting apart, opening an extension of the Tethys Sea between them that today is the part of the Atlantic Ocean between the Mediterranean and Caribbean. As North and South America were still attached to the rest of Laurasia and Gondwana, respectively, the Tethys Ocean in its widest extension was part of a continuous oceanic belt running around the Earth between about latitude 30° N and the Equator. Thus, ocean currents at that time—around the Early Cretaceous—ran radically differently from the way they do today.

Between the Jurassic and the Late Cretaceous (which started about 100 Ma), even Gondwana began breaking up, pushing Africa and India north, across the Tethys and opening up the Indian Ocean. As these land masses pushed in on it from all sides, up until as recently as the Late Miocene (15 Ma), the Tethys ocean continued to shrink, becoming the Tethys Seaway or (second) Tethys Sea.

Today, India, Indonesia, and the Indian Ocean cover the area once occupied by the Tethys Ocean, and Turkey, Iraq, and Tibet sit on Cimmeria. What was once the Tethys Sea has become the Mediterranean Sea. Other remnants are the Black, Caspian, and Aral Seas (via a former inland branch known as the Paratethys). Most of the floor of the Tethys Ocean disappeared under Cimmeria and Laurasia. Geologists like Suess have found fossils of ocean creatures in rocks in the Himalayas, indicating that those rocks were once underwater, before the Indian continental shelf began pushing upward as it smashed into Cimmeria. We can see similar geologic evidence in the Alpine orogeny of Europe, where the movement of the African plate raised the Alps.

Paleontologists also find the Tethys Ocean particularly important because much of the world's sea shelves were found around its margins for such an extensive length. Marine, marsh-dwelling, and estuarian fossils from these shelves are of considerable paleontological interest.

Historical theory

Terminology and subdivisions

The western part of the Tethys Ocean is called Tethys Sea, Western Tethys Ocean or Alpine Tethys Ocean. The Black, Caspian and Aral Seas are thought to be its crustal remains (though the Black Sea may in fact be a remnant of the older Paleo-Tethys Ocean. However, this "Western Tethys" was not simply a single open ocean. It covered many small plates, Cretaceous island arcs and microcontinents. Many small oceanic basins (Valais Ocean, Piemont-Liguria Ocean, Meliata ocean) were separated from each other by continental terranes on the Alboran, Iberian, and Apulian plates. The high sea level in the Mesozoic era flooded most of these continental domains forming shallow seas.

During the Oligocene, large parts of central and eastern Europe were covered by a northern branch of the Tethys Ocean, called the Paratethys. The Paratethys was separated from the Tethys by the formation of the Alps, Carpathians, Dinarides, Taurus and Elburz mountains during the Alpine orogeny. It gradually disappeared during the late Miocene, becoming an isolated inland sea.

The eastern part of the Tethys Ocean is likewise sometimes referred to as Eastern Tethys.

As theories have improved, scientists have extended the "Tethys" name to refer to similar oceans that preceded it. The Paleo-Tethys Ocean, mentioned above, existed from the Silurian (440 Ma) through the Jurassic periods, between the Hunic terranes and Gondwana (later the Cimmerian terranes). Before that, the Proto-Tethys Ocean existed from the Ediacaran (600 Ma) into the Devonian (360 Ma), and was situated between Baltica and Laurentia to the north and Gondwana to the south. Neither Tethys oceans should be confused with the Rheic Ocean, which existed to the west of them in the Silurian period.

See also

References

External links

Category:Historical oceans Category:Plate tectonics Category:Permian Category:Mesozoic Category:Paleogene