This area of Mongolia was once an ocean for 115 million years, after molten rock from the Earth’s crust rose up and tore apart a vast region.
According to Live Science, a new study has found evidence that the desert country of Mongolia today was once an ocean. Even more astonishing, it was an unusual ocean formed when a mantle plume unexpectedly tore through the Earth’s crust.
Previously, the authors were intrigued by volcanic rocks in northwestern Mongolia from the Devonian period (419 million to 359 million years ago).
The northwestern desert of Mongolia once housed the Mongol-Okhotsk Ocean, formed by the tearing of the Earth’s crust – (Photo: ESCAPE TO MONGOLIA).
The Devonian period is also known as the “Age of Fishes,” when fish diversity unexpectedly surged, and their numbers increased dramatically in the oceans, while plants began to cover the land.
At that time, the Earth was made up of only two supercontinents, Laurasia and Gondwana, along with a long strip of microcontinents that would eventually become present-day Asia. These microcontinents gradually collided and merged in a process known as accretion.
The research team conducted field surveys in northwestern Mongolia, where rocks from the continental collision are exposed on the surface.
They discovered that around 410 to 415 million years ago, an ocean known as the Mongol-Okhotsk Ocean opened up in the region.
The chemical composition of the volcanic rocks associated with this rift revealed the presence of a bubbling mantle plume that tore through the Earth’s crust, allowing the aforementioned ocean to form.
A mantle plume is an unusual column of hot material that rises from deep within the Earth’s mantle.
Professor Mingshuai Zhu from the Chinese Academy of Sciences explained: “Mantle plumes often play a role in the initial stage of the Wilson cycle, marking the breakup of continents and the opening of oceans, such as the Atlantic Ocean.”
In many cases, this occurs right in the middle of a solid continental block, tearing it apart.
The geological factors in the case of Mongolia are particularly complex, as this mantle flow tore through a crust that had just fused together through the process of accretion.
According to Professor Zhu, this could be because the newly accreted continent still had weaknesses, which the mantle plume exploited.
However, this ocean only existed for 115 million years before the Earth closed it up again, which is why today we see Mongolia situated on a vast desert.
The formation process of this ancient ocean was very slow, with land opening up by only a few centimeters each year. Other places on Earth may currently be experiencing similar mantle plume rifting events.
A prime example is the Red Sea, with its shores gradually widening by about 1 cm each year.
The rift in the Red Sea is even larger than what was seen in Mongolia in the past. Therefore, in the coming tens of millions of years, the narrow Red Sea could transform into a vast new ocean in East Africa.
