Where does the last drop of seawater disappear in the Himalayas?

Qinghai-Tibet Plateau

It is the best place to study the changes of the world.

Because these ancient lost oceanic plates

Difficult to trace

But in the Qinghai-Tibet Plateau

But it is very well preserved

here

Perfect verification of the theory of plate tectonics

Photography: Pubu Tashi

Source: Xinhuanet

01

The oldest

How old is Mount Gangdise?

Since the beginning of this century, foreign scientists have come to different places in the Gangdise Mountains to conduct research. They revealed that the Gangdise Mountains may have reached their current height around 15 million years ago.

However, Chinese researchers have discovered that the Gangdise Mountains are much older. Their research revealed that around 55 million years ago, the Gangdise Mountains had reached a height of 5,000 meters.

However, this result has been questioned. Some people believe that the oxygen isotopes of the ancient soil in the Gangdise Mountains (oxygen isotopes are used as a reference for dating in geography) may have been modified by current rainwater.

How did our scientific researchers prove it?

In their ancient soil profile, researchers found limestone deposited at the bottom of the lake, which generally contained fossils of a type of ostracod. The shell of this ostracod can be divided into many layers, one bright and one dark, which is repeated about five or six times.

Image source: Screenshot of CCTV1's "Let's Talk"

Researchers have studied oxygen isotopes in its bright and dark layers and found that the dark layer is mainly formed in the summer. Because it is rich in nutrients and has a high organic matter content, it is the dark layer of sedimentation. In the winter, due to the lack of nutrients, the shells deposited in this place are brighter. There are regular changes in the bright and dark layers. If it has been modified by modern times, this isotopic feature will no longer exist.

Therefore, it is believed that the Gangdise Mountains had already formed a 5,000-meter-high mountain before the collision.

After the uplift and collision of the Qinghai-Tibet Plateau, it is no longer in the Gangdise Mountains, but in other places, the most obvious of which is the Himalayas.

02

Himalayas

The last drop of sea water

Where did it disappear?

Image source: Screenshot of CCTV1's "Let's Talk"

The picture above is probably the scene at the moment when the Indian and Eurasian plates collided. Behind it is the Gangdise Mountains. At that time, there were volcanoes all around, and the height may have exceeded 5,000 meters, forming snow-capped mountains. Its southern slope, covered with eucalyptus, banyan trees, and palm trees, is where the Himalayas are located. There was still some residual seawater here at that time, and the Himalayas rose from such a foundation.

To solve this problem, the researchers conducted in-depth studies on some residual marine strata on the northern slope of the Himalayas.

Image source: Screenshot of CCTV1's "Let's Talk"

The picture above shows a famous geological site in Gangba County, Tibet. You can see that the limestone formations towering into the sky on the south side (right).

Image source: Screenshot of CCTV1's "Let's Talk"

These limestone formations are deposits of the continental slope of the Indian plate, deposited immediately after the collision.

Image source: Screenshot of CCTV1's "Let's Talk"

This set of green sediments and the red sediments above are called the Neotethys Ocean.

Image source: Screenshot of CCTV1's "Let's Talk"

Many marine fossils can be found in the green sediments, indicating that it was connected to the Pacific Ocean at that time. The green immediately turns red, which means there is no sea water and ancient soil has been formed, which must have occurred on land.

Therefore, the boundary between green and red is the location where researchers believe the last drop of sea water in the Himalayas dried up. The sea water completely disappeared here within a period of about 55 million or 50 million years.

From then on, there was no more seawater intrusion into the Qinghai-Tibet Plateau, and the Himalayas rose completely from sea level.

However

Qinghai-Tibet Plateau

There is something magical about it

After the collision of the Indian and Eurasian plates, their story did not end. Immediately afterwards, the Indian continent subducted under the Qinghai-Tibet Plateau. After the collision, the Qinghai-Tibet Plateau still had strong tectonic deformation, volcanic eruptions and large-scale mineralization. Therefore, the Qinghai-Tibet Plateau's shaping of China's landforms and topography did not end after the collision. It is still active and shaping our country's landforms and topography.

Image source: Screenshot of CCTV1's "Let's Talk"

At the same time, it brought a large amount of minerals, but was also accompanied by many disasters, such as the Wenchuan earthquake and the Kunlun earthquake, which were largely related to the fact that the Qinghai-Tibet Plateau was still colliding.

03

What would happen if the Qinghai-Tibet Plateau disappeared?

Some studies believe that the Qinghai-Tibet Plateau has begun to collapse. The most obvious sign on the Qinghai-Tibet Plateau is the appearance of seven large rift valleys, which are caused by extension. If something is stretched, its thickness will become thinner, so the height of the plateau will decrease.

Image source: Screenshot of CCTV1's "Let's Talk"

If this stretching of the Qinghai-Tibet Plateau continues one day, perhaps our plateau will no longer exist, our Jiangnan region will become a desert, and rice can grow again in the desert Gobi of the northwest.

No matter what, we still have to thank the Qinghai-Tibet Plateau for shaping China's colorful mountains and rivers.

Source: CCTV1 "Let's Talk" Producer: Ma Lian Editor: Wu Nan

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