And they found the earliest evidence of collision of land masses in the world containing relics of ancient oceanic lithosphere - a suture at least 200 kilometers in length.

Li Jianghai, an associate professor with Peking University, found the relics of oceanic lithosphere - with a history of 2.5 billion years - last May in Zunhua, North China's Hebei Province.

He and his team found other relics of the same period in the western part of Liaoning Province this October.

These discoveries proved the suture of the two ancient plates in North China is at least 200 kilometers in length.

It is much older than those sutures found in the Qinghai-Tibet Plateau in western China, where two other continents collided with each other in prehistoric times.

"The whole suture is estimated to be far longer than the section which we discovered," said Li. "I suppose it will be altogether 600 kilometres in length."

Li said he and his team were going to do further field research next year to look for further evidence.

Plate tectonics was advanced in the late 1960s, and in the past 30 years scientists tried to look for the evidence - sutures - of plates collisions, according to Li.

"Scientific circles believe, 2.5 billion to 2.7 billion years ago, there was an ancient super continent but the final situation where parts collided and got together remains a mystery," said Li.

"The collision in North China is probably the final action that formed the super continent.

"In the following 2.5 billion years, the ancient super continent split and got together many times, finally forming the continents of our planet," Li explained.

(China Daily November 29,2001)