Chinese scientists are trying to drill a 5,000-meter-deep hole in an area along the Yellow Sea in east China, to unravel the secrets of the earth.

This is China's first scientific drilling on the continent and is expected to take five years to complete, said Xu Zhiqin, the project's chief scientist and a member of the Chinese Academy of Sciences.

"Human beings have lived on the earth for ages, but we still know virtually nothing about what lies under the earth's crust," Xu said.

"We can directly observe the lithosphere and get a better understanding of the movements of oceans and continents by drilling. We can also have a more clear idea of the relations between the crustal stress and earthquakes, examine volcanic movements and resources lying deep beneath the earth's crust, as well as the origins of life and differences in climate around the globe," Xu said.

Drilling exploration of the earth is no less significant than launching manned spacecraft into the space, according to the scientist.

The project, known as "Telescope Inside the Earth," is conducted in Donghai County in the city of Lianyungang, Jiangsu Province, near the Tancheng-Lushan Mountain fracture belt, China's largest fracture belt. Tancheng was hit by an earthquake measuring 8.5 degrees on Richter scale in 1688.

At the drilling site, Chinese and foreign geologists have found tiny diamonds and coesite -- a high-pressure form of silica. These finds indicate that the area lies on the world's largest high-pressure metamorphism belt.

Scientists from France, the United States, Britain, Japan and Turkey consider the area as extremely important for studying the movements of continents. The project is of global significance, Xu said.

The worldwide drilling of continents began some 30 years ago. So far, 13 countries have drilled nearly 100 holes in continents across the globe, with the deepest reaching 12 kilometers underground. Of the 100 holes drilled, 20 are between four to five kilometers deep.

Xu, who also works at a continental drilling center affiliated with the Ministry of Land and Resources, said the goal of the project is to drill a hole 5,000 meters deep and 155 mm in diameter.

The project was designated as one of China's major scientific projects in June 1997. In April 1998, an international continental drilling committee approved the project and provided 1.5 million U.S. dollars in funds and engineering equipment.

To choose the right site for the project, Chinese scientists did a lot of preliminary research. They drilled two experimental holes in the target area, one 430 meters deep, and the other one kilometer deep. These initial efforts laid a solid foundation for launching the project in September last year, Xu said.

She also revealed plans to drill a 10-kilometer hole into the earth on the Qinghai-Tibet Plateau in western China before 2010.