Chinese scientists have begun digging a 10,000-metre-deep hole in the Earth, the deepest attempt ever in the country.

By excavating 10 layers of rock, the team hopes to find rocks from the Cretaceous period, known as the 145-million-year-old Cretaceous System. According to Bloomberg, the recently launched project could be used to identify mineral resources as well as assess environmental risks such as earthquakes and volcanic eruptions.

The team discovered that rocks deep in the ground were much wetter than they had expected. Before the well was created, scientists thought that water would not penetrate the rock so deeply. They also hoped to find a layer of basalt beneath the continent’s granite, as it is what is found in oceanic crust. Instead, they discovered that beneath the igneous granite was a metamorphic granite. This was evidence of plate tectonics, as the continental crust was thoroughly granitic; this theory was only recently accepted when they started drilling the well.

Soil digging doesn’t always go so smoothly. In the 1960s, an American team traversed 13 meters of basalt in the upper layer of the oceanic crust, reaching 183 meters below the seafloor, before the project was canceled due to mismanagement and financial problems. Despite these issues, it’s still a big deal.

“The complexity of building a drilling project can be compared to a large truck moving on two thin steel cables,” Sun Jinsheng, an academic from the Chinese Academy of Engineering, told China’s state-owned Xinhua News Agency.