Image Credits: China Geological Survey China’s deep-sea drilling ship Mengxiang has returned to Guangzhou after completing its first scientific drilling trip in the South China Sea. During the 30-day expedition, the ship reached 4,929.17 metres below the ocean surface and drilled 864.77 metres into the seabed. It also brought back a 4.27-metre-long piece of basalt rock. The expedition was organised by the China Geological Survey and carried out by the Guangzhou Marine Geological Survey. The team worked at two sites in the South China Sea, where the water was about 4,100 metres deep. The drilling set a new national record for scientific drilling. It also made China the third country, after the United States and Japan, to recover hard rock from a deep ocean basin using a drilling ship. The samples could help scientists understand how the South China Sea formed and changed over millions of years. Early tests of the samples suggest that large volcanic eruptions took place after a geological event called a spreading ridge jump. A spreading ridge is a place on the ocean floor where tectonic plates move apart. Magma rises through the gap and forms new ocean crust. In a ridge jump, this spreading centre moves to another location. Scientists are studying this process to understand how the South China Sea basin developed. Mengxiang used a rotary drilling tool developed in China to recover the basalt core. Getting a complete piece of basalt is difficult because the rock is hard and brittle. There are also thick layers of sediment on the seabed in parts of the South China Sea. Drilling teams therefore have to pass through the sediment before reaching the rock below. Sun Zhen, chief scientist of the expedition and a scientist at the Guangzhou Marine Geological Survey, said getting a complete core is difficult and requires both equipment and skill. The basalt samples will help scientists test ideas about the ridge jump and the formation of the South China Sea. The team also set u