GEOLOGY

Detailed explanation-1: -In terms of depth below the surface, the Kola Superdeep Borehole SG-3 retains the world record at 12, 262 metres (40, 230 ft) reached in 1989 and is still the deepest artificial point on Earth.

Detailed explanation-2: -After five years, the Kola well had reached 7km (about 23, 000ft). Work continued until the project was abandoned in 1989 because the drill became stuck in rock at a little over 12km (almost 40, 000ft or 8 miles) deep. That is the current record for a depth reached by humans.

Detailed explanation-3: -Deepest drillings Because the continental crust is about 45 km thick on average, whereas oceanic crust is 6–7 km thick, deep drillings have penetrated only the upper 25-30% of both crusts.