New Delhi, April 24 -- Scientists have found something strange under the Sierra Nevada mountains in California. And, it may change a lot about how the Earth looks in future.

Earthquakes usually happen close to the surface, about 10 to 18 kilometres deep. But recently, researcher Deborah Kilb noticed quakes happening much deeper, around 20 to 40 kilometres underground.

This is quite unusual because, at that depth, the Earth's crust is normally too hot. It is under too much pressure for quakes to happen.

Kilb told another scientist, Vera Schulte-Pelkum, who was already studying odd rock patterns in that area, CNN reported. Together, they used a special method called receiver function analysis to look deep inside the Earth.

What they fou...