People will reach the mantle and find there creatures

Sir Arthur Conan Doyle : writer
A group of scientists drills into the earth until he reaches the mantle, convinced that it is a sentient being, akin to an echinus, and that by doing so he will be the first person to alert it to mankind's presence. He awakens the giant creature, which then proceeds to destroy his excavation, covering the spectators with a noxious liquid in the process.

Conan Doyle, A., (1928) When the World Screamed, London, Liberty Magazine