From:
https://en.wikipedia.org/wiki/Elepha...ot_(Chernobyl)


The Elephant's Foot is the nickname given to a large mass of corium, composed of materials formed from molten concrete, sand, steel, uranium and zirconium. The mass formed beneath Reactor 4 of the Chernobyl Nuclear Power Plant, near Pripyat, Ukraine, during the Chernobyl disaster of April 26 1986, and is noted for its extreme radioactivity. It is named for its wrinkled appearance and large size, evocative of the foot of an elephant.