atomic bomb tests

If the atomic bomb exploded in the ground, what horrible thing would happen?
when an atomic bomb is detonated on the ground, a giant mushroom-shaped column of smoke appears, and of course comes with a huge heat source, destroying everything around it. so what if an atomic bomb is activated underground then what will happen?
Horror secret at the island of humans do not dare to set foot
a deserted island with blue sea, white sand, golden sunshine but no one has the courage to live here. it was bikini atoll, which had more than 20 atomic bomb tests of the us military from 1946 to 1958.