what do you make of this ?

[link to en.wikipedia.org]

Storax Sedan was a shallow underground nuclear test conducted in Area 10 of Yucca Flat at the Nevada Test Site on 6 July 1962 as part of Operation Plowshare.


Sedan was a thermonuclear device with a fission yield less than 30% and a fusion yield about 70%.The explosive device was lowered into a shaft drilled into the desert alluvium 194 m (636 ft) deep. The fusion-fission blast had a yield equivalent to 104 kilotons of TNT (435 terajoules) and lifted a dome of earth 290 feet (90 m) above the desert floor before it vented at three seconds after detonation, exploding upward and outward displacing more than 11,000,000 t (11,000,000 LT; 12,000,000 ST) of soil.

The resulting crater is 100 m (330 ft) deep with a diameter of about 390 m (1,280 ft).

see pic . [link to en.wikipedia.org]

this bomb was 104 kilotons and 636 feet below ground.