It takes the explosion of an atomic bomb to just detonate a hydrogen bomb.

The device detonated in the Mike shot, called the Sausage, was the first H-Bomb ever tested, built upon the Teller-Ulam principles of staged radiation implosion. The 10.4Mt device used two stages, with a fission bomb as the primary, and a secondary stage of liquid deuterium fuel in a cylindrical dewar. The dewar was surrounded by a uranium pusher/tamper weighing 5 tons. The steel housing was 2m wide and 6.1m long, with walls 30cm thick. The inside surface of the casing was lined with sheets of lead and polyethylene to form a conduit from the primary to the secondary. The entire device weighed 82 tons making it un-usable weapon. The test island of Eluelab was completely obliterated, the resulting crater was 1.9km wide and 50m deep. 77% (8mt) of the yield was due to fast fission of the natural uranium pusher/tamper making this an extremely "dirty" test showering high levels of radiation over the atoll. The mushroom cloud climbed to 17,000m in only 90 seconds, entering the stratosphere. Within 1 minute it had reached 33,000m, eventually stabilizing at a ceiling of 36,500m. Half an hour after the test the mushroom stretched 96km across. Additional clip using time lapse photography.

"Mike" is the first fusion bomb: Explosion of Mike completely obliterated the island.