Mike (It was a play on megaton), or the "Mike Shot" the first hydrogen bomb, and the first physical proof of Edward Teller's "superbomb" theory following the end of World War II. Originally his theory was rebuffed as impossible, but following the Soviet Union's development of an atomic bomb and Los Alamos National Labratory scientist, Klaus Fuchs' confession of passing secrets on the the Russians, his idea was viewed with much interest.
Prior to the detonation of Mike, Teller had left the Manhattan Project, choosing instead to join Enrico Fermi in other ventures. This is why he had to use a seismograph as mentioned in the above writeup.
Mike was setup on Elugelab Island in the Enewetak Atoll consisting of a cylinder about 20 feet high. The unstable hydrogen isotope used was liquid deuterium. When Mike was detonated at 7:52 AM on November 1, 1952 it was far greater than the awesome distruction of Hiroshima and Nagasaki with a yield of 10 megatons (The atomic bombs yielded only a few kilotons).
Elugelab no longer existed, instead a 6240 feet wide and 164 ft deep underwater crater was in its place. More than 80 million tons of dirt, rock, vegetation, sea life, etc. were sucked into the atmosphere only to come down shortly after as radioactive rain and mud. Mike's mushroom cloud rose to 57,000 ft in 90 seconds, and topped out in 5 minutes at 135,000 ft. Its fireball expanded to 3 miles wide, and unlike the atomic bomb, it could have easily wiped out all 5 of New York City's boroughs.
The inital success of Operation Ivy (As it was called) would be followed by one more H-Bomb test, and then continuted with Operation Castle.