A series of
surface waves moved outwards from the center. The first wave was about 94 ft (29 m) high at 1,000 ft (300 m) from the center. Other waves followed, and at further distances some of these were higher than the first wave. For example, at 22,000 ft (6,700 m) from the center, the ninth wave was the highest at 6 ft (1.8 m). Gravity caused the column to fall to the surface and caused a cloud of mist to move outwards rapidly from the base of the column, called the
base surge. The ultimate size of the base surge was 3.5
mi (5.6
km) in diameter and 1,800 ft (550 m) high. The base surge rose from the surface and merged with other products of the explosion, to form clouds which produced moderate to heavy rainfall for nearly one hour.
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