It is , however , unlikely that a well-funded belligerent with nuclear weapons would waste their weapons with fuzing to explode below or on the surface , as both test shot Baker , and Castle Bravo were respectively . Instead , to maximize the range of city blast destruction and immediate death , an air burst is preferred , as the ≈ 500 meter explosion heights of the only nuclear weapons used on cities , Little Boy and Fat Man also attest to . Moreover , with air bursts the total amount of radiation contained in the fallout , in units of activity/becquerel , is somewhat less than the total that would be released from a surface or subsurface burst , as in comparison , depending on the height of burst , little to no neutron activation or neutron induced gamma activity of soil occurs from air bursts . Therefore , the initial danger from concentrated local / ' early ' fallout ( which takes on the color of the soil around the fireball , commonly with a dusty pumice or ash-like appearance , as experienced by the crew of the Lucky Dragon ) remains low in a global nuclear war scenario . Instead the fallout most likely to be encountered by most survivors in this scenario is expected to be the less dangerous but widely spread global / ' late ' fallout . An air burst at optimum height will produce a negligible amount of early fallout
Castle Bravo
Castle Bravo
Duck and cover