Immediate Effects on an Urban Center
from a 20 Megaton Bomb Detonation
- Within one hundredth of a second, a fireball would envelope
everything within two miles.
- Temperatures rise to 20 million degrees Fahrenheit
(comparable to the inside of the sun) during the detonation,
cooling rapidly as the fireball forms. After a minute, no
significant amount of heat is given off.
- Everything at ground zero is vaporized
2-4 miles from ground zero
- Air pressure reaches 25 psi and wind speed reaches 650 mph.
- Steel-framed buildings and steel-reinforced concrete buildings
are torn apart and leveled.
4-10 miles from ground zero
- The heat would still be high enough to vaporize sheet metal
found in cars and melt glass.
- Winds reach speeds of up to 200 mph, leveling brick and cinder
block structures as well as structures with wooden frames.
16 miles from ground zero
- The heat would be high enough to ignite easily combustible
materials such as houses, wood, trees, cloth, gasoline, and
heating fuel. This would trigger hundreds of thousands of
- Winds reach speeds of over 100 mph and reach 2 psi,
still enough to shatter windows, cause damage to most houses
and buildings, and knock a person off their feet.
29 miles from ground zero
- Heat still reaches temperatures that will cause third degree
burns on any exposed skin.
- Wind speeds as a result of the explosion are negligible.
Up to 40 miles away from ground zero
- Flash blindness may be caused by anyone looking in the
direction of the explosion.
- Permanent blindness may occur to anyone looking directly at
the explosion if the light is focused through the eye’s lens in
a way which causes burning of the retinas.