Nuclear fallout, or just simply fallout, known also as Black Rain, is the residual radioactive material that is propelled into the upper atmosphere after a nuclear black or a nuclear reaction that is conducted in an unshielded facility. It is so called because it “fall out” of the sky after the explosion and the shock wave have passed. It most commonly refers to the radioactive dust and ash that is created when a nuclear weapon explodes, but such dust can also come from a damaged nuclear plant.
This radioactive dust, made up of material either directly vaporized by a nuclear blast or charged by exposure, is highly dangerous radioactive contamination.
This can lead to the contamination of aquifers or soil and damage the affected ecosystems for years after the initial exposure.
Image Caption: Fallout shelter sign on a building in New York City upper east side. Credit: Gesalbte/Wikipedia