Thule Air Base Incident

In 1968, a B-52 bomber carrying 4 Hydrogen bombs crash-landed near the airbase of Thule in Greenland. The bombs detonated on impact spreading radioactive material over a large area. Bad weapon design ensured that a nuclear explosion was not triggered. The radioactive debris scattered in nearly 3 miles radius, melted through the ice, sunk, and then was frozen over.