The fireball touched the ground, reached nearly as high as the altitude of the release plane, and was seen and felt almost 1,000 kilometres (620 mi) from ground zero. The heat from the explosion could have caused third degree burns 100 km (62 miles) away from ground zero. The subsequent mushroom cloud was about 64 kilometres (40 mi) high (nearly seven times higher than Mount Everest) and 40 kilometres (25 mi) wide. The explosion could be seen and felt in Finland, breaking windows there and in Sweden. Atmospheric focusing caused blast damage up to 1,000 kilometres (620 mi) away. The seismic shock created by the detonation was measurable even on its third passage around the Earth.