How often does a Tunguska-sized event happen?
Objects about 40 to 60 metres across, like the one that caused the Tunguska event of 1908, are thought to strike Earth roughly once every few hundred to a thousand years.
The Tunguska event of 30 June 1908 flattened about 2,000 square kilometres of Siberian forest. It is thought to have been caused by a stony asteroid or a comet fragment roughly 40 to 60 metres across, exploding several kilometres above the ground with an energy estimated at roughly 3 to 15 megatonnes of TNT.
Frequency. Estimates based on surveys of near-Earth asteroids suggest that objects of this size strike Earth on average once every few hundred to a thousand years. Some estimates are shorter, others longer, because the numbers of small asteroids are still being measured, and because the energy of Tunguska itself is uncertain.
Where they strike. Because most of Earth is ocean or sparsely inhabited, most such events would occur away from people. An airburst of this size over a city, however, would cause severe damage over a wide area.
Detection. Asteroids of 40 to 60 metres are hard to detect in advance. Surveys have found only a small fraction of them so far. New telescopes, such as the Vera C. Rubin Observatory, which began its survey in 2025, and NASA's planned NEO Surveyor space telescope, aim to find many more.
Response. If such an asteroid were found years in advance, it might be possible to deflect it, as tested by the DART mission in 2022. If discovered only days before impact, evacuation of the affected area could save lives.
Perspective. Even so, the chance of a Tunguska-sized event affecting any particular place in your lifetime is very small.