If Tunguska occurred over a major city

I am sure you are familiar with the infamous Tuguska event where a body (asteroid or comet) entered the atmosphere and probably exploded about 5 miles above the surface in Russian Siberia.

I was half watching a documentary on one of the documentary TV channels last night and the usual comment was made about what would happen if this had occured over a major city as opposed to a near-deserted forest.

That got me thinking – just how big was the impact zone, and what would it actually look like if overlaid on modern cities?

For example, according to Wikipedia, “The Guinness Book of World Records (1966 edition) states that due to the rotation of Earth, if the collision had occurred 4 hours 47 minutes later, it would have completely destroyed the city of St. Petersburg.”

The images below are a series of Google Map screenshots resized to include an overlay of the Tunguska impact zone.

It should be remembered that a Tunguska event over a major modern city would cause considerable damage, but not catastropic to most structures, as most buildings in the tree flatened area would survive (concrete being stronger than wood) – although windows etc would be smashed and there would be considerable loss of life from the burning in the central area, and secondary loss of life from the impact of the shattered glass in offices, falling trees and people being “blown” off their feet for some significant distance.

Also worth noting is that while there is the area with the flattened trees – the zone affected is considerably larger as the wind force would have still been strong beyond that immediate area and would have caused some damage.

The source for the overlay map is based on one found at the University of Georgia website.

The central grey circle represents the approximate area with trees subject to physiological light scorching. The red area is where trees were flattened – and the two circles are just helpful distance markers, 20km apart. The actual area affected is about twice the diameter of the outer circle, although there was no long-term damage – but anyone standing (for example) 60km away from the center would still feel the air-blast as a short-lived, but strong gale force wind.








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Posted in Science
5 comments on “If Tunguska occurred over a major city
  1. Joustin says:

    Very interesting indeed. It is amazing to see it scaled to a city where the size can be compared to something other than a forest.

  2. George W. Bush says:

    I was worried there for a bit, but I am glad to see that it won’t hit DC.

  3. Yay LA! says:

    Yay! Tunguska Missed Los Angeles! W00t!

  4. MadRocketScientist says:

    Of course, the blast damage would also be mitigated by geographic terrain (hills, valleys, etc) and structural obstacles (large structures which remain standing).

    I could be wrong, but I thought the original impact zone was a relatively flat place which allowed for the blast wave to move unhindered.

  5. IanVisits says:

    Agreed that local terain would affect the blast zone, as would a large number of other factors.

    However, the explosion is thought to have occured some 5 miles above the land – so I doubt that even a sizable hill in a city would offer any significant protection from the blast.

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