400 megatonnes of TNT

[Chrisemo1]

How large would an explosion of 400 megatonnes of TNT be?

[Buenchico]

The actual damage done would depend upon the location and environment where the explosion occurred. (The Hiroshima and Nagasaki bombs were designed to detonate about �km above the ground, which greatly increased the damage they caused). Each bomb was around 13 kilotons (although estimates of the exact power vary), so 400 megatons is roughly equivalent to 30,000 Hiroshima bombs.

As stated, the actual physical damage caused by the explosion (as opposed to the radiation damage) is hard to assess but a 400 megaton bomb exploded over, say, Birmingham, would certainly see total blast damage (with absolutely nothing left standing) across the much of central England and it's likely that large parts of the UK would suffer some effects from the blast.

The Tunguska event was probably around 10 to 15 megatons. It flattened over 800 square miles. With roughly 30 times the power, a 400 megaton explosion would obviously have far greater destructive power:
http://en.wikipedia.org/wiki/Tunguska_event

Chris

[delboy3]

The most powerful nuclear weapon ever tested was "only" 60 megatons and would have been enough to flatten a modest sized city. Something on the magnitude of 400m would probably be like an asteroid strike.

[jake-the-peg]

Specifically this:

http://news.bbc.co.uk/1/hi/sci/tech/7265608.st m

Yes?

Well to put it in perspective the Asteroid strike that was believed to have wiped out the dinosaurs is estimated at 100 million megatonnes.

And the largest man made nuclear bomb is 50 megatonnes.

So yes it would spoil your day!

[heathfield]

It's been estimated that the eruption of Krakatoa was the equivalant of 200 megatons of TNT. The sound was heard in Perth, Australia, and the atmospheric shock waves were recorded all over the globe. And your 400 megatons would be twice as powerful. The mind boggles!