Hypothetical: Large Thermonuclear Detonation

vociferous

I guess this is more a geophysics question, but I was wondering about what the geophysical and atmospheric consequences would be of a single, massive energy release at a single location, caused by the simultaneous detonation of several large thermonuclear bombs or an antimatter explosion; something in the range of >1000 megatons of TNT equivalence.

The energy released would be enormous; would it be enough to cause widespread geological instability? Would it kick up enough dust to block the sun out for decades?

mgb_phys

1000 MT is still pretty insignificant compared to nature on a bad day!
Thats about a supervolcano which might put 300-500 km^3 of material into the atmosphere.
A tiny volcano like Mt St Helens is 25MT.

A tropical storm (cyclone) is even more energetic, of the order of 30-50Mt/hour of continual power output!

LURCH

As mgb_phys said, the blast from a supervolcano like Craktoa is about the size of energy release you're talking about, and in the right form, too (explosion). Try looking at some of the geological studies of that event, and you'll get a pretty good idea of what would happen with a super-nuke. Just add poisonous levels of radiation to the dust cloud, and you're pretty much there.

Borek

50 MT was tested by Russians in 1961, look for Tsar Bomba if you need details.

vociferous

According to Wikipedia, Krakatoa was a ~200MT explosion. Which equations would be suited to calculating the yield from a massive release of energy in terms of the radius of vaporization, thermal effect, lethal neutron and gamma explosions?

I am thinking about writing a novel, and one of the plots is going to involve a very large explosion, but I do not want to under or over estimate the effects and the fallout. Also, if the explosion involved antimatter instead of fusion, would the radiation effects be similar? Obviously, very little neutron radiation would be produced; it would be mostly electromagnetic.