One of the destructive devices mentioned in Guardian Dawn, is an ex-Soviet nuclear weapon described as 50 Megaton. The story’s fictitious weapon is based on the real Tsar Bomba that was detonated back in 1961. You can follow the links if you would like to know more.
Here is the Wikipedia Info.
Here is a clip showing the original 50 Megaton blast.
Even today, the Google Map location shows a green, glassy melt zone over 500 foot acrossed and a totally barren and burnt landscape about 20 miles wide.
If you want to see a more modern device, this video clip is very pretty, but really, really scary!