Noah Explodes London, Again

Greater London forms the core of a larger metropolitan area (with a proportionately larger population) that extends as far as 45 miles (70 km) from the centre. Area 607 square miles (1,572 square km).

0.5((x/0.28)^3)/1000) = y

Where x is equal to the radius in km and y is the yield in megatons of TNT

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0.5((70/0.28)^3)/1000) = 7812.5 mt or 3.26875e+19 J
(6-C) Island Level

Final Yield
(6-C)
Island Level