I'm going to assume that the 10.97 km/s is the velocity at the end of the cannon.
vi = 0
d = 220m
vf = 10.97 km/s = 10970 m/s
a = ???
vf^2 = vi^2 + 2*a*d
10970^2 = 0 + 2*a*220
10970^2 / 440 = a You are right this is a pretty big number.
2.73 * 10^5 = a
The answer is it increases the amount of solar
radiation that is redirected into space. Most of the particles emitted
from volcanoes cool the earth by covering entering solar radiation. The cooling
result can last for months to years contingent on the features of the eruption.