"Konstantin Sivkov wrote that Russia needs a new 'asymmetric' weapon
He says detonating nuclear weapons on seafloor would unleash tsunamis
Seismic activity would trigger volcano, pour feet of ash over the US
He says tsunamis could affect 240 million Americans and hit Europe too
Analyst says new weapons could be ready within 10 years
TV presenter previously said Russia could turn US to 'radioactive dust' "