I dont know if anyone has noticed this before if so my bad.
I've been going over season 4 again, looking for the little extras they put in.
Like a tree trunks shaped shrapnel when gunther blows up the wall in "Reign of Gunthers".
I was wondering how the huge hole got in the earth, i just chalked it down to a giant bomb,but then i saw this
looks like there was a meteor some time around the great mushroom war.