somebody forgot

Thats fuckin nuts... What would cause that?

not vented i would guess.

ya it wasnt vented i have seen pictures of fire tankers that have imploded like this from not opening the vent

What would make it implode as opposed to explode is more or less what I was asking...

i think just like if you took a straw and continued to suck you run out of air. then the outside air pressure is more than the tank or straw can handle forcing it to colaspe 

Dooghe think about when you tip up an oil bottle when its full it "Glugs" you know it is getting air and if it cant do that it will just collapse inward "implode"