I was a cinema projectionist at the time of this release and it came out at the end of the 'disaster movie' era in the seventies (in the UK).
I ran this at a press screening and it was obvious from the first minute this was a disaster movie of it's own kind. What initially was mildly amusingly bad soon went to so bad it's funny but thereafter, and very quickly and for most of the film, it reached that rare distinction of 'so bad, it really is baaaaaaaaaaaaaaad'.
OK, so I've seen lots of rubbish films but what sticks in the mind with this one is the level of money and the cast involved. I had/have no expectations that some cheap budget film with no-name actors in it might be awful but this had a decent cast and money thrown at it and for that simple reason I personally regard it a THE WORST FILM I HAVE EVER SEEN.
Avoid like the plague