Just a word about that volcano erruption that delayed and cancelled so many cruises...the trip insurance DID NOT COVER THIS. It was considered an act of God.....
Some do, some don't. Every insurer has its own list of exclusions buried in the fine print. That's certainly something worth looking for when considering a travel insurance purchase.
For most US travelers, covering an act of God is a large part of why they buy insurance in the first place. I suspect many carriers are re-thinking their volcano riders after last year's events, but I wouldn't buy a policy that didn't cover other "acts of God" like rain, snow or hurricane-related delays.