The only real threat is if Mt. Rainier blows. That could be devastating for the people affected. Might not be covered in most policies.
I checked my policy... I'm covered against ash damage and lava from Rainier isn't an issue. I asked them if I was covered in case of a lahar, and was met with silence.
They had to look up the definition of "lahar" and call me back. Short answer, a lahar is considered to be a flood. So I would need flood insurance (if I wasn't at 550ft.)