Fun fact: If your house is under 5 ft of ash, it's not covered by volcano insurance. That only covers you if your home is destroyed by the actual eruption/explosion.

What you need is "pyroclastic event" insurance to cover you for ash and lahar.

/ It cost something like $15/year when I lived in Seattle.

// The macOS spell checker doesn't know "lahar."

This basically covers the financial model of the whole insurance industry;

    - get insurance to cover you for X
    - get hit by X
    - realise you actually got hit by Y after reading the policy small print (or you really did get hit by X, but your policy only covers you for Y)