Nice photos, but I think the setting is misunderstood.

The kayakers are not paddling "through" or "across" a volcano; they are in the ocean, I believe. Lava from the Pu'u O'o vent, 700m above sea level, flows down to meet the ocean, and they are apparently paddling around it.

Their activities are nonetheless "extreme"; lava is seriously nasty stuff.

well, I hope he didn't burn his lungs with all the acidic vapor he inhaled :/