Magma Surf

Welcome to Montana, 10,000 A.D.
Much of the world is in the bitter grip of a second ice age, but this is a volcanic disaster. The cold was caused by ash from Yellowstone National Park's largest eruption recorded. Montana, Wyoming, and Idaho are now partially covered in a layer of lava 200 feet deep. It may seem like the last place anything could survive, but humankind has lived, and is much more technologically advanced than before.
And who'd have thought that the ninth circle of hell would become a thrill-seeker's paradise?
Every year, hundreds of the remaining humans gather here with Plasma-coated Platinum armor to ride the largest waves in history. Calling the sport Magma riding, it is possibly the greatest risk any man has ever taken. Most stay in the main crater or in the surrounding sea, but the bravest ride the lava flows leading down Mount Yellowstone, slaloming to avoid the shores and boulders. Undoubtedly, the sporters agree that this is the most intense sport ever played.
Rendered in Photoshop.