Painted volcanic pinnacles, Crater Lake National Park, Oregon

Painted pinnacles

While this national park is devoted to the United States' deepest lake, other wonders await well above the water's surface. These tricolor ripples of rock, named the Pinnacles, were formed by thermal activity around Mount Mazama—the dormant volcano whose water-filled caldera we now know as Crater Lake. Such formations are called fossil fumaroles, because each ridge was once a tube that vented hot gases. The gas compressed the sediment surrounding each tube, hardening it into a lower layer of pumice and an upper layer of darker scoria. As erosion gradually exposed the vents, this wavy, ash-topped layer cake emerged.