Visit Pinnacles Overlook, Crater Lake National Park, Oregon

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On the Crater Lake's southeast slopes, the canyons of Wheeler and Sand Creeks became submerged in a searing pyroclastic flow during the massive blast 7,700 years ago. Gases from the superheated rock below were released to the surface via narrow vents, welding the pyroclastic deposits in their immediate vicinity. They may be viewed from overlooks at the end of the access road and along the half mile Pinnacles Trail. Hike along the forested rim of Wheeler Creek, past a group of amazingly tall and narrow volcanic pinnacles, colored various shades of grey. These towering needle-like formations of rock, called fossil fumaroles, projecting from the Sand Creek Canyon floor, were formed under sheets of volcanic pumice that preceded Mazama's collapse. As the surface of the hot pumice cooled over the years, steam and gases were released by the hot rocks underneath through vents and tubes that were welded into cement hardness by their passage. These ancient vents now stand alone due to the erosion of the surrounding softer materials.

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