Editing Hells Canyon (section)

==Geology==
The geologic history of the rocks of Hells Canyon began 300 million years ago with an [[Volcanic arc|arc of volcanoes]] that emerged from the waters of the Pacific Ocean. Over millions of years, the volcanoes subsided and [[limestone]] built up on the underwater platforms. The basins between them were filled with [[sedimentary rock]]. Between 130 and 17 million years ago, the ocean plate carrying the volcanoes collided with and became part of the [[North American continent]]. A period of volcanic activity followed, and much of the area was covered with floods of [[basalt]] [[lava]], which smoothed the [[topography]] into a high [[plateau]]. The Snake River began carving Hells Canyon out of the plateau about 6 million years ago. Significant canyon-shaping events occurred as recently as 15,000 years ago during a massive outburst flood from Glacial [[Lake Bonneville]] in Utah.<ref>{{cite web|title=Hells Canyon National Recreation Area: Geology of Hells Canyon |publisher=U.S. Forest Service |url=http://www.fs.fed.us/hellscanyon/life_and_the_land/geology/ |access-date=December 26, 2010 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20110315085105/http://www.fs.fed.us/hellscanyon/life_and_the_land/geology/ |archive-date=March 15, 2011 }}</ref>  The canyon contains dense forests, scenic overlooks and mountain peaks. At the bottom of the canyon, the area is a dry, desert environment.<ref name="Hells Canyon"/>