Gaze 180 feet down into Box Canyon, a narrow slot canyon only 15-30 feet wide carved by the Muddy Fork of the Cowlitz River. The greenish-grey stone lining the canyon is part of the bedrock Ohanapecosh Formation, dense metamorphic breccia from 26-28 million years ago. The river slowly eroded the canyon after the last ice age glaciers receded. Have you stopped along Stevens Canyon Road to view Box Canyon during the summer? 
NPS Video. Description: A river rushes through a deep slot canyon, with moss-covered, smooth rock walls. One side of the canyon is bordered by forest, while a fenced path parallels the opposite bank.
<a rel="nofollow" class="external text" href="https://www.youtube.com/user/MountRainierNPS">Mount Rainier National Park</a>
CC BY 3.0
<bdo lang="en" dir="ltr"><a href="//commons.wikimedia.org/wiki/Commons:YouTube_files" title="Commons:YouTube files">YouTube</a>: <a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=zpJIlFeU8VE"><bdi lang="">Mountain Moment: Box Canyon</bdi></a> – View/save archived versions on <a rel="nofollow" class="external text" href="https://web.archive.org/web/*/https://www.youtube.com/watch?v=zpJIlFeU8VE">archive.org</a> and <a rel="nofollow" class="external text" href="https://archive.today/https://www.youtube.com/watch?v=zpJIlFeU8VE">archive.today</a></bdo>