Block glide at Mile Marker 23 along <a href="https://en.wikipedia.org/wiki/I-99" class="extiw" title="en:I-99">I-99</a> in <a href="https://en.wikipedia.org/wiki/Blair_County,_Pennsylvania" class="extiw" title="en:Blair County, Pennsylvania">Blair County</a>, <a href="https://en.wikipedia.org/wiki/Pennsylvania" class="extiw" title="en:Pennsylvania">Pennsylvania</a>.  Part of a hill of <a href="https://en.wikipedia.org/wiki/Devonian" class="extiw" title="en:Devonian">Devonian</a> <a href="https://en.wikipedia.org/wiki/shale" class="extiw" title="en:shale">shale</a> was removed to make the road, forming a dip-slope. The upper block detached along a bedding plane and is sliding down the hill, forming a jumbled pile of rock at the toe of the slide.  Photo taken in 1997 and uploaded by James Stuby.
<a href="https://en.wikipedia.org/wiki/User:Jstuby" class="extiw" title="en:User:Jstuby">Jstuby</a> at <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>
<span class="int-own-work" lang="en">Own work</span><br>Transferred from <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>