Most of you have probably noticed and some have pitched their tent in such "ridge trenches" usually called ridge-top grabens by geologists, i.e. longitudinal cracks or structural hollows at the top of a ridge that have developed over time into several-meter-deep ditches. Some can result from (or can be initiated by) gravitational forces pulling the rock mass in opposite directions. This nice one runs along the Polish-Slovak border, at the saddle NW of Starorobociański Wierch (Klin). It's a late September afternoon: warm in the sun on the south slope whereas frost holds on the shaded north slope.
(Please see the comments below for a little discussion)