BOULDER COLLUVIUM ON THE SOUTHEAST-FACING SLOPE OF BLUE MOUNTAIN IN CUMBERLAND COUNTY, PENNSYLVANIA
During the Pleistocene, freeze and thaw action in the periglacial climate that affected all of the non-glaciated parts of PA utilized the numerous bedrock parting planes to break down the TQ into a multitude of boulders and blocks. This material gradually descended the slope of BM to create a covering of BC. The upper, steep-slope BC comprises, basically, broken rock that fell, slid, and rolled down slope assisted by snow and ice and additional freeze-thaw breakdown action. There is no surface pattern in the upper slope BC.
Once the downward moving BC achieved the lower, gentler, Martinsburg slope, the movement process changed to one controlled by solifluction in an often water-saturated environment. This BC moved in masses generally having the form of low, rounded, elongate, curved mounds with steep fronts, rounded tops, and less steep backs. These masses are called solifluction lobes. This BC generally has more, smaller pieces of rock and some dirt that contributed to its lobe-forming tendency. Solifluction lobes are very common in PA on lower, gentler slopes of mountains. Multiple soil profiles on the BM mountain slope indicate that at least 3 periglacial episodes occurred during which BC movement took place.