The modern-day Appalachians host a variety of complex landscapes, many of which still have very steep slopes despite the old age of the Appalachian system. Steep slopes and cliffs can produce boulders, which slide or roll away from the cliff to end up as free-standing rocks. So, how big can a boulder be? This video shows some of the largest boulders in the Appalachians and talks about how geology made them what they are. Boulders in central and southern Appalachia can be larger because freezing and thawing have been less intense and the rock is less shattered. Areas with thick sandstone layers or granite-like rock are also good at making huge boulders. Where the right factors combine, boulders weighing literally tens of millions of pounds can break free and slide away down the mountainside, ending up as really cool natural features to visit. If you like hiking, bouldering and climbing, and cool spots in the outdoors, check out this video.