I think they were as tall as the Alps are now - because the crust essentially “floats” on the mantle as mountains are eroded (and glaciers slide off), the land gradually rises
Comment on Roots of Mother Appalachia
immuredanchorite@hexbear.net 8 months ago
One thing that will never seem to leave my head is that I had read that the current mountain tops of the Appalachians are actually the original valleys of the mountain range. The mountains were so old and large that the valleys of todays Appalachian’s were the footprint of what was once maybe the largest mountain range earth has seen
ElHexo@hexbear.net 8 months ago
uniqueid198x@lemmy.dbzer0.com 8 months ago
What we see now are the ancient roots. Before the continental colision, there was a sea and subduction zone. This gave us sandstones, diorite, and granite… All of which were crushed at incredible pressure and temperature by the continental collision. At the deep roots of the mountains, this transformed the rock into gneiss, marble, and other extremely hard rock. Additionally, the forces were so great that the very bottom melted and became fresh granite.
All of these stones are very hard and resistant to erosion, and are what we see todayas the Appalachians