Excellent talk. Learned so much. The green rocks fascinated me. Lovely to hear their history. Thx from Blue Ridge near Asheville NC. ✌🏻

Great talk, particularly because in this talk the speaker combats the long-standing fiction promulgated by countless GEO101 and K-12 earth science textbooks that the Appalachian Mountains are “the oldest mountains in the world”. This fiction is has been widely disseminated across a huge section of the general population. Very few people understand that, while the rocks that form the mountains are rather old, the mountains themselves-the relief/landforms/geomorphic surface-is Miocene age and younger, and the original mountains formed during the Paleozoic continental collision-the series of orogenies that culminated in the formation of Pangaea-would have been peneplained down to hydrological equilibrium level just tens of millions of years after they were first uplifted. It’s also probable that some form of “Appalachian” mountains appeared concomitant with the formation of the Atlantic Ocean, as “Rift Shoulders”, or tilted block uplifts associated with the formation of the Triassic to Jurassic extensional basins that developed during early rifting of the Atlantic margin, but these, too, would have been eroded down to nothing for most of remaining Mesozoic and Cenozoic time. It is, however, unknown if during this time, some sort of long-lived “high-relief” geomorphic surface like that which we see today in the Appalachians-primarily caused by differential erosion, as the speaker points out-could have existed, making the mountain range a very long-lived erosional feature. My understanding, however, is that the Atlantic margin was more or less a region of low relief until Miocene time, and the appearance of high relief occurs with a global change in climatic patterns (cooling and development of the Jet Stream), and that most of the relief we observe occurred in focused pulses, first in Miocene time, and then in Pleistocene time, with the glaciation of the Northern Hemisphere. The late great Peter Molnar talked about this-the occurrence of young (