Throughout geological history, various points on the Earth’s surface have been lifted up to great elevations and worn down into low, flat-lying regions.  Determining surface elevation histories is difficult because rocks that were once on the surface are usually eroded away or buried.  Furthermore, most rock-forming processes are not directly affected by elevation.  But it turns out that we can overcome these challenges, as Carmie Garzione explains in the podcast.  Carmie Garzione is Dean of the College of Science at the University of Arizona.  She has managed to pin down the history of elevation changes by analyzing stable isotopes of carbon and oxygen in carbonate rocks.  She describes how the method works, and presents her findings for the Tibetan plateau and the Andes.  They show pulses of very rapid (geologically speaking) uplift.  What might this be telling us about what has been going on in the lower crust and upper mantle in these regions?