https://touchterrain.geol.iastate.edu/ is a great place to do this
(some notes I took on how to use it are at The three volcanoes of N Oregon and S Washington - #4 by fenrus)
https://touchterrain.geol.iastate.edu/ is a great place to do this
(some notes I took on how to use it are at The three volcanoes of N Oregon and S Washington - #4 by fenrus)