The Forces That Shape the Earth: Shrinking, Isostasy, Drift

How are mountains formed? they are pretty big—look at the Alps, the Andes, the Himalaya, the Rockies—and, if you think about it, it’s not obvious that they should be there, thousands of meters above sea level, as rocks are heavy, and we know of a force called gravity that pulls them towards sea level, but we don’t know, or Hutton and Lyell and company didn’t know, of any physical force capable of moving such great masses in the opposite direction—away from sea level and up into the sky. We’ve seen that Werner and his followers figured there was no such thing as uplift, but simply deposition of sediments and then erosion digging through them to create relief. But then the ideas of Werner, at least those on the history of the earth, are pretty much dead at this point. In Hutton’s theory there had to be some episodes of uplift: and only after the uplift valleys would be carved out, and the overall level of the land worn down by erosion, resulting in the landscape that we know. Hutton didn’t know exactly what the force that caused the uplift was, but he figured (today we would say: correctly) that force was related to heat.