The tallest peaks in the famous Rocky Mountains of Colorado are half the height of most of the those in the Himalayas and are dwarfed by many mountains in the South American Andes. Why is that? And, where do mountains come from? What makes some mountains grow taller and others grow faster? If mountains affect the weather and thus the climate, is it possible that climate and weather could affect the growth of mountains?
I don’t know about you, but such questions have been with me ever since I realized that the mountains I drove through or flew over were not just rocks and dirt that had somehow been there forever. Living in Marin County, California in the eastern shadow of Mt. Tamalpais helps keep such questions alive. The chert beds so clearly visible, folded back and forth in enormous vertical S’s, on the road to the peak just beg as I drive by: exssssplain this! The green serpentine taunts: how did I get here from miles below the ocean floor? In my daily life of making a living and living with family those questions pop up and recede during the length of a Sunday drive. But they swarm out again, bothering and bewitching me when in the company of many mountains, as I was recently in the Peruvian Andes. Along the way I found the perfect book to consult and bring me a little closer to understanding the mysteries.
Devil in the Mountain: A Search for the Origin of the Andes (2004, Princeton) by Simon Lamb, a British geologist of wide experience in both mountains and in explaining mountains, is a very good book. It will draw in anyone with the stirrings of curiosity of how did these mountains come to be?
It turns out the Andes are young, only 40 million years or so, with many sections of it much younger, rising up as the lower layers skidded up the wedge shaped, and much more solid, Brazilian Shield. The youngest portions of the Canadian-US Rockies by contrast, are 100 to 65 million years old.
Simon’s approach is not pure geology. (more…)
