Horseback in the Andes

Tomas Alarcon trotted his horse up to ride beside mine and pointed to the vertical layer cake of limestone and shale that rose above the ugly scar of a mining road across the valley.

"I climbed those cliffs when I was a child," said my Chilean guide. "And you know what? There are millions and millions of seashell fossils in the rock. Here, at nearly five thousand meters!"

We rode in silence for a minute, pondering the massive tectonic forces that could lift what was once the bed of the Pacific Ocean more than 16,000 feet above sea level and create the cut-glass peaks of the Andes mountains.... Full Story