A Billion Years Before the Grand Canyon, a Giant Cliff May Have Stretched Across America

A new study suggests that the Grand Canyon’s oldest and deepest rocks were exposed by a massive ancient cliff that stretched across the United States. Long before the Colorado River carved the Grand Canyon, an enormous wall of cliffs may have been exposing some of the ancient rocks that now lie at its heart. New [...]

from SciTechDaily https://ift.tt/8E9elRj