"Just east of where the Colorado River used to trickle into the Gulf of California, the dunes of the Gran Desierto de Altar are slowly migrating. Sand blows up their gentle sides; at the top, grains tumble down, and the dunes creep stealthily along. Observing these incremental processes IRL can illuminate the story of rock outcroppings like the Grand Canyon's Coconino sandstone, which features sweeping diagonal lines signaling the direction wind traveled 280 million years ago."
"But the rock record also documents far-reaching and sometimes global catastrophes, like the "Big Five" mass extinctions that irrevocably changed our planet, shaping everything that came after. As it turns out, the past - with its mix of both incremental and catastrophic happenings - can inform our present, and even our future. But to grasp what the rocks have to say requires grappling with how a formation like the Coconino, which spans thousands of square miles, could have been deposited over millions of years."
Migrating desert dunes provide live examples of sedimentary processes, with wind-driven sand accumulating and slipping down dune crests. Such incremental processes are recorded in rock formations like the Grand Canyon's Coconino sandstone, where diagonal bedding preserves ancient wind directions from 280 million years ago. The rock record also preserves global catastrophic events, including the "Big Five" mass extinctions that reshaped life. Understanding how widespread formations were deposited over millions of years requires thinking in deep time. Grasping deep time connects past incremental and catastrophic events to present conditions and potential future repercussions of human choices.
Read at High Country News
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