January 6, 2012
A layer of 230-million year old Kaibab Limestone caps the rim.
The Grand Canyon reveals a 1.8-billion year glimpse into Earth’s past from views like these along the 1.2-mile-long Trail of Time, with displays of rocks from each of the two dozen rock layers in the mile-deep canyon.
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I took a step — a long step — a million years step. Then I stopped, turned and faced north. Perched on the jagged edge of my life, I looked down deep into the shadowed layers of lost worlds — terrible deaths, fractured continents, vanished seas, mass extinctions. Taking a breath, I took another step — a long step — another million years. Curiously, I felt better — my troubles for the moment shrunk to no more than a ledge of Tapeats Sandstone in the wall of the Grand Canyon opposite. A layer of fossilized beach sand laid down 570 million years ago, the Tapeats Sandstone lies atop a mystery of missing stone — dubbed the “Great Unconformity.”