Geologic dating activity

With the formation of the earth pegged at h (midnight), our work day finishes at h, just as we pull up to the present. Each hour corresponds to 0.875 billion years (Ga), each minute to 3.125 million years (Ma) and each second to 52.1 thousand years (Ka).Conversely, 1 Ga takes 4 hours, 20 minutes out of the day; 1 Ma, 19.2 seconds; and 1 Ka, 19.2 millisecondsliterally the blink of an eye.

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The entire Mesozoic Era (295 Ma long) shot by in under an hour, the dinosaurs departed just 20 minutes ago (thank goodness), and we've been comfy and relatively ice-free for only a mere 0.2 seconds.

A healthy human female can expect to live just under 2 milliseconds in a developed country.

This geologic overview focuses primarily on the Colorado Rockies and the Colorado Plateau, but adjoining portions of Wyoming, Utah and the High Plains as far east as the Black Hills of South Dakota also have important and related stories to tell.

Throughout this article, I'll refer to Colorado and these adjoining areas as our region of interest, which closely coincides both with the area shown in the NASA photo at Bearings just below and also with the area affected by Laramide uplift.

Under great confining pressures, or at depths where temperatures reach a significant fraction of their melting points (typically 10-15 km), rocks that are quite brittle at the surface become sufficiently plastic to deform without fracture at rates comparable to the rate at which fingernails grow (~10 mm/yr).

Granted, that makes molasses look downright mercurial, but then relative viscosity is the whole idea here.

And so it goes with the bending of seemingly rigid rocks, the cutting of majestic canyons, the raising and erasing of entire mountain ranges, the opening and closing of globe-girdling oceans, and the incessant splitting and regrouping of the dancing continents.

Our usually reliable day-to-day sensibilities tell us that such things can't happen, but they can and do happen because solid rock reveals its malleability only over time scales very long compared to human eventstypically in spans of tens of thousands if not millions of years.

Colorado's generous endowments of accessible mineral wealth and fertile farmland were not inevitable birthrights. This overview ventures a "to the best of our knowledge" summary of Colorado geologic evolution current as of late 2004.

Colorado's story still includes many gaps and controversies, often around events and structures shrouded in deep time, deep earth or both.

Colorado's also part of an immense, heterogeneous and longstanding tectonic upland covering the entire western third of the United States and ultimately can only be understood in that context.

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