As the Mesozoic Era ended 65 million years ago, the dinosaurs
were dying out, and the Rocky Mountains were crumpling skyward. In
concert with their rise, the forces of erosion began to work on
these highlands and aprons of debris. Carried by wind and water,
they spread out from their flanks. Throughout much of the Tertiary
Period, the mountain summits barely poked above these vast plains
of debris.
Then, in the Miocene Epoch (some 20 million years ago) a second,
more general uplift of the Mountain West began, adding 5000 feet to
elevations across the Colorado Plateau and Rocky Mountain Province.
This uplift, which continued into the Pliocene, accelerated stream
erosion throughout the region; the process was further enhanced by
the cold, wet climate of the Pleistocene, as mountain glaciers
carved deep canyons and massive amounts of meltwater carried away
much of the erosional debris that had enveloped the mountains.
“The Gangplank” is a bridging grade between soft sedimentary
rocks of the Plains and the hard granites of the Rockies, which
here eroded down to less than 1,000 feet of additional climb above
the plains surface. From the coordinates, the sedimentary rocks to
the east (Late Miocene) are 10 million years old.
Recent History of El Tablón (The Plank)
When the transcontinental railroad was built n the 1860’s,
Wyoming was the natural choice for crossing the Rockies. The
railroad was built across Southern Wyoming, climbing west from
Cheyenne on” the gangplank” of tertiary sediments that lapped onto
the Laramie Range to the North, then across the Laramie Basin,
crossing between the Snowy Range and Medicine Bow Mountains to the
south.
"The Gangplank" is a wide, natural pass west of Cheyenne that
offers a gradual climb between the watersheds of the North and
South Platte Rivers. The Union Pacific line and Interstate 80 use
this route today.
To log this cache, you must do the following:
A. Answer the questions in your own words, and to the best of
your ability.
Bonus: B. Post a photo of yourself in the parking lot with the
either the plains, the granite rocks, or the informational sign in
the background. The pavement does not have to be included in your
photo. ? You might also want to share any photos you take of the
scenery, wildlife, or plant life in the area.
Photo not required, but answers are :)
QUESTIONS:
1. The large granite rocks to the West of the coordinates are
Pre-Cambrian in age. Estimate how old the rocks are in years
(Example: Three million)
2. What does erosion mean?
Email your answers to: isisfan1@yahoo.com
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