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This is field trip leader Wayne Belcher starting out
the day with a reading of Psalm 19. "Let the words of my mouth and
the meditations of my heart be acceptable in Thy sight, O LORD, my
rock and my Redeemer." |
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The view from Stop 1 includes the Las Vegas valley and
the Spring Mountains. |
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The rock of Frenchman Mountain. was shoved up, partly
by movement along the Front Range Fault. The fault is seen trending
diagonally across the photo to the left of the man on the right. |
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The rocks in the mountain, now tilted, were once connected
to the horizontal layers of rocks in the Colorado Plateau, such as
those exposed at the Grand Canyon in Arizona. Stretching of the crust
caused a large block to break away from the Colorado Plateau. Further
stretching fragmented the crust into smaller blocks that moved laterally
along a nearly horizontal master fault beneath the blocks. The Frenchman
Mountain block is the farthest one from where detachment occurred,
having moved west about 50 miles from its original position. The movement
occurred between 10 and 6 million years ago. Rock mechanics and heat
flow properties of the earth require that such movement could not
happen in less than millions of years. This deformation is related
to the interactions between the North American and Pacific lithospheric
plates, which today slide past one another along the San Andreas fault
in California. |
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