Audio
Erosion
Transcript
Go ahead and stop here before walking through the tunnel. If you look to the left of the tunnel along the rock face you will see what is called “breakdown”. This is a good example of the effects erosional forces have on the sandstone and siltstone which make up most of this bluff. Wind and water have, over time, sliced away a portion of the rock that was connecting this to the rest of the bluff. Erosion of the bluff occurs slowly and is usually unseen by humans. Wind, rain, and snow wears the bluff away. It slowly washes away the grains and the particles of sand, silt, and ash. Most of the rockslides that occurred in the monument happen within this, Brule Formation. The Brule Formation is large and it makes up one third of the exposed rock of the bluffs.
Now look just above the tunnel entrance. Notice the thick band of volcanic ash. It’s a whitish color on top and a brownish color on the bottom. This layer is several feet thick in some places. Geologists say between 28 to 32 million years before now, massive volcanic eruptions occurred in mountain ranges west of here, some as far away as present-day Nevada. Ash from these eruptions was carried eastward by the winds. It then fell as ashfall on the land that would one day become known as Western Nebraska.
Go ahead and walk through the tunnel. Try to imagine what it would have been like for the young men who built this trail and hand dug this tunnel. Yes, we said hand dug. The rock formations here are so fragile and so easily eroded that the decision was made to have the walking trail tunnel hand dug rather than blasting with dynamite.
Once on the other side of this tunnel you will begin to climb a series of steep switchbacks. Once completed you will be on the top of Saddle Rock, the location of stop number five.
Description
Stop 2 on the Scotts Bluff National Monument Saddle Rock Trail Audio Tour.
Credit
Audio recording by Ray Richards
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