Plains formations

Far out on the western edge of Nebraska the geology of the Great Plains starts to be interfered with by the Black Hills and Rockies, each with their uplifting actions that raise the western edge of the Plains higher and higher.  After millions of years of flat, even land being deposited with hundreds of feet of sediment slowly growing at the bottom of ancient oceans, the western and northern mountain building pressure gradually tilted the land upward, draining waters to the east.  As the waters drained away, their erosive action removed the softer sediments.  Year after year, as the Plains tilted more to the east, the departing ocean water washed away any material soft enough to be removed.

That sediment was composed of varying layers of silt, ash, sand and the remains of marine and land animals that lived at each time.  Never exposed to the heat and pressure responsible for the granites of the mountains that pushed it upward, this sediment consolidated weakly into siltstones, sandstones and other sedimentary rocks.  Layers up on layers, each showing differences in color, texture and appearance based on the conditions during its formation.  These were gradually changed by the movement of the waters, both then and now.

Geologists draw elegant diagrams and charts to show these layers and their relationship to history but at Toadstool Geologic Park all you have to do is stroll along the 1 mile trail to see it all laid out before you.  The “toadstools” are made of sandstone caps perched on siltstone stems, the caps being more resistant to the effects of erosion than the stems.  Gradually the stems are being diminished in size and strength, and the caps fall off or collapse onto their base.  In other areas caps and stems are being actively created by the action of rain and wind.  You can walk around and see the beds of ancient streams that deposited multiple layers of sediment, much like a tree that shows off rings as evidence of its growth.

Visiting the park is an act of intention – it’s at the end of a gravel road, off another gravel road that doesn’t really go anywhere else.  Once there all you really have is the park – no displays, no museum, no gift shop, no attractions.  It’s isolated, quiet and peaceful.   You can almost hear in geologic time.  For a landscape photographer it’s a great way to get in touch with the scenes and learn how to use light to portray what is almost a monochromatic environment.


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