of paleorivers, or "ancient rivers" can be seen Toadstool Park. It is thanks
to these rivers that the unique "toadstools" exist which give the park its
you see sandstone in Toadstool Park you can know that an ancient river once
flowed there. Fast flowing rivers from the Rockies to the west and the Black
Hills to north flowed through this area and deposited coarse-grained sand
which was cemented into sandstone over time.
was accumulating in the river bed, silt was slowly being deposited in the
river's flood-plain. This silt, over time, became siltstone. The river, over
hundreds of thousands of years, changed course many times and left alternating
layers of sandstone and siltstone.
million years ago, this region was lifted higher and the climate became drier.
All the layers that had been built up over millions of years, began to wear
away. This process continues today. The hard sandstone is more resistant to the
forces of erosion than the softer siltstone. It often forms a protective "cap"
over a "stem" of siltstone below, forming a "toadstool." These toadstools are
just brief snapshots in the ongoing movie of geology. The park's most famous
toadstools recently collapsed during a violent storm. Others are being formed