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Toadstool Geologic Park Interpretive Loop | Oglala National Grassland

Harrison, NE | 05/20/21 | 1.07 miles | 89′ gain

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Phew, what a day. Diana and I had driven up through Nebraska, visiting both Scotts Bluff and Agate Fossil Beds National Monuments. We had one more planned stop just before the South Dakota border and we were in a serious time crunch as the approaching storm was nearly upon us. Toadstool Geologic Park hosts a small campground, picnic area, and a handful of trails. We chose the quick one-mile interpretive loop and grabbed one of the paper trail-guides available at the trailhead. There are no signs along the trail, but numbered posts correspond to the pamphlet. After paying the small day-use fee ($3), we set out around the loop. The storm clouds loomed over us but they provided me some of my favorite pictures I’ve ever taken.

The trail leads out across the prairie to Nebraska’s badlands, a rugged area full of fossils and interesting geology. Toadstool Geologic Park is named for its numerous mushroom- (or toadstool-) shaped rock formations. The toadstools are created by wind and water erosion. Their hard sandstone caps are more resistant to weathering than the soft claystone pedestals. Eventually the clay will erode too much and the cap will topple over, but new toadstools are slowly forming as erosion continues. We saw many toadstools in various stages of their “life” cycle.

The badlands began their creation 34 million years ago, when streams and wind carried ash from Great Basin volcanoes and other sediments to this area, depositing them layer by layer over tens of millions of years. The different layers in the rock indicate different periods of deposition; the ones at the bottom are the oldest. The layers (and the fossils they contain) were exposed as an ancient river flowed through, carving the valley. Wind and water continue to erode the badlands at a rate of about one inch per year.

The first part of the loop is pretty easy but it soon becomes much more rugged. In addition to the overhanging cliff, there are some drop-offs, slick areas, and short sections of easy scrambling.

The ancient river that flowed through this area 30 million years ago attracted prehistoric wildlife that left their tracks in the sand. The trackway at Toadstool extends nearly 3/4-mile and is the longest and most diverse prehistoric mammal trackway in North America from this time period. The majority of the footprints belong to two species of rhinoceros (Hyracodon and Subhyracodon) and an entelodont (a giant wild pig). The clues from the tracks indicated to scientists that the rhinos were heading downstream, using the streambed as a path. The scavenging entelodonts were following the migrating rhino herd, in the hopes that food would become available as individuals perished. Other tracks found in this trackway belong to Stylemys (a giant tortoise) and Dinictis (a cat).

Back at the trailhead, we explored the soddie (or sod house). This one is a replica built in 1984, but early homesteaders built one just like it here in 1930. Clay soil held together by a strong root system was plowed from the prairie and stacked like bricks. Soddies were the main type of home built by prairie homesteaders as other building materials (like wood) weren’t available.

We made it back to the car just as it began to sprinkle. What we thought was great timing turned out to not be so great after all as the dirt roads leading to and from Toadstool turned into a sticky, sloppy mess. Unfortunately by the time we realized this, it was too late and we were unable to turn around. As there was nowhere to pull over, we were forced to continue, constantly fishtailing in the slick mud. Eventually the 2wd car bogged down in the middle of the road. Luckily Diana had phone service so we attempted to call for a tow, but since we were in the middle of nowhere, it would take hours for a tow if they could even come at all that night. The idea of spending the night in the middle of the road wasn’t very appealing.

The local tow company was shocked that we were driving the dirt roads when wet, as in this area it’s apparently common knowledge that the roads are made of “gumbo” (bentonite). Bentonite is a type of clay that is very hard when dry, but when it becomes wet, it absorbs water and expands, essentially turning into a mudhole. Of course we’d never heard of this phenomenon before and we couldn’t believe there had been no signs warning unsuspecting travelers (like us) to stay off the dirt roads when they’re wet.

After a bit of a lecture from the tow driver (kind of late now, buddy), he mentioned something about the wind drying out the gumbo. The storm had moved south of us and it had stopped sprinkling. A light breeze was blowing across the road and amazingly it began to dry out. We waited fifteen minutes before starting the car to see if we could get any closer to the highway and somehow the car started to move. We crawled along, fingers crossed, breath held until we reached pavement. Back on solid ground, we screamed for joy and quickly called off the tow. A little late and slightly worse for wear, we were finally on the road to our hotel, dinner, and bed.

Oh, did you think that would be the end of it? We sure did, but it certainly wasn’t! After dark, insane thunderstorms pounded the Black Hills. Lightning flashed every few seconds, lighting up our surroundings as if it were daytime, while rain and hail pelted the car. We eventually found a safe spot to pull over to wait out the worst of the storm. As soon as conditions became more safe, we continued to our hotel, now hours behind schedule and completely exhausted. We really hoped this wasn’t a bad omen for the rest of our trip, as I don’t think either of us could have taken another minute of gumbo or thunderstorms. Our only regret was not getting a single photo of our ordeal to prove how incredibly awful and ridiculous the entire situation was.

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I would like to acknowledge that Toadstool Geologic Park is on the ancestral land of the Očhéthi Šakówiŋ (Great Sioux Nation) and Cheyenne.

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Chelsea

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