Johnson Shut-Ins, Proffit Mountain, and Elephant Rocks

photo by Ellen Dai

September 27, 2013

In our campsite at the shut-ins, we found and briefly caught a Northern Fence Lizard (Sceloporus undulatus hyacinthinus). From head to tail It was about 7-8 cm, brownish-gray in color with a white and light-grey belly. According to my amphibians and reptiles book (The Amphibians and Reptiles of Missouri by Tom R. Johnson), the average length is about 10-18 cm, but we also learned that the hatchlings are generally born in late August so it fits that this one would be small.

The next day as we were hiking the scour, we saw more lizards. Although we weren’t able to catch any of them, we took some observations and tried to ID them later with the help of the field guide. We determined that we saw more Northern Fence Lizards and a few Six-lined Racerunners (Cnemidophorus sexlineatus sexlineautus). Six-lined Racerunners are commonly found in almost parts of Missouri, including the area in southeast Missouri that Taum Sauk is located. We could see distinctive lines running down its back, and given its speed and choice of habitat (rocky, open areas), it's plausible that we would find a racerunner.

-Entry by Annie Gocke

The trip to the flood scar was the first time I had seen the rock foundation below the soil. Huge solid pieces of bedrock were exposed where there had once been forest. Everything is founded on rock. I also was excited to see primary succession occurring as rock was being broken down into soil by lichens. However, the thing that really stood out to was how powerful water is. The water wiped out an entire stretch of forest and laid bare the rock foundation in mere minutes.

-Entry by John Evan Lee

The flood scour is a key resource for any form of geological study because it provides a view of the past geological history of Missouri. The flood revealed cambrian dolomite, cambrian conglomerate, mungar granite, weathered mafic dike and taum sauk rhyolite. The area of the scour is mostly clear of vegetation, but in some parts primary succession is visible. Large loose rocks, known as float, are common and signal the presence of outcrops of the same rock at higher elevation. What stood out most to me was that despite the strength of rock it is still highly susceptible to the forces of nature. For instance, there are ripples on the rocks from the water. Asymmetrical ripple on the rocks indicate one way current and symmetrical ripples indicate an oscillating current, both of which were present in the scour. On a clear day, which we were lucky to have, the view from the top of the scour near the dam is beautiful and not to be missed.

-Entry by Sam Schell

The Taum Sauk Hydroelectric Power Station started construction in 1963 and then one of the largest in the world. In fact, the hydraulic pressure of the dam is greater than that of the Hoover dam! The upper reservoir holds 1.5 billion gallons of water, which is used by the two hydroelectric turbines to generate over 450 megawatts. In context, thats about ¾ of the power given off by an advanced coal-fired power plant, only the hydroelectric power plant gives off no carbon emissions or pollution of any kind. Well, that was true until December 14th, 2005, when the dam burst and flooded the valley. The engineers at the plant unwisely let the water level reach an unsafe height, which then flooded over and eroded the ground directly in front of the dam, causing the dam to bend and break under the immense pressure. Thankfully, no one was killed but the park ranger and his family were in their home at the time, which was lifted up by the flood and carried downriver. They suffered non-critical injuries, with the only member of the family needing to go to the hospital being one of the ranger’s children who received severe burns from the heat packs put on him by the EMT’s to prevent hypothermia. It is truly amazing that they were all relatively unhurt.

-Entry by Neil Stein

More information about Johnson’s Shut-Ins State Park:

Taum Sauk Scour:


October 10, 2014 Trip- Class of 2018

Proffit Moutain is part of Missouri's St. Francois Mountain Range, one of the oldest geologic formations in the midwest. While walking along the Scour, the aptly named section of exposed bedrock exposed by the 2005 dam break of the Tom Sauk Hydroelectric Plant atop the mountain, we passed over rubble from numerous epochs of Earth's history. The oldest rock we observed was igneous granite, formed by volcanic activity and tectonic collision in the region nearly 1.5 billion years ago. Older rock lies beneath newer layers, and is harder due to the increased pressure it has undergone. As a result of the upper rock being softer, the mass of rubble and boulders running along the bottom of the Scour is newer rock, Cambrian dolomite and conglomerate rock from more than 400 million years ago that the rush of water ripped from the earth. While most of the Scour we saw was devoid of animal and plant life, signs of reclamation by the surrounding forest is apparent. Pioneer species like mosses and grass popped out of cracks and fissures in the rock, while farther down the Scour various species of deciduous trees had begun to grown amongst the scattered stones, boulders, and sediment. We saw very few animals while on the Scour itself, but signs of reclamation of the area by animal life since the flood look promising: we spotted a frog sitting immobile amid a scrim of ice, bathing in the trickle of water than ran between the rocks.

-Entry by August Gremaud

The immense power of the water that scoured Profitt Mountain when the dam broke made it easy to visualize the geologic history of the region. While much of the southern parts of the Midwest share the alternating layers of sedimentary sandstone, shale, and limestone, southeastern Missouri is unique because of the St. Francois mountains. While most of the unusual features of the region are generally hidden by forest, the scour clearly showed the rhyolite layers that erupted from what was likely a hotspot underneath the region. Rhyolite is not a commonly found igneous rock, as volcanic activity in the interior of continents is not caused by common tectonic processes. The scour made it easy to visualize the nonconformity of the overlying sedimentary layers over the ingeous granite and and especially the rhyolite, which is very specific to the St. Francois Mountains.

-Entry by Anton Beer

Along the way back to school, we stopped by Elephant Rocks State Park. After years of unique erosion patterns, giant "elephant" crystalline red granite boulders have formed on a tor, a small rocky hill. Along with the unique rock formations, one can find the different names of miners that are carved into the rock from the 19th century. Here are photos of the elephant rocks and the granite quarries that are now filled with water. 

-Entry by Thomas Kong


Back to Geography