Tectonic pressures from continental collisions during the Pennsylvanian Period (which simultaneously created the Appalachian Mountains) caused the layers of rocks to bend into the folds in Missouri. Folds are seen in road-cuts in the layers of rock in two orientations: either domed upward (an anticline) or downward (a syncline). In the event when rock cannot respond by bending into folds because forces are too sudden or powerful, the rock breaks, forming structures called joints. One such structure is a fold, which forms because sedimentary rocks bend under pressure rather than breaking immediately. There are several common geologic structures in Missouri. Geologic Structures in Missouri: Folds, Joints, and Faults As water between the sediment is pressed out, the grains of sediment bind together in a process called lithification, which forms the sedimentary rocks (Spencer 2011). Gradually the initial layers of sediment are subjected to pressure and chemical reactions due to the sediment above. In large basins of sediment, which often are found in areas such as river bottoms, depressions in the Earth, and lake bottoms, layers of sediment gather over a large period of time.

As weather conditions erode existing rocks, grains of sediment collect and are carried to a sediment deposit, often by means of water or glacial transport. Sedimentary rocks are formed by a very long process of erosion and compression. Sedimentary rocks are very common in Missouri, as many cycles of ocean rise and fall deposited sediment across the basement rocks, most often leading to limestone formation. The only partially exposed examples in Missouri are the Hawn Park Gneiss found in Hawn State Park (and there is debate as to whether or not this rock is actually metamorphic), and some samples housed in glacial sediment in Northern Missouri. Metamorphic rocks are rare in Missouri, and they are usually only found in basement rock. Metamorphic rocks are formed when rock changes because it is subjected to different extreme conditions that have the potential to morph rocks, including high pressures and temperatures. The most common igneous rocks in Missouri are rhyolite, granite, diabase, and volcanic tuff, each of which can be seen exposed in the St. Missouri contains each of the three classes of rocks that forms the basement rock and bedrock: igneous, metamorphic, and sedimentary rocks. It is sometimes exposed on the surface, but it is typically hidden by layers of dirt and sediment hundreds or thousands of feet thick. Bedrock is not sediment rather, it is dense, hard rock, most often igneous or metamorphic. Additionally, bedrock, which is the layer above the basement rock, was added to the craton over the course of geologic history. Basement rock is the rock that forms the core of all continents, and in Missouri, this basement rock was first pushed into the North American Craton by tectonic forces to form what would become the base of Missouri. This is a rugged 13 mile trail section that was cut by boy scouts back in the 1950’s.Missouri is situated on an ancient geologic structure called the North American Craton, which is the core basement rock forming the North American continent. Johnson’s Shut-Ins State Park & Taum Sauk Mountain State Park connect via the Taum Sauk Section of the Ozark Trail. There is also a small museum and gift shop. T he Black River Center is a great place to pick up maps, hiking trails and information. If you do get the opportunity to visit Johnson’ Shut-Ins State Park, you will find an easy paved trail to the water, amenities like changing rooms and modern restrooms. There are many shut-in areas all throughout the Ozarks. S hut-in is a new term for us! It’s used in the Ozarks to mean a river that is limited in width because of natural rock which doesn’t erode. We wish we could have experienced swimming and exploring these amazing shut-ins, however, the area was closed during our visit due to high flood waters. A 100 car limit means that weekends can leave visitors waiting in line.

Johnson’s Shut-Ins State Park is a popular summer time swimming destination. Our family was so worn out that we didn’t get to hike on all of our planned trails. Arcadia Valley offers more state parks and hiking then can be accomplished in just one visit.

Johnson shut in state park from owasso