When you arrive at this location on the river right, heading down stream you will notice different colors of sedimentary layers. You will need to read the information below and then answer a few questions about the area.
How Sedimentary Rock Is Formed
For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
There are 3 types of Sedimentary
Clastic Sedimentary Rocks Clastic sedimentary rocks are formed mainly from fragments of other rocks and minerals. Geologists call these individual fragments clasts, a word derived from the greek word klastos meaning broken. Individual clasts, or grains if you prefer, vary in size from clay at a few thousandths of a millimetre found in claystones and shales through silt (a few hundredths of a millimetre) in siltstones, sand (0.1mm to 2mm) in sandstones through gravel, cobble and even boulder sized fragments found in conglomerates and breccias. A type of Clastic Sedimentary Rock would be Sandstone - a very grainy rock that comes in many colors, including gray, red, or tan. Under a magnifying glass you can see the grains in the rock clearly.
Organic Sedimentary Organic sedimentary rocks are formed from accumulations of organic debris such as leaves, roots and other plant or animal material which are then compressed to form solid rock. Examples include Coal, Dolomite, some Limestones and Chert. These are often darker in color.
Chemical Sedimentary Chemical sedimentary rocks are formed when minerals dissolved in water precipitate out of the solution as solid crystals. Examples include iron ore (Haematite) rock salt (Halite), Gypsum and some Limestones.
The Congaree River was the major cause of erosion of the sedimentary rocks in this area. But the river sometimes deposits sediment as well. The river is a meandering river which, when seen from above, consists of a series of horseshoe-shaped meander bends. During high water flows the river erodes sediment on the outer curve of the meander bends—the cut bank side and it deposits loose sediments (sand and gravel) as point bars on the inside curve of the meander bends. Fast moving water can erode away the top layers of point bars revealing layers of sediment as well.
Looking at the river bank you will see 2 distinctive sedimentary layers.
Question #1 - What is the color of the top layer?
Question #2 - What is the color of the 2nd layer? (directly beneath the top layer)
Question #3 - What type of sedimentary rock do you think the top layer is and why?
Question #4 - What type of sedimentary rock do you think the 2nd layer is and why?
Question #5 - What do you think caused the exposure of the layers here?
Question #6 - Given the location of these layers, are they on the Cut Bank side or the Point Bar (sandbar) side?
Question #7 - What is your elevation reading at this location?
Please email answers through my profile. Thanks!
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Dedicated on June 2nd, 2007, the 50 mile Congaree River Blue Trail (CRBT) starts near Columbia and runs to Hwy 601 near St. Matthews. Paddlers will pass through the Fall Line and enter the Coastal Plain known for its countless sandbars, high bluffs, and extensive floodplains. The highlight of the trail is the section along the Congaree National park, a protected wilderness that is home to the largest tract of old growth bottom-land hardwood forests in the U.S.
The Congaree River is vibrant corridor for wildlife and provides excellent opportunities to view common and not so common wildlife anywhere along the river. This includes deer, raccoons, snakes, wild pigs, turtles, turkeys and more. It is home to endangered species including the shortnose sturgeon, a fish that migrates from coastal waters to spawn in the Congaree near Columbia. Bald Eagles often visit the river as well.
You can download a copy of the trail map at Blue Trails Guide or stop by any of the local outfitters and pick up a semi-waterproof copy for free.