The Barren Riven runs 135 miles from its rise in Monroe County, Kentucky, to the Green River, which itself drains into the Ohio River. The term "river" is a generalized term. The U.S. Geological Survey classifies the Barren as a "stream," which is a "linear body of water flowing on the Earth's surface (anabranch, awawa, bayou, branch, brook, creek, distributary, fork, kill, pup, rio, river, run, slough)." Over time a stream carves its way through the underlying rock, forming deep channels in the earth's topology.
At this point in its run, the Barren River flows over and around rocks from the Mississippian geological strata, which was formed between 318 and 359 million years ago. Surface rock from this period is characterized by limestone, shale, and sandstone. Limestone is a sedimentary rock composed of calcite and aragonite, which are forms of calcium carbonate. Limestone can be many colors, and typically has a banded appearance. Limestone is common in Bowling Green. Shale is also a sedimentary rock formed from the compaction of silt and mud. Because it is composed of clay minderals and quartz grains, the typical color is gray. Sandstone is a sedimentary rock composed of small grains of quartz and feldspar. Colors range from tan, brown, yellow, red, gray, pink, to white, and sandstone beds often form highly visible cliffs and other topographic features.
A thick sequence of Mississippian limestone contains numerous oil reservoirs where it occurs beneath the surface; the same limestone is quarried where it occurs at the surface. The Reed quarry, in western Kentucky, produces more limestone than any other quarry in the United States, from Mississippian strata. The limestone also contains large cave systems, including the Mammoth Cave-Flint Ridge cave system, the longest in the world.
The geological map looks like this:
For most of its run, the Barren River flows through and over what is known as "Karst Topography." From Dr. Andrew Wulf, karst geologist at Western Kentucky University:
Karst Landscapes: These regions are characterized by rapid subsurface drainage through limestone and cave systems. They account for approximately 20% of the Earth's land surface, 25% of the continental United States and 45% of the area east of the Mississippi River. Approximately 40% of the U.S. population relies upon karst aquifers for drinking water.
Karst Topography: Formed by solution of limestone; usually in humid areas where groundwater is slightly acidic and under-saturated with respect to calcite.
Generalized equation:
CaCO3 + (H+ + HCO3-) ---à Ca2+ + 2HCO3 ----à H2O + CO2
Calcite + carbonic acid Calcium ion + bicarbonate ion
Development of Karst Landscape: Groundwater percolates through limestone along joints and bedding planes. Solution activity creates caverns at or below water table. Joints act as conduits for water in cave networks. So, caves and passageways lie along joints.
Features of Karst Topography include: Caves, Sinkholes, Springs, Karst Valleys, Solution Valleys, Disappearing Streams, Deeply Entrenched Permanent Streams
Groundwater Contamination in Karst Region: Surface waters get into karst aquifers very quickly along joints, fractures, sinkholes, etc. Once in the caves, water travels very quickly underground in cave streams. Karst regions typically have thin soil cover, so contaminants are not filtered out before percolating water gets to the water table. Groundwater in regions with thick soil cover (e.g. western Oregon, Pennsylvania) generally have better quality groundwater: Microbes in the soil “eat” some of the petrochemical wastes and other chemicals. Silt and other material gets filtered out as groundwater moves through pore spaces in sediments. Groundwater moves more slowly, allowing more filtration .
(http://geoggeol.wku.edu/awulff/111/Karst.htm)
Rivers generally develop in three stages—Youthful, Mature, Old—and are characterized by the following features:
Youthful (Upper Stage) River
Narrow
V-Shaped
Steep Sides
Steep Gradient
No Floodplain
Fast-Moving
Movesd Small-Large Sediments
Has Rapids
Mature (Middle Stage) River
U-Shaped
Narrow Floodplain
Medium Velocity
Moves Medium-Small Sediments
Lateral Erosion
Old Age (Lower Stage) River
Broad U-Shape
Wide Floodplain
Slow Moving
Moves Silty Sediment in Suspension
Lateral Erosion
To complete this Earthcache, please send me the following answers:
From the bridge:
- Estimate the height of the street-level bank above the river
- Based on the above description, estimate the age/stage of the river
- Based on the description above, what is the type of rock along the upper banks of the river
At the map:
- What landmark is at confluence of Barren and Gaspar Rivers?
- What landmark is at the confluence of Barren River and Drakes Creek?
- What lakes are on map?
It is not a requirement, but please post a picture of yourself with the river or the map in the background.