Earth Science Themed Essays
History of Rocks and Landforms
Hidden between two hilltops in Roane County, West Virginia, lies a beautiful natural bridge, carved by the hands of nature. Nearby runs a meandering stream, which created this work of art. It was in this area around the natural bridge that I based my collection of rocks.
The rocks I collected ranged from the Saltsburg sandstone, which is in the Glenshaw Formation of the Pennsylvanian System, to the Lower Connelsville sandstone, which is in the Casselman Formation of the Pennsylvanian System. The Saltsburg sandstone, the oldest rock layer, indicates that a beach was on this site for a relatively long time while these rocks were forming. The Pittsburgh Red Beds, which is the next layer up, is shale. Shale is made up of finely decayed feldspars, micas, and tiny sand or silt grains. These rocks indicate where there once was a delta, caused by an inland sea increasing in size.
According to the geologic table, there is supposed to be a layer of Harlem coal, but it was not found in that particular area of Roane County because the swamp may not have reached that far. A swamp here would indicate that the inland sea shrunk.
Ames shale and limestone is the next layer up. Limestone is made up of minerals from seawater, and because the inland sea would increase and decrease in size over the period of time these rocks formed, the two types of rock mixed. Grafton sandstone indicates a beach, which means the inland sea was shrinking, and that is the next layer up. The layer above that is West Maford coal, which again indicates a swamp. The layer above West Maford coal is Birmingham red shale. The shale again indicates a delta caused by the inland sea growing in size. The next two layers up are Elk Lick limestone and Elk Lick coal. The limestone indicates the variating ocean, and the coal again indicates a swamp. The two layers above that are Clarksburg red shale and the Clarksburg limestone. The red shale indicates that it was made of sediment with a high iron content, and the limestone was formed by the variating inland sea. The final layer that I sampled in my collection was Lower Connelsville sandstone, which was formed by a beach in the area.
Over hundreds of millions of years after the Pennsylvanian period, the sediments turned to rock, and the whole area of western West Virginia became a plateau because of North America and Africa colliding. The mountains and valleys in the area from which I collected my rock samples were formed by erosion from rivers and streams. I collected rock samples from the ground around the natural bridge in Green Creek, near Walton, West Virginia. The rocks underneath the bridge were made of a shaley sandstone and could erode easily, making the layer that had eroded away the opening under the bridge. The Saltsburg sandstone that formed the bridge was stronger and was more resistant to erosion than the shaley sandstone that was beneath it. The bridge was found at approximately 1,000 feet above sea level, and the gully that was formed by the water that formed the bridge eventually ran to a meandering stream. The meandering stream is at approximately 800 feet above sea level. A meandering stream indicates that it is an old stream and that it has slowed down and is not cutting down as much as it used to hundreds of millions of years ago.
Rock sample #3 came from a hillside along the road leading to the bridge, and rock samples #4-10 came from a road cut along West Virginia Route 119 in Roane County.
At different angles the bridge has quite a different appearance. Also, the bridge has watermarks from water dripping or splashing on it in the same spots for thousands of years.
So there still sits the beautiful bridge, almost a living presence, changing a tiny bit each day, but always as magnificent as it was the day before.
The Saltsburg sandstone is a massive sandstone that in Roane County reaches a thickness of 30 to 40 feet. Samples of the Saltsburg sandstone show that the rock is composed of quartz, sand, and pebbles.
This rock is the mix of the Saltsburg sandstone and the layer under it. It is also composed of quartz, sand, and pebbles.
Pittsburgh Red Shale
Pittsburgh red shale is a soft, red or purple shale made of clay, feldspars, micas, and tiny sand or silt grains with a high iron content.
Elk Lick Limestone
Elk Lick limestone, like other limestones, formed in sea water. It is made of calcium carbonate. This piece contains the fossils coral, crinoids, and mollusks.
Elk Lick Limestone
Like rock #4, this is Elk Lick limestone. This piece, however, contains only crinoids and corals.
Clarksburg Red Shale
Clarksburg red shale is also a shale that is made up of micas, feldspars, clay, and tiny sand or silt grains with a high iron content.
Lower Rock #7|
Lower Connelsville sandstone is made up mostly of medium quartz grains and smaller amounts of feldspar, muscovite, and clay minerals.
Birmingham Red Shale
Birmingham red shale is like Pittsburgh red shale and Clarksburg red shale, composed of micas, feldspars, clay, and tiny sand or silt grains with a high iron content.
Morgantown sandstone is composed of quartz, sand, and pebbles. It reaches a thickness of nearly 30 feet in Roane County.
Grafton is another sandstone that is composed of sand and pebbles because
of beaches in the area when these rocks were being formed.
Arkle, Thomas, Jr. Sandstones of West Virginia. Morgantown, West Virginia: West Virginia Geological Survey, 1957.
Hennen, Ray V., and Roane Wirt. Calhoun Counties. Morgantown, West Virginia: West Virginia Geological Survey, 1911.
Janssen, Raymond E., Ph. D. Earth Science...A Handbook on Geology of West Virginia. Clarksburg, West Virginia: 1973.
Zim, Herbert S. Rocks and Minerals. New York:, 1957.
Less than 1 period
Supplement a study of Earth science with an activity drawn from this winning student essay.