Click Here to Return To Milestones Vol 20 No 1
The story of Beaver Valley began long before any human eyes gazed upon its towering hills and rich valleys. The little piece of the Earth's crust which we call home can be traced back more than 300 million years. Each layer of rock in an exposed hillside tells the story.
A vein of coal represents a period of extensive forest growth, the fossilized remains of which have become our rich heritage of fossil fuel. The thicker the coal sewn, the longer the time that lush vegetation was the prominent, and probably the only feature of our landscape.
Many times, this part of the surface of the Earth was depressed below the level of the oceans. Each time that this occurred, a thick bed of limestone was deposited, representing the shells of incredible numbers of a vast variety of sea animals. As with the coal deposits, Beaver County's economic success was significantly aided by these extensive deposits of limestone.
The layers of shale, clay and sandstone tell a different story, and bring out the strangest facts of all. These materials were deposited by the rivers and streams which were busy eroding away a huge mountain range to the east. East of the Appalachians, because they are composed of the same kinds of rocks as the Allegheny Plateau which we live on, East of the ancient Blue Ridge, and even east of our present coastal plain, lies the answer to our quest. The answer is surprising.
Recent discoveries have led geologists to conclude that when the rocks that underlie Beaver Valley were being formed, there was no Atlantic Ocean and the American continents were joined to Europe and Africa. Eons of erosion had worn down the unknown mountain range, spreading vast layers of silt and sand over the central basin of this huge landmass. Then the Earth slowly began to split open and pour volumes of molten rock into the gap. Science fiction? No, this is a simplified explanation of the incredible changes which began taking place on the earth about 300 million years ago.
In fact, it's still happening! When the fissure between the continents became wide enough, the waters of the world ocean (Pacific) spilled over into it and formed the beginning of a new ocean, the Atlantic. Even now, the continents are still moving and spreading the shores of the Atlantic a few inches further apart each year. Moving where? Well, the western edge of the floating continent is bumping against the edge of the Pacific ocean floor, and the line of contact is roughly along the San Andreas fault, the notorious earthquake zone. When the eastern part of the continent began moving west faster than the western half, the surface wrinkled, compressing some 82 miles of landscape into 65 miles. This is how the Appalachian Mountains were formed. Of course, the big wrinkles have mostly been eroded away, and all we see are the rough edges of some of the hardened layers of rock.
The wrinkles become smaller toward the west of the mountain zone, and one of them, a slight upswelling of rock deep underground called the Homewood Anticline, passes through Beaver County.
No one knows how much higher the layers of sediment extended, in Beaver County, before the process of erosion began to wear the hills down to their present level. We know that in relatively recent times the land was worn down to a fairly level plain. This is evident in the present peneplain at about 1200 feet in elevation, where you will see from the top of nearly any hill that the other hills are about the same height. The exceptions to this, such as Stewart Hill and Big Knob, represent an older, higher erosion surface.
The latest several periods of glaciation drastically changed the drainage pattern in Beaver Valley. The Monongahela River drained north into the Great Lakes Basin, through the valley of the present Beaver, Mahoning and Grand Rivers. When the Wisconsin Glacier moved southward about 15,000 years ago, it stopped at a point near Koppel, blocking the northward flow of the ancient river.
Much of the Beaver Valley was then covered with a vast lake, which geologists call Lake Monongahela. Seeking a new outlet to the sea, the lake eventually spilled over a low ridge near Industry, joining another ancient drainage system, whose northward flow through the Little Beaver Valley had similarly been blocked by the glacier.
Eventually, an outlet to the South was discovered by the everrising water, and soon the present valley of the Ohio was being carved by the rushing waters, augmented by the run-off from the glacier when it began to recede. The level terraces high above the present riverbeds were shaped by the shoreline of ancient Lake Monongahela. The plains along the rivers were formed by debris (sand and gravel) contributed by the departing ice sheet.
Nature's plan requires a continued erosion until the hills are reduced to a vast plain, level with the new drainage pattern. This process was slowed by the thick growth of forest which the early pioneers found when they first wandered into the Beaver Valley. The damming of the rivers and intelligent land management would seem to halt the erosion process altogether, but the history of man's occupancy of the Beaver Valley is only a fraction of an instant of time. The geological processes will continue.