Geological Features
The 12-mile (19 km) long Cumberland Gap consists of four geologic features: the Yellow Creek valley, the natural gap in the Cumberland Mountain ridge, the eroded gap in the Pine Mountain, and Middlesboro crater.
Middlesboro crater is a 3-mile (4.8 km) diameter meteorite impact crater in which Middlesboro, Kentucky, is located. The crater was identified in 1966 when Robert Dietz discovered shatter cones in sandstone, which led to the further identification of shocked quartz. Shatter cones, a rock shattering pattern naturally formed only during impact events, are found in abundance in the area. In September 2003 the site was designated a Distinguished Geologic Site by the Kentucky Society of Professional Geologists.
Without Middlesboro crater, it would have been difficult for packhorses to navigate this gap and improbable that wagon roads would have been constructed at an early date. Middlesboro is the only place in the world where coal is mined inside an impact crater. Special mining techniques must be used in the complicated strata of this crater. (Milam & Kuehn, 36).
The gap was formed by an ancient creek, flowing southward, which cut through the land being pushed up to form the mountains. As the land rose even more, the creek reversed direction flowing into the Cumberland River to the north.
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