The Middlesboro crater (or astrobleme) is a

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

Kentucky Kentucky (, ), officially the Commonwealth of Kentucky, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Illinois, Indiana, and Ohio to the north, West Virginia to the ...

, United States. It is named after the city of

Middlesboro, Kentucky Middlesboro ()Rennick, Robert. ''Kentucky Place Names'', University Press of Kentucky (Lexington), 1987p. 196 Accessed 26 August 2013. is a list of Kentucky cities, home rule-class city in Bell County, Kentucky, United States. The population was ...

, which today occupies much of the crater. The crater is approximately 3 miles (about 5 km) wide and its age is estimated to be less than 300 million years (

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

). The impactor is estimated to have been about 100 m in diameter.

History

The Middlesboro crater is located in the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

, between the

Cumberland Mountains The Cumberland Mountains are a mountain range in the southeastern section of the Appalachian Mountains. They are located in western Virginia, southwestern West Virginia, the eastern edges of Kentucky, and eastern middle Tennessee, including the ...

and Pine Mountain. It forms part of the string of geological features that made the

Cumberland Gap The Cumberland Gap is a Mountain pass, pass in the Eastern United States, eastern United States through the long ridge of the Cumberland Mountains, within the Appalachian Mountains and near the tripoint of Kentucky, Virginia, and Tennessee. At&n ...

a critical westward passage during the settlement of

and the

Ohio Valley The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its mouth on the Mississippi River in Cairo, ...

in the late 18th and early 19th centuries.

Settlements

The town of Middlesboro, built in the crater, was established in 1886 to exploit

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

deposits, although the town's founder, Alexander A. Arthur, apparently did not know of the crater's extraterrestrial origin. K. J. Englund and J. B. Roen, working for the U. S. Geological Survey, identified the impact basin in 1962.

Geological features

The long Cumberland Gap consists of four geologic features: the Yellow Creek valley, the natural gap in the Cumberland Mountain ridge, the eroded gap in Pine Mountain, and Middlesboro crater. Middlesboro crater is a diameter

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

in which

, is located. The crater was identified in 1966 when Robert Dietz discovered shatter cones in

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, which led to the further identification of

shocked quartz Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal. These pla ...

. Shatter cones, a rock shattering pattern naturally formed only during

impact event An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effe ...

s, 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, formed by differential erosion along one of the subsequent cross faults, and improbable that wagon roads would have been constructed at an early date. Middlesboro is the only place in the world where

is mined inside an impact crater. Special mining techniques must be used in the complicated strata of this crater. (Milam & Kuehn, 36).

Industrial activity

While

coal mining Coal mining is the process of resource extraction, extracting coal from the ground or from a mine. Coal is valued for its Energy value of coal, energy content and since the 1880s has been widely used to Electricity generation, generate electr ...

is still the town's primary economic driver, local leaders hope to turn the crater into a tourist destination. In 2003, the Kentucky Society of Professional Geologists designated the area a Distinguished Geologic Site, and the construction of the

Cumberland Gap Tunnel The Cumberland Gap Tunnel is a dual-bore, four lane vehicular tunnel that carries U.S. Route 25E under Cumberland Gap National Historical Park near the intersection of Kentucky, Tennessee, and Virginia. The tunnel consists of two separate bo ...

makes the town a convenient source of supplies for visitors to

Cumberland Gap National Historical Park The Cumberland Gap National Historical Park is a United States National Historical Park located at the border between Kentucky, Tennessee, and Virginia, centered on the Cumberland Gap, a natural break in the Appalachian Mountains. The park lies ...

References

External links

Exploration of the Middlesboro impact crater
{{DEFAULTSORT:Middlesboro Crater Landforms of Bell County, Kentucky Impact craters of the United States Landforms of Kentucky Geology of Kentucky Permian impact craters