The Middlesboro crater (or astrobleme) is a

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

crater Crater may refer to: Landforms *Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet *Explosion crater, a hole formed in the ground produced by an explosion near or below the surfac ...

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

, United States. It is named after the city of Middlesborough (both spellings are used), 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 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 251.9 Mya. It is the last period of the Paleoz ...

). 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, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

, 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 pass through the long ridge of the Cumberland Mountains, within the Appalachian Mountains, near the junction of the U.S. states of Kentucky, Virginia, and Tennessee. It is famous in American colonial history for its rol ...

a critical westward passage during the settlement of

and the

Ohio Valley The Ohio River is a long river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing southwesterly from western Pennsylvania to its mouth on the Mississippi River at the southern tip of Illinoi ...

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 with symbol Fe (from la, ferrum) 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, right in f ...

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 elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

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 circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

in which

Middlesboro, Kentucky Middlesboro ()Rennick, Robert. ''Kentucky Place Names'', University Press of Kentucky (Lexington), 1987p. 196 Accessed 26 August 2013. is a home rule-class city in Bell County, Kentucky, United States. The population was 10,334 at the 2010 U.S ...

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

shatter cone Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions. They are evidence that the rock has been subjected to a shock with pressures in the rang ...

s in

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

, 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 physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...

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 extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from ...

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