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Middlesboro Impact Crater EarthCache

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The posted coordinates will take you to the Pinnacle Overlook. Follow the paved trail from the parking area to the overlook for viewing the Middlesboro Impact Crater.


The view from the Pinnacle Overlook affords a breath taking view of the Middlesboro Impact. You will also enjoy views of Virginia and Tennessee. Fall is the best time to view this geological wonder. A special thanks to Geologist Keith A. Milam for his research on the Middlesboro Impact Crater.


It's a good thing our lives are short. Stick around longer, a million years or so, and we'd learn just how ugly nature can be. A half-mile-wide asteroid strikes Earth on average every 500,000 years. Objects the size of an aircraft carrier hit ten times as often, and football-field-size rocks come every 10,000 years or so. An asteroid that size moving at 20 miles a second can punch out a crater more than a mile wide, slamming into Earth with 80 megatons of energy, more than the largest hydrogen bomb ever exploded. A three-mile-wide object--still much smaller than the one that most likely killed the dinosaurs--delivers more energy at the moment of impact than all our planet's earthquakes, volcanoes, and tsunamis typically release over hundreds of years. Short of the sun going nova, an asteroid impact is the worst natural disaster that can befall us. Don't take comfort in the frequency estimates, either: They are only statistical averages. Any of these things could happen tomorrow.

Every age needs its conception of the apocalypse, whether it's The Flood, The Plague, or The Bomb. The one that has prevailed since the 1980s, when scientists first linked the demise of the dinosaurs to an impact, has been The Asteroid. The odd thing about this one is that it lies so far outside human experience. We have trouble accepting the reality of impact because it hasn't ever happened to people, or so we think. Yet the evidence of cataclysm is all around, if we take the trouble to look.

The Middlesboro Impact Structure lies at one end of the Cumberland Gap, a narrow notch in the Appalachian mountains through which Daniel Boone led settlers from Tennessee into Kentucky at the close of the 18th century. Though they didn't know it at the time, when they descended from the gap, they were walking into the eroded remnant of a 3.4-mile-wide crater caused by a collision with a giant space rock some 300 million years ago.


In the 1920s, a German-born geologist named Walter Bucher began a survey of formations termed "cryptovolcanic"-the "crypto" implying that some volcano-like trauma had obviously occurred, but that no volcanoes were in sight. Middlesboro didn't catch Bucher's attention, but he noticed circles like Serpent Mound, Ohio, and Wells Creek, Tennessee, both within driving distance of there. Even though other scientists of the time began to suspect that craters like Ries in Germany and the Pretoria Salt Pan (now called Tswaing) in South Africa had been caused by meteorite hits, Bucher stuck with purely Earthbound interpretations, such as gas explosions from rising blobs of magma that had blistered the surface.

By the 1950s, however, the tide was turning toward extraterrestrial explanations. Astronomers had made the connection between lunar craters and meteorite impacts, and in 1963 Eugene Shoemaker of the U.S. Geological Survey finally settled a 50-year argument over the origin of Canyon Diablo in Arizona, a nearly mile-wide bowl carved 50,000 years ago out of the desert floor. Today we know it as Meteor Crater. A key bit of evidence found at Canyon Diablo is a type of mineral called shocked quartz, which has since become the most accepted proof for identifying impact craters. Under a microscope, the rock grains are arrayed in a distinctive criss-cross pattern, the lattice structure of the quartz having been knocked off kilter by a sudden, intense blast of pressure. In only two places can you find rocks that have been so profoundly crunched. One is a meteor crater. The other is the bottom of a nuclear test pit.


Middlesboro's status as a confirmed, rather than suspected, crater comes largely from the discovery of shocked quartz there in the 1960s. Geologists also have found another telltale sign of impact-"shatter cones," caused when the shock wave from a sudden blast moves through rock at supersonic speeds.

The Middlesboro impact was big enough to form what's called a complex crater. The initial excavation was followed by a rebound of material from the center, creating a central uplift feature, the way a pebble dropped in water splashes up a jet of water. Fractured material then slumped back into the crater, and the outer rim became terraced, unlike the neat bowl you find at the smaller Meteor Crater. In this case the central uplift feature-ground zero-is on the grounds of the Middlesboro Golf Course, which dates back to 1889 and bills itself as the oldest golf club in the country. On the golf course is an old, weathered block of sandstone that shouldn't be there. By rights this particular rock should be buried 1,300 feet below, with the rest of the Lee Sandstone formation. The asteroid that hit some 300 million years ago yanked it up in a horrifying instant, the central peak uplifted from underneath the now empty bowl.

Out at the perimeter of the original crater,there rock beds turned completely upside down, a disorder that can't easily be explained by trivial events like earthquakes. "When professional geologists come here who aren't familiar with impacts, they just scratch their heads. In the normal course of geological research, they would never encounter forces like the ones on display here in Middlesboro, Kentucky.


The Middlesboro Impact is considered as a astrobleme. In the broadest sense, the term impact crater (astrobleme) can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with larger body. In most common usage, the term is used for the approximately circular depression in the surface of a planet, or other solid body in the Solar System, formed by the hyper-velocity impact of a smaller body with the surface. This is in contrast to the pit crater which results from an internal collapse. Impact craters typically have raised rims, and they range from small, simple, bowl-shaped depressions to large, complex, multi-ringed, impact basins.Middlesboro Impact Crater is one of three astrobleme craters in Kentucky.

These impacts from meteorites creat shatter cones. Shatter cones are rare geological features that are only known to form in the bedrock beneath large meteorite impact craters. They have a distinctively conical shape with thin grooves that radiate from the top of the cone. Shatter cones can range in length from 2.5 centimeters to several meters.

If you drive north from Middlesboro on Highway 25, you will see that the exposed rock on either side of the road returns to its normal pattern. Stacks of beds, the once-muddy floors of ancient seas, are as flat and regular as the layers of a cake. Order is restored. Leaving this place of past violence.

To get credit for this EC, post a photo of you (I do not accept pictures of just a hand) at the posted coordinates and with the Middlesboro Impact (town of Middlesboro) in the background and please answer the following questions.

1. Estimate the width of the crater.

2. What is the elevation at the posted coordinates?

3. What type of rock do meteor impacts create?

Cav Scout has earned GSA's highest level

This is a National Park Service-approved EarthCache site. The information here has been reviewed and approved by the Cumberland Gap National Historic Park. Thanks to the staff for their assistance.

Why do I ask for a face in the picture of the EarthCacher finding any of my EarthCaches? A face shot is the same as a signature in a log book. Many geocachers feel in order to get a find you must sign the log book, period. EarthCaching is special and a human face is the same as a signature in a log book. I do not accept hand shots (pictures of a hand with GPS) because it does not show who’s really visiting the ECs I set up for all to enjoy. Besides, there is no log book for you to sign at a EarthCache.

For anyone who doesn’t want to post a picture of their face, then log the find as a note or don’t do it at all. Nobody is forcing anyone to come and visit any of my EarthCaches. I could argue that signing a log at a traditional cache is violating my personal rights because I have to sign a piece of paper. Maybe someone will forge my signature and steal my identity!

An argument that a photo violates a persons identity is foolish. Geocaching is a social activity. Eventually someone will meet you and know you are geocaching. If you want to live a secretive life then geocaching is not the place to do so. Cache on!

Do not log this EC unless you have answered the questions and have a picture ready to post! Logs with no photo of the actual cacher logging the find or failure to answer questions or negative comments will result in a log deletion without notice. Exceptions will be considered if you contact me first (I realize sometimes we forget our cameras or the batteries die). You must post a photo at the time of logging your find. If your picture is not ready then wait until you have a photo.

Sources of information for the EarthCache quoted from the Cumberland National Historic Park. I have used sources available to me by using google search to get information for this earth cache. I am by no means a geologist.. I use books, internet, and ask questions about geology just like 99.9 percent of the geocachers who create these great Earth Caches. I enjoy Earth Caches and want people to get out and see what I see every time I go and explore this great place we live in.

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