A balancing rock, also called a balanced rock, precariously balanced rock (PBR), or precarious boulder, is a naturally occurring geological formation featuring a large rock or boulder, sometimes of substantial size, resting on other rocks, bedrock, or on glacial till. Some formations known by this name only appear to be balancing, but are in fact firmly connected to a base rock by a pedestal or stem.
No single scientific definition of the term exists, and it has been applied to a variety of rock features.
A boulder that was transported and deposited by glaciers or ice rafts to a resting place on soil, on bedrock, or on other boulders. It usually has a different lithology from the other rocks around it. Not all glacial erratics are balancing rocks; some are firmly seated on the ground. Some balancing erratics have come to be known as rocking stones, also known as logan rocks, logan stones, or logans, because they are so finely balanced that the application of just a small force may cause them to rock or sway. A good example of a rocking stone is the Logan Rock in Cornwall, England, United Kingdom; another is the Trembling Rock in Brittany, France.[1]
Perched block
Also known as a perched boulder or perched rock, this is a large, detached rock fragment that most commonly was transported and deposited by a glacier to a resting place on glacial till, often on the side of a hill or slope. Some perched blocks were not produced by glacial action, but were the aftermath of a rock fall, landslide, or avalanche.[2]
Erosional remnant
A persisting rock formation that remains after extensive wind, water, and/or chemical erosion. To the untrained eye, it may appear to be visually like a glacial erratic, but instead of being transported and deposited, it was carved from the local bedrock. Many good examples of erosional remnants are seen in Karlu Karlu/Devils Marbles Conservation Reserve in the Northern Territory of Australia.
Also known as a rock pedestal or mushroom rock, this is not a true balancing rock, but is a single continuous rock form with a very small base leading up to a much larger crown. Some of these formations are called balancing rocks because of their appearance. The undercut base was attributed for many years to simple wind abrasion, but is now believed to result from a combination of wind and enhanced chemical weathering at the base where moisture would be retained longest. Some pedestal rocks sitting on taller spire formations are known as hoodoos.
Notable balancing rocks
Africa
Mother and Child balancing rocks, Matobo National Park, Zimbabwe
The balancing rocks of Zimbabwe are a series of geological formations found in Zimbabwe. The Balancing Rocks of Epworth are famous for being featured on the nation's banknotes, including those issued during periods of hyperinflation, such as the Zimbabwean 100 trillion dollar note, one of the highest denomination banknotes ever issued.
The Mother and Child balancing rocks are a well-known feature in Matobo National Park.
The Balancing Rock at Appukal village, Vellore district at Tamilnadu. This formation shows marked resemblance the balancing rock formation present in Zimbabwe. It is to be noted the site is believed to be a historical site but without any evidence. [citation needed]This rock formation appears like a bird and a baby alligator from specific angles.
A balancing rock is located near Madan Mahal fort in Jabalpur city of Madhya Pradesh.[5]Balancing rock near Madan Mahal Fort, Jabalpur, Madhya Pradesh, India
Hòn Đá Ba Chồng/Thị trấn Định Quán, Huyện Định Quán, Tỉnh Đồng Nai.[clarification needed][7][circular reference] Three rocks overlapping with a height of 36m, lying precariously right next to a highway.
The boulder, which gleams golden and popularly known as the Golden Rock on which the small Kyaiktiyo Pagoda has been built, is about 25 ft (7.6 m) in height and has a circumference of 50 ft (15 m). The boulder sits on a natural rock platform that appears to have been naturally formed to act as the base to build the pagoda.
A huge sandstone boulder hangs precariously near the roadway in Garden of the Gods park near Colorado Springs.Garden of the Gods, Colorado Springs, Colorado
Idaho
Balanced Rock is located south of Buhl in Salmon Falls Creek Canyon; created some 15 million years ago and comprising rhyolite lava, it stands 8 feet (2.4 m) tall, weighs 30 tons (27.215 metric tons), and is perched on a 3 foot by 17 inch (0.395 m2) pedestal.[11]
In Balance Rock Park, in Pittsfield State Forest, a field of massive boulders left on a hillside by receding glaciers is crowned by Balance Rock, a tremendous rock balancing almost unbelievably upon a smaller rock protruding from the ground.
Balanced Rock in North Salem, in Westchester County, New York. A glacial erratic that rests securely on five other rocks pointing upright, the Balanced Rock itself is a heavily weathered pink granite that is not local to the area, and is in fact found further north in the Hudson Highlands.
North Carolina
The Devil's Head is a large boulder perched on the ledge of a cliff in the Chimney Rock State Park, North Carolina.
The Piedra Movediza was a balancing rock located close to the city of Tandil, Buenos Aires Province, Argentina. Its weight was about 300 tons, and its pedestal was so thin it moved with the wind. It attracted attention and tourists because of the way it was balanced on the edge of a cliff. The stone fell and broke on 29 February 1912, possibly due to human intervention. A replica of the stone was put in place in 2007.
