A rock-cut basin is a natural cylindrical depression cut into stream or river beds, often filled with water. Such plucked-bedrock pits are created by kolks; powerful vortices within the water currents which spin small boulders around, eroding out these rock basins by their abrasive action. These basins are frequently found in streams and rivers with a relatively soft rock substrates such as limestones and sandstones. The rather unusual and man-made appearance of such depressions has led to various folk-tales becoming associated with them, such as their identification as petrosomatoglyphs, including knee prints, elbow prints, etc. of saints, heroes, kings or supernatural beings. [1]
Rock-cut basins are formed by the action of fast running water currents that cause small boulders to move in a circular motion or vortex. The friction created by these kolks propelling small boulders in a circular motion erodes the natural rock substrate to create concavities called rock-cut basins, that increase in depth and circumference over the years. One or more rounded stones may be found within them, often of varying sizes as these stones also wear away with the physical abrasion effect. [2] [3]
The conditions on the river bed must be just right, so that the 'abrasion stones' remain in approximately one area as they circle, allowing the processes which create the rock-cut basins to occur. During times of heavy flood, river currents provide considerable energy to stones lying on the bottom, as can be witnessed beside many rivers where audible sounds are made by boulders as they are tumbled downstream over the bedrock or as they clash against other boulders. The term Bed load is used to describe the material carried by a river by being bounced or rolled along its bed. [4]
If a rock-cut basin forms on an overhanging ledge at a waterfall or drop in the river level, then a circular holed stone may eventually form. [5] These may have been used in the construction of megalithic monuments, especially tombs. Such holed stones are often associated with folklore as healing stones through which sick children are passed etc., as with the Mên-an-Tol in Cornwall, where the legend is that passage through the stone will cure a child of rickets (osteomalacia), also scrofula as well as spinal conditions in men and women. [6] For centuries, children with rickets were passed naked through the hole in the middle stone nine times, [7] or three times against the sun. [6]
Below the confluence of the North Teign River and the Walla Brook on Dartmoor there is a large boulder covered with rock-cut basins, one of which the kolks have completely worn through and therefore the stone has an almost perfectly circular hole. The holed stone thus produced is called the 'Tolmen' stone and it has, like others, been the focus for some stories of magical cures and mystical activities. [5] It is said that passing through the hole is a cure for rheumatism or arthritis, [8] whilst children would be cured of whooping-cough or tuberculosis. [9] [10] Another legend is that if you pass through the hole you will see the future. [11] This may be linked to the belief, recorded elsewhere, that looking through a holed stone gives a person 'second sight', and some later Christian pilgrim sites retain the holed stones which exist in the area so that pilgrims may get a 'glimpse of heaven.' Connected with this was the belief by that looking through a piece of grass made into a circle one was given second sight into the land of the supernatural, making fairies visible, etc. [12]
Passing through the stone may be symbolic of 'rebirth', however it seems that the idea of transferring the disease or condition to the stone was uppermost in the thoughts of the practitioners. To add weight to this idea it has been recorded that sick children were also passed through double-rooted bramble hoops, split ash trees and even holes in the ground. [6]
Faithless wives and wantons were punished and put back on the 'right track' by forcing them first to wash in Cranmere Pool on Dartmoor, then to run round Scorhill circle three times, then they had to pass through the Tolmen stone and finally they went up to the Grey Wethers stone circle where they knelt and asked forgiveness. If the stones remained standing then all was well, but if their penance was not sincere then a stone would fall and crush them. [13]
Folklore connected with holed stones [14] indicates that they were also used for a ceremony of grasping hands to form a Teltown marriage, this being a marriage of a year and a day in which either party could return to the spot a year later, renounce the marriage and walk away from the stone and their partner. It is also recorded that hands shaken through a holed stone created unbreakable agreements or contracts. [6] [15] [16]
Tolmen stones, said to derive from the Cornish tol (hole) maen (stone), were thought to have been used by Druids for purification and that the wrongdoer was lowered through into the water for 'lustration', a purification rite or cleansing ritual. [17]
Until recently the role of perforated stones may have been twofold; use in fertility or healing rites and as traditional settings for the pledging of vows between couples. The hole in the stone might also represent the female birth canal in the Druid or 'pagan' mind and by passing through it a person was symbolising the act of rebirth and therefore regaining innocence or being cleansed of post-parturition illness, etc. [18]
The Killoch Burn and glen near Neilston in East Renfrewshire, Scotland has become associated with a witch because at low water the numerous 'pot-holes' have worn into one another, giving fantastic shapes. Locals named some of these the witch's floor, hearth, cradle, water-stoup and grave. [19]
All around the coastline of the island of Coll are found rock-cut holes and basins which some people believe them to be prehistoric, related to the cup marks found in many places. Others think that they are bait holes, used for grinding shellfish such as limpets in order to attract fish. Another theory is that they were used for offerings in order to help the safe return of people out at sea. The prehistoric village at Maes Howe had similar sized and shaped basins made from flat stones and possibly sealed with clay, used perhaps for storing bait. Although some of the holes on Coll may be natural, such as this large basin washed by the tide, many others are in locations and are of shapes which show that they are definitely man-made. [20]
Many examples exist, created for a wide range of purposes from the grinding of fish bait to a possible ritual use for the inauguration of kings such as at Dunadd. [21] Bullauns may fall into this category.
These photographs were all taken on the Caaf Water, Lynn Glen, Dalry, Ayrshire, Scotland. The water conditions must be precisely right to create a fully formed kolk as shown by their absence or partial formation in sub-optimal parts of the same river system. Large basins form where the water flow is forceful and many small basins occur where the flow is fast, but the water shallower, such as near the edge of a waterfall. The stone substrate is made of fossiliferous limestone in these photographs.
Dunadd is a hillfort in Argyll and Bute, Scotland, dating from the Iron Age and early medieval period and is believed to be the capital of the ancient kingdom of Dál Riata. Dal Riata was a kingdom, that appeared in Argyll in the early centuries AD, possibly after the Romans had abandoned Southern Britain and at the time when the Anglo Saxons were crossing the North Sea to counter incursions over Hadrian's Wall by the Picts and Dalriadan Scots.
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
The Mên-an-Tol is a small formation of standing stones in Cornwall, UK. It is about three miles northwest of Madron. It is also known locally as the "Crick Stone".
Ice fishing is the practice of catching fish with lines and fish hooks or spears through an opening in the ice on a frozen body of water. Ice fishers may fish in the open or in heated enclosures, some with bunks and amenities.
Lake Passaic was a prehistoric proglacial lake that existed in northern New Jersey in the United States at the end of the last ice age approximately 19,000–14,000 years ago. The lake was formed of waters released by the retreating Wisconsin Glacier, which had pushed large quantities of earth and rock ahead of its advance, blocking the previous natural drainage of the ancestral Passaic River through a gap in the central Watchung Mountains. The lake persisted for several thousand years as melting ice and eroding moraine dams slowly drained the former lake basin. The effect of the lake's creation permanently altered the course of the Passaic River, forcing it to take a circuitous route through the northern Watchung Mountains before spilling out into the lower piedmont.
The geology of the Grand Teton area consists of some of the oldest rocks and one of the youngest mountain ranges in North America. The Teton Range, partly located in Grand Teton National Park, started to grow some 9 million years ago. An older feature, Jackson Hole, is a basin that sits aside the range.
Grand Coulee is an ancient river bed in the U.S. state of Washington. This National Natural Landmark stretches for about 60 miles (100 km) southwest from Grand Coulee Dam to Soap Lake, being bisected by Dry Falls into the Upper and Lower Grand Coulee.
A glacial erratic is glacially deposited rock differing from the type of rock native to the area in which it rests. Erratics, which take their name from the Latin word errare, are carried by glacial ice, often over distances of hundreds of kilometres. Erratics can range in size from pebbles to large boulders such as Big Rock in Alberta.
The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods within the southeastern part of Washington. The Channeled Scablands were scoured by more than 40 cataclysmic floods during the Last Glacial Maximum and innumerable older cataclysmic floods over the last two million years. These floods were periodically unleashed whenever a large glacial lake broke through its ice dam and swept across eastern Washington and down the Columbia River Plateau during the Pleistocene epoch. The last of the cataclysmic floods occurred between 18,200 and 14,000 years ago.
Petroforms, also known as boulder outlines or boulder mosaics, are human-made shapes and patterns made by lining up large rocks on the open ground, often on quite level areas. Petroforms in North America were originally made by various Native American and First Nation tribes, who used various terms to describe them. Petroforms can also include a rock cairn or inukshuk, an upright monolith slab, a medicine wheel, a fire pit, a desert kite, sculpted boulders, or simply rocks lined up or stacked for various reasons. Old World petroforms include the Carnac stones and many other megalithic monuments.
Elephant Rocks State Park is a state-owned geologic reserve and public recreation area encompassing an outcropping of Precambrian granite in the Saint Francois Mountains in the U.S. state of Missouri. The state park is named for a string of large granite boulders which resemble a train of pink circus elephants. The park was created following the donation of the land to the state in 1967 by geologist Dr. John Stafford Brown. The park is used for picnicking, rock climbing, and trail exploration. It is managed by the Missouri Department of Natural Resources.
Dalry is a small town in the Garnock Valley in Ayrshire, Scotland. Drakemyre is a northern suburb.
The River Garnock, the smallest of Ayrshire's six principal rivers, has its source on the southerly side of the Hill of Stake in the heart of the Clyde Muirshiel Regional Park. About a mile and a half south of this starting point the untested stream tumbles over the Spout of Garnock, the highest waterfall in Ayrshire, once thought to be the river's origin. The river then continues, for a total length of 20 miles (32 km) or so, through the towns of Kilbirnie, Glengarnock, Dalry and Kilwinning to its confluence with the River Irvine at Irvine Harbour.
There are many large stones of Scotland of cultural and historical interest, notably the distinctive Pictish stones, but also the other types discussed below.
A kolk (colc) is an underwater vortex created when rapidly rushing water passes an underwater obstacle in boundary areas of high shear. High-velocity gradients produce a violently rotating column of water, similar to a tornado. Kolks can pluck multiple-ton blocks of rock and transport them in suspension for thousands of metres.
A petrosomatoglyph is a supposed image of parts of a human or animal body in rock. They occur all over the world, often functioning as an important form of symbolism, used in religious and secular ceremonies, such as the crowning of kings. Some are regarded as artefacts linked to saints or culture heroes.
A bullaun is the term used for the depression in a stone which is often water filled. Natural rounded boulders or pebbles may sit in the bullaun. The size of the bullaun is highly variable and these hemispherical cups hollowed out of a rock may come as singles or multiples with the same rock.
The Mohaka river is on the North Island of New Zealand in the east central region of Hawke’s Bay. Mohaka is a Maori word, roughly translated it means “place for dancing”. The iwi associated with the Mohaka River are Ngāti Pāhauwera, Ngāti Hineuru, Ngāti Tūwharetoa and Mana Ahuriri. The headwaters are found in the Kaweka and Kaimanawa ranges. From the range it winds southeast before twisting northeast and finally southeast again to empty into the Pacific Ocean near the town of Mohaka. There are many gorges on the Mohaka; some as steep as 200m. Its main tributaries are the Waipunga, Taharua, Hautapu rivers. The full length is 172 kilometres (107 mi) and it drains a basin of 2,357 square kilometres (910 sq mi).
Fort Rock–Christmas Lake Valley is a basin of a former inland sea that existed in that region from Pliocene through late Pleistocene time.
In Earth science, a pothole is a smooth, bowl-shaped or cylindrical hollow, generally deeper than wide, found carved into the rocky bed of a watercourse. Other names used for riverine potholes are pot, (stream) kettle, giant's kettle, evorsion, hollow, rock mill, churn hole, eddy mill, and kolk. Although somewhat related to a pothole in origin, a plunge pool is the deep depression in a stream bed at the base of a waterfall. It is created by the erosional forces of turbulence generated by water falling on rocks at a waterfall's base where the water impacts. Potholes are also sometimes referred to as swirlholes. This word was created to avoid confusion with an English term for a vertical or steeply inclined karstic shaft in limestone. However, given widespread usage of this term for a type of fluvial sculpted bedrock landform, pothole is preferred in usage to swirlhole.