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What causes potholes?
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WHY SALT CAUSES POTHOLES ?
what causes potholes on river bed?
WHAT ARE THE CAUSES OF POTHOLES ON RIVER BEDS?
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Mystery of Pothole Origins ( more in web URL ) see definition below in MORE INFO 1 http://www.sentex.net/~tcc/pothole.html
Eagle's Nest Potholes
Along the top of the spectacular cliffs of the Niagara Escarpment in Ontario there are several locations where potholes occur. On the Bruce Peninsula, a large pothole is exposed in the face of the cliff near Lion's Head. It is locally known as the "Eagles' Nest" because of several rounded boulders that remain in it, that are visible from boats on the lake. Its location is in the center of the cliff in the photo at right.
According to the conventional uniformitarian explanation of potholes found in many geology text books, potholes like these were caused by vortices in former streams that rotated and vibrated "grinding stones" over long ages of time, the process gradually wearing down a deep, cylindical hole into the rock. In this case, however, the circumstances seem to discredit this explanation. Of course it is unlikely vortices could have existed high on the face of a steep cliff, and rotation could not be maintained in a hole if one side of it was missing.
It is common to find partial potholes, where only a portion of a vertical cylindical hole remains in the side of a gorge or cliff. The theory of vortices whirling those grinding stones appears absurd when one tries to imagine how the stones could be down in the holes whirling around and around where one wall of the pothole was missing. And with part of the wall of a pothole missing, how could the currents have continued to circulate? What would keep the "grinding stones" from falling out, and tumbling down the cliff?
Rivers may have removed partially unconsolidated material, and sand, gravel, or drift, from potholes, and are often still doing so today. My research indicates the rivers had nothing to do with forming the potholes, but merely exposed them. The conditions in which the potholes formed were unlike those of the present. Potholes in some rocks probably formed during compaction, as joints formed in the rock. Many of the intersecting potholes are aligned along joints.
The dolomite rock of the Niagara Escarpment where these potholes occur is part of the Amabel formation.
The rock is deeply fissured, and because of this, there are no surface streams in the area that could have eroded potholes. The distribution of the potholes does not suggest the action of streams, as they are scattered over a wide area above the escarpment. Many potholes are situated in locations that seem unlikely to have ever been the sites of former streams.
Niagara Glen Potholes
The pothole at left is about 3 feet in diameter. An agile person could climb up through it to the top of the crag in which it occurs. The pothole is in an isolated crag in the gorge of the Niagara River at Niagara Glen, a park on the Canadian side of the Niagara River. There is a distinct spiral shape to the hole, a feature commonly seen in potholes, that has not been very well explained in conventional geologic theories of pothole origin.
Also at Niagara Glen a pair of potholes in a sloping slab of rock presents a puzzle: in the conventional interpretation, how would the hypothetical current vortices remain in their places, and drill vertical cylindrical potholes such as these? How were those grinding stones able to remain in position, when the holes were initiated?
MORE INFO 1
pothole (sometimes called kettle and known in parts of the Western United States as a chuckhole) is a type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a hole. Most potholes are formed due to fatigue of the pavement surface. As fatigue cracks develop they typically interlock in a pattern known as "alligator cracking". The chunks of pavement between fatigue cracks are worked loose and may eventually be picked out of the surface by continued wheel loads, thus forming a pothole. The formation of potholes is exacerbated by cold temperatures, as water expands when it freezes and puts more stress on cracked pavement. Once a pothole forms, it grows through continued removal of broken chunks of pavement. If a pothole fills with water the growth may be accelerated, as the water 'washes away' loose particles of road surface as vehicles pass. In temperate climates, potholes tend to form most often during spring months when the subgrade is weak due to high moisture content. However, potholes are a frequent occurrence anywhere in the world, including in the tropics.
Potholes can grow to feet in width, though they usually only become a few inches deep, at most. If they become large enough, damage to tires and vehicle suspensions can occur.
Pothole (northern Britain) is also a term for a deep cave; from this sense, the derivation potholing is a synonym for caving and a potholer is a caver.
Pothole (or kettle-hole) is also a term for a formation in rivers caused by a whirlpool eroding a hole into rock. The abrasion is mainly caused by the circular motion of small sediments such as small stones in the river. The interiors of potholes tend to be smooth and regular, unlike a plunge pool.
The world's largest pothole was formed by a glacier and is found in Archbald, Pennsylvania in Archbald Pothole State Park.
Potholes are caused by simple properties of concrete. Concrete is very durable under compressive stress but not tensile stress. Concrete is also a very porous which allows water to seep in. In winter this water freezes causing tensile stress on the concrete. Once it melts holes are created as soon as a car drives over it.
Potholes form because asphalt road surfaces eventually crack under the heat of the day and the constant stresses of traffic. These cracks allow snow and rainwater to seep into the underlying dirt and gravel. During cold winter nights, this water freezes and expands. Some of the dirt and gravel is pushed out as a result, leaving a hole when the water eventually melts. Drivers continue to drive over these unseen holes, putting even more stress on the thin asphalt layer covering them.
Eventually, the asphalt layer over these divots collapses, creating the traffic hazards we call potholes.