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16-661: The Baltic Klint is active landform showing some retreat in the present. However it is not known to which degree the Baltic Klint originated in postglacial time or if it evolved from cliff-like forms sculpted by the Fennoscandian Ice Sheet . In Gotland 20th century cliff retreat rates have been estimated at 0.15 to 0.78 cm/year. Retreat of the Baltic Klint in Gotland has widened shore platforms . The Baltic Klint extends approximately 1200 km from

32-421: A caprock is not essential for scarp retreat to occur as higher humidity and weathering at the foot ensures erosion at the foot drives (or keeps up with) the erosion of the free face. The most common way in which a scarp retreats is through rockfall, where individual blocks calve from the cliff or large sections of the cliff face collapse at once. In some high-energy situations, much of the rock may be powdered in

48-586: A layer of Karoo basalts about 1,000 metres (3,300 ft) thick, which overlay Clarens formation sandstones. They have long been considered a classic example of a landform created by scarp retreat following continental break-up, with the retreat controlled by an inland drainage divide. However, they have inland-facing scarps as well as seaward-facing scarps, so factors other than continental break-up have contributed to their formation. A 2006 paper argued that surface process models may be inadequate in explaining rates of scarp retreat, which can also be greatly affected by

64-408: A rockfall and easily eroded. Generally, though, the fallen debris must be weathered and the rampart eroded before scarp retreat can continue. Mechanical and chemical weathering followed by wind erosion may operate in arid regions, where cliffs may retreat for long distances. In such regions, large areas of shale badlands may be left behind as the scarp retreats. Erosion may be caused by the sea where

80-415: Is a line of cliffs that has usually been formed by faulting or erosion. If it is protected by a strong caprock , or if it contains vertical fractures, it may retain its steep profile as it retreats. Scarps in dry climates typically have a near-vertical upper face, that may account for 10% - 75% of the total height, with a talus-covered sloping rampart forming the lower section. The caprock is undermined as

96-405: Is an example of a scarp or escarpment . At Niagara Falls, the caprock is the riverbed above the falls, and is what prevents the river from eroding the face of the falls very quickly. The Niagara caprock is made of dolomitic limestone . Other common types of caprock are sandstone and mafic rock . In processes such as scarp retreat , the caprock controls the rate of erosion of the scarp. As

112-750: Is cut by numerous rivers (including the Narva , Luga , Izhora and the Tosna ), many of which form waterfalls and rapids. Valaste Falls (in Kohtla Parish) with a drop of 25 m is the highest. In Öland and Gotland a series of sea stacks known as rauks exist along the klint. In the case of Gotland, rauks are formed in limestone representing reefs that existed in the Silurian epoch. As waves batter against limestone cliffs, pre-existing vertical fractures begin to erode and widen. Eventually this leads to

128-581: The Great Escarpment in Australia along the river valleys in the New England region appears to be progressing at about 2 kilometres (1.2 mi) per million years. A study of cuesta scarp retreat in southern Morocco showed an average rate of 1.3 kilometres (0.81 mi) per million years in areas with thin conglomerate caprocks. Where there were thicker, more resistant limestone caprocks

144-424: The formation of caves that merge with the remaining central rockmass, becoming a rauk. Areas with particularly high concentrations of rauks are Fårö in northern Gotland and Byrum in northwestern Öland. While some rauks occur next to, or as part of cliffs, some have a more tenuous relation to the cliff and some lack a relation altogether. Scarp retreat Scarp retreat is a geological process through which

160-639: The island of Öland in Sweden through the continental shelf and the Estonian islands of Osmussaar and Suur-Pakri to Paldiski , then along the southern shore of the Gulf of Finland and Neva River to the area south of Lake Ladoga in Russia, where it disappears under younger sedimentary deposits. The cliff reaches 55.6 m above sea level at its highest at Ontika, Kohtla Parish , Ida-Viru County of Estonia. It

176-399: The location of an escarpment changes over time. Typically the cliff is undermined, rocks fall and form a talus slope, the talus is chemically or mechanically weathered and then removed through water or wind erosion , and the process of undermining resumes. Scarps may retreat for tens of kilometers in this way over relatively short geological time spans, even in arid locations. A scarp

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192-399: The rampart and face are eroded, and eventually a section collapses. A strong caprock will typically create a relatively high cliff, since more undermining is needed to cause it to fail. Other factors determining how easily a cliff will fail are the bedding and jointing , direction of dip and thickness of the caprock. A thin caprock will result in low cliffs that retreat quickly. However,

208-652: The rate of retreat was slower, about 0.5 kilometres (0.31 mi) per million years. The Colorado Plateau has a cuesta scarp topography, consisting of slightly deformed strata of alternating harder and softer rocks. The climate has been mostly dry throughout the Cenozoic . The conspicuous scarps on the plateau have massive sandstone caps over easily weathered rock such as shale. Freeze-thaw and groundwater sapping contribute to scarp retreat in this region. The Drakensberg mountains in South Africa are capped by

224-467: The scarp runs along a coast, or by streams in humid areas. The rate of retreat depends on the types of rock and the factors causing erosion. A study published in 2006 determined that the rate of scarp retreat in the Colorado Plateau today varies from 0.5 to 6.7 kilometres (0.31 to 4.16 mi) per million years depending on the thickness and resistance to erosion of the caprock . Retreat of

240-487: The softer rock is cut away, periodically the caprock shears off. Caprock is also found in salt domes and on the top of mesa formations. In the petroleum industry , caprock is any nonpermeable formation that may trap oil, gas or water, preventing it from migrating to the surface. This caprock can prevent hydrocarbons from migrating to the surface, allowing them to accumulate in a reservoir of oil, gas and water. These structures, also known as petroleum traps , are

256-418: The types of rock encountered as the scarp retreats, and by other factors such as climate, tectonic processes and possibly plant cover. Citations Sources Caprock Caprock or cap rock is a more resistant rock type overlying a less resistant rock type, analogous to an upper crust on a cake that is harder than the underlying layer. The Niagara Escarpment , over which Niagara Falls flows,

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