Wave-cut platform

A wave-cut platform, shore platform, coastal bench, or wave-cut cliff is the narrow flat area often found at the base of a sea cliff or along the shoreline of a lake, bay, or sea that was created by erosion. Wave-cut platforms are often most obvious at low tide when they become visible as huge areas of flat rock. Sometimes the landward side of the platform is covered by sand, forming the beach, and then the platform can only be identified at low tides or when storms move the sand.

Wavecut platform southerndown pano
Wave-cut platform at Southerndown, South Wales, UK

Formation

Wave cut platform
The formation of a wave cut platform

Wave-cut platforms form when destructive waves hit against the cliff face, causing an undercut between the high and low water marks, mainly as a result of abrasion, corrosion and hydraulic action, creating a wave-cut notch. This notch then enlarges into a cave. The waves undermine this portion until the roof of the cave cannot hold due to the pressure and freeze-thaw or biological weathering acting on it, and collapses, resulting in the cliff retreating landward. The base of the cave forms the wave-cut platform as attrition causes the collapsed material to be broken down into smaller pieces, while some cliff material may be washed into the sea. This may be deposited at the end of the platform, forming an off-shore terrace.

Because of the continual wave action, a wave-cut platform represents an extremely hostile environment and only the toughest of organisms can utilize such a niche.

Use of ancient examples

Ancient wave-cut platforms provide evidence of past sea and lake levels. Raised and abandoned platforms, sometimes found behind modern beaches, are evidence of higher sea levels in the geological past,[1] and have been used to identify areas of isostatic adjustment. By using scientific dating methods, or examination of marine fossils found on the platform, it is possible to work out when the platform was formed, thus giving geographers and geologists information about sea levels at known times in the past. This has been used in the United Kingdom and other previously glaciated areas to calculate the rate at which land is rising now that it is no longer covered in ice.

Where the coastline itself is changing due to seismic action, there may be a series of platforms showing earlier sea levels and indicating the amount of uplift caused by various earthquakes.

Usage of term 'wave-cut'

According to Trenhaile,[2] Sunamura,[3] and Massalink and Hughes,[4] the term 'wave-cut platform' should no longer be used as it assumes that shore platforms are the result of wave action, which is not always true. Shore platforms, like comparable river and lake platforms, are erosional features that develop when removal of saprock and other debris by waves and currents leaves behind a bedrock surface below the water table.[5]

BleikRaisedBeach&Platform

Raised beach and shore platform, Bleik, Norway

WaveCutPlatformsAntelopeIslandUT

Shore platforms from Lake Bonneville (Pleistocene), Utah, United States

St bees head fleswick bay wave cut platform

Shore platform at St Bees Head, UK

Tedbury Camp unconformity

Jurassic wave-cut platform at Tedbury Camp, southern England

See also

References

  1. ^ Wilson, M.A., Curran, H.A. and White, B. 1998: Paleontological evidence of a brief global sea-level event during the last interglacial. Lethaia 31: 241-250."Archived copy" (PDF). Archived from the original (PDF) on 2011-01-12. Retrieved 2009-10-28.CS1 maint: Archived copy as title (link)
  2. ^ Trenhaile, A. S. 1987: The Geomorphology of Rock Coasts. (Oxford University Press, Oxford, U.K.) 393 pp.
  3. ^ Sunamura, T., 1992. Geomorphology of rocky coasts. New York: John Wiley.
  4. ^ Masselink, G and Hughes, M. 2003. Introduction to Coastal Processes and Geomorphology. Hodder Arnold
  5. ^ Retallack, G.J. and Roering, J.J. 2012: Wave-cut or water-table platforms of rocky coasts and rivers? GSA Today 22(6), 4-9.
Cliffed coast

A cliffed coast, also called an abrasion coast, is a form of coast where the action of marine waves has formed steep cliffs that may or may not be precipitous. It contrasts with a flat or alluvial coast.

Emergent coastline

An emergent coastline is a stretch along the coast that has been exposed by the sea by a relative fall in sea levels by either isostasy or eustasy.Emergent coastline are the opposite of submergent coastlines, which have experienced a relative rise in sea levels.

The emergent coastline may have several specific landforms:

Raised beach or machair

Wave cut platform

Sea cave such as King's Cave, Isle of ArranThe Scottish Gaelic word machair or machar refers to a fertile low-lying raised beach found on some of the coastlines of Ireland and Scotland (especially the Outer Hebrides.

Hudson Bay, in Canada's north, is an example of an emergent coastline. It is still emerging by as much as 1 cm per year. Another example of emergent coastline is the Eastern Coastal Plains of the Indian Subcontinent.

Grimes Point

Grimes Point, in Churchill County, Nevada near Fallon, is a 720-acre (290 ha) archeological site that was listed on the U.S. National Register of Historic Places in 1972. It was listed for its potential to yield future information.Along the 'Grimes Point Trail', many petroglyphs can be seen. The land is managed by the Bureau of Land Management.

Hallett Cove Conservation Park

Hallett Cove Conservation Park is a protected area in the Australian state of South Australia located in the suburb of Hallett Cove on the coast of Gulf St Vincent about 22 kilometres (14 miles) south of the centre of the state capital of Adelaide.

Hallett Cove is one of the best known geological sites in Australia and is known for its international significance. The area has been declared a Geological Monument by the Geological Society of Australia and placed on the South Australian Heritage Register for its educational and scientific significance.

Kimmeridge

Kimmeridge ( ) is a small village and civil parish on the Isle of Purbeck, a peninsula on the English Channel coast in Dorset, England. It is situated about 4.5 miles (7.2 km) south of Wareham and 7 miles (11 km) west of Swanage. In 2013 the estimated population of the civil parish was 90.

Kimmeridge is a coastal parish and its coastline forms part of the Jurassic Coast, a World Heritage Site. The coast is also part of a Site of Special Scientific Interest, and the whole parish is part of the Dorset Area of Outstanding Natural Beauty.

Kimmeridge is the type locality for Kimmeridge clay, the geological formation that covers most of the parish. Within the clay are bands of bituminous shale, which in the history of the village have been the focus of several attempts to create an industrial centre. An oil well has operated on the shore of Kimmeridge Bay since 1959.

The roughly semi-circular Kimmeridge Bay is southwest of Kimmeridge village. It is backed by low cliffs of Kimmeridge clay, and beneath the cliffs is a large wave-cut platform and a rocky shore with rock pools and attendant ecology. Kimmeridge Bay is a surfer and diver area.

Kimmeridge Bay

Kimmeridge Bay ( ) is a bay on the Isle of Purbeck, a peninsula on the English Channel coast in Dorset, England, close to and southeast of the village of Kimmeridge, on the Smedmore Estate. The area is renowned for its fossils, with The Etches Collection in the village of Kimmeridge displaying fossils found by Steve Etches in the area over a 30-year period. It is a popular place to access the coast for tourists. To the east are the Kimmeridge Ledges, where fossils can be found in the flat clay beds.

List of landforms

Landforms are categorised by characteristic physical attributes such as elevation, slope, orientation, rock exposure, and soil type.

Little Taiwan

Little Taiwan (Chinese: 小臺灣; pinyin: Xiǎo Táiwān) is a wave-cut platform in Qimei Township, Penghu County, Taiwan.Visible at low tide, the platform has the shape of Taiwan. Together with the Double-Heart of Stacked Stones it is a tourist attraction on the island of Cimei.

Long Reef (New South Wales)

Long Reef is a prominent headland in the Northern Beaches of Sydney, Australia. Connected to the mainland by a tombolo, the reef has an extensive wave-cut platform. Long Reef is a popular recreational destination and is one of the more interesting geological areas in Sydney.

Marine transgression

A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water (or decreasing in capacity). Transgressions and regressions may be caused by tectonic events such as orogenies, severe climate change such as ice ages or isostatic adjustments following removal of ice or sediment load.

During the Cretaceous, seafloor spreading created a relatively shallow Atlantic basin at the expense of deeper Pacific basin. This reduced the world's ocean basin capacity and caused a rise in sea level worldwide. As a result of this sea level rise, the oceans transgressed completely across the central portion of North America and created the Western Interior Seaway from the Gulf of Mexico to the Arctic Ocean.

The opposite of transgression is regression, in which the sea level falls relative to the land and exposes former sea bottom. During the Pleistocene Ice Ages, so much water was removed from the oceans and stored on land as year-round glaciers that the ocean regressed 120 m, exposing the Bering land bridge between Alaska and Asia.

Mudflat

Mudflats or mud flats, also known as tidal flats, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A recent global analysis suggested they are as extensive globally as mangroves. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and marine animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily.

In the past tidal flats were considered unhealthy, economically unimportant areas and were often dredged and developed into agricultural land. Several especially shallow mudflat areas, such as the Wadden Sea, are now popular among those practising the sport of mudflat hiking.

On the Baltic Sea coast of Germany in places, mudflats are exposed not by tidal action, but by wind-action driving water away from the shallows into the sea. These wind-affected mudflats are called windwatts in German.

Raised shoreline

A raised shoreline is an ancient shoreline exposed above current water level. These landforms are formed by a relative change in sea level due to global sea level rise, isostatic rebound, and/or tectonic uplift. These surfaces are usually exposed above modern sea level when a heavily glaciated area experiences a glacial retreat, causing water levels to rise. This area will then experience post-glacial rebound, effectively

raising the shoreline surface.

Examples of raised shorelines can be found along the coasts of formerly glaciated areas in Ireland and Scotland, as well as in North America. Raised shorelines are exposed at various locations around the Puget Sound of Washington State.

St Bees Head

St Bees Head is a headland on the North West coast of the English county of Cumbria and is named after the nearby village of St Bees.

It is the only stretch of Heritage Coast on the English coastline between the Welsh and Scottish borders, and is a Site of Special Scientific Interest. The sea off the Head is protected as part of the Cumbria Coast Marine Conservation Zone.

It lies on two long-distance footpaths, the Cumbria Coastal Way and Wainwright Coast to Coast. Both long-distance footpaths follow the edge of the cliffs, which rise to 90 metres above sea level and have views of the Cumbrian mountains and coast.

Surf zone

As ocean surface waves come closer to shore they break, forming the foamy, bubbly surface called surf. The region of breaking waves defines the surf zone. After breaking in the surf zone, the waves (now reduced in height) continue to move in, and they run up onto the sloping front of the beach, forming an uprush of water called swash. The water then runs back again as backswash. The nearshore zone where wave water comes onto the beach is the surf zone. The water in the surf zone, or breaker zone, is shallow, usually between 5 and 10 m (16 and 33 ft) deep; this causes the waves to be unstable.

Terrace (geology)

In geology, a terrace is a step-like landform. A terrace consists of a flat or gently sloping geomorphic surface, called a tread, that is typically bounded one side by a steeper ascending slope, which is called a "riser" or "scarp." The tread and the steeper descending slope (riser or scarp) together constitute the terrace. Terraces can also consist of a tread bounded on all sides by a descending riser or scarp. A narrow terrace is often called a bench.The sediments underlying the tread and riser of a terrace are also commonly, but incorrectly, called terraces, leading to confusion.

Terraces are formed in various ways.

Tidal island

A tidal island is a piece of land that is connected to the mainland by a natural or man-made causeway that is exposed at low tide and submerged at high tide. Because of the mystique surrounding tidal islands many of them have been sites of religious worship, such as Mont Saint-Michel with its Benedictine Abbey. Tidal islands are also commonly the sites of fortresses because of their natural fortifications.

Tung Ping Chau

Tung Ping Chau (Chinese: 東平洲) is an island in Hong Kong. It was known as Ping Chau (Chinese: 平洲). Tung (Chinese: 東, meaning east) is prepended to the name so as to avoid possible confusion with Peng Chau, another island in Hong Kong with an identically pronounced name in the Cantonese language. Administratively, the island is part of the Tai Po District in the New Territories.

Vot Tande

Vot Tande (IPA: [βɔt.taˈⁿdɛ]) is an uninhabited islet of the Banks Islands of northern Vanuatu. It is located about 50 km (31 mi) due north of the island of Mota Lava. The islet of Vot Tande has never been inhabited. It is host to thousands of sea birds—especially frigatebirds, which have given their name to the islet.

Whale Cave

The Whale Cave (Chinese: 澎湖逍遙遊; pinyin: Pēnghú Xiāoyáoyóu) is a wave-cut platform in Xiaomen Village, Xiyu Township, Penghu County, Taiwan.

Landforms
Beaches
Processes
Management
Related

Languages

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.