A peninsula [1] [2] is a landform that extends from a mainland and is surrounded by water on most sides. [3] [4] [5] Peninsulas exist on all continents. [6] [2] The largest peninsula in the world is the Arabian Peninsula. [7] [8]
Peninsula derives from Latin paeninsula , which is translated as 'peninsula'. Paeninsula itself was derived from paene 'almost',and insula 'island', or together, 'almost an island'. [3] The word entered English in the 16th century. [3]
A peninsula is generally defined as a piece of land surrounded on most sides by water. [5] [9]
A peninsula may be bordered by more than one body of water, and the body of water does not have to be an ocean or a sea. [10] A piece of land on a very tight river bend or one between two rivers is sometimes said to form a peninsula, for example in the New Barbadoes Neck in New Jersey, United States. [5] A peninsula may be connected to the mainland via an isthmus, for example, in the Isthmus of Corinth which connects to the Peloponnese peninsula. [11]
Peninsulas can be formed from continental drift, glacial erosion, glacial meltwater, glacial deposition, marine sediment, marine transgressions, volcanoes, divergent boundaries or river sedimentation. [12] More than one factor may play into the formation of a peninsula. For example, in the case of Florida, continental drift, marine sediment, and marine transgressions were all contributing factors to its shape. [13]
In the case of formation from glaciers (e.g., the Antarctic Peninsula or Cape Cod), peninsulas can be created due to glacial erosion, meltwater or deposition. [14] If erosion formed the peninsula, softer and harder rocks were present, and since the glacier only erodes softer rock, it formed a basin. [14] This may create peninsulas, and occurred for example in the Keweenaw Peninsula. [14]
In the case of formation from meltwater, melting glaciers deposit sediment and form moraines, which act as dams for the meltwater. [14] This may create bodies of water that surround the land, forming peninsulas. [14]
If deposition formed the peninsula, the peninsula was composed of sedimentary rock, which was created from a large deposit of glacial drift. [15] [16] The hill of drift becomes a peninsula if the hill formed near water but was still connected to the mainland, for example during the formation of Cape Cod about 23,000 years ago. [17] [18]
In the case of formation from volcanoes, when a volcano erupts magma near water, it may form a peninsula (e.g., the Alaskan Peninsula). [15] Peninsulas formed from volcanoes are especially common when the volcano erupts near shallow water. [19] Marine sediment may form peninsulas by the creation of limestone. [20] A rift peninsula may form as a result of a divergent boundary in plate tectonics (e.g. the Arabian Peninsula), [21] [22] while a convergent boundary may also form peninsulas (e.g. Gibraltar or the Indian subcontinent). [23] Peninsulas can also form due to sedimentation in rivers. When a river carrying sediment flows into an ocean, the sediment is deposited, forming a delta peninsula. [24]
Marine transgressions (changes in sea level) may form peninsulas, but also may affect existing peninsulas. For example, the water level may change, which causes a peninsula to become an island during high water levels. [25] Similarly, wet weather causing higher water levels make peninsulas appear smaller, while dry weather make them appear larger. [26] Sea level rise from global warming will permanently reduce the size of some peninsulas over time. [27]
Peninsulas are noted for their use as shelter for humans and Neanderthals. [28] The landform is advantageous because it gives hunting access to both land and sea animals. [28] They can also serve as markers of a nation's borders. [29]
A glacier is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.
A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a very long period. Some valleys are formed through erosion by glacial ice. These glaciers may remain present in valleys in high mountains or polar areas.
A drumlin, from the Irish word droimnín, first recorded in 1833, in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated till or ground moraine. Assemblages of drumlins are referred to as fields or swarms; they can create a landscape which is often described as having a 'basket of eggs topography'.
Till or glacial till is unsorted glacial sediment.
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
A kame delta is a glacial landform formed by a stream of melt water flowing through or around a glacier and depositing material, known as kame deposits. Upon entering a proglacial lake at the end (terminus) of a glacier, the river/stream deposit these sediments. This landform can be observed after the glacier has melted and the delta's asymmetrical triangular shape is visible. Once the glacier melts, the edges of the delta may subside as ice under it melts. Glacial till is deposited on the lateral sides of the delta, as the glacier melts.
A jökulhlaup is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland, which are triggered by geothermal heating and occasionally by a volcanic subglacial eruption, but it is now used to describe any large and abrupt release of water from a subglacial or proglacial lake/reservoir.
A kettle is a depression or hole in an outwash plain formed by retreating glaciers or draining floodwaters. The kettles are formed as a result of blocks of dead ice left behind by retreating glaciers, which become surrounded by sediment deposited by meltwater streams as there is increased friction. The ice becomes buried in the sediment and when the ice melts, a depression is left called a kettle hole, creating a dimpled appearance on the outwash plain. Lakes often fill these kettles; these are called kettle hole lakes. Another source is the sudden drainage of an ice-dammed lake and when the block melts, the hole it leaves behind is a kettle. As the ice melts, ramparts can form around the edge of the kettle hole. The lakes that fill these holes are seldom more than 10 m (33 ft) deep and eventually fill with sediment. In acid conditions, a kettle bog may form but in alkaline conditions, it will be kettle peatland.
An outwash plain, also called a sandur, sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and carries the debris along. The meltwater at the snout of the glacier deposits its load of sediment over the outwash plain, with larger boulders being deposited near the terminal moraine, and smaller particles travelling further before being deposited. Sandurs are common in Iceland where geothermal activity accelerates the melting of ice flows and the deposition of sediment by meltwater.
Glacial landforms are landforms created by the action of glaciers. Most of today's glacial landforms were created by the movement of large ice sheets during the Quaternary glaciations. Some areas, like Fennoscandia and the southern Andes, have extensive occurrences of glacial landforms; other areas, such as the Sahara, display rare and very old fossil glacial landforms.
A terminal moraine, also called an end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge of the ice, is driven no further and instead is deposited in an unsorted pile of sediment. Because the glacier acts very much like a conveyor belt, the longer it stays in one place, the greater the amount of material that will be deposited. The moraine is left as the marking point of the terminal extent of the ice.
A subglacial volcano, also known as a glaciovolcano, is a volcanic form produced by subglacial eruptions or eruptions beneath the surface of a glacier or ice sheet which is then melted into a lake by the rising lava. Today they are most common in Iceland and Antarctica; older formations of this type are found also in British Columbia and Yukon Territory, Canada.
A tunnel valley is a U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets such as that now covering Antarctica and formerly covering portions of all continents during past glacial ages. They can be as large as 100 km (62 mi), 4 km (2.5 mi) wide, and 400 m (1,300 ft) deep.
A Rogen moraine is a subglacially formed type of moraine landform, that mainly occurs in Fennoscandia, Scotland, Ireland and Canada. It is one of the three main types of hummocky moraines. They cover large areas that have been covered by ice, and occur mostly in what is believed to have been the central areas of the ice sheets. Rogen moraines are named after Lake Rogen in Härjedalen, Sweden, the landform's type locality. Rogen Nature Reserve serves to protect the unusual area.
Fluvioglacial landforms or glaciofluvial landforms are those that result from the associated erosion and deposition of sediments caused by glacial meltwater. Glaciers contain suspended sediment loads, much of which is initially picked up from the underlying landmass. Landforms are shaped by glacial erosion through processes such as glacial quarrying, abrasion, and meltwater. Glacial meltwater contributes to the erosion of bedrock through both mechanical and chemical processes. Fluvio-glacial processes can occur on the surface and within the glacier. The deposits that happen within the glacier are revealed after the entire glacier melts or partially retreats. Fluvio-glacial landforms and erosional surfaces include: outwash plains, kames, kame terraces, kettle holes, eskers, varves, and proglacial lakes.
Subglacial streams are conduits of glacial meltwater that flow at the base of glaciers and ice caps. Meltwater from the glacial surface travels downward throughout the glacier, forming an englacial drainage system consisting of a network of passages that eventually reach the bedrock below, where they form subglacial streams. Subglacial streams form a system of tunnels and interlinked cavities and conduits, with water flowing under extreme pressures from the ice above; as a result, flow direction is determined by the pressure gradient from the ice and the topography of the bed rather than gravity. Subglacial streams form a dynamic system that is responsive to changing conditions, and the system can change significantly in response to seasonal variation in meltwater and temperature. Water from subglacial streams is routed towards the glacial terminus, where it exits the glacier. Discharge from subglacial streams can have a significant impact on local, and in some cases global, environmental and geological conditions. Sediments, nutrients, and organic matter contained in the meltwater can all influence downstream and marine conditions. Climate change may have a significant impact on subglacial stream systems, increasing the volume of meltwater entering subglacial drainage systems and influencing their hydrology.
The glacial series refers to a particular sequence of landforms in Central Europe that were formed during the Pleistocene glaciation beneath the ice sheets, along their margins and on their forelands during each glacial advance.
The Edaga Arbi Glacials are a Palaeozoic geological formation in Tigray and in Eritrea. The matrix is composed of grey, black and purple clays, that contains rock fragments up to 6 metres across. Pollen dating yields a Late Carboniferous to Early Permian age.
A meltwater channel is a channel cut into ice, bedrock or unconsolidated deposits by the flow of water derived from the melting of a glacier or ice-sheet. The channel may form on the surface of, within, beneath, along the margins of or downstream from the ice mass. Accordingly it would be referred to as supraglacial, englacial, subglacial, lateral or proglacial.
Lake Washburn is a lake that formerly existed in the Taylor Valley, McMurdo Dry Valleys, Antarctica. It formed when climatic changes and an expansion of ice caused the flooding of the valley, between 23,000 and 8,340 radiocarbon years ago. Its extent and elevation are unclear but Lake Bonney and Lake Fryxell are considered to be its present-day remnant.
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