A tarn (or corrie loch) is a mountain lake, pond or pool, formed in a cirque (or "corrie") excavated by a glacier. A moraine may form a natural dam below a tarn. [1]
A tarn (or corrie loch) is a mountain lake, pond or pool, formed in a cirque (or "corrie") excavated by a glacier. A moraine may form a natural dam below a tarn. [1]
The word is derived from the Old Norse word tjörn ("a small mountain lake without tributaries") meaning pond. In parts of Northern England – predominantly Cumberland and Westmorland (where there are 197), [2] but also areas of North Lancashire and North Yorkshire – 'tarn' is widely used as the name for small lakes or ponds, regardless of their location and origin (e.g. Talkin Tarn, Urswick Tarn, Malham Tarn). [3] Similarly, in Scandinavian languages, a tjern or tjørn (both Norwegian) or tjärn or tärn (both Swedish) is a small natural lake, often in a forest or with vegetation closely surrounding it or growing into the tarn. The name of the Tjörnin in Reykjavik, Iceland is also from a related word.
The specific technical use for a body of water in a glacial corrie comes from high number of tarns found in corries in the Lake District, an upland area in North-West England. [4] Nonetheless, there are many more bodies of water called 'tarn' in the Lake District than actually fit this technical use.
Tarns are the result of small glaciers called cirque glaciers. Glacial cirques (or 'corries') form as hollows on mountainsides near the firn line. Eventually, the hollow in which a cirque glacier develops may become a large bowl shape in the side of the mountain, caused by weathering, by ice segregation, and as well as being eroded by plucking. The basin will become deeper as it continues to be eroded by ice segregation and abrasion. [5] [6] A cirque typically will be partially surrounded on three sides by steep cliffs, with a fourth side a form of moraine constructed from glacial till, which forms the lip, threshold or sill, [7] from which either a stream or glacier will flow away from the cirque.
Tarns form from the melting of the cirque glacier. They may either be seasonal features as supraglacial lakes, or permanent features which form in the hollows left by cirques in formerly glaciated areas. [4]
A glacier is a persistent body of dense ice that is constantly moving downhill 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 and typically containing 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 moraine is any accumulation of unconsolidated debris, sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sheet. It may consist of partly rounded particles ranging in size from boulders down to gravel and sand, in a groundmass of finely-divided clayey material sometimes called glacial flour. Lateral moraines are those formed at the side of the ice flow, and terminal moraines are those formed at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines and medial moraines.
Glaciology is the scientific study of glaciers, or, more generally, ice and natural phenomena that involve ice.
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
An arête is a narrow ridge of rock that separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys. Arêtes can also form when two glacial cirques erode headwards towards one another, although frequently this results in a saddle-shaped pass, called a col. The edge is then sharpened by freeze-thaw weathering, and the slope on either side of the arête steepened through mass wasting events and the erosion of exposed, unstable rock. The word arête is French for "edge" or "ridge"; similar features in the Alps are often described with the German equivalent term Grat.
A pyramidal peak, sometimes called a glacial horn in extreme cases, is an angular, sharply pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point. Pyramidal peaks are often examples of nunataks.
The Pirin Mountains are a mountain range in southwestern Bulgaria, with the highest peak, Vihren, at an altitude of 2,914 m (9,560 ft).
Pirin National Park, originally named Vihren National Park, encompasses the larger part of the Pirin Mountains in southwestern Bulgaria, spanning an area of 403.56 square kilometers (155.82 sq mi).
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 acidic conditions, a kettle bog may form but in alkaline conditions, it will be kettle peatland.
A cirque is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie and cwm. A cirque may also be a similarly shaped landform arising from fluvial erosion.
Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes. Most lakes in the world occupy basins scoured out by glaciers. Glacial motion can be fast or slow, but is typically around 25 centimetres per day (9.8 in/d).
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 glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land and then melts, filling the depression created by the glacier.
Glaciokarst is a geological term that refers to a specific type of karst landscape that has been influenced significantly by past glacial activity.
A paternoster lake is one of a series of glacial lakes connected by a single stream or a braided stream system. The name comes from the word Paternoster, another name for the Lord's Prayer derived from the Latin words for the prayer's opening words, "Our Father"; Paternoster lakes are so called because of their resemblance to rosary beads, with alternating prayer beads connected by a string or fine chain.
U-shaped valleys, also called trough valleys or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with steep, straight sides and a flat or rounded bottom. Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice, called glacial till or glacial erratic.
Popovo Lake is a glacial lake situated in the northern section of the Pirin mountain range, south-western Bulgaria. It is one of the eleven Popovi Lakes. The lake and its surroundings are among the most popular places for summer tourism in Pirin National Park. It is situated at the bottom of the Popovski cirque and is surrounded by the peaks Sivria (2,591 m), Dzhano (2,668 m), Kralev Dvor (2,680 m), Momin Dvor (2,723 m) and Dzhengal (2,730 m).
Snezhnika is a glacieret in the Pirin Mountains of Bulgaria, a remnant of the former Vihren Glacier. The glacieret lies at an elevation between 2,425 m (7,956 ft) and 2,480 m (8,140 ft) in the deep Golemiya Kazan cirque at the steep northern foot of Vihren, Pirin's highest summit. Due to the relatively easy access and its location along a popular hiking trail, Snezhnika is Bulgaria's most famous glacieret. Snezhnika has an average area of 0.01 km2 (0.0039 sq mi) and in 2006 it had a volume of 30,000 m3 (1,100,000 cu ft).
The southernmost persistent glacial masses in Europe are mainly small glaciers, glacierets, and perennial firn fields and patches, located in the highest mountains of the three big southern European peninsulas - the Balkan, the Apennine, and the Iberian, the southernmost ranges of the Alps and the glaciers on the european northwestern slopes of the Greater Caucasus mountains in Russia. There are summer lasting snow patches in Sierra Nevada, in Mount Olympus (40°05′08″), in Mount Korab (41°47′28″), in Rila Mountain, in Picos de Europa (43°11′51″) in the Cantabrian Mountains, in Mount Maglić (43°16′52″) and others. However, none of them have both persistency and indications of dynamic motion. In southern direction, some 4000 km away, are the glaciers in Africa in Rwenzori Mountains (00°23′09″N), Mount Kenya (00°09′03″S) and Mount Kilimanjaro (03°04′33″S).
Media related to Tarn (lake) at Wikimedia Commons
The dictionary definition of tarn at Wiktionary
