A ribbon lake is a long and very deep, finger-shaped

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

, usually found in a

glacial trough U-shaped valleys, also called trough valleys or glacial troughs, are formed by the process of Glacial period, glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with s ...

. As such, a ribbon lake is one of a number of glacial landscapes, including

arête 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 frequ ...

s, corries, rock lips, rock basins and terminal moraines. Such a lake's formation begins when a

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, 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 ...

moves over an area containing alternate bands of hard and soft

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

. The sharp-edged

boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In ...

s that are picked up by the glacier and carried at the bottom of the glacier erode the softer rock more quickly by abrasion, thus creating a hollow called a rock basin. On either side of the rock basin, the more resistant rock is eroded less and these outcrops of harder rock are known as rock bars, which act as dams between which rainwater may accumulate after the retreat of the

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

, filling up the rock basin and creating a ribbon lake. A ribbon lake may also form behind a terminal or recessional

moraine A moraine is any accumulation of unconsolidated debris (regolith and Rock (geology), rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a gla ...

, both of which also act as dams, enabling water to accumulate behind them. A ribbon lake may also occur if a tributary glacier joins a main glacier. The increase in power can create a trough, which is filled with water from a river/meltwater to create a ribbon lake. Examples of ribbon lakes include

Windermere Windermere (historically Winder Mere) is a ribbon lake in Cumbria, England, and part of the Lake District. It is the largest lake in England by length, area, and volume, but considerably smaller than the List of lakes and lochs of the United Ki ...

, the largest natural lake in

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

; Panguipulli Lake, in southern

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

;

Lake Washington Lake Washington () is a large freshwater lake adjacent to the city of Seattle, Washington, United States. It is the largest lake in King County, Washington, King County and the second largest natural lake in the state of Washington (state), Was ...

, in the state of

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

;, Lake Ruda Woda in northern

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

and Llyn Ogwen, in northwestern

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

References

*
Online at Google Books
Glacial erosion landforms Lakes by type {{geo-term-stub