Glacial lake: what it is and how it is formed

A glacial lake is a body of water that is formed from the retreat or melting of a glacier. These originate when enormous masses of ice, as they move, erode the terrain and excavate depressions in areas where the slope decreases. As time goes by, the ice melts and the depressions fill with water from melting ice, creating a lake.

A curiosity is that many of these lakes were formed during the Pleistocene, an era characterized by intense climatic modifications and extensive glaciations. In some cases, large blocks of ice were trapped between glacial hills (drumlins) and, when melted, generated small lakes surrounded by typical formations such as moraines, striae and eskers.

Glacial lakes have unique characteristics: during winter, the densest water accumulates at the bottom at about 4 °C, while the surface can freeze, generating a layer of ice that is maintained depending on the altitude and the prevailing conditions. In addition, its waters can have whitish or greenish tones due to the presence of fine mineral particles that also influence aquatic life.

Due to their isolation and extreme conditions, these lakes often host unique species, making them valuable ecosystems from a biological point of view.

1. Glacial lakes are created by the action of moving ice. As glaciers slowly advance over the land, they act like huge files that wear away the surface beneath them. This erosion process forms deep depressions and furrows, leaving the landscape marked with traces that will later become basins.
2. When the glacier begins to retreat due to warming or melting, these depressions can fill with water from the melting of the glacier, forming a lake.
3. However, this is not the only way these bodies of water appear. Glaciers often carry and accumulate rock fragments and sediments, forming natural barriers called moraines. These structures can act as dams that retain water, giving rise to temporary or permanent lakes.
4. In certain cases, even the ice itself can form a dam. This occurs when a surging glacier (moving at high speed) blocks a valley or fjord, trapping meltwater and creating a lake.
5. However, these lakes are not always stable. Dams formed by moraines, although sometimes solid, can leak or give way under the pressure of accumulated water, especially during periods of intense snowmelt. This can cause sudden overflows or breaks that release large volumes of water, destroying everything in its path downstream.

• Lake Buenos Aires: it is the largest of glacial origin in the Andes and is shared by Argentina and Chile (where it is known as General Carrera Lake). It has a surface area of ​​approximately 2,240 square kilometers and a maximum depth of 585 meters. Did you know that it constitutes one of the best examples in the world of conservation of landscapes shaped by glacial action?
• Lake Frías: in the Nahuel Huapi National Park within the province of Río Negro is Lake Frías, an elongated lake mirror of glacial origin, surrounded by steep rock walls. This lake receives meltwater from the glaciers of Cerro Tronador and its turquoise color is the product of fine sediments transported by the Frías stream. During winter, some parts of the lake become frozen.
• Lake Geneva: also known as Lake Geneva, it is the largest lake in Western Europe. Located in the north of the Alps, between France and Switzerland, it has an area of ​​582 km², of which 60% (348 km²) corresponds to Switzerland and 40% (234 km²) to France. It constitutes an important tourist site where a large number of boats sail.
• Jökulsárlón: is the most emblematic glacial lake in Iceland, located south of the Vatnajökull glacier. It was formed around 1934 and 1935 and has grown rapidly, going from about 7.9 km² in 1975 to approximately 18 km² today. About 200 meters deep, it is famous for the icebergs that break off from the Breiðamerkurjökull glacier and float in its waters.
• Moraine Lake – This lake is located in Banff National Park within the Rocky Mountains of Alberta and is an emblem of the alpine glacial lake. Fed by the melting of the Wenkchemna glacier, it stands out for its intense turquoise blue color caused by the refraction of light due to the sediments that are suspended in the water.
• Peyto Lake: within Banff National Park, in Alberta, this lake of glacial origin is located that is fed by the melting of the Peyto Glacier. It has an area of ​​approximately 5.3 km² and is famous for its wolf-head shape when viewed from certain viewpoints. It has an intense turquoise color and is one of the most photographed landscapes in the Canadian Rockies.

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