• Bilbo Baggins

Lago Sarmiento: Overlooked Place in Torres del Paine National Park

Torres del Paine National Park is well known for its imposing mountains and granitic vertical walls, as well as for its pure glaciers and multi-coloured lakes. Among them you might have seen pictures of the turquoise waters of Pehoe lake (which means “hidden” in the local indigenous language), the cyan-green surface of Nordenksjöld lake (which got its name from Swedish nineteenth century explorer Otto Nordenskjöld) and of course Grey lake, located at the feet of the homonymous glacier.


However, among the lakes that dotted this corner of Chilean Patagonia, there is one which is often overlooked by local tours and local agencies, despite being the first one you encounter on the way to Torres del Paine National Park’s main entrance, Laguna Amarga.

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Lago Sarmiento and Torres del Paine mountains

Lago Sarmiento gets its name after fifteenth-century Spanish sailor and explorer Pedro Sarmiento de Gamboa. It is a body of water located at the southern edge of Torres del Paine with a surface of approximately 80 km2 (around 25 square miles) making it the second largest lake in the park after Toro lake, and a maximum depth of 310 meters (900 feet approx.). As the majority of the Torres del Paine lakes its major axis is oriented west-east, since this was the main direction of the ice flow during the late Pleistocene era which is considered to be the moment of maximum extension of the Patagonian Ice Cap around 20 to 18 thousand years ago.


While driving around the Magallanes region during your trip to Patagonia, Sarmiento lake will be the first photographic stop you must take on the way to Torres del Paine National Park. Its cobalt deep blue waters create a perfect setting for a picture with Torres del Paine mountains in the background. A great introduction to this remote corner of Chilean Patagonia. Once standing at the lookout you will not fail to notice a broad and whitish strip of rocks which contours the whole lake’s surface. This is Sarmiento lake’s unique and peculiar feature, thrombolites formations.

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The white shore of Calcium Carbonate around Sarmiento

Thrombolites are ancient forms of microbial communities which are found in shallow and alkaline waters. These are clotted accretionary structures formed by microorganisms like cyanobacteria, during their lifetime and reproductive cycle. Cyanobacteria capture, bind and cement sedimented grains they find in the water to create layers of accretions mostly composed by calcium carbonate (CaCO3). If the accretion of the deposits have a clotted structure they are called Thrombolites, otherwise in case of a laminated structure the name given is Stromatolites.


These calcium carbonate structured deposits are now only found in few places around the world and their ancestors are thought to have contributed to the increase of oxygen in the Earth’s atmosphere thus bringing the ideal conditions for the development of life on the planet.

Locations where we can find thrombolites are for instance Southwestern Australia Shark Bay, a few shallow lagoons in the Bahamas, the area of Cuatro Cienegas in Mexico Nuevo Leon state and Lago Sarmiento in Torres del Paine National Park.

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Thrombolites formations and Caribbean-like beach in Torres del Paine National Park

Sarmiento lake possesses three main characteristics that have permitted throughout the centuries the survival and thriving of cyanobacteria. First of all it is a closed basin with no streams or rivers outflowing the waters of the lake. Sarmiento is located in a geographical area where the average precipitation is lower than the evaporation, therefore the water level is constantly and slowly dropping century by century giving space to the old thrombolites to be exposed, and last but not least the absence of predators like fishes allow the cyanobacteria to survive and reproduce.


Most of park visitors en route to Torres del Paine W Trek miss the beauty and peculiarity of this place, however, during our Torres del Paine hiking program which consist in driving and hiking on the four corners of Torres del Paine we have thought of giving you the chance to approach the western shores of Sarmiento lake via a short but scenic half day hike. This off-the-beaten-path location will make you forget of being in Patagonia while you’ll rather find yourself in a white Caribbean beach.

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Sarmiento lake blue cobalt waters in Chilean Patagonia

All our trekking itineraries in Torres del Paine National Park can be found in the following links:

www.middleearthpatagonia.com/torres-del-paine-w-trek

www.middleearthpatagonia.com/torres-del-paine-trekking

www.middleearthpatagonia.com/torres-del-paine-hiking

www.middleearthpatagonia.com/torres-del-paine-o-circuit

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