Lago Sarmiento – Sendero de los Trombolitos

This easy 4.95 km (3.1 mi) out-and-back reaches the south shore of Lago Sarmiento, where pale thrombolite formations make the walk worth the effort. Allow about 2.5 hours with time to look around. One current guided itinerary lists a shorter 4 km version, so confirm your operator’s start and route before using this distance.

The mapped route begins at a footpath beside Ruta Y-150, crosses open low vegetation, then descends to the lake shore and returns the same way. The Paine Horns and Almirante Nieto rise in the wider view. The recorded route is easy, with about 100 m of ascent and descent; the exact footing beyond the mapped path is not well described.

Those knobbly carbonate structures are thrombolites, built as microbial communities help deposit calcium carbonate. Living forms continue below the water, while older structures are exposed along the shore. Their microbial lineage is ancient, but the visible formations are not billions of years old; that age refers to early microbial life, not these deposits.

This is the shore walk to the formations, not the separate route between Portería Sarmiento and Laguna Amarga. Public self-guided access and parking for this exact start are not confirmed. Arrange the outing with an operator or check with CONAF, and confirm the meeting point before driving out; the published guided versions do not all use the same distance.