Natural rock formations known as the Marble Caves are situated along the shores of General Carrera Lake in Chile’s Aysén Region. These caverns, accessible only by water, are famed for their ethereal blue interiors caused by light reflecting off glacial waters onto their mineral-rich walls. Geologists estimate that the caves began forming 10,000 to 15,000 years ago when retreating glaciers exposed the limestone to erosion from the lake’s waters.

Formation and Geological History

According to Francisco Hervé Allamand, a geology professor at Andrés Bello National University, who spoke to the BBC in 2019, the Marble Caves were initially composed of limestone, a sedimentary rock made of calcium carbonate. Over millions of years, the limestone transformed into marble under intense heat and pressure during tectonic shifts. Reportedly, the impurities trapped within the limestone created the rippling patterns of brown and yellow veins now visible on the walls.

The caves were hollowed out by the gradual dissolution of minerals in the rock by lake water. The smooth, undulating walls resemble scoops of ice cream, shaped by thousands of years of weathering.

Turquoise Waters and Visual Impact

The lake’s striking turquoise hue, which illuminates the caverns, is attributed to glacial silt, or “rock flour,” present in the water, as per reports. This sediment absorbs shorter wavelengths of light and reflects blues and greens, while longer wavelengths like red and yellow are absorbed. Despite its tropical appearance, the water remains icy cold due to its glacial origin.

Visiting the Marble Caves

The Marble Caves can only be accessed by boat or kayak, enabling visitors to navigate the winding passages carved into the marble. The Marble Caves stand as a testament to nature’s ability to create extraordinary formations over millennia through the slow process of erosion and transformation.