Fossilised tubes of algae and sediments on shore of Salar de Uyuni at Aguaquiza, Nor Lipez Province, Potosí Department, Bolivia

These tubes of fossilised algae and sediments are next to the Gruta de Galaxias cave at Aguaquiza. They were formed from material ejected from underwater thermal springs and small geysers from the period when this part of the altiplano was a gigantic prehistoric lake.