Volcán Ollagüe (also known as Oyahué) is a massive andesitic stratovolcano in northern Chile on the border with Bolivia. It contains a dacitic summit lava dome. No historical eruptions have been confirmed from Ollagüe, but there is intense fumarolic activity and a persistent steam plume emanates from a fumarole on the south side of the summit dome.
There are active sulphur mines on the upper western and southern flanks of the volcano which are serviced by a now disused switchback road which reaches 5650 m elevation and rank as one of the highest in the world.
Ollague Volcano suffered flank collapse during the Pleistocene and produced a large debris-avalanche deposit which extends westward and separates the Salar de San Martín from the Salar de Ollagüe salt flats.
3 youthful-looking silicic lava flows were emplyed after the collapse, but are probably still older than the last glaciation about 11,000 years ago.
A youthful-looking scoria cone on the lower WSW flank, La Poruñita, was long believed to be relatively young, but has been dated to an age of 420,000 to 680,000 years.
