Aracar is a large conical stratovolcano in northwestern Argentina, just east of the Chilean border.

The volcano has formed, starting during the Pliocene, on top of a lava platform and an older basement.

[13] Tertiary sedimentary rocks in the east and arenites in the south form the rest of the basement.

[15] Some deep gorges cut into the volcano,[8] and erosion has removed 1.8 km3 (0.43 cu mi) of rock.

[14] Moraines, mainly occurring on the volcano's eastern side, descend to 4,500 metres (14,800 ft).

The main andesitic cone is 900 m (3,000 ft) high and 5 km (3.1 mi) wide, forming on top of older dacitic lava flows.

Xenoliths containing quartz and gabbro nodules also play a part in the rock composition.

No historical activity is recorded but in March 1993, inhabitants of Tolar Grande 50 km (31 mi) southeast of Aracar observed a high ash or steam column rising from Aracar, which may be either an eruption or the result of landslides.

[8] Satellite images did not detect edifice deformation during this episode, probably due to aliasing.

[18] The mountain was climbed in 1958 by European climbers, including Mathias Rebitsch, who found an archeological site in the summit area.

Minefield are present on the northeastern flanks of Aracar, making exploration from that side impossible.