Sima Pumacocha is a limestone cave located in the Yauyos province of central Peru near the village of Laraos, high in the Andes mountains. It is one of the deepest caves in South America.
Following the steeply-dipping limestone beds, Sima Pumacocha generally consists of several vertical shafts connected by short sections of horizontal to steeply-sloping passages. Although closely grouped together, the three main entrances each lead to extensive independent passages before meeting underground. SP1 and SP2 are within 60 m of each other but their passages join at about the -300 m level, while SP3, a further 30 m away, is thought to join the main cave at a depth of -550 m based on observations of relative water volumes (SP3 is blocked at -120 m). All three entrances lead to big shafts: SP1 has the deepest shaft in the Andes (282 m), SP2 leads to the 113-meter-deep Ammonite Shaft, and SP3 is a 120 m shaft.
Several fossilized ammonites up to 20cm in diameter were observed within Ammonite Shaft’s walls. Below the junction of SP1 and SP2 are several wet shafts between 15 m and 75 m in depth, leading to a gravelled sump at -638 m. All explored passages have been surveyed, with a total length of 1,427 m. It was hoped that the strong inward draught indicated a junction with a large underground river, but after losing the draught near the sump some cavers concluded that it might be due to the cave’s own stream.