[2] The salt flat is probably bordered by a fault on its western side, and a river delta forms much of its northern edge; it is now crisscrossed by stream channels.

In the Pleistocene the salt flat was covered by a lake that was identified through its clay and diatomite sediments and which has left well preserved shorelines and terraces.

[8] The salt covers a surface of about 50–60 square kilometres (19–23 sq mi)[9] with a roughly rectangular shape, the long sides extending northwest-southeast.

[15] The salt flat is covered by an intricate web of canals and lagoons, which constitute areas with distinct flora and fauna.

[13][30] The watershed of Salar de Huasco lies in the Altiplano and Andes, covering an area of about 1,500 square kilometres (580 sq mi).

[6] It is surrounded by mountain chains with volcanoes, except to the west and south where the Altos de Pica highland delimits the basin.

The basin probably formed in the Tertiary through tectonic processes, and was initially open to the east until volcanic activity at the beginning of the Quaternary closed it there.

[33] Three separate aquifers have formed in the basin fill,[34] and are hydrologically connected both to the Collacagua River and the Salar del Huasco.

[39] It is about 43 kilometres (27 mi) long and forms through the union of the easterly Piga and the northern Caquina rivers, far north from Salar del Huasco.

[27] The vegetation consists of a high-elevation steppe[34] and includes several endemic and globally important species, like Polylepis tarapacana and the yareta.

[49] Several plant communities are found, including bofedales wetlands with Oxychloe andina and Zameioscirpus atacamensis and salt meadows with Carex misera.

Other animals[a] are Trichomycterus and Orestias fishes, the Peru water[53] and Telmatobius chusmisensis frogs,[54] Liolaemus lizards,[53] Biomphalaria snails[55] and oribatid mites.

[20] Salar del Huasco is a major stopover for bird migrations[6][64] of American golden plovers, Baird's sandpipers, lesser yellowlegs and peregrine falcons.

[70][71] Environmental conditions are extreme, with the lack of water, harsh climate, high insolation, intense wind-driven mixing, lack of oxygen at high elevations and plenty of toxic arsenic,[68][72] and the genomes of microbes found at Salar del Huasco show evidence of adaptations.

They go back to the last ice age, when the lake was larger and its environment drew hunter-gatherers to Salar del Huasco.

[89] The Salar del Huasco National Park was declared on 5 June 2010,[15] reversed in February 2014,[54] due to failure to involve the indigenous population in the process,[90] then reinstated in March 2023.