The Andes range is split on most of its length into two or three Cordilleras : Occidental, Central and Oriental.
For Ecuador, two SP pages describe the Occidental and Oriental Cordilleras. The purpose of this page is to cover the Occidental Cordillera that runs along the Chile / Bolivia border.
Up north it joins the Volcanoes of Arequipa (Peru). Down south it reaches the Puna de Atacama (Argentina / Chile).
Historically, this region was entirely part of Bolivia. However following the War of Pacific (1879 - 1883), Bolivia lost the territory between the Cordillera Occidental and the Pacific Ocean to Chile.
Nowadays the border runs through most of the important summits of the region.
As far as landscapes are concerned, the Cordillera Occidental is essentially mineral with rich brown / red / orange colors. A few colorful lakes here and there give peace to this rough and moon-look-alike environment.
In the Northern part (Sajama region) due to higher rains falls in January and February the summits are covered with snow, giving wonderful views.
A few salt flats bring bright white contrast, among others the Salar de Atacama and of course the incredible Salar de Uyuni.
All of its summits are from volcanic origin and therefore represent easy non-technical ascent (apart from some routes on Sajama). Most of the time on rocks, sometimes on snow. Sajama (Bolivia), Parinacota (Chile) and Licancabur (Chile) are probably the most climbed of all. But be sure that this area is far more quiet than Aconcagua (Argentina), Cordillera Blanca (Peru) or Cordillera Real (Bolivia).
NB : a special "thank you" to Peter (a.k.a Ski Mountaineer) for his useful comments and for adding pictures specifically for this page.
The Cordillera Occidental stretches over 600 kms. There are volcanoes to ascend throughout the whole the length. I won't cover every single summit in this page, only the main ones.
I have split this range into four main areas. It is quite complicated to move around in the region, as there no public transportation (apart from the Arica - La Paz road and the San Pedro - Calama road), and hardly any clear 4x4 trails to reach some of these summits. So I gathered in a table the summits close to a main access town : Arica/La Paz - Uyuni - Calama/Ollagüe - San Pedro de Atacama.
These mountains can be climbed all year long, most of them having very little snow even during the rainy season (December to March). Only Sajama, Parinacota and Pomerape should be prepared with more care, as they have a thicker snow layer, with crevasses and penitents.
Note that the Southern part described below as the "Licancabur group", could also be part of the Puna de Atacama.
But as it wasn't included in Corax's page, I've decided to mention it here. Corax's page concentrates on the area around Paso San Fransisco.
*click on the left map to see the whole*
Mountain groups within the Cordillera Occidental
1. Northern Part : Sajama group
To access this region, you can easily come from Arica (Chile, by the Pacific Ocean) or from La Paz with long-distance buses.
In all cases take a bus from a Chilean company rather a Bolivian one.
On that precise road I saw a crashed bus (Bolivian one) with a lot of harmed people.
If you plan to climb Sajama ask to be dropped off near Sajama village (Bolivia).
For Parinacota and Pomerape ask for Parinacota village (Chile).
The buses don't go throught these villages, you will have to hitch-hike or walk the last few kilometers.
Another option would be to book an agency or rent a 4x4 in Arica. Easier solution to reach Guallatire and Acotango for example.
This part is especially known for its huge salt flat called Salar de Uyuni.
There are no public transportation to reach these Volcanoes.
You would have to book an agency from Uyuni (Bolivia) or Iquique (Chile) to drive you there, or rent a 4x4.
As for the Tunupa region, the summits will require you to book an agency or rent a 4x4 to reach this area.
However from the big city of Calama (Chile), things are much easier than from Uyuni.
Especially if you intend to climb San Pedro or/and San Pablo.
Note that there is a weekly train that climbs from Calama to the village of Ollagüe, not really convenient to prepare an ascent !
This part is as convenient for transport as the Northern part.
To reach San Pedro de Atacama (the main town, which is more like a village actually),
you can take an overnight bus (daily) from Santiago or Arica in Chile, and from Salta and Jujuy (Northwest Argentina) with a day bus.
For Licancabur, Juriques and Guayaques you can see with agencies going to Bolivia to visit the South Lipez Desert,
and asked to be dropped off at the border. For Lascar, Pili and Aguas Calientes, a 4x4 would be required.
Transportation : 1. Terrestrial
Buses in Chile are well organised and safe. Roads are in good condition.
One good recommendation (especially for the trip bewteen La Paz and Arica) is Pullman Bus.
In Bolivia roads and bus quality are far lower and might present a danger.
Avoid journeys at night time as they are many more chances to have an accident (poor visibilty and drunk drivers). 2. Air
To reach Arica and Calama by plane, you can fly with the national company : LAN.
Or use the low-cost Sky Airline. Both of excellent quality. Sky being cheaper.