I had initially planned to travel north through the renowned Quebrada de Humahuaca and to enter Bolivia at Villazón but I changed my mind when I heard about four day tours from San Pedro de Atacama in Chile to Uyuni in Bolivia.
I am glad I did for I can show you a few pages of fabulous mountain scenery thanks to that last minute decision.
This small graph shows how wide the Andes altiplano is between San Pedro de Atacama at 2470 m and Purmamarca at 2250 m. More than 400 km of the route lies above 3000 meters where the air is thin!
This wide alluvial plain narrows as it rises to higher altitudes further north.
At Purmamarca, we leave the Humahuaca valley to climb east in a lateral valley towards the Andes.
The valley is mostly arid and wind swept but humans have settled wherever a local microclimate allowed a minimum of vegetation. The river has cut a deep gorge through the hills that can be seen behind the homestead in this photo.
Only a trickle of water flows across the road now but it can grow into a torrent in the wet season. That is why the roadbed is reinforced with concrete passage.
Further up, the road hugs the side of a narrow canyon carved by the violent action of a mountain stream.
We climb the Cuesta de Lipán up to 4000 m and then descend some 600m to the windswept altiplano.
Beautifully impressive, the altiplano commands respect. Huge, hot at noon and frozen at night, it is swept by violent dry winds that don't provide all the oxygen that humans normally require.
How people survive in this harsh environment is a mystery but they look happy and are friendly enough to wave as we drove by.
Maybe we find the altiplano impressive and beautiful because we cannot dominate and degrade it like we do in most areas of our blue planet.
Some people not only survive here, they thrive when they accept to be a part of the environment instead of its master.
The rain that falls on the altiplano does not all drain into the Pacific and Atlantic oceans. Some of it drains into low areas where it remains trapped. It turns into brine as it evaporates and deposits the excess salt in wide salt pans or "salars" that can be several meters deep in places. The great salt lake of Utah in the US is an example of such a "salar".
With the passage of time, mountains rise and wear down and other sediments can be deposited
over the salt bed. Millions of years later, a salt bed can be buried under thousands
of meters of rock. Under high pressures it becomes plastic and
can flow just like glaciers that flow under the pressure of accumulated snow.
Salt being lighter than rock, it eventually manages to squeeze
through the overlying rock to form salt domes that rise almost to the surface. This
process is important for man,
a) because it provides most if not all our salt mines and
b) because in rising through layers of sediments, the salt creates traps for the oil and natural gas that also seek to escape to the surface. Many important oilfields have been found around salt domes.
Finally we approach the pass at 4 425 meters, on the other side, it is Chile.