Colette's Grand Detour

The last 90 minutes before you land in Chile’s capital of Santiago, make the 14-hour flight from the UK totally worth it. We were treated to clear skies and had perfect views as we crossed the Andes mountain range. The geologically features of this region are so pronounced and big in scale, that it is easy from a bird’s eye view to read the mountains and watch as the geographic formations change below as you approach the central spine of the mountain range.

The foothills of the Andes on the Argentinian side, are known as the precordillera and are a series of uplifted sedimentary layers, ancient seabeds and limestones pushed up by the subduction of the Nazca plate under South America. You can see clear fold-and-thrust belts where strata bend in parallel waves like corrugated cardboard. This is a transition zone where the flat pampas start to wrinkle into the Andes.

One you reach the main spine of the Andes, you see sharply ridged mountains with snowfields, glaciers and deep glacial troughts. This is the highest and youngest part of the Andes, formed by intense compression along the plate boundary. You can clearly see folded layers exposed along ridge lines and volcanic cones in the distance. Some slopes have striking color bands of reds, purples and ochres. This is due to the presence of iron, copper and sulfur and is a result of mineral oxidation. If you are on the left-side of the plane (which I was not) you get a great view of Aconcagua, a massive strato-volcano remnant, made up of uplifted marine sediments and volcanic rock, and standing at just under 7000m in height.

As you descend into the Central Valley of Chile and the Santiago basin, the landscape abruptly flattens, and you’ll see a patchwork of farmland and rivers. The Central Valley is a tectonic depression, a fore-arc basin formed between the coastal ranges to the west and the main Andes. It is filled with Quaternary-period alluvial sediments, making it fertile for vineyards and agriculture. We will see the coastal range of mountains when we head to Valparaiso on a day trip later this week.

A spectacular view at the end of a very long plane journey, that woke me up for the day ahead.