The first time I realised how utterly colossal the Andes were was when I saw them drawn onto the side of the world.
It was one of those geology-facts infographics that always do well on social media, and it showed how much of the Earth’s circumference the entire mountain range covers, which is quite a bit of it. Stretching 8,900km (5,530 miles) and connecting Argentina, Chile, Bolivia, Peru, Ecuador, Colombia and Venezuela, it just seems to go on and on.
(That said, it’s not the longest mountain chain in the world, as you may have heard. That honour belongs to the Mid-Oceanic Ridge Systems at the bottom of our seas, connecting together to run for a total of 65,000km (40,000 miles) – which is long enough to wrap around the Moon six times!)
Stand at one end of the Andes – in western Venezuela at one end, or at Tierra del Fuego at the tip of South America at the other – and if you’re asked to point to where the opposite end of the Andes is, you have to point not at the horizon, but at the ground, at a spot somewhere nearer your toes. A vast swathe of the curve of the planet will be in your way.
Unless you actually live in the Andes, all this is on a scale that’s barely comprehensible. In European terms, it’d stretch from the northernmost tip of the UK to the middle of Namibia in southern Africa – or from London to South Korea.
Exactly why these mountains came into being is currently something of a geological mystery. The broad explanations are simple enough: the surface of our planet is made of a series of enormous plates of rock, each jostling against each other. When a denser and therefore heavier plate meets a lighter counterpart, it doesn’t just buckle the land as you’d expect – it subducts, diving underneath it (imagine the edges of two carpets pushing against each other until one gives way, allowing the other to slip underneath.)
But it’s what happens next that usually creates the world’s biggest mountain ranges. As that denser rock heads downwards and sinks, it melts – and that melted rock heads towards the surface, creating violent volcanic activity and thrusting massive mountain ranges high into the air (a process known as progeny).
The Andes are on the edge of the famous Ring Of Fire, circling most of the Pacific. Scientifically speaking this isn’t a single geological feature – it’s a chain of different subduction zones at the edges of different tectonic plates. Around 90% of the world’s earthquakes happen along these margins. In the case of the Andes, is the Nazca Oceanic plate (containing the sea floor off the western coast of South America) plunging underneath the South American continental plate.
From our perspective, this process is happening incredibly slowly – about the speed that our nails grow! But over millions of years, and at mysteriously different speeds, the hundreds of mountains of the Andes were lurched into being above the landscape, some of them up to 7 kilometres above sea level. (This raises many questions, the chief one being: why did this happen here and not elsewhere?)
Mountains like these aren’t just neat-looking localised geological features, something to gawk at when you visit and disregard when you’re elsewhere. The size of the Andes means it affects weather patterns much further afield – not just across South America, but worldwide.
Ever had a look at a satellite photo of Madagascar, off the coast of Africa? It’s one of our planet’s most spectacular displays of the effect of mountains on rainfall: even if you can’t see the mountains running down its western side, you can see how the island is a lush green to the west of them, and dusty-looking desert to the east. That’s because when the easterly winds (coming from the east) hit Madagascar’s mountains, they’re forced to drop all their water before they cross the mountains – creating a “rain shadow” to the west where very little rain falls and agriculture is much more challenging.
The same is true with the Andes. The easterly winds coming from inland drop all their rain, that water floods down the eastern slopes – and ultimately, that’s how the Amazon, the largest river in the world, gets most of its water that goes on to feed the largest expanse of rainforest in the world (5.5 million square km), so big that it’s been nicknamed “the lungs of the planet” for its ability to scrub our atmosphere clean of carbon dioxide.
Meanwhile, to the west of the Andes are some of the world’s most desiccated and inhospitable places, including Chile’s thousand-mile-long Atacama Desert, the driest non-polar desert in the world.
It’s partly created by the the rain-shadow of the Andes (which you can see in satellite photos, with the land to the west of them visibly less covered in greenery), and intensified by a cold, low-salinity ocean current and a permanent anti-cyclone of winds sweeping up South America’s coastline.
The result is a landscape so spectacularly harsh that NASA is using it to test the equipment it’ll be sending to Mars, where temperatures often drop to −63 °C (−81 °F).
This is the wonder of the world that you’d be crossing if you join Wheel & Anchor next March. There’s nothing like it on Earth – and this is your chance to see it in person. How about it?
Join Wheel & Anchor for an in-depth experience in South America’s southernmost countries. In the spirit of slow travel, we’ll spend a week exploring each of the capital cities of Buenos Aires and Santiago and their surroundings. In between we’ll have the chance to explore Mendoza, the hub of Argentinian wine making, and we’ll end in its Chilean counterpart, the Colchagua Valley. All the details here.