Tinto River
Interesting facts
- The sulphide ore beneath the river formed more than 300 million years ago, in the Carboniferous, from hydrothermal activity on an ancient seafloor.
- Mining here began around 3000 BC with the Tartessians and Iberians and continued under Phoenicians, Greeks, Romans, Visigoths and Moors.
- After centuries of neglect the old workings were rediscovered in 1556, and the Spanish state began operating them again in 1724.
- British investors founded the Rio Tinto Company in 1873 to run the mines, which at their height employed as many as 20,000 people.
- Copper output peaked in 1930; copper mining ended in 1986 and gold and silver in 1996, before copper production restarted in 2016.
- Iron-oxide terraces built by microbes lie up to 60 metres above today's river and 20 kilometres from its course, hinting the acid ecosystem predates mining.
- Despite a pH of around 2, red and green algae thrive in the water and make up more than half of the river's living biomass.
- The vivid colour lasts for roughly 50 kilometres, fading past the town of Niebla as other streams dilute and neutralise the acid.
- Scientists have compared its chemistry directly with the water in which the rocks of Meridiani Planum on Mars were laid down.
- In Spanish tinto means coloured, but it is also the everyday word for red wine, a fitting double meaning for this river.
Why it is worth it
The water here runs wine-red to burnt orange, acidic enough — pH as low as 1.7 — to strip metal, and the mining along its banks is only part of the story. Five thousand years of extraction did plenty of damage, but the color and acidity are sustained by naturally occurring iron- and sulfur-oxidizing bacteria that keep breaking down sulfide minerals in the rock on their own, a chemical reaction that would keep running here even if every mine shut down tomorrow.
That chemistry made the river irresistible to NASA. Its combination of acidity, dissolved iron and the mineral jarosite turned out to closely match conditions later found on Mars, so in the early 2000s a joint NASA–Spanish project called MARTE drilled some 150 metres into the ground near the river's source, testing robotic techniques for detecting subsurface life — essentially rehearsing a Mars mission on a riverbank in Andalusia.
The river's name traveled a lot further than Mars analog research. It's where the mining company Rio Tinto — now one of the largest mining corporations on the planet — got its name and its start. And a short way downstream, where the Tinto meets the Odiel at the coast near Huelva, sits Palos de la Frontera, the small port from which Columbus's three ships set out on 3 August 1492.
Getting there
6 km from Huelva. Jerez Airport (XRY) is about 94 km away.
On these lists
From the encyclopaedia
The Río Tinto is a highly toxic river in southwestern Spain that rises in the Sierra Morena mountains of Andalusia. It flows generally south-southwest, reaching the Gulf of Cádiz at Huelva. The Río Tinto river has a unique red and orange colour derived from its extremely acidic chemical makeup with very high levels of iron and heavy metals. The name río tinto means "coloured river" in Spanish, in contrast to most rivers, which are clear. However, "tinto" is also an expression for red wine in Spain, so it is also related to this second meaning.
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