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Understanding the World's Biggest Mirror: The GEOLOGY of SALAR DE UYUNI Bolivia EXPLAINED

Sometimes referred to as “the world’s biggest mirror” or “the mirror of the sky”, Salar de Uyuni in Bolivia is known for its breathtaking views of a perfectly reflected landscape. But what causes this mesmerizing, picture-perfect landscape of the world’s largest salt flat? Here, we will learn what is Salar de Uyuni, how it was formed, what factors contribute to Salar de Uyuni being labeled as the world’s largest natural mirror, and the treasure that Solar de Uyuni holds for our global technology.

What is Salar de Uyuni?

Salar de Uyuni salt flat in Bolivia

Salar de Uyuni is the world’s largest salt flat, and it is located in the southwest region of Bolivia, South America. It spans over an area of more than 10,000 square kilometers (more than 4,000 square miles).

Salar de Uyuni is located in the Altiplano, at an elevation of around 3,650 meters (about 11,980 feet) above sea level. 

What is the Altiplano?

The Altiplano is a vast and high plateau situated between the eastern and western ranges of the Andes Mountains. While covering a wide area encompassing parts of Bolivia, Peru, and Chile, the bulk of the Altiplano is located in Bolivia.

The Altiplano plateau formed with the tectonic uplift of the Andes, and it consists of high mountain peaks as well as lakes of fresh and salt water. Considering the lack of drainage outlets, all the water gathered in the lowest point of the plateau - the area of Salar de Uyuni. This created a giant prehistoric lake that dwelled in this area of the Altiplano Basin. With the passing of time, the climate started changing, getting drier. Because of this, about 40,000 years ago, the water from this giant lake started evaporating, ultimately resulting in the formation of the salt flat once the evaporation stopped, about 10,000 years ago. 

The chemical composition of the salt flat

The salt flat consists of a thick layer of salt, mainly sodium chloride, that is a few meters thick, in general, but that can be as thick as 140 meters in some areas of the Salar. Beneath this layer of salt, there’s a layer of brine that contains other important chemical elements such as magnesium, potassium, and lithium.

Why is Salar de Uyuni a salt flat?

I think the first part is obvious by now - it’s salt, plain and simple.

But why flat? That’s because this entire area is so flat that it exhibits an average elevation change of less than one meter across the entire span of the salt flat. Because of this feature, Salar de Uyuni is used to calibrate altimeters on board of satellites. Satellite altimeters are instruments that measure the topography of sea surface, and they are especially useful in monitoring the climate-related sea level changes.

World's Biggest Mirror

The remarkable flatness of the area contributes to its designation as the world’s biggest natural mirror, providing a mesmerizing backdrop to capture mirror-like images when visiting Bolivia. Another contributing factor is the presence of a thin layer of water over the salt crust formed as nearby lakes overflow during the rainy season of the year. This thin layer of water acts as the world’s largest mirror, perfectly reflecting the mountains, the sky, and all the surrounding landscape that we typically see in the images depicting Salar de Uyuni.

Salar de Uyuni in Bolivia - The World's Biggest Mirror

Even if you don’t go there during the rainy season, do not worry. You will still get the chance to capture stunning images of the landscape during the dry season. When the water evaporates, it leaves behind the white salt crust adorned with intriguing honeycomb patterns, creating an otherworldly ambiance.

Why is the salt crust organized in a hexagonal pattern? 

Salar de Uyuni hexagonal pattern on the salt crust

There have been various hypotheses over time that were trying to explain the reason behind the honeycomb pattern. According to a new study, the hexagonal patterns result from groundwater movements beneath the salt crust. Layers of salty and less salty water circulate up and down in donut-shaped currents, creating a regular hexagonal pattern as the rolls of subsurface currents are squeezed against each other horizontally.

If you had to choose between visiting Salar de Uyuni during the rainy season or the dry season, which one would you choose? Would you prefer to see the mirrored landscape or would you rather walk on the honeycomb patterned salt crust?

Salar de Uyuni's Salt Hotel

Here’s a fun fact if you decide to visit, regardless of which season you choose for your trip. If you want a memorable experience, you can choose to stay in a salt hotel. That’s right! There’s so much salt at Salar de Uyuni that they even built a hotel almost entirely out of salt. Just imagine having your breakfast at the hotel when you realize that the dish is not salty enough. No problem! Just scrape a bit of your chair or the table you’re eating on and sprinkle it over your food. While that might be a tad trickier than picking up the salt shaker, just the idea of spending your holiday in a salt hotel sounds like so much fun.

The treasure that Salar de Uyuni holds for global technology

Lithium - chemical element

One of the chemical elements present in the brine beneath the salt crust is a true treasure for global technology. It’s lithium! Lithium is sometimes referred to as “white gold” because of its light color and high market value, since lithium is a crucial component of today’s electronic devices. From something as small as a cell phone battery to batteries of much larger machines, like electric cars, lithium is a key component in powering these devices. And the more our technology evolves, the more we are dependent on lithium.

Salar de Uyuni contains a considerable portion of the world’s lithium reserves, estimated to be around 50% of the world’s known lithium resources. These abundant reserves of lithium could contribute to meeting the current and future global demand for lithium as required by new technological advancements.

But at what cost? 

Extracting lithium involves extensive water usage, which can become a threat to the flamingo populations residing in the area. With the decrease of water resources in these areas, lakes inhabited by flamingos become inhospitable for the organisms they feed on, forcing the birds to either migrate or face starvation. Moreover, studies have shown that ingesting the lithium from groundwater can be harmful to human health.

While mining for lithium is important, we also have to consider its consequences. We have to be aware of and work towards lessening the impact of mining on biodiversity and potential harm to humans. As we strive to improve certain areas of our lives, we end up harming others, often with consequences to our natural heritage


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