Salar de Uyuni


Salar de Uyuni is the world's largest salt flat. In a rainy season, it could appear as a huge mirror spanning over a large distance all the way to the horizon. Flat Earthers take the flatness of Salar de Uyuni (and salt flats in general) as 'evidence' the Earth is flat.


In reality, salt flats are not perfectly flat. Like the ocean, they curve and follows the curvature of the Earth. Unlike the ocean, though, flat salts are solid and we can stand on them. And thus, it should have been much easier to demonstrate the curvature of the Earth than on oceans, if only we are there ourselves.

Evidently, Salar de Uyuni is a very popular tourist destination, and there are a lot of tourists made 360° photosphere in the area. So I started to look at some of the pictures and tried to find if there's an easily recognizable landmark in the area which we can use to show the obstruction from the curvature of the Earth.

One such landmark is Mount Tunupa. It is a dormant volcano over the northern edge of Salar de Uyuni. It is 5321m above sea level, or about 1665 m above Salar de Uyuni (3656 m above sea level). Mount Tunupa is visible all the way to the southern edge and it can be hard to determine the amount of obstruction from the shape of the volcano alone. But there's a smaller unnamed hill to the east. It is 4140 m above sea level or only about 484 m above the salar.

Coincidentally, there are transport routes from the volcano going south to Isla Incahuasi, and further south to the edge of the salt flat, forming a straight line from the volcano all the way to the southern edge of the salt flat. There are many photospheres taken by tourists along the route showing the same side of the volcano. We can use them to observe the progression of the obstruction of the volcano by Earth's curvature as we go farther from the volcano.

The topology of Mount Tunupa (from


The notable features are the hill on the right and the valley connecting it to the peak of Tunupa.

The following is the compiled result of 19 photospheres along the route. The photos are rotated and scaled so that both peaks are level and aligned. Discontinuities in the pictures are stitching glitches, which are not unusual in casually taken 360° panoramas.


Google Earth Web Photosphere URLs for each scene: #1, #2, #3, #4, #5, #6, #7, #8, #9, #10, #11, #12, #13, #14, #15, #16, #17, #18, #19

Map showing the positions where the photosphere was taken. There are the possibilities of GPS errors, so I took as many pictures as possible along the route.


As we can see, everything is as expected on a spherical Earth. We see less of the volcano as we go farther, and it disappears from the bottom up.