April 25, 2022 - Uyuni Salt Pan Drying Out

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Uyuni Salt Pan Drying Out
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Seated on the high Altiplano of Bolivia, the Salar de Uyuni shimmers
bright white in satellite imagery, thanks to the thick, salt-rich
mineral crust that spans roughly 4,000 square miles (10,000 square
kilometers). The Altiplano plateau was formed during the uplift of the
Andes Mountains, which surround the region. The plateau harbors fresh
and saltwater lakes as well as several salars (salt flats) but the
largest salar in all of Bolivia—and the largest on Earth—is the Salar
de Uyuni.

Most of the year, this enormous salt flat wears a thick, nearly
unbroken, salty crust. During the rainy season, however, water often
collects in the Salar de Uyuni, melting some of the salt and expanding
the size of the salt flat. The expansion is always temporary, as the
hot dry season drives rapid evaporation that once again shrinks the
Salar de Uyuni as well as the other salars of the Altiplano.

Abundant rainfall around the Altiplano in the 2021-2022 rainy season
filled the Salar de Uyuni beyond the brim. According to an article
published by NASA’s Earth Observatory on February 19, 2022, hydrologist
Jorge Molina Carpio of the Universidad Mayor de San Andrés explained
that the extent of the filling of Salar de Uyuni this year is above
normal. The rainy season started earlier than previous years (it began
in November 2021), and rainfall was well above average over the
southern Altiplano. He stated, “This was probably related to the onset
of a significant La Niña event. Strong La Niñas during the rainy season
are related to positive rainfall anomalies in the southern Altiplano.”
Despite the abundance of water in the Salar de Uyuni by February 2022,
the onset of the dry season has seen rapid shrinking.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board
NASA’s Aqua satellite acquired a true-color image of the Salar de Uyuni
on April 21, 2022. Most of the salt flat appears bright white,
indicating dry conditions. A few gray and blue-gray areas mark
remaining moisture both in the Salar de Uyuni as well as the smaller
Salar de Coipas. This is in marked contrast to the conditions seen on
February 11, 2022, when the salt crust of the Salar de Coipas was
almost entirely dissolved as that salt flat filled with fresh
rainwater. The salty crust of the Salar de Uyuni was still present,
especially in the western section, but it was also filled with water,
coloring it with swirls of blue, gray, and brown.

Although a single image can give an informative view of an area at a
specific time and date, comparing two images acquired on different
dates gives a much better understanding of change over time. Thanks to
the NASA Worldview App, it is easy to view a roll-over comparison
between the Aqua MODIS image acquired on April 21 and the one acquired
on February 11. To see this comparison, simply click here.

Image Facts
Satellite: Aqua
Date Acquired: 4/21/2022
Resolutions: 1km (51.5 KB), 500m (123.7 KB), 250m (259.8
KB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2022-04-25

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