CRC Daily: The science behind Costa Rica's sky-blue waterfall

Rio Celeste isn’t even the only place where this phenomenon occurs.

One of Costa Rica’s most iconic destinations is Tenorio Volcano National Park, home to the unforgettable Río Celeste waterfall:

Incredibly, the public hiking trail within the park takes visitors to the exact spot where two transparent rivers — the Quebrada Agria and the Buena Vista — converge to create the sky-blue Celeste River.

What causes that spectacular blue color? In 2013, researchers from the University of Costa Rica (UCR) and the National University (UNA) unraveled the mystery after analyzing water samples under electron microscopes:

They discovered a type of mineral called aluminosilicates. It is composed of aluminum, silicon and oxygen, and being suspended in water, it is responsible for reflecting sunlight.

But why is the blue visible in the Río Celeste, but not its two tributaries? This comes down to chemistry: The Quebrada Agria is acidic, and it causes the naturally ocurring aluminosilicates in the Buena Vista River to clump into larger sizes:

In the Buena Vista River, the particles are 184 nanometers (nm) in size. In the Rio Celeste itself they are much larger, 566 nm.

It is precisely by having this size that the particles scatter sunlight reflecting the shades of the blue group of the spectrum. 

Río Celeste is special, but it’s not entirely unique. In fact, there are other rivers in Costa Rica where you can experience the sky-blue optical effect. One of our favorites is Bajos del Toro, a lesser-known destination with swimmable blue pools.

Safe travels!

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