Tenorio Volcano National Park in Costa Rica is home to one of the world’s most beautiful rivers, Rio Celeste. This 14-km river is straight out of a fairy tale; nature has painted it neon-turquoise!
For centuries, the unique color of this river has been a mystery to scientists. Some claimed it was high levels of copper that made the river turquoise. When tests were conducted, there was no trace of copper. This led some to speculate that the color was caused by high concentration of other chemicals like calcium carbonate and sulfur while others believed it was due to the river’s proximity to Tenorio Volcano.
© Rio Celeste / Facebook
A couple of years ago, the research team from University of Costa Rica and National University were finally able to solve this mystery. Their findings were astonishing – Rio Celeste’s turquoise color is an optical phenomenon created by the scattering of sunlight and reflected by the riverbed, and not a chemical effect!
© Rio Celeste / Facebook
Rio Celeste is formed by the confluence of two completely transparent rivers – Quebrada Agria and Buena Vista. It is right at this confluence that the water turns turquoise. During their investigation, the research team found no unusual chemical reactions. However, when they collected water samples from Rio Celeste, they were baffled; the water collected was completely transparent!
With transparent water samples and the lack of any unusual chemicals, scientists were forced to consider the possibility of an optical phenomenon. They noticed that the rocks on the riverbed were covered by a whitish substance composed of aluminosilicates – a combination of aluminum, silicon, and oxygen. Aluminosilicates are capable of absorbing all colors present in sunlight, except blue. These unabsorbed blue rays of sunlight create a visual illusion that makes the river water look blue-turquoise to the human eye!
However, the mystery wasn’t completely solved. During their research, scientists also found an abundance of aluminosilicate in Rio Buena Vista, yet its water looked transparent! The answer lied in particle size. When they analyzed the samples from both the rivers, scientists found that the aluminosilicate particles in Rio Celeste were much larger (566 nanometers (nm)) than those in Rio Buena Vista (184 nm). “This increase in size is what causes the scattering of sunlight, such that it occurs principally in the blue region of the visible spectrum. So that’s why we have that spectacular light blue color of the Rio Celeste” said Dr. Max Chavarría Vargas, who lead the scientific investigation. Well certainly this has become one of the best tourist spots in Costa Rica.
This natural phenomenon is seen nowhere else in the world.
How to get there?
Rio Celeste is located in Tenorio Volcano National Park in Guatuso in Costa Rica’s Alajuela region. Even though it’s quite a schlep to reach Rio Celeste, it’s worth the trouble. The water color turns brighter as you go further upstream. Along the way, you’ll see a gorgeous water, but the highlight, of course, is Los Tenideros, where the two rivers meet to form the blue Rio Celeste as if by magic.
The best way to get here is by taking a public bus in San Jose until Ciudad Quesada and then another bus to Guatuso. From there, take a taxi to the national park and then hike up to the river. The national park is open from 8am to 5pm.
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