Boiling River, in the Amazon

A mysterious, four-mile long river, deep in the heart of the Amazon, is so hot that it boils.
The river has long been a legend in Peru, but when geoscientist Andrés Ruzo’s heard about it, he thought such a phenomenon couldn’t possibly exist.
He believed that it would require a huge amount of geothermal heat to boil even a small river, and the Amazon basin is far from any active volcanoes. 
But then, Ruzo saw the legendary boiling river with his own eyes.

Ruzo first heard about the Mayantuyacu river when his grandfather told him a story about how Spanish conquistadors killed the last Inca emperor.
He said that after the murder, the Spanish conquistadors headed into the Amazon rainforest in search of gold.
When they returned, the men spoke of a terrifying experience that involved poisoned water, man-eating snakes and a river that boils from below.
Twelve years later, at a family dinner, Ruzo heard the river mentioned again when his aunt said that she had visited it.
The river fascinated him growing up. As a PhD student in geophysics at Southern Methodist University in Texas, Ruzo wanted to find the river for himself. 
‘I began asking that question. Could the boiling river exist?, Ruzo said in Ted Talk. 
‘I asked colleagues from universities, the government, oil, gas and mining companies, and the answer was a unanimous no. 
‘And this makes sense. You see, boiling rivers do exist in the world, but they’re generally associated with volcanoes. You need a powerful heat source to produce such a large geothermal manifestation.
Part of the river in Mayantuyacu boils because of fault-fed hot springs. 
When rain falls on the surrounding area, it gathers into the porous sedimentary rock.
As it move through the rock, it heats up from the primal heat of the Earth. 
Eventually, it comes across a large thrust fault, or crack. 
As water falls behind it, it forces the now heated water to ascend along the fault-line to surface as a hot or warm spring.