An enormous underground river has been reported flowing thousands of feet below the Amazon.
Scientists from Brazil's National Observatory analyzed temperature variations at 241 defunct oil wells dating from the 1970s and 1980s and owned by Brazil's state-run oil company, Petrobras.
And, they say, their results indicate moving water 13,100 feet down, forming a river 3,700 miles long - about the same length as the Amazon. It's been named Hamza, after the head of the research team that discovered it.
The volume of flow is about 3,090 cubic meters per second, compared with 133,000 cubic meters for the Amazon. Both flow from west to east.
"To get an idea of the importance of this system is sufficient to note that the groundwater flow in Amazon region is higher than the average flow of the Rio San Francisco River in Eastern Brazil," says the team.
The water flows almost vertically to about 2,000 feet deep, but becomes almost horizontal at greater depths.
Hamza runs from the region of Acre, through the basins Solimões, Amazonas and Marajó and emerging in a deep lake in County Amazon near the mouth of the Amazon itself. This could explain pockets of low salinity that have been found in the ocean near here.
The team expects to confirm the discovery over the next three years.