Dozens of previously unknown pre-Columbian earthworks found in the depths of the Amazon

Two dozen previously unknown pre-Columbian earthen structures have been discovered deep in the Amazon rainforest, according to a new study. There may be more than 10,000 such structures still waiting to be discovered.

Throughout the Amazon basin, tropical forests stretch for millions of kilometers. In the ground far below the treetops are ancient, long-hidden remains of human habitation. They are preserved in the form of ditches, paths and wells, sometimes forming geometric patterns. Known as earthworks, they were built by the indigenous peoples who lived in the area approximately 500 to 1,500 years ago.

Such buildings are associated with ceremonial and defensive purposes, and they provide insight into what ancient settlements may have looked like.

Many Amazonian earthworks, dating back to before the arrival of European colonizers, have been discovered in deforested areas. But researchers suspected that there were even more such places, which today are almost invisible and hidden under thick foliage. To find them, scientists analyzed scans of the area taken using a remote sensing technique called light detection and ranging, or lidar. This method probes the ground with laser pulses, measuring changes in distances to the ground. When the light is reflected, it is combined with other data to create 3D maps of the landscape below, the study’s lead author wrote in the journal Science.

The study authors also analyzed data collected from decades of recording tree species throughout the Amazon, looking for signs of species that were used and domesticated by pre-Columbian peoples. The new study brings together 160 researchers and 80 years of data, combining lidar and Amazon tree distribution records to predict where as-yet-unknown structures of pre-Columbian peoples might be found.