A vast expanse of approximately 200 million low earth cones covers an 88,000-square-mile region in northeastern Brazil. Visible via satellite imagery, this evenly spaced grid system spans an area roughly the size of Great Britain.
A Continental Grid Built by Insects
These massive subterranean networks and surface spoil heaps represent one of the largest earthworks ever constructed by any animal. They were created by insects measuring only half an inch long over a timespan reaching back nearly four millennia.
Dimensions That Rival the Pyramids
The surface structures, locally known as murundus, present an unusual pattern across the dry, thorny plains of eastern Brazil. Individual cones measure about 30 feet wide at the base and stand between 6 and 13 feet tall, comparable in size to a small backyard shed built of packed earth.
The entire field occupies a footprint close to that of Minnesota. It contains roughly 2.4 cubic miles of excavated earth—an amount sufficient to fill about 4,000 Great Pyramids.
Spoil Heaps, Not Nests
Satellite observations reveal a faint, dimpled texture across the landscape, with cones separated by a regular rhythm of about 60 feet. Despite their impressive dimensions, these piles are not nests.
Each cone functions as a spoil heap where termites pushed out soil excavated from below, leaving the true colony structure hidden entirely underground.
Decades of Observation and Tunnels
Environmentalist Roy Funch has studied the murundus for 30 years and has observed termites building the mounds directly. As worker termites forage for fallen leaves, they construct vertical upward tubes without top openings, featuring only small side-holes around the rim to cast out excavated soil.
The primary driver behind this monumental excavation is sustenance. The builder species feeds on dead leaves dropped by the dry caatinga scrub. To harvest this seasonal windfall safely without crossing dangerous open ground, the insects developed an extensive subterranean tunnel network linking the mounds.
Dating the Ancient Construction
Colleague Paul Hanson conducted research analyzing sand grains from the center of 11 different mounds, which determines when the grains were last exposed to sunlight.
This testing established that the youngest mound was 690 years old, while the oldest began construction approximately 3,820 years ago.
Unified Colonies Across Vast Territories
The vast spacing of the mounds initially suggested millions of isolated colonies, but Funch’s research challenges that assumption. By collecting soldiers from beneath different mounds and testing whether they would fight, researchers discovered that a single colony actually inhabits and maintains multiple mounds simultaneously across an expansive territory.
Many of these ancient structures remain operational. Numerous cones continue to house active colonies of termites digging below the surface, extending a subterranean engineering project that began centuries before the founding of many ancient cities.
