What Are 'Sinkites and Floatites'? Here's How North Sea’s Mysterious Giant Structures Challenge Earth’s Geological Rules

For years, giant sand mounds hidden beneath the North Sea have baffled scientists. New research now reveals that these massive structures were formed by a previously unknown geological process occurring on an unprecedented scale.

A study published on June 21 in Communications Earth and Environment outlines the discovery, made using seismic data and rock samples from the northern North Sea, off Norway’s coast. The findings show that these miles-wide mounds are actually younger, denser sands that sank into older, lighter "ooze," a soft sediment largely composed of ancient microorganism remains. As the sand sank, it displaced and lifted the ooze above, creating mounds deep beneath the seabed.

Origin of Buried Mounds

For years, scientists speculated about the origin of these buried mounds, suggesting theories ranging from landslide debris to upwardly forced sandstone or mud extrusions through brittle rock. However, this new study offers a clearer explanation. By analyzing 3D seismic imagery and rock samples, researchers observed that the sand mounds were chemically similar to nearby younger sands and were connected to them via fractures in the rock, a strong indicator that the mounds sank from above.

This phenomenon disrupts the conventional order of the geological record, where older layers typically lie beneath younger ones. Instead, the denser sands pushed down through the less dense ooze, flipping the expected pattern.

"This discovery reveals a geological process we haven't seen before on this scale," said study co-author Mads Huuse, a geophysicist at the University of Manchester, as per a report. "What we've found are structures where dense sand has sunk into lighter sediments that floated to the top of the sand, effectively flipping the conventional layers we'd expect to see and creating huge mounds beneath the sea," he added.

What Compelled Sand to Behave Like Fluid

The team believes that earthquakes or shifts in pressure may have caused the sand to behave like a fluid, allowing it to slip through fractures and displace the ooze. They coined the term “sinkites” for these sunken sand mounds and “floatites” for the uplifted ooze rafts.

Beyond solving a long-standing mystery, the discovery has implications for future carbon capture and storage. Understanding how such geological structures form could help scientists better evaluate underground reservoirs, sealing capabilities, and fluid migration, all crucial factors for securely storing carbon dioxide.

Also read: Guess Which Favourite Sweet Shubhanshu Shukla Shared with His Ax-4 Crew?