Geological scars reveal the liquid history of Earth's ancient, unsolidified landscapes

Nature · Published 3 October 2026 Swipe more like this →

In short: Before sediment turns to stone, it behaves like a liquid. When rapid deposition or seismic tremors strike these loose layers, they warp into bizarre, complex shapes. These soft-sediment deformation structures act as frozen records of ancient environments, from deep-water basins to the tracks left by prehistoric animals in saturated mud.

Soft-sediment deformation occurs during the initial stages of consolidation, requiring the material to remain in a liquid-like, unsolidified state. These formations typically emerge in environments characterized by high deposition rates, such as river deltas, shallow-marine areas, or deep-water basins subjected to turbidity currents. Because these settings allow sediment to pack loosely, they become prime candidates for structural transformation shortly after deposition.

The variety of these structures is vast, often categorized by their specific mechanical origins. Flame structures and load casts, for instance, form when denser sand is deposited onto less dense mud, creating an interplay of upward-reaching mud fingers and downward-descending sand knobs. Other features, such as dish and pillar structures, are direct results of dewatering, where escaping fluid leaves behind distinct, vertical, or dish-shaped geometries within siltstones and sandstones. Convolute bedding, meanwhile, manifests as complex, crumpled laminations that can range from a few centimeters to several meters in thickness.

Beyond simple depositional shifts, these structures serve as vital geological indicators. Sole markings on the underside of sedimentary rocks provide researchers with a way to determine the flow direction of ancient currents. Similarly, seismites—beds disturbed by earthquake waves—help geologists interpret the seismic history of a region. Even biological activity leaves a mark; vertebrate tracks pressed into water-saturated sediment can create deformations that mimic the patterns of convolute bedding or seismic activity. By studying these features, scientists can reconstruct the dynamic, shifting conditions of the Earth's surface long before the layers were permanently hardened into the rock record.

While these structures are widespread, their classification remains nuanced. Lowe (1975) grouped many of these features under the umbrella of water-escape structures, highlighting the role of fluid movement in their creation. Whether through the displacement of sediment on steep slopes, as seen in slump structures, or the violent shaking of an earthquake, these formations capture a fleeting moment in geological time when the ground beneath our feet was still fluid and malleable.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Sedimentary structures are the three-dimensional physical fingerprints of ancient environments preserved in rock.
• How ripples and dunes reveal the hidden history of ancient river flows
• How a slowing current writes history in the earth's crust
• Ancient mudcracks act as a geological compass to reveal which way was once up.
• How moving water carves the earth into ripples, dunes, and complex patterns
• Soil is not just dirt; it is a complex chemical reactor managing our waste.
• Beneath our feet, massive tectonic plates are shifting in slow motion without a sound.
• Why the six-inch layer of soil beneath our feet is our greatest natural asset
• Beneath Canada's North lies a 4-billion-year-old fragment of Earth's earliest continental crust.
• Soil erosion is a natural sculptor, but human activity has accelerated it twenty-eightfold.
• Why do tectonic plates move? It is not a conveyor belt beneath your feet.
• The unseen allies driving 95 per cent of our food production

More in Geology · More in Nature · Latest · A–Z · All topics