Loess Formation and Soil Development

Loess deposits are extensive blankets of wind-blown silt that accumulate downwind of glacial outwash plains, deserts and river terraces. Grain-size distributions and mineralogical composition reflect source area dynamics, transport pathways and depositional energy. Initial packing of fresh loess involves rearrangement of particles into a coarse/fine fabric that imparts inherent cohesion. During soil development, biotic activity creates biopores, while chemical reactions, such as carbonate or gypsum precipitation, modify pore networks and cement grain contacts. Palaeosols preserved within loess sequences record intervals of stability, bioturbation and pedogenic horizonation. Key processes in these horizons include illuviation of clay minerals, organic matter accumulation and redox transformations of iron oxides. The high porosity and connectivity of loess-derived soils facilitate rapid infiltration, but also underlie collapsibility and slope instability when saturated. Globally, loess landscapes support productive agriculture, serve as archives of Quaternary climate change and pose geohazard challenges on slopes and embankments.

Research from Nature Portfolio

Recent studies have employed mechanical X-ray computed tomography and controlled infiltration experiments to characterise undisturbed loess structure before and after water ingress. Findings demonstrate that infiltration preferentially removes fine silt, coarsening the residual fabric and shifting pore shapes from spherical to angular and dendritic forms. Overall porosity increases by about 20 %, driven by expansion of meso- and macropore fractions, while network connectivity rises from below 60 % to over 90 %. These alterations amplify seepage channels, explaining enhanced water filtration, fine-particle migration and the initiation of collapsible behaviour and slope failure under hydrostatic and saline influences.

Loess Formation and Soil Development publication trend

The graph below shows the total number of articles in loess formation and soil development across all publications each year (not limited to Nature Index journals).

Technical terms

Loess: A predominantly silt-sized, wind-deposited sediment forming extensive blankets and serving as fertile soil parent material.

Palaeosol: A fossil soil horizon preserved within sedimentary sequences, recording past surface stability and environmental conditions.

Porosity: The volume fraction of void spaces in a sediment or soil, classified into micropores (<2 nm), mesopores (2–50 nm) and macropores (>50 nm), governing water and air fluxes.

Illuviation: The downward translocation and accumulation of clay, iron or organic matter from upper to lower soil horizons.

Aeolian deposition: The process by which wind transports and deposits fine sediment, responsible for the formation of loess.

References

1. Evolution of soil porosity in loess-palaeosol sequences of the Ebro Valley, NE Iberia. Catena (2023).
2. The structural evolution of undisturbed loess due to water infiltration. Scientific Reports (2024).
3. Clay mineralogy fingerprinting of loess-mantled soils on different underlying substrates in the south-western Poland. Catena (2022).