Nearsurface

Near-surface is a term used across the geosciences and related fields to describe the region close to the planetary surface where surface processes and conditions strongly influence properties and behavior. Depending on the discipline, the near-surface can refer to the uppermost crustal layers, the lowest part of the atmosphere, or the upper ocean where exchange with the surface is most active. It denotes a zone where properties change rapidly with small depth or height and where interactions with the surface dominate system dynamics.

In geology and geotechnical engineering, the near-surface encompasses weathered rock and soils above bedrock, typically extending from the surface to a depth of several meters to tens of meters. Its physical properties—grainsize distribution, density, porosity, shear strength, and hydraulic conductivity—control foundations, slope stability, and subsurface construction. Investigations rely on boreholes, cone penetration tests, excavation, and geophysical methods such as seismic refraction and reflection, electrical resistivity tomography, and ground-penetrating radar.

In the atmosphere, the near-surface layer is the lowest portion of the air column, commonly extending from the ground to tens or a few hundred meters above it. This planetary boundary layer is strongly influenced by surface roughness, heat and moisture fluxes, and diurnal cycles, affecting wind, temperature profiles, and pollutant dispersion. In the ocean, the near-surface or upper mixed layer includes the upper several meters to tens of meters, where wind-driven mixing, light penetration, and salinity and temperature gradients govern gas exchange and surface ecology.

Measurement and modelling of near-surface regions integrate multidisciplinary approaches and are crucial for engineering safety, climate studies, contaminant transport, and resource management. Depth limits and definitions are context-dependent and should be specified for each study.