subsurface

Subsurface refers to the part of a body or environment that lies beneath its surface. It contrasts with the surface layer that is directly exposed to weather, contact, or observation.

In Earth science, the subsurface includes the crust and, in broader sense, the upper mantle beneath the surface. It contains soil, rocks, groundwater, and other fluids and is shaped by processes such as deformation, mineral deposition, and fluid flow. Subsurface investigations employ boreholes, seismic reflection, electrical resistivity, and gravity surveys to map structure and to locate resources or assess geohazards.

In hydrology and environmental engineering, subsurface hydrology studies groundwater movement through soils and rock, the vadose and saturated zones, aquifers, and the transport of contaminants. Groundwater is a major resource and a pathway for pollution, necessitating monitoring and remediation strategies.

In marine science, the term describes water or sediments beneath the surface layer of the ocean, including the thermocline and deeper zones. Subsurface ocean conditions influence biogeochemical cycles, heat transport, and submarine ecosystems.

In materials science and computer graphics, subsurface can describe processes internal to a translucent material. Subsurface scattering refers to light penetrating a material and scattering within it before exiting, an effect important in realism for plastics, skin, and jade.

In engineering, understanding the subsurface is essential for construction, tunneling, and underground utilities, as soil and rock properties govern stability, drainage, and risk management.