Subsidence

Subsidence is the downward movement of the Earth's surface relative to a stable reference frame, resulting in a permanent lowering of the ground surface. It can occur gradually or abruptly and is caused by a range of natural and human factors.

Natural causes include tectonic subsidence, which occurs as rocks deform or relax over time, and the compaction and settlement of sedimentary layers as they are buried and lose pore pressure. In karst regions, dissolution of soluble rocks can create underground voids that lead to surface collapse. Permafrost thaw and related processes can also contribute in some areas.

Human activities are a major driver in many regions. Groundwater pumping, oil and gas extraction, mining, and underground construction can remove fluids or create voids, leading to consolidation and subsidence. Drainage of wetlands and inappropriate loading from buildings and infrastructure can further compact soils, especially in soft clays and peat.

Mechanisms typically involve consolidation of unconsolidated soils as pore pressure declines, mechanical collapse of cavities in karst terrain, or long-term soil compaction under load. The result is permanent surface lowering and, often, ground cracks.

Effects include structural damage to buildings, roads, and pipelines; cracked pavements and foundations; changes in drainage patterns; and increased flood risk, particularly in coastal or low-lying areas.

Monitoring and mitigation rely on survey methods such as leveling, GPS, InSAR, and LiDAR, combined with groundwater management, controlled recharge, foundation reinforcement, and careful urban planning. Notable subsidence cases include Mexico City and other regions where heavy groundwater withdrawal has accelerated ground lowering.