Subsidence and Uplift

Additional scientific description

Subsidence and uplift can be localized associated with near-surface, relatively shallow crustal, or human-generated processes such as mining or tunnelling, consolidation, permafrost loss (permafrost thaw - HIP EN0305), sinkholes, karst collapse, groundwater fluctuations and moisture changes on expansive soils (BGS, 2020). Several crustal scale processes drive subsidence and uplift that tend to be regional or global in scale. Crustal movements occur in response to several different mechanisms, including tectonics, changes to surface loading caused by glacier and ice sheet changes (glacial isostatic adjustment), sediment transport (erosion and accretion), water loading (hydro-isostatic adjustment) and mantle flow (upwelling and downwelling). These operate over different temporal and spatial scales. Tectonic uplift and subsidence are the distributed persistent vertical ground deformations (warping) that result from displacement on a dipping (inclined) fault (Styron, 2019). Earthquake surface ruptures and fissures are localized ground displacements that develop during and immediately after an earthquake, where the fault which hosted the earthquake intersects the Earth's surface. Surface ruptures represent the upward continuation of fault slip at depth, while fissures are smaller displacements, or more distributed deformation in and around the rupture area (PNSN, no date).

Ground-level rise is commonly associated with plate convergence, such as the Himalayas where the Eurasian and Indian plates converge (USGS, 2015). Subsidence can also be associated with plates moving apart, for example the Ethiopian rift valley. The relative motion of the crust on either side of faulting associated with earthquakes results in persistent or permanent deformation of the Earth's surface. Surface ruptures, fissures, and uplift and subsidence are all manifestations of this longer-term deformation, and although less dramatic, may all pose hazards during and after earthquakes.

Volcanic uplift and subsidence are deformations of the ground associated with volcanic unrest and eruptions (Dzurisin, 2007). During unrest at volcanoes, ground deformation is usually on the order of millimetres to centimetres per year and it is not uncommon for the centre of uplift to move (Di Vito et al., 2016). Some caldera volcanoes may show deformation rates of metres per year and some calderas show very long-term ground deformation ('resurgence') which may cause uplift of up to 1 km over hundreds to thousands of years (Acocella, 2019). The Campi Flegrei caldera (Italy) is 12 km across and lies under the outskirts of Naples. At least 5 m of uplift was observed in the hours to days before the last eruption at Campi Flegrei in 1538 (from Monte Nuovo) resulting in the seaward retreat of the shoreline (Acocella, 2019 and references therein). Campi Flegrei experienced major uplifts in 1950-1951, 1969-1972 and 1982-1984 which cumulatively raised the town of Pozzuoli by 4 m. Pozzuoli experienced a maximum of 1.8 m of uplift during unrest in 1982-1984 (Acocella, 2019 and references therein).

Erosional/depositional-isostatic deformation occurs in response to the stress changes induced by changing sediment load (erosion/deposition). Changes to terrestrial water loads may have anthropogenic or climatic drivers and may be seasonal. Changes to ocean water heights and the resulting crustal response have a long-term component related to global glacial isostatic adjustment, as well as important seasonal and climate cycles (e.g., El Nino/Southern Oscillation) contributions.

In the marine coastal environment, sediment transport and global sea-level fluctuations drive shore-line change. Sediment loading can exacerbate regional subsidence, thereby increasing relative sea-level. Glacial isostatic adjustment crustal motion (both uplift and subsidence) arises from the delayed response to past ice mass changes, where the Earth's mantle responds as a viscous fluid (e.g., Simon et al., 2016), and to the present-day, instantaneous elastic response to present-day ice mass change (e.g., Jiang et al., 2010) due to changing surface ice mass loads. In coastal areas where accelerated glacial wasting has been reported, the elastic component of glacial isostatic adjustment results in a relative rise in ground level and concomitant fall in relative sea-level.

Local-to-regional scale subsidence and uplift resulting from changes in groundwater or porewater pressures occur in areas that are underlain by compressible and elastically deforming soils responding to groundwater fluctuations. Cohesive soils commonly exhibit seasonal changes in moisture content that can be associated with local subsidence or uplift (e.g., Simic et al., 2015). Anthropogenic impacts on ground level, primarily result from dewatering for potable supply or for subsurface mining or engineering (Cigna et al., 2017).

Metrics and numeric limits

Global sea-level rise was of the order of 1.3 mm/yr early in the 20th century (1901 to 1971) but has recently increased to about 3.7 mm/yr (2006 to 2018) (IPCC, 2021). Relative sea-level change varies considerably, depending on vertical land motion and other factors. Where the land is subsiding due to compaction (which can arise from natural causes or from groundwater pumping) isostatic subsidence or mantle downwelling, relative sea-level may be much larger than the global values, while in regions that are rapidly uplifting (e.g., Iceland, Hudson Bay (Canada), Fennoscandia, Glacier Bay (Alaska, USA), Patagonia (Chile)), relative sea-level has been falling and is projected to continue to fall. High rates of uplift in Iceland (25-29 mm/yr) have been related to glacial isostatic adjustment (Schmidt et al., 2013). It should be noted that coastal regions may also subside because of human activities (e.g. Bateson et al. 2023).

The size and spatial extent of surface rupture, fissures and uplift/subsidence associated with earthquakes depends on the type, magnitude and depth of the earthquake as well as the distance from the earthquake (Biasi et al., 2006).

Rates of uplift in the Himalayas are reported to be in the order of 1 cm/yr (USGS, 2015). Tectonic uplift and subsidence are generally as large or larger than the displacement of the surface rupture; moderate to large earthquakes in the crust that do not rupture to the surface will still broadly warp the region. The magnitude of the displacement will decrease with increasing distance from the earthquake, but in the case of ruptures on inclined faults such as subduction zones (rather than vertical strike-slip faults) uplift or subsidence of at least 1 m may extend for more than 200 km from the fault trace for the largest earthquakes (Styron, 2019). Both effects will extend along the length of the seismically active fault, a distance of a few kilometres for Magnitude 6 earthquakes to more than 1000 km for Magnitude 9 earthquakes.

Ground-level response to groundwater dewatering is a global issue. Subsidence values of up to 53 mm/yr have been determined using InSAR monitoring of Kabul (Meldebekova, 2020) and in Indonesia (Rygus et al., 2025).