Land subsidence

Definition

Land subsidence is the gradual sinking or settling of the Earth's surface due to various factors such as natural processes and human activities. This phenomenon can significantly impact landscapes, particularly in areas with karst topography, where the dissolution of soluble rocks like limestone leads to the formation of caves and sinkholes, making the ground more susceptible to collapse.

5 Must Know Facts For Your Next Test

1. Land subsidence can occur due to the extraction of groundwater, oil, or natural gas, leading to a decrease in pore pressure and ground level.
2. In regions with karst formations, land subsidence can be accelerated by the dissolution of limestone, which weakens the ground and creates voids beneath the surface.
3. Areas with extensive irrigation can experience land subsidence if groundwater is extracted faster than it can be replenished, causing the ground to compact.
4. Land subsidence can lead to significant problems such as increased flooding risk, damage to infrastructure, and altered drainage patterns.
5. Monitoring and management practices are essential in areas prone to land subsidence to mitigate its effects on both natural landscapes and human development.

Review Questions

• How does land subsidence impact karst topography and what are some potential consequences?
  • Land subsidence has a direct effect on karst topography by exacerbating the formation of sinkholes and enlarging existing voids beneath the surface. As soluble rocks like limestone dissolve over time, any additional pressure or removal of groundwater can cause further collapse. This can lead to serious consequences such as property damage, disruption of transportation networks, and increased vulnerability to flooding in affected areas.
• What role does groundwater extraction play in land subsidence and how does it relate to karst landscapes?
  • Groundwater extraction significantly contributes to land subsidence by reducing the water pressure that supports soil and rock layers. In karst landscapes, this process is particularly problematic because the removal of groundwater can accelerate the dissolution of limestone, creating larger cavities. As these cavities grow and support is removed, it increases the likelihood of surface collapse and sinkhole formation.
• Evaluate the long-term implications of land subsidence on urban areas situated over karst topography.
  • The long-term implications of land subsidence on urban areas located over karst topography can be severe. Increased frequency of sinkholes can threaten buildings and infrastructure, leading to costly repairs and safety hazards. Additionally, the shifting ground can disrupt utilities and drainage systems, resulting in higher maintenance costs for municipalities. Urban planners must consider these factors when designing sustainable development strategies in these regions to reduce risks associated with land subsidence.

Related terms

karst topography: A landscape formed from the dissolution of soluble rocks, characterized by features such as sinkholes, caves, and underground drainage systems.

sinkhole:

A depression or hole in the ground caused by the collapse of a surface layer, often occurring in regions with karst topography.

groundwater depletion: The reduction of groundwater levels due to excessive extraction for agricultural, industrial, or urban use, contributing to land subsidence.