LAND SUBSIDENCE

Disclaimer: Copyright infringement not intended.

Context:

• Almost a week after cracks appeared in many roads and hundreds of houses of Joshimath, Uttarakhand, authorities declared it a landslide and subsidence-hit zone.

What is Land Subsidence?

• Land subsidence is a gradual settling or sudden sinking of the Earth's surface due to the removal or displacement of subsurface earth materials. The principal causes include: aquifer-system compaction associated with groundwater withdrawals. drainage of organic soils.
• It can happen for a host of reasons, man-made or natural, such as the removal of water, oil, or natural resources, along with mining activities. Earthquakes, soil erosion, and soil compaction are also some of the well-known causes of subsidence.

What can be the reasons behind Joshimath’s subsidence?

• The exact reason behind Joshimath land subsidence is still unknown but experts suggest that the incident might have occurred because of unplanned construction, over-population, obstruction of the natural flow of water and hydel power activities.
• Not only this, the area is a seismic zone, which makes it prone to frequent earthquakes.
• As per the reports, residents have also blamed NTPC’s Tapovan Vishnugad Hydro Power Project for the incident. They allege that the tunnel had water seepage “from a punctured aquifer, leading to the drying of water sources in Joshimath. Experts suggest that it could be one of the reasons for the collapse of the area.
• Reports have also pointed out that subsidence in Joshimath might have been triggered by the reactivation of a geographic fault — defined as a fracture or zone of fractures between two blocks of rock — where the Indian Plate has pushed under the Eurasian Plate along the Himalayas.

https://indianexpress.com/article/explained/explained-climate/joshimath-what-is-land-subsidence-and-why-does-it-happen-8370817/