Why in news? Uttarakhand’s Joshimath has witnessed a rapid subsidence of nearly 5.4 cm in the past 12 days as report  released by the National Remote Sensing Centre of the Indian Space Research Organisation

Highlights

• The pictures were released by Cartosat-2S satellite.
• Subsidence zone resembling a generic landslide shape was identified as tapered top and fanning out at base located near Joshimath-Auli road at a height of 2,180 metres.

What is land subsidence?

• According to the National Oceanic and Atmospheric Administration (NOAA), subsidence is the “sinking of the ground because of underground material movement”.
• 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 is the main reason for subsidence in Joshimath ?

• The town is in Zone V, denoting highest risk, in India’s seismic zonation scheme.
• This area’s geological setting, together with the unplanned and rampant construction, unplanned construction, over-population, obstruction of the natural flow of water and hydel power activities.
• A report published by the Uttarakhand State Disaster Management Authority (USDMA) in 2022 said that floods in June 2013 and February 2021 heightened erosion in the area and worsened the subsidence and vulnerability to landslides
• Joshimath city has been built on an ancient landslide material meaning it rests on a deposit of sand and stone, not rock, which doesn’t have high load-bearing capacity. This makes the area extremely vulnerable to ever-burgeoning infrastructure and population.
• 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.

About Cartosat-2

• It is an Earth observation satellite in a Sun-synchronous orbit and the second of the Cartosat series of satellites.
• Developed by: Indian Space Research Organisation
• Rocket: Polar Satellite Launch Vehicle

Uses: Satellite will be used for detailed mapping and other cartographic applications at cadastral level, urban and rural infrastructure development and management, as well as applications in Land information system (LIS) and Geographic information system (GIS).