6 people were killed and 10 are believed to be missing after a bus and some pedestrians were swallowed by a sinkhole in China’s Xining city on January 13, 2020.
- Sinkholes are depressions formed in the ground when layers of the Earth’s surface start collapsing into caverns.
- They can occur suddenly and without warning, because the land under the surface of the Earth can stay intact for a period of time until the spaces get too big.
- Their formation can be caused due to natural processes or human activity.
- Typically, sinkholes form in areas of “karst” terrains, where the rock below the surface of the Earth can be easily dissolved by groundwater.
- Essentially, this means that when rainwater seeps into the ground, the rock below the surface of the Earth starts dissolving, leading to the creation of spaces. This process is a slow and gradual one and can sometimes take hundreds or thousands of years.
- Such terrains are most commonly found in areas with limestone, gypsum or carbonate rocks. The formation of karst terrains is dependent on geology and climate.
- Sinkholes can also be formed due to human activity. This can happen due to broken land drains, water mains and sewerage pipes, increased rainfall, storm events, underlying limestone and diverted surface water, among other reasons.
Source : Indian Express