Explained: Discovery of a primitive forest at the bottom of a giant sinkhole in China

What is the News?

A cave exploration team has discovered an ancient forest at the bottom of a giant karst sinkhole in Leye County in Guangxi Zhuang Autonomous Region, China.

About the new findings

The sinkhole volume exceeds 5 million cubic meters. Given these dimensions, the sinkhole can be categorised as a large sinkhole. In Mandarin, giant sinkholes are called Tiankeng or “heavenly pit”.

The sinkhole has three big caves in the walls and its bottom has a well-preserved primitive forest with trees nearly 40 metres high.

What are sinkholes?

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.

Formation: Sinkholes can be formed due to natural processes or human activity.

Natural process: Typically, sinkholes form in areas of “karst” terrains, where the rock below the surface of the Earth can be easily dissolved by groundwater. This process is a slow and gradual one and can sometimes take hundreds or thousands of years.

Human activities: This can happen due to broken land drains, water mains and sewerage pipes, and diversion of surface water, among other reasons.

Note: According to the United States Geological Survey (USGS), karst terrain is created from the dissolution of soluble rocks, mostly limestone and dolomite. Further, they are characterised by distinctive landforms such as caves, sinkholes and springs.

Few prominent sink holes around the world:

About 20 percent of the US is made up of karst landscapes. The largest sinkhole in the US is called the “Golly Hole”, which collapsed suddenly in 1972 and is over 325 ft long, 300 ft wide and 120 ft deep.

As per NASA, karst geology covers about 13 per cent of eastern and southeastern Asia. Other sinkhole-prone areas around the world include Mexico, parts of Italy and Russia.

Source: The post is based on the article “Explained: What is retinoblastoma, the common eye cancer in children? published in Indian Express on 24th May 2022.