Darvaza water crater, Turkmenistan

The Darvaza Water Crater is a collapsed sinkhole filled with water located roughly 24 km south of the famous Darvaza Gas Crater ("Gates of Hell") in the Karakum Desert of Turkmenistan. Turkmenistan is in Central Asia. Darvaza is also known as Derweze. It is roughly in the middle of the country - see red pin -

Google Earth image showing the water crater -

The crater is approximately 50 m in diameter and 15 m deep. It probably formed after a cavern collapse which may be related to prospecting and drilling for natural gas. The Soviet Union were drilling in the 1970s.  

The water is a turquoise green colour, due to minerals and sulphur content. Bubbles of gas can be seen. According to this article on Researchgate the water crater seems to be from the Neogene period, 23 million and 2.6 million years ago. [Although I am not sure if it falls within the green area, which is the older Paleogene period, 66 million to 23 million years ago.]  ResearchGate geological map -

The layers of rock are horizontal.