At https://phys.org/news/2024-05-earth-mysterious-d-layer-relic.html … a relic of ancient oceans and planetary collisions, we are told – earth’s mysterious D layer. It is located roughly 3000 km deep inside the earth. It sits just above the boundary between the outer core and the Mantle. Hence, this is at the bottom of the Mantle – and nowhere near the crust. It is actually only a suggestion that the D layer may have originated from earth’s earliest time. The idea relies on a giant impact. A planet sized body that struck earth and created a magma ocean in the aftermath. All modelled by computer buffs. The D layer is a leftover, we are told, from the impact.
Interestingly, Dr Jie Deng realises there was a lot of water within the magma ocean. The origin of the water is subject to dispute. Several theories have taken on a life of their own. Deng suggests water could have concentrated towards the bottom of the magma ocean as it cooled. Later, the magma above the core would have shed its water, too. Indeed, water volumes may have been comparable to the amount found in modern oceans. A lot of water – inside the earth. Are several mysteries about to be solved?
This leads into another story at https://www.livescience.com/planet-earth/scientists-just-discovered-an-enormous-lithium-reservoir-under-pennsylvania …. and if fracking had not occurred the lithium would never have been found. In fact, it was found in waste water from a Pennsylvania fracking site. Presumably the lithium was located originally in the Marcellus shale deposit.
However, the sink hole story can be found at https://www.livescience.com/planet-earth/geology/chinas-heavenly-pits-the-giant-sinkholes-that-have-ancient-forests-growing-within … giant sink holes that have ancient forests growing within them. These exist in China’s karst landscape, located in the SW region of the country. Dozens of enormous sink holes – known as ‘heavenly pits’ – but where do the heavens come into this? They look as if they were punched out of the landscape. However, most were unknown until recently as they are found in jagged mountain scenery, surrounded by lush forest growth.