An ocean that opened up in what is now Mongolia 410 million years ago was created by a hot upwelling of rock known as a mantle plume.

Boiling rocks from Earth's crust tore an ocean into Mongolia 410 million years ago

Source: space
Source Link: https://www.space.com/boiling-rocks-from-earth-crust-tore-ocean-into-mongolia-410-million-years-ago