A section of Earth’s mantle beneath Oman appears to be unusually warm, according to researchers who believe it may be the first known “ghost plume”. A ghost plume is a column of hot rock emanating from the lower mantle without volcanic activity on the surface.
Mantle plumes are upwellings of molten rock that transmit heat from the core-mantle boundary to the Earth’s surface, often located near the edges of tectonic plates. Examples include Yellowstone and the East African rift, where volcanism is present. However, Oman lacks volcanic clues, making its discovery a significant find.
Source: https://www.newscientist.com/article/2484146-earths-mantle-may-have-hidden-plumes-venting-heat-from-its-core