diapir

1. (geology) An intrusion of a ductile rock into an overburden.Examples: ""If a diapir is outside an established plume it rises at a much slower rate," Loper says."; "This final stage is characterized by the cooling and resolidification of the partially molten diapir within the mantle, slow subsidence at the surface, and greatly diminished rates of crustal addition."; "Deeply buried deposits of sea-salt dome upwards and pass through the overlying strata, as a kind of intrusive lobe, eventually emerging at the surface – the rising tongue is called a diapir."