Large low-shear-velocity provinces

Large low-shear-velocity provinces (LLSVPs), also called large low-velocity provinces (LLVPs) or superplumes, are characteristic structures of parts of the lowermost mantle, the region surrounding the outer core deep inside the Earth.^[2] These provinces are characterized by slow shear wave velocities and were discovered by seismic tomography of deep Earth. There are two main provinces: the African LLSVP and the Pacific LLSVP, both extending laterally for thousands of kilometers and possibly up to 1,000 kilometres vertically from the core–mantle boundary. These have been named Tuzo and Jason respectively, after Tuzo Wilson and W. Jason Morgan, two geologists acclaimed in the field of plate tectonics.^[3] The Pacific LLSVP is 3,000 kilometers (1,900 miles) across and underlies four hotspots on Earth's crust that suggest multiple mantle plumes underneath.^[4] These zones represent around 8% of the volume of the mantle, or 6% of the entire Earth.^[1]

Other names for LLSVPs and their superstructures include superswells, superplumes, thermo-chemical piles, or hidden reservoirs, mostly describing their proposed geodynamical or geochemical effects. For example, the name "thermo-chemical pile" interprets LLSVPs as lower-mantle piles of thermally hot and/or chemically distinct material. LLSVPs are still relatively mysterious, and many questions remain about their nature, origin, and geodynamic effects.^[5]