LLSVPs

Large low-shear-velocity provinces, often abbreviated as LLSVPs, are two massive regions of unusually slow seismic wave speeds located deep within the Earth's lower mantle. These structures are situated directly beneath the Pacific Ocean and the African continent. Seismic tomography, a technique that uses earthquake waves to image the Earth's interior, reveals that seismic waves travel more slowly through these areas compared to the surrounding mantle. This slower wave speed is interpreted as an indicator of higher temperature and/or a different chemical composition.

The exact nature and origin of LLSVPs remain a subject of active scientific research and debate. One prominent hypothesis suggests they are remnants of ancient subducted oceanic plates that have accumulated over billions of years. Another theory proposes they represent primordial material from the Earth's formation that has not yet fully mixed with the rest of the mantle. Their sheer size and longevity suggest they play a significant role in mantle convection, the slow churning of rock that drives plate tectonics and volcanic activity at the surface. The interaction between LLSVPs and shallower mantle processes is thought to influence the location and intensity of mantle plumes, which are columns of hot rock rising from the deep mantle. Understanding LLSVPs is crucial for comprehending the Earth's thermal and chemical evolution.