Earth is layered like an onion, with a thin outer crust, a thick viscous mantle, a fluid outer core and a solid inner core. Within the mantle, there are two massive blob-like structures, roughly on opposite sides of the planet. The blobs, more formally referred to as Large Low-Shear-Velocity Provinces (LLSVPs), are each the size of a continent and 100 times taller than Mt. Everest. One is under the African continent, while the other is under the Pacific Ocean.