Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01×10²⁴ kg and makes up 67% of the mass of Earth. It has a thickness of 2,900 kilometers making up about 46% of Earth's radius and 84% of Earth's volume. It is predominantly solid but, on geologic time scales, it behaves as a viscous fluid, sometimes described as having the consistency of caramel. Partial melting of the mantle at mid-ocean ridges produces oceanic crust, and partial melting of the mantle at subduction zones produces continental crust.