Location and Orbit
Surface to Core
References & Links
Earth: Surface to Core
Facts in Brief
Lithosphere, Mantle, and Core
The crust is characterized as dark, rocky, and rigid and is further broken down into the upper and lower crusts. The sialic, or upper crust, is what makes up the continents. They are mostly igneous and sedimentary. The simatic, or lower crust, forms the ocean floors. Beneath the crust is denser material composed of iron and magnesium silicates. This region is known as the upper mantle and accounts for 10.3% of Earth's total mass. It is separated from the crust and lower mantle by the Moho and asthenosphere, respectively. The Moho averages 32 km under the continents and a meager 8 km in depth under the oceans. The asthenosphere is noticeably thicker at several hundred kilometers in depth. It is mostly deformable rock.
As expected, the material closer to the Earth's core is more closely packed, or dense. The lower mantle is the layer directly beneath the lithosphere, which comprises a whopping 49.2% of the Earth's mass. It is found 650 to 2,890 km beneath the surface and is a mixture of several oxides. These include magnesium, silicon, and iron.
The core is the central spherical region within the Earth and is further divided into the outer and inner cores. The outer core has a shell 2,890 to 5,510 km beneath the surface and accounts for 30.8% of the planet's mass. Studies indicate that it is rigid with both peaks and depressions. The solid inner core has radius 1,275 km and is 1.7% of the Earth's mass. The inner core's temperature may be a scorching 6,650 degrees Celsius. The entire core is mostly iron with a small percentage of nickel and other elements. The internal heat generated here is possibly energy emitted from radioactive decay of uranium and other elements found in the core. Convection currents within the mantle transfer this heat to the surface. These currents may also be the source of continental drift.