How deep does Earth's outer core begin beneath the surface?
Earth's outer core begins approximately 2,890 kilometers beneath the surface. Seismology reveals that seismic shear-waves do not pass through this layer to confirm its fluid nature.
Earth's outer core begins approximately 2,890 kilometers beneath the surface. Seismology reveals that seismic shear-waves do not pass through this layer to confirm its fluid nature.
Eddy currents flow within the nickel-iron fluid of the outer core to generate Earth's magnetic field through dynamo action. The average magnetic field strength reaches 2.5 millitesla inside the core and is fifty times stronger than the magnetic field measured at the surface.
Scientists propose that light elements with low atomic numbers compose part of the structure alongside iron and nickel. Estimates indicate the outer core contains 0 to 0.26 percent hydrogen by weight while carbon makes up 0.2 percent of the total mass.
The solid inner core grows at an estimated rate of one millimeter per year as liquid freezes at the inner core boundary. Approximately 80,000 tonnes of iron freeze every second during this process.
One estimate suggests the core would not be expected to freeze up for approximately 91 billion years. This timeline extends well after the Sun is expected to expand and sterilize the surface of the planet.