Why does the Earth have a magnetic field?
21st century scientists believe the magnetic field is generated from the Earth’s iron core which is approximately two thirds the size of the moon and as hot as the surface of the sun, around 5,700oC to be exact. Theoretically, this should cause the solid iron inner core to melt, however, the extreme pressure of gravity on the core prevents it melting. Closer to the Earth’s surface, surrounding the inner core is a 12,000 mile thick layer of molten material primarily consisting of iron and nickel.
Subsequent differences between this outer and inner core such as temperature and pressure cause convection currents in the molten layer. A convection current occurs when hot liquid rises into a cooler area and cooler, more dense material sinks. The spin of the Earth on its axis also causes swirling currents and as the liquid iron flows, it generates electrical currents, and, where there is an electrical current there is always a magnetic field. For the Earth’s magnetic field to last over billions of years it relies on these convection currents to continually generate. This self-sustaining cycle is known as the geodynamo.
Why does the Earth have a magnetic field?21st century scientists believe the magnetic field is generated from the Earth’s iron core which is approximately two thirds the size of the moon and as hot as the surface of the sun, around 5,700oC to be exact. Theoretically, this should cause the solid iron inner core to melt, however, the extreme pressure of gravity on the core prevents it melting. Closer to the Earth’s surface, surrounding the inner core is a 12,000 mile thick layer of molten material primarily consisting of iron and nickel.Subsequent differences between this outer and inner core such as temperature and pressure cause convection currents in the molten layer. A convection current occurs when hot liquid rises into a cooler area and cooler, more dense material sinks. The spin of the Earth on its axis also causes swirling currents and as the liquid iron flows, it generates electrical currents, and, where there is an electrical current there is always a magnetic field. For the Earth’s magnetic field to last over billions of years it relies on these convection currents to continually generate. This self-sustaining cycle is known as the geodynamo.
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