the outer core is the part of the earth's core that is liquid.
which part of the earth's core is liquid?
outer core
the iron-rich core region of the earth is divided into a radius solid inner core and a radius liquid outer core. the rotation of the earth creates convective eddies in the outer core region that cause it to function as a dynamo. this generates a magnetosphere about the earth that deflects particles from the solar wind, which prevents significant erosion of the atmosphere from sputtering. as heat from the core is transferred outward toward the mantle, the net trend is for the inner boundary of the liquid outer core region to freeze, thereby releasing thermal energy and causing the solid inner core to grow. this iron crystallization process has been ongoing for about a billion years. in the modern era, the radius of the inner core is expanding at an average rate of roughly per year, at the expense of the outer core. nearly all of the energy needed to power the dynamo is being supplied by this process of inner core formation.
future of earth
all of the rocky inner planets, as well as the moon, have an iron-dominant core. venus and mars have an additional major element in the core. venus’ core is believed to be iron-nickel, similarly to earth. mars, on the other hand, is believed to have an iron-sulfur core and is separated into an outer liquid layer around an inner solid core. as the orbital radius of a rocky planet increases, the size of the core relative to the total radius of the planet decreases. this is believed to be because differentiation of the core is directly related to a body's initial heat, so mercury's core is relatively large and active. venus and mars, as well as the moon, do not have magnetic fields. this could be due to a lack of a convecting liquid layer interacting with a solid inner core, as venus’ core is not layered. although mars does have a liquid and solid layer, they do not appear to be interacting in the same way that earth's liquid and solid components interact to produce a dynamo.
planetary core