Ian Marr·June 25, 2020Architect
There are several ways to answer your question.
The whole earth? The mantle makes up the bulk of the Earth, so liquid.
From the ground up? By volume? That would be the atmosphere mostly, so gas.
From the ground up? By mass? Either liquid (the oceans) or solid (solid matter) depending on how you define things.
Ahh, not so fast. You have forgotten temperature and pressure. By the time you get down to the Nickel-Iron core, we are dealing with a gas which is under hypercritical pressure The so called solid core is this same hypercritical gas so compressed that it behaves as if it were solid. The temperature is so high that chemical bonds are completely unstable, so technically it is a PLASMA. It is an interesting property of plasmas, that their electical resistance is close to zero. Very nearly superconductive. Have you noticed that when a household filament lamp bulb fails, it often takes out the house fuse. The electric arc created as the filament fails has a much lower resistance than the intact filament. It is this very high conductivity of the Nickel Iron core which is responsible for the Earth’s magnetic field, and the fact that the inner core behaves as if it were solid, which maintains the system of differential flow which sets up the self exciting electric generator, possibly driven by the Moon, which is responsible for the Earth’s magnetic field.
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