Why is the inner core hot?
1) The inner core is compressed by the liquid outer core, mantle and crust (compaction). This creates pressure. The thick layers surrounding it prevent heat from escaping. Liquid in the outer core is a poor conductor of heat, which makes it slower for the heat in the inner core to escape. 2) Since it takes up a very small space, heat tends to be more concentrated. 3) It is solid, primarily made of iron and nickel, which are metals. The atoms of metals are closely packed, meaning that the transfer of heat is faster, which is why it is hotter. 4) Since it is homogeneous, consisting of a single piece of iron, the atoms are closer than ever, which is why the temperature is extremely high.
