The high‐pressure triple points of iron and their effects on the heat flow from the Earth's core

The triple point joining the ϵ (hcp), and γ(fcc), liquid phases of iron has been estimated by a number of authors, using (in the words of Birch (1972)) “speculative projections.” Three of these projections would place this triple point at or below 100 GPa, while the third locates it at 280 GPa. The methods used in each case are quite interesting historically, because they reveal the state of the art in iron physics and its application to geophysics at the times of the respective publications. The subject is not closed yet, and no doubt future publications will point out new trip1e‐point locations.