continents created 2.5 Gya ?

I understand, that 2.5 Gya, there was a major 'pulse' of continent creation, associated with the solidification, of magnesium-rich Upper-Mantle (UM) rock, under-plating the bottoms of crustal continents (Science News). Such under-plated rocks, e.g. kimberlite & komatite, derived from UM material that was then 500K warmer, than present epoch (ABC AU). Today, the UM is colder than its solidification temperature (Wikipedia).

Is this accurate ? Does this mean, that the UM is enriched, in iron-rich olivines, if all the magnesium-rich olivines have under-plated continents ? At surface temperatures & pressures, the magnesium-rich material freezes at ~1900K, vs. ~1200K for the iron-rich material. And, the UM is ~1400K today. Can I conclude, that in the Archaean, 2.5Gya, the UM was liquid; and, that 2.5 Gya, at the Archaean-Protozeroic transition, the UM "half solidified", i.e. the magnesium material "solidified & surfaced", floating up, under-plating continents, and "lifting continents out of the oceans", in a "reverse Atlantis" effect ? And, that today, the iron-rich material is starting to solidify, which will "geologically soon" turn earth, into a "one plate planet" ?