EARTH

Lava Too Hot to Exist Today

~3.5 to 2.7 billion years ago

Archean · Paleoarchean

These lavas erupted so hot that they flowed like water rather than creeping like modern lava, and they crystallised into blades of olivine as long as a hand. Nothing quite like them has erupted since: the Earth's interior has cooled too far to produce them again.

Why it matters

These flows are a thermometer for the young Earth: they show, more directly than any other rock, how far the planet had cooled from its violent beginnings. They are also why a good part of the nickel we mine comes from rocks of this age.

Dating & uncertaintyDisputed

They erupted at temperatures of up to 1,600 degrees, some three hundred degrees hotter than any lava today. Whether that requires a mantle hundreds of degrees hotter, or only wet rock melting at ordinary temperatures above a sinking plate, has been argued for fifty years. Water measured inside the crystals now favours the hot mantle.

Sources

1. Grove & Parman (2004), Earth and Planetary Science Letters · Thermal evolution of the Earth as recorded by komatiites
2. Sobolev et al. (2016), Nature · Komatiites reveal a hydrous Archaean deep-mantle reservoir
3. Grosch & Viljoen (2023), Journal of African Earth Sciences · The discovery and petrogenetic significance of komatiites

Earth history as one day

05:29:5218 h 30 min before midnight

if Earth’s 4.54 billion years were compressed into a single day