Why did ancient Earth produce rocks like komatiites?

Komatiites are unique igneous rocks that are no longer formed today because Earth's internal heat production has significantly decreased. Roughly three billion years ago, radioactive decay and residual planetary accretion generated much higher temperatures and larger geothermal gradients. These intense conditions drove rapid mantle convection and plate tectonics, enabling the generation of ultramafic magmas that created komatiites.

What we know

• Earth's internal heat comes from residual planetary accretion, radioactive decay, latent heat from core crystallization, and possibly other sources. [2]
• Major heat-producing nuclides in Earth include potassium-40, uranium-238, uranium-235, and thorium-232. [2]
• Magma is produced by the melting of the mantle or the crust in various tectonic settings such as subduction zones, continental rift zones, mid-ocean ridges, and hotspots. [4]
• Heat production was twice that of the present-day at approximately 3 billion years ago, resulting in larger temperature gradients and the production of komatiites that are no longer formed. [2]

Where to go next

• the bigger pictureWhat is the geothermal gradient?
• how it workedHow does radioactive decay generate planetary heat?
• a case in pointWhat processes form igneous rocks like magma?
• what caused itHow do mantle convection and plate tectonics function?
• an unexpected connectionWhat is talc and how does it relate to magnesium minerals?

Sources

• [1]geothermal gradient (Wikidata Q636340) · CC0 1.0
• [2]Geothermal gradient · CC BY-SA 4.0
• [3]Earth · CC BY-SA 4.0
• [4]Magma · CC BY-SA 4.0
• [5]Talc · CC BY-SA 4.0