Facts
Why OpenThe rock and mineral record old enough to settle it is scarce and heavily altered: the Hadean and early Archean left almost no surviving crust to read directly, so estimates for when a single, stable, mobile-lid system of plates first organized range from roughly 4 billion to under 3 billion years ago, and some researchers argue the earliest crust moved under a different regime entirely before plate tectonics as it now works took over. 1 What Would ResolveEither a substantially larger surviving sample of Hadean and early Archean crust than currently exists, or a geochemical or isotopic proxy, read from what does survive, that can distinguish plate-tectonic from non-plate-tectonic crustal recycling with confidence. 1 Discipline Needed Open Question
The rock and mineral record old enough to settle it is scarce and heavily altered: the Hadean and early Archean left almost no surviving crust to read directly, so estimates for when a single, stable, mobile-lid system of plates first organized range from roughly 4 billion to under 3 billion years ago, and some researchers argue the earliest crust moved under a different regime entirely before plate tectonics as it now works took over.
What would resolve this Either a substantially larger surviving sample of Hadean and early Archean crust than currently exists, or a geochemical or isotopic proxy, read from what does survive, that can distinguish plate-tectonic from non-plate-tectonic crustal recycling with confidence.
OpenGeology, GeochronologyPlate Tectonics (Wikipedia)
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