WHAT ON EARTH HAPPENED 2.7 BILLION YEARS AGO? Kent C. Condie Dept. Earth and Environmental Science New Mexico Tech Socorro, NM 87801 USA EXOGENIC Atmosphere < 103 y Ocean Biosphere ENDOGENIC 107-108 y PLANETARY CATASTROPHIES 2.7 Ga Arc Systems Large Igneous Provinces (LIPS) Accretionary Orogens 3.0 2.5 2.0 1.5 1.0 0.5 0 AGE (Ga) TECTONIC SETTINGS IN TIME 2.7 Ga 1.9 Ga 3.0 2.5 2.0 1.5 1.0 0.5 0 AGE (Ga) JUVENILE CONTINENTAL CRUST AGE DISTRIBUTION 2.7 Ga Zimbabwe 2.5 Ga Southern India TTGs 4.0 Ga Yellowknife Canada DEFORMED GRANITOID ZIRCON AGES WITH E (cid:1) +1 ND DEFORMED GRANITOID ZIRCON AGES WITH E (cid:1) +1 ND CATASTROPHIC MANTLE PLUME EVENT c = e - r c = crustal preservation rate e = crustal extraction rate r = crustal recycling rate s = sediment subduction b = subduction erosion d = lithosphere delamination r = s + b + d