National Geographic : 2006 Dec
ROAD TO LIFE Formation of planets Earliest life? Formation of moon Cyanoba I first strong ___ I cteria and natolites Oxygenated atmosphere I First land plants First reptiles First algae First mammals 2,400 4,600 4,500 3,800 3,500 Millions of years ago 1,800 470 310 210 CONSULTANT:STEVENM. STANLEY,UNIVERSITYOFHAWAII;GRAPHIC:NGM ART A scene from the early Earth unfoldsfrom the rim ofPu'u 'O'o crater on Hawaii'sBig Island. Lava that burstsfrom spattercones in the distance hasfilled the craterfloor and cooled into afracturedgray crust.Over and over in early Earth history its surface cooled and hardened, only to be melted again by giant impactsfrom space. EARLY EARTH 61 "