The Geologic Time scale Mountain Eras Periods Building Life The prese nt CENOZOIC QUATERNARY Himal ayas Ma MESOZOIC TERTIARY Rocky Mins PALEOZOIC m y CRETACEOUS 1000 9Roubm ONo山 JURASSIC Birds 20 my La st Ou 2000 Tril obits PERMIAN UraLs Appalachians· Re piles CARBONIFEROUS 3000 DEVON IAN Sharks 400 des Northern First life Fossil SILURIAN Appalachia Continents Ide st ORDOVIC AN 4000 a corals CAMBRIAN 570 Trilobites
4 glacial cycles recorded in the Vostok ice core 280 260 240 220 0 200 g 700 A 50g 400 100 150 200 250 350 400 Age( kyr BP) PAGES CHANGE J. R. Petit et al. Nature, 399. 429-36. 1999