Geologic Time Scale Flashcards
determine whether a rock is younger or older than other rocks
relative dating
uses radiometric dating techniques to determine how long ago a rock formed in the exact number of years
absolute dating
accounts for 88% of the earth’s history; earth had a hot, steaming, hostile landscape
precambrian period
little is known because few rocks existed; condition is like hell
hadean
crustal building and formation of volcanic belts and sedimentary basins due to plate tectonics
archaean
rifting of continental crust and subsequent filling with sedimentary and volcanic rocks
proterozoic
earth forms, first prokaryotic cells in stromatolites appear, first eukaryotic cells appear, multicellular organisms appear
precambrian period
marked by the beginning of life
paleozoic era
invertebrates dominate and marine algae prosper
cambrian
invertebrates diversify and jawless fishes appear
ordovician
seedless vascular plants and first jawed fishes appear
silurian
first seed plants appear and jawed fishes diversify
devonian
known as age of fishes
devonian
amphibians diversify and first reptiles appear
carboniferous
reptiles diversify and conifers appear
permian
pangea rifted into ___________ and ___________
northern laurasia and southern gondwanaland
during this time, pangaea rifted into 2
mild mesozoic
new trees such as conifers appeared and mammals were just beginning to emerge
mesozoic era
first mammals and dinosaurs appear; corals and mollusks dominate seas
triassic
dinosaurs prosper and birds appear
jurassic
placental mammals and modern insects appear
cretaceous
known as age of mammals or age of recent life
cenozoic era
last 66 mil years of earth’s history
cenozoic era
