Geologic Timeline 2

Updated 2007-04-23 08:02

Geologic Timeline Key Points

Key points along the geologic timeline. Data from

Geologic Timeline Key Points I

TimespanKey Points
Archeozoic(1) Earth's crust forms
(2) 700 million year span of heavy asteroid and comet bombardment
Precambrian(1) Archaean - single celled organisms
(2) Proterozoic - earliest fossil animals & plants
Cambrian(1) extinction of first great expansion of marine life
(2) first animals with hard skeletons (mollusks, corals)
(3) first chordates evolve (give rise to vertebrates)
(4) first traces of vascular plants
Ordovician(1) first land-based plants
(2) second great expansion & diversity of marine life (jawless fish)
Silurian(1) jawed fish
(2) first land animals (arthropods)
(3) widespread distribution of plants on land
Devonian(1) amphibians appear
(2) fish groups develop
(3) insects appear
(4) first forests
(5) advanced plants evolve
Carboniferous(1) mammal-like reptiles begin to dominate land
(2) first reptiles develop & colonize land
(3) amphibians evolve
(4) trees dominate, club mosses, horsetails, ferns
(5) gymnosperms (seed-bearing plants) first appear

Geologic Timeline Key Points II

TimespanKey Points
Permian(1) trilobites & other types of marine life disappear
(2) mammal-like reptiles & archosaurs dominate land
Triassic(1) primitive true mammals evolve
(2) mammal-like reptiles disappear
(3) dinosaurs appear
(4) reptis diversify & dominate
(5) gymnosperms evolve
Jurassic(1) first birds evolve
(2) dinosaurs reach gigantic forms
(3) dinosaurs dominate animals
(4) cycads, conifers
Cretaceous(1) extinction of dinasaurs & marine reptiles
angiosperms (flowering plants) evolve, modern plant type begins to appear
(3) modern mammal begin to evolve
(4) bird groups continue to evolve
Tertiary(1) upright hominids appear
(2) first apes appear
(3) bird groups continue to evolve
(4) mammal groups evolve & become dominant life on Earth
Pleistocene(1) formation of agriculture & permanent communities
(2) cro-magnon man, neanderthal man
(3) ice age mammals, mammoths prominent
Quaternary(1) growth of civilization
(2) early civilization
(3) modern man


Geologic Timeline - geologic timeline with dates
Geologic Timeline 2 - geologic timeline with key points