Geologic Time The History of the Earth and

Geologic Time The History of the Earth and It’s Life

Birth of the Solar System. • 5 billion years ago (bya) a super giant star explods (super nova) creating a cloud of elements (nebula) made in the star’s core • Swirling cloud of dust and gas is pulled together by gravity • Nuclear fusion starts on the sun. • Denser parts of the cloud sweep up debris along their orbit eventually forming planets

History of the Earth • The longest time periods are called eons. • Time measured in billion years ago (bya) Eon Start End Length Hadean 4. 6 3. 8 800 m. y. Archean 3. 8 2. 5 1300 m. y. Proterozoic 2. 5 0. 58 1920 m. y. 0 580 m. y. Phanerozoic 0. 58 Clock of Eons Phanerozoic

• • Hadean Events Event 1: Pressure and radioactive materials melt protoearth. Event 2: Earth cools, first rocks become solid (like ice forming) Event 3: Moon Forms (first seasons) Event 4: Heavy bombardment of meteors and comets adds water and chemicals for life to early Earth. • Event 5: Crust covers entire Earth • Event 6: Crust cools enough for rain to become rivers, streams and oceans

Hadean Atmosphere • Made from gases coming out of molten Earth • Poisonous to human life • No free oxygen to breathe • Lots of lightening

Hadean Ocean • Salt comes from minerals dissolved by water (erosion) • Organic “soup” of molecules brought in during the heavy bombardment and natural processes

Hadean Land Life • Only one type of crust (basalt, like the oceanic crust today) • Faster plate tectonics • Only mountains are volcanoes • No life, only the molecules to make

From here on…The Data is in the Strata • The story of the Earth’s history is told in it’s layers • The rest of this presentation is a description of what we know from the layers We’re going to start with the oldest layers and work our way forward in time to today (top layer)

Archean Eon: 3. 8 BYA to 2. 5 BYA: Events • • Sun 1/3 as bright Planet 3 times hotter than today First life First protocontinents

Archean Land • 3 billion years ago hot spot volcanoes erupt granite-like islands • First protocontinent is named UR • Oldest pieces of continental crust are, called “cratons” = shield • Several supercontinents may have formed, tectonics faster • First folded and faulted mountains form as continents collide

Archean Eon: Atmosphere and Oceans • Atmosphere toxic to most life on our planet today, • Starts with no oxygen • Oceans warm (due to warm crust), more acidic than today (no carbonate rocks)

Archean Eon = First Life • Our oldest fossils are bacteria that date to roughly 3. 5 billion years ago • Cyanobacteria form stromatolites and use photosynthesis which produces 1 st oxygen in air • 1 st oxygen causes the first rusted iron in rocks

Proterozoic Eon: Events, Atmosphere, Oceans • Life goes from simple soft bodied creatures to life with shells and armor plate. • Oldest evidence of ice ages • Oxygen levels equal to today • Atmosphere similar to today • Oceans similar to today

Proterozoic Life: Part I • 1 st life is single cell bacteria • Different types join together to form the first eucaryotic cell (symbiotic evolution) • Mitochondria are an example • Sexual reproduction begins, evolution goes faster

Proterozoic Life Part II • Tissues and organs evolve next, first bodies are soft and squishy • Oldest evidence that skeletons and shells are evolving • Organs and organ systems evolve, and shells, armor, eyes, etc evolved. • Oldest known chordate (ancestor of

Proterozoic Land • First true continents and 2 supercontinents form then break up, first is Rodinia, next is Pannotia

Phanerozoic Eon 575 m. y. a. - today Eons are divided into eras. There are three eras in the Phanerozoic Paleozoic = invertebrates to reptiles Mesozoic = Age of Dinosaurs Cenozoic = Age of mammals

Paleozoic Era: Life “Explodes” • In many places the Cambrian is the first layer to have fossils, probably because hard parts evolved and conditions were good for fossilization. • Trilobites (first eyes) • Brachiopods, crinoids, ammonites, sponges, coral National geo

Paleozoic: First Life on Land • 1 st plants on land • 1 st animals on land (arthropods)

Paleozoic Era II The Age of Fishes • In the Devonian, fishes appear, evolve jaws and dominate the Oceans • In mammals the gills have become the jaw, inner ear bones and hyoid bone (which has no purpose)

Paleozoic life III: Vertebrates Move onto Land • Legs and toes evolve from fins for moving through shallow swamps, amphibians crawl onto land evolve into reptiles • Pangea joins together • Vast swamps form huge beds of coal

• Paleozoic IV: Therapsid reptiles evolve into reptiles, protomammals, and protodinosaurs • Dimetrodon, and early mammals ruled at the end of the Paleozoic

Mesozoic Era Dinosaurs Dominate the Land • Mammals are mostly small and nocturnal • First birds and Flowers • Pangea splits up

Mesozoic: Age of Dinosaurs • Many or all were warm blooded. • Chinese fossils show many may have had feathers • Not all dinosaurs are extinct: birds still live. Chinese Photo Gallery

Mesozoic Era II: Ends Extinction of Most Dinosaurs Causes of dino extinction • Many suspect a comet or asteroid that landed near the Yucatan put so much ash into the atmosphere that it altered the climate. • Disease, continental drift, volcanic activity and competition are other suspects

Cenozoic: Mammals Take Over • Early mammals evolve into many forms including giant Pantotheres • Mammals develop unique teeth and start preying upon each other.

The Oldest Known Upright Walking Primate Footprints • 3. 6 million years ago ash spewed from an African volcano • A family of three walked across the fresh ash. The female stepped on the males footprints, and a youngster occasionally walked on its own. • They were hominids, a type of ape that walks on two feet. • Their species is nicknamed “Lucy” after the first fossil found.

Cenozoic Humans Evolve • Homo habilis: Handy man made stone tools • Homo erectus: made better tools • Homo neanderthal : Cave man: buried their dead with tools and flowers

Homo Sapiens: Recorded History • Our species evolved in Africa and migrated from there • They developed art… • and religion

Cenozoic: Recent Life • • Most of Oregon forms Last Ice Age Missoula floods Recorded history i. e. Social Studies, begins.

Cenozoic Animals • Mammals dominate