How the earth was made time line one third land, two thirds water Hutton finds layers or rock perpendicular and figures they had to be millions of years old (layers also could not have been laid down in 6000years) Meteors collide to form earth-surface was molten rock up to a mile deep, temps=8000 degrees F Kelvin predicts age to be 20 million years old due to his calculations to cool. Heat inside earth produced by decay of radioactive materials Radiometric dating used to date the age of the earth to billions of years Uranium decays to Lead Accepted age = 4.5 billion years Earth cools to form crust and pillow lavas give evidence that oceans were present 4.4 bya Meteors still bombarding earth Crystals containing zircons contain fingerprints of water Origin still a mystery but theory is water from out gassing but most from meteors and comets CO2 and water vent to form first atmosphere at 4 bya It would rain for million upon millions of years at 4bya forming a vast ocean with small volcanic islands-CO2 was great in atmosphere Temps of atmosphere exceeded 200 degrees F. 3.4 bya: Earth was a vast ocean and an upsurge in volcanic activity creates granite continental crust. Over the next few billion years the continents grew Shallow coast lines allowed Stromatolites to grow and produce mass amounts of oxygen As far back as 2.5 billion years ago Stromatolites were prolific. Over 2 billion years Stromatolites pumped out lots of O2 and dilute the atmosphere (CO2 levels drop relatively) 1. 5 billion years ago blue oceans appear because O2 ____ Continents are moving (fossil evidence and glacial evidence who plate tectonics to be true) 1 billion years ago Rodenia was formed-was lifeless, dry, hot 700 mya Rodenia triggers “snowball” Earth by blocking polar waters from mixing with equatorial waters. All but a tiny fraction of living organisms died off. 650 mya Ice was 1 mile thick, temps=-40. 650 mya volcanic activity beneath the ice eventually leads to warming under the ice. Heat and CO2 is released and the ice sheets draw back. O2 levels increased so and Ozone layer begins to form 500 mya life explodes 300 mya life can move onto land because of the Ozone layer 250 mya Volcanic activity goes nuts (rare mantle plume eruption) which leads to more land and toxic gases which leads to the extinction of over 95% of all life. 240 mya Pangea now dominates Reptiles (dinosaurs) evolve 180 mya Pangea begins to split 100 mya continents split to near current positions Dinosaurs flourish in the warmer and wetter world climate. 65 mya Meteor 6 miles across collides with earth Clouds of dust block sun and volcanic upsurge (toxic gases) increase which leads to the extinction of dinosaurs and about 70% of all life. 50 mya Mammals begin to evolve, continents continued to move apart. Current landscapes formed from volcanic eruptions, glaciers, wind and rain. 2 mya ancestors of modern humans evolved 2 mya Earth begins to cool-Ice ages arrive 10,000 ya -Last glaciers retreat Weight of these glaciers leave behind erratics, scour marks and glacial polish as evidence. Future of Earth: More extinctions Climate will be biggest challenge Human civilizations have flourished during a very stable climate over the past 10, 000 years Continents continue to move and will eventually collide again in about 15,000 years another ice age may cover North America 200 my in the future=Pangea Ultima will begin to form as continents collide 2 by in the future Earth will no longer have its atmosphere because core will no longer rotate and the magnetic field will die.