Goal: To understand the geologic history of the earth.
The beginnings of life Life in the ocean Plants onto land Amphibians and Reptiles Dinosaurs! Continents and Supercontinents Age ages and warm periods After the dinosaurs. When you think about the geologic history of the earth, what is the part of geologic history (it can be a time, event, ect) that sticks out the most in your mind? Start of class Welcome to 5 billion years ago.Earth does not exist yet. There is a large cloud of dust and gas which will form the solar system called a Giant Molecular Cloud. 6th minute of class 4.6 billion years ago formation of the earth.
The cloud of dust and gas creating the sun forms a disc. Inside that disc objects clump together making small meteoroids (10-100k). These meteoroids crash into each other.Sometimes they will break each other apart, but mostly they combine to make bigger meteoroids. Eventually the cores of planets are formed. The core materials in the planets depend on where they form (as it is cooler the further out you go). Sometime in this periods an object the size of Mars crashes into the earth to form the moon. 7.5 minutes of class (Precambrian Time, Hades Eon)
The earth has formed.It is 4.5 billion years ago. Earth is still molten.Any land formed gets pushed underneath the surface and is remelted. There is probably no life here.The atmosphere is bars and is mostly water vapor (50%), Carbon Dioxide (24%), and Sulfur Dioxide (13%).The atmosphere comes from volcanoes mostly.The original atmosphere made of mostly Hydrogen and Helium is gone. The earth is not a pleasant place, and it is being bombarded constantly by meteorites! 16.5 minutes into class. (Precambrian Time, Archaean Eon)
3.9 billion years ago. The bombardment is over.Land starts to form. Earliest rocks on earth date back to this period, but are rare. The water in the atmosphere, which has come from out-gassing volcanoes and impacts from comets and asteroids, has formed an ocean. Carbon dioxide has been dissolved into this rain water.The atmospheric levels have dropped to about 1-10 bars, but the atmosphere is now about 35% Carbon Dioxide and 35% Nitrogen. Life has formed! 16.5 minutes into class. (Precambrian Time, Archaean Eon)
However, this world is NOT like ours today! The life is single celled organisms in the oceans (blue-green algae). Life is anaerobic and does not use oxygen. There is very little Oxygen, and almost no Ozone.The atmosphere would look red. 16.5 minutes into class. (Precambrian Time, Archaean Eon)
Also, the land forms are just islands (in chains). There are no continents. The earth is very geologically active (lots of volcanoes). The islands over time crash into each other to form bigger islands.Eventually this will form the cores of later continents. 22.5 minutes into class. (Precambrian Time, Archaean Eon)
3.5 billion years ago.First fossils (well microfossils)! Soon the earliest continents will form. Carbon Dioxide down to 20%, and Nitrogen is up to 65% of the atmosphere. 36 minutes into class. (Precambrian Time, end of Archaean Eon)
2.6 billion years ago.Bacterial life makes its way from the ocean to the land (reef like structures). Atmosphere is still has a lot of Carbon Dioxide (0.1 bars), but also has a lot of Nitrogen at this point (80%). Continent building is nearing its completion.85% of the continental mass has been formed by now. 37.5 minutes into class. (Precambrian Time, Proterozoic Eon)
2.5 billion years ago.Rust bands. This shows there was oxygen in the ocean. This oxygen immediately would react with the iron so that the oxygen would not stay in the ocean, and would not go out of the ocean. First supercontinent! Oddly enough, climate was COLD!The sun was probably about 20% less bright at this time.There is some evidence for large glaciers ON THE EQUATOR! Energy transport inside the earth:
Heat is continuously being lost by the inner core (so the core cools with time). The outer core convects. So does the mantel. This convection pushes on the plates, moving them. Supercontinental break up
If force pushes on part of the supercontinent, it will be torn apart much like current Africa is (Rift Valley). With time the supercontintent breaks apart, and all the pieces go in their separate directions. Eventually these pieces will collide with each other forming the next supercontinent. When the supercontinent is formed, mountain ranges are formed as are shallow inland seas. 45 minutes into class. (Precambrian Time, Proterozoic Eon)
2.0 billion years ago.Rust beds. Now the Iron in the ocean has all rusted. So, the Oxygen goes into the air where it will react to the Iron in the ground. Oxygen is all used up, so does not stay in the air. Carbon Dioxide levels are still at about 0.1 bars (which would be 300 times higher than today). Still cool, but no glacier evidence. NOTE:recent evidence is putting the start of oxygen in the atmosphere back to 2.3 billion years ago. 46.5 minutes into class. (Precambrian Time, Proterozoic Eon)
1.9 billion years ago. Oxygen levels are at 3% (compared to 21% today). 48 minutes into class. (Precambrian Time, Proterozoic Eon)
1.8 billion years ago. First Eukaryote fossils. Still single celled organisms, but more complex and bigger. Can contain more DNA, and has a nucleus. 57 minutes into class. (Precambrian Time, Proterozoic Eon)
1.2 billion years ago. First multicellular fossils. Atmosphere at still 20 to 30 times the Carbon Dioxide levels of today. Oxygen is at 10%, which is half of today. 58.5 minutes into class. (Precambrian Time, Proterozoic Eon)
1.1 billion years ago. Rodinia, the 2nd supercontinent formed. 61.5 minutes into class. (Precambrian Time, Proterozoic Eon)
0.9 billion years ago. First soft bodied creatures (wormlike creatures) formed. Did they evolve into animals, or is this a evolutionary dead end? Carbon Dioxide is now times todays levels and Oxygen levels are now closer to 15%. 63.8 minutes into class. (Precambrian Time, Proterozoic Eon)
0.75 billion years ago. 4 global ice ages!Each followed by hyper greenhouse. Lots of extinctions. Snowball earth has ice all the way to the equator more than likely. This lasted for more than 100 million years. 64.5 minutes into class. (Precambrian Time, Proterozoic Eon)
0.7 billion years ago. Rodinia breaks up into the smaller continents of Laurentia, Baltica, Siberia, and Gondwana. 66 minutes into class. (Precambrian Time, Proterozoic Eon)
0.6 billion years ago. Ozone forms! Before this time life can only thrive in the ocean because deadly solar UV rays pelted the land. Soft bodied creatures diversify and evolve. 67 minutes into class.(Phanerozoic eon, Paleozoic Era, Cambrian Period)
543 million to 488 million years ago. We are now in the current eon! At the start is a slight extinction. A lot of species disappear, but did they die, evolve, or are we just not getting fossils of them? 67 minutes into class.(Phanerozoic eon, Paleozoic Era, Cambrian Period)
There were large shallow seas ripe conditions for life. So, there was an explosion of evolution during this time period. All the types or phyla of animals were created here including vertebrates. Climate was warm and stable as Carbon Dioxide levels went back up to times the levels of today. At the end of this Period the next supercontinent Gondwana forms. However, still nothing on land (other than bacteria close to shores)! 67 minutes into class. (Paleozoic Era, Ordovician Period)
488 to 433 million years ago. First fish and land plants develop. At end of period, first sharks. Gondwana drifts to the South Pole. The end is marked by a giant ice age which kills off 50% of all plant life and 25% of the animal life in the sea. 69 minutes into class. (Paleozoic Era, Devonian Period)
420 to 350 million years ago. Explosion of land plants and oxygen reaches modern levels. Arthropods (including insects and spiders) start to live on land. First 4 legged fish evolve (tetrapods) and soon become Amphibians. Carbon dioxide levels drop from 15X today to 5X today. 364 million years ago extinction! Life on land not much affected. > 50% of marine species go extinct. First seed plants and first forests. At end of Devonian Period, you have the start of reptiles! 71 minutes into class. (Paleozoic Era, Permian Period)
300 to 250 million years ago. First mammal like reptiles! Period starts with temperatures and Carbon Dioxide levels similar to today. The supercontinent Pangaea forms. 71 minutes into class. (Paleozoic Era, Permian Period)
Paleozoic Era ends with a HUGE extinction event (actually 2 pulses separated by 8 million years)! 90-95% of marine species and 70% of land species went extinct! Largest known extinction! While cause is unknown (volcanic, to meteorite impact, to nearby supernova), what is known is that Carbon Dioxide levels shot up by a factor of 6 and global temperatures went up by 11 C or 20 F. Only mass extinction for insects. Most plant life disappears. 71.7 minutes into class. (Mesozoic Era, Triassic Period)
220 million years ago. First mammals (small), first dinosaurs (small), first crocodiles, and first flying reptiles. Temperatures are warm and dry with cold winters. No polar glaciers. At 210 million years ago there is a lot of volcanic activity, Pangaea starts to rift and huge, and global temperatures go down. This is followed by extinctions of most marine reptiles and many other species (50%) as did many land reptiles and some primitive dinosaurs. 72.8 minutes into class. (Mesozoic Era, Jurassic Period) 72.8 minutes into class. (Mesozoic Era, Jurassic Period)
200 million to 148 million years ago. Climate more moist Allosaurus, Brachiosaurus (largest known dinosaur), Diplodocus, Pterodactylus, and Stegosaurus all lived during this period. Atlantic Ocean starts. First small birds. 72.8 to 74 minutes into class. (Mesozoic Era, Cretaceous Period)
148 million to 65 million years ago. Climate very warm.No polar ice.High sea levels.Shallow seas. Deep ocean C warmer than today!Therefore, warmer much farther from equator than before. First flowering plants. Ankylosaurus Triceratops Tyrannosaurus Rex Velociraptor 74 minutes into class 65 million years ago
A 10 km asteroid (maybe comet) strikes the earth of the coast of the Yucatan peninsula. Shortly after 70% of all species go extinct including most of the dinosaurs. The meteor crater has been discovered. What exactly is the impact like? (big long speech here) Lets watch the continents!
74 to 74.2 minutes into class.(Cenozoic Era, Paleogene Period, Paleocene Epoch)
65 to 56 million years ago Birds ruled the world! Huge birds which could no longer fly dominated the ground. 60 million years ago first primates. 57 million years ago first rodents Demise of birds:got too large, so had to nest on the ground where their eggs were devoured by insects. 74.2 to 74.5 minutes into class.(Cenozoic Era, Paleogene Period, Eocene Epoch)
56 to 33 million years ago Mammals take over. First whales and horses. Climate starts to dry and cool.Carbon dioxide levels fall from 3X today to about todays levels. Cooling triggers a global extinction especially at higher latitudes. Forests become more open. 74:39. 3 to 74:55. 7 minutes into class
74:39.3 to 74:55.7 minutes into class.(Cenozoic Era, Neogene Period, Milocene Epoch) 23 to 5.3 million years ago 25 million years ago Ape/Human line evolves. First grasses more adapted to cool, dry climates. 21-14 million years ago, warming, then sudden drop with a 2nd drop 8 million years ago. Oceans cool. 20-10 million years ago Cascades, Andes, and Himalayas form. 6 million years ago Chimpanzees separate from hominids. 74:55. 7 to 74:58. 38 minutes into class
74:55.7 to 74:58.38 minutes into class.(Cenozoic Era, Neogene Period, Pliocene Epoch) 5.3 to 1.8 million years ago 3 million years ago, permanent ice sheets in Antarctica. 2 million years ago start of global ice ages! 74:58. 38 to 74:59. 99 minutes into class
74:58.38 to 74:59.99 minutes into class.(Cenozoic Era, Quaternary Period, Pleistocene Epoch) 1.8 million to 12k years ago. Ice ages have glaciers progress then retreat. 600k years ago early humans. 100k years ago first Homo Sapiens 30k years ago Neanderthal goes extinct. End of Pleistocene Wooly Mammoth, Sabertooth Tiger, Mastodons, Cro-Magnon, and a lot of other species go extinct end of last ice age. Conclusion The earth has changed a LOT during its history.
Many factors influence a planets climate. Life if greatly influenced by a planets climate, but can be affected by other external factors. As we head into the future, we will see many of the conditions for climate in the past re-emerge, and we must adapt to them or become another statistic on the timeline of the history of the earth.