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Fossils & The Geologic Time Scale

Fossils & The Geologic Time Scale. Events in Your Life. Construct a timeline of the important events in your life. Be sure to include all of the events listed below and any other events you feel are important. Your timeline should be constructed TWO ways: Numerical Order (use actual dates)

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Fossils & The Geologic Time Scale

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  1. Fossils & The Geologic Time Scale

  2. Events in Your Life • Construct a timeline of the important events in your life. Be sure to include all of the events listed below and any other events you feel are important. Your timeline should be constructed TWO ways: • Numerical Order (use actual dates) • Sequential Order (most recent at top) • ___When you started second grade • ___When you were born • ___ When you started kindergarten • ___When you learned to ride a bike. • ___ When you learned to walk. • ___ When you learned to read. • ___ When you lost your first tooth. • ___ Today’s date.

  3. What is the Earth’s time scale? • The Geological time scale is a record of the life forms and geological events in Earth’s history. • Scientists developed the time scale by studying rock layers and fossils world wide. • Radioactive dating helped determine the absolute divisions in the time scale.

  4. Eras are subdivided into periods...periods are subdivided into epochs. Divisions of Geologic Time Era Period Epoch E + P = EP

  5. Divisions of Geologic Time • Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.

  6. FOUR Eras… • PRE-CAMBRIAN – 88% of earth’s history • Paleozoic (ancient life) • 544 million years ago…lasted 300 million yrs • Mesozoic (middle life) • 245 million years ago…lasted 180 million yrs • Cenozoic (recent life) • 65 million years ago…continues through present day

  7. Today… • Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era. Which unit is the largest? Which unit is the smallest?

  8. Fossils • Preserved remains or traces of an organism that lived in the past. • Fossils are formed when organisms die and are buried in sediment. Eventually the sediment builds up and hardens to become sedimentary rock. • Sediments are pieces of solid material that have been deposited on Earth’s surface by wind, ice, gravity, or chemical precipitation. • Paleontologist-scientist who study the remains of organisms in the rock record.

  9. Kinds of fossils • Petrified - when minerals replace the remains and they become rock things like wood. • Mold - when the shell remains and the contents dissolve (hollow) like in art class you use a mold to get the correct shape of a bowl. • Cast- when the mold becomes filled with minerals that are not a part of the original organism. • Index- a fossil found in a narrow time range but widely distributed around the earth; used to date rock layers. • Trace fossil-a fossilized mark that is formed in soft sediment by the movement or actions of an animal.


  11. Sometimes whole animals become preserved intact, but this is very rare. If an organism is surrounded by ice or tar they might be discovered looking much the same as they did when they died. AETOSAUR FOUND IN THE NATIONAL PETRIFIED FOREST

  12. Relative Dating Relative dating: looks at where the fossil is located to determine its age relative to other fossils. This only works if the area has been undisturbed.

  13. Absolute Dating • Uses radioactive elements near the fossils to determine the actual age of the fossils. • By determining the age of the radioactive element, scientists can calculate the age of the fossil buried nearby. The absolute age of fossils is estimated by dating associated igneous rock and lava flows.

  14. Fossil Record • The dating of all fossils is included in the Geological Time Scale. This scale divides the time that the earth has existed into 4 eras. • Eras are then divided into periods based on common events in that time period.

  15. Vocabulary • Copy the definitions below in your notebook on your definitions page. • geologic time scale – a model scientists use to describe the timing of events and the relationships between those events in earth’s history. • era – one of three long periods of geologic time from Precambrian to the present. • period– geologic time periods that eras are divided into. 4. epoch – a division of geologic time; a subdivision of a period.

  16. Paleozoic Era • Divided into 5 periods: • Cambrian period - Sponges, snails, clams and worms evolve • Ordovician period - First fishes evolved and other species become extinct • Silurian period - Land plants, insects and spiders appear

  17. Devonian period - Amphibians evolve and cone-bearing plants start to appear. • Carboniferous period - Tropical forests appear and reptiles evolve. • Permian period - Seed plants become common and insects and reptiles become widespread. Sea animals and some amphibians begin to disappear.

  18. Mesozoic Era • Divided into 3 periods: • Triassic period - Turtles and crocodiles evolve and dinosaurs appear. • Jurassic period - Large dinosaurs roam the world. First mammals and birds appear. • Cretaceous period - Flowering plants appear, mammals become more common, dinosaurs • become extinct.

  19. Cenozoic Era • Divided into 2 periods: • Tertiary period - First primates appear and flowering plants become the most common. • Quaternary period - Humans evolve and large mammals like woolly mammoths become extinct.

  20. ASSIGNMENT • Read back through the notes you have just taken. Design 4 multiple choice questions about the content. • Design one question which asks for a description or explanation with details.

  21. Paleozoic Era (Ancient Life) • The Cambrian period is the 1st period of the Paleozoic Era. “Age of the Trilobites” • Explosion of life in the oceans began during this era. • Most of the continents were covered in warm, shallow seas. • Invertebrates were dominate - Trilobites • Fish emerged during this time • Fish led to the arrival of amphibians • The end of the Paleozoic era is called the “Age of Amphibians” • Early land plants including mosses, ferns and cone-bearing plants. • The early coal forming forests were also formed during this time.

  22. Paleozoic Era • Much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic. • The Cambrian (beginning) opened with the breakup of the world-continent Rodinia and closed with the formation of Pangaea, as the Earth's continents came together once again. • This event is thought to have caused the climate changes that led to mass extinction event. • The Appalachian mountains were formed during this time.

  23. Paleozoic Era • At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals. • Possible causes of this Mass Extinction Event • Lowering of sea levels when the continents were rejoined as Pangaea (convergent boundary) • Increased volcanic activity (ash and dust) • Climate changes – cooler climate

  24. Lived in Earth’s ancient seas Extinct before the dinosaurs came into existence Cambrian Period is know as the “Age of the Trilobites” (put in on table) Trilobites

  25. Brachiopods • Marine animals that resemble clams.

  26. Early Fish Early fish did not have jaws. Some species of sharks were in existence at this time.

  27. Frilled Shark that was found in Japan in January 2007. This shark was considered a “living fossil”

  28. Early Land Plants Mosses Cone bearing plants Ferns

  29. Mesozoic Era – Middle Life • At the beginning of this era the continents were joined as Pangaea. • Pangaea broke up around the middle of this era. • Reptiles became the most abundant animals because of their ability to adapt to the drier climate of the Mesozoic Era. • Skin maintains body fluids • Embryos live in shells

  30. Mesozoic Era • Dinosaurs were also very active in this era. • First small dinosaurs appeared in the Triassic Period. • Larger and more abundant dinosaurs appeared in the Jurassic Period. • Small mammals and birds also appeared during this era. • The mammals were small, warm-blooded animals. Hair covering their bodies. • These characteristics help them survive in changing environments.

  31. Mesozoic Era • The main plant life of this time were Gymnosperms or plants that produce seeds, but no flowers. • Pine Trees • Flowering plants appeared during the END of this era.

  32. Mesozoic Era • This era ended with a mass extinction event about 65 million years ago. • Many groups of animals, including the dinosaurs disappeared suddenly at this time. • Many scientists believe that this event was caused by a comet or asteroid colliding with the Earth.

  33. Crater sites on Earth

  34. Mesozoic Era – Mass Extinction Event • Asteroid or Comet collides with Earth. • Huge cloud of smoke and dust fills the air • Blocks out sunlight • Plants die • Animals that eat plants die • Animals that eat plant-eaters die. • However, not all forms of life died during this event. Many animals that you see today are descendants from the survivors of this extinction event.

  35. Dinosaurs

  36. Mesozoic Reptiles

  37. Mesozoic Mammals

  38. Mesozoic Plants Flowering plants evolved towards the end of the Mesozoic Era.

  39. Cenozoic Era – Recent Life • Began about 65 million years ago and continues today!!!!! • Climate was warm and mild. • Marine animals such as whales and dolphins evolved. • Mammals began to increase and evolve adaptations that allowed them to live in many different environments – land, air and the sea. • Grasses increased and provided a food source for grazing animals • Many mountain ranges formed during the Cenozoic Era • Alps in Europe and Himalayas in India; Rocky Mountains in the USA

  40. Cenozoic Era • Growth of these mountains may have helped to cool down the climate • Ice Ages occurred late in the Cenozoic Era (Quaternary Period). • As the climate changed, the animals had to adapt to the rise and fall of the oceans caused by melting glaciers. • This era is sometimes called the “Age of Mammals”

  41. Cenozoic Era • Marine animal examples: • Algae, Mollusks, Fish and Mammals • Land animal examples: • Bats, Cats, Dogs, Cattle and Humans • Humans are thought to have appeared around 3.5 million years ago (during the most recent period – Quaternary). • Flowering plants were now the most common plant life.

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