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NOTE CHECK

NOTE CHECK. What is the difference between relative and absolute dating? What is superposition? What era did humans first appear?. Fossils & The Geologic Time Scale. Exploring Geologic Time Geologic time notes - page 23. 1. Exploring Geologic Time (geologic time notes page 29). 2.

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NOTE CHECK

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  1. NOTE CHECK • What is the difference between relative and absolute dating? • What is superposition? • What era did humans first appear?

  2. Fossils & The Geologic Time Scale

  3. Exploring GeologicTimeGeologic time notes - page 23

  4. 1 Exploring GeologicTime(geologic time notes page 29)

  5. 2 Geologic Time Scale • The geologic time scale – a “calendar” of Earth history • Subdivides geologic history into units • Originally created using relative dates • Structure of the geologic time scale • Eon – the greatest expanse of time • Era – an eon is divided into eras

  6. 3 Geologic Time Chapter 8

  7. 4 The 4.6 billion years of Earth’s history can be divided into major time segments called eons. • Earth = 4.6 billion years • PreCambrian Eon • 4600 to 542 mya • This boundary continually changes as older soft bodied fossils are recognized • Phanerozoic Eon • 543 mya to present • mya means million of years ago

  8. 5

  9. 6 An Eon is divided into eras.Then each era can be subdivided into periods.Periods can be subdivided into epochs. EON to ERA to PERIOD TO EPOCHBIGGEST ………………………..SMALLEST

  10. 7 How do scientists pick when to start a new time segment? • Each time segment is characterized by changes in landforms (tectonics changes), climate, and in life forms.

  11. 8 Precambrian Eon is whenEarth Formed • 85% of Earth’s history • Intense volcanic activity; oceans form; meteorite bombardment • Atmosphere develops • (blue-green algae and bacteria) andLife begins with one cell organisms evolves to multi-cell organisms like worms • Few fossils exist because most did not have hard parts

  12. 9 The Phanerozoic Eon began when life developed hard bodies.The Phanerozoic Eon is divided into time segments called eras. • Paleozoic 542 Mya to 251 Mya • Mesozoic 251 Mya to 65 Mya • Cenozoic 65 Mya to present

  13. 10 The Paleozoic Era-Age of Ancient Plants and Animals • The formation of Pangaea • Six periods are marked by significant differences in lifeforms • Appearance of fish, insects, amphibians, and some reptiles

  14. 11 The Mesozoic Era Age of Dinosaurs • Known as age of reptiles; dinosaurs are prominent life forms • Last part of this period (Cretaceous) witnesses large-scale extinction of marine and flying reptiles as well as dinosaurs; extinction may be due to massive asteroid collision with Earth and massive volcanic eruptions • Pangaea breaks up

  15. 12 The Cenozoic Era Age of Mammals and Flowering Plants • Age of mammals and flowering plants • Climates cool generating widespread glaciation • Humans evolve • High level of tectonic activity as plates separate and evolve

  16. 13 What is a fossil? • A fossil is the preserved remains of a once-living organism. What do fossils tell us? • Fossils give clues about organisms that lived long ago. • They help to show that evolution has occurred. • They also provide evidence about how Earth’s surface has changed over time. • Fossils help scientists understand what past environments may have been like.

  17. 4. Erosion Erosion from rain, rivers, and wind wears away the remaining rock layers. Eventually, erosion or people digging for fossils will expose the preserved remains. 1.Sediment An animal is buried by sediment, such as volcanic ash or silt, shortly after it dies. Its bones are protected from rotting by the layer of sediment. 2. Layers More sediment layers accumulate above the animal’s remains, and minerals, such as silica (a compound of silicon and oxygen), slowly replace the calcium phosphate in the bones. 3. Movement Movement of tectonic plates, or giant rock slabs that make up Earth’s surface, lifts up the sediments and pushes the fossil closer to the surface. 14 HOW IS A FOSSIL FORMED?

  18. Petrified Fossils Molds and Casts CarbonFilms Trace Fossils Preserved Remains 15 FIVE MAIN TYPES OF FOSSILS

  19. PETRIFIED FOSSILThe Field Museum in Chicago displays a fossil of aTyrannosaurus rex. 16 PETRIFIED FOSSILS • The word “petrified” means “turning into stone.” • Petrified fossils form when minerals replace all or part of an organism. • Water is full of dissolved minerals. It seeps through the layers of sediment to reach the dead organism. When the water evaporates, only the hardened minerals are left behind.

  20. MOLD FOSSIL This mold, or imprint, is of an extinct mollusk called an ammonite. CAST FOSSILThis ammonite cast was discovered in the United Kingdom. 17 MOLDS AND CASTS • A mold forms when hard parts of an organism are buried in sediment, such as sand, silt, or clay. • The hard parts completely dissolve over time, leaving behind a hollow area with the organism’s shape. • A cast forms as the result of a mold. • Water with dissolved minerals and sediment fills the mold’s empty spaces. • Minerals and sediment that are left in the mold make a cast. • A cast is the opposite of its mold.

  21. FERN FOSSILThis carbon-film fossil of afern is more than300 million years old. 18 CARBON FILMS • All living things contain an element called carbon. • When an organism dies and is buried in sediment, the materials that make up the organism break down. • Eventually, only carbon remains. • The thin layer of carbon left behind can show an organism’s delicate parts, like leaves on a plant.

  22. 19 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.

  23. 20 Absolute Dating • By determining the age of the radioactive element, scientists can calculate the age of the fossil buried nearby. • Uses radioactive elements near the fossils to determine the actual age of the fossils. The absolute age of fossils is estimated by dating associated igneous rock and lava flows.

  24. 21 TRACE FOSSILS • Trace fossilsshow the activities of organisms. • An animal makes a footprint when it steps in sand or mud. • Over time the footprint is buried in layers of sediment. Then, the sediment becomes solid rock. FANCY FOOTWORKThis dinosaur footprint was found in Namibia, Africa.

  25. TarAn organism, such as a mammoth, is trapped in a tar pit and dies. The tar soaks into its bones and stops the bones from decaying. Ice An organism, such as a woolly mammoth, dies in a very cold region. Its body is frozen in ice, which preserves the organism—even its hair! 22 PRESERVED REMAINS Some organisms get preserved in or close to their original states. Here are some ways that can happen. Amber An organism, such as an insect, is trapped in a tree’s sticky resin and dies. More resin covers it, sealing the insect inside. It hardens into amber.

  26. 23 Index Fossils • Organisms are constantly changing or evolving. Some die out. • Some fossils remain unchanged for only a specific, short period of time. • These organisms produce the index fossils.

  27. Four features of an index fossil. 24 • Existed for short period of time • Abundant • Widespread geographically • Easily recognizable

  28. 25 What is the index fossil of the Paleozoic Era? Trilobite

  29. 26 Superposition The idea that younger rock lies above older rock.

  30. 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.

  31. For more on fossils visit: Video: Becoming a Fossil http://www.pbs.org/wgbh/evolution/library/04/3/l_043_01.html PBS Article: Major Fossil Find http://www2.scholastic.com/browse/article.jsp?id=3751945 Scholastic News Online Online Exhibit: Fossil Halls http://www.amnh.org/exhibitions/permanent/fossilhalls American Museum of Natural History Interactive Game: Fossil Hunt http://channel.nationalgeographic.com/episode/dino-death-trap-2998#tab-fossil-hunt National Geographic Scholastic Classroom Magazines. www.scholastic.com Photo Credits: PAGE 1: UTAH MUSEUM OF NATURAL HISTORY (DINOSAUR); PHOTOTAKE INC./ALAMY (ANT). PAGE 3: 5W INFORGRAPHIC (GRAPHIC). PAGE 4: Jason Lindsey/Alamy (DINOSAUR); Peter Bowater/Alamy (MOLD); David Lyons/Alamy (FERN); Hoberman Collection UK/Alamy (FOOTPRINT); John Cancalosi/Alamy (MANTIS). PAGE 5: Gary Crabbe/Alamy (DINOSAUR). PAGE 6: Peter Bowater/Alamy (MOLD); Detail Heritage/Alamy (CAST). PAGE 7: David Lyons/Alamy (FERN). PAGE 8: Hoberman Collection UK/Alamy (FOOTPRINT). PAGE 9: John Cancalosi/Alamy (MANTIS); R1/Alamy (TAR PITS); Gianni Dagli Orti/Corbis (MAMMOTH).

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