Earth history nc honors 13

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Earth history nc honors 13

  1. 1. Earth HistoryEarth History
  2. 2. A. Geologic EventsA. Geologic Events  The history of the changing Earth is told inThe history of the changing Earth is told in EarthEarth’s’s geologic eventsgeologic events..  The interpretation of these geologic eventsThe interpretation of these geologic events is a form ofis a form of puzzle solvingpuzzle solving ..
  3. 3. Earth HistoryEarth History I.I. Fossils andFossils and the Pastthe Past a. A fossil is:a. A fossil is: thethe remains orremains or the evidencethe evidence of a livingof a living thing, usuallything, usually preserved inpreserved in rock.rock.
  4. 4. b. Formation of Fossils:b. Formation of Fossils: 1. a. Most fossils are1. a. Most fossils are incompleteincomplete becausebecause usuallyusually only the hard parts of a plant oronly the hard parts of a plant or animalanimal become fossils.become fossils. b.b. The soft flesh of deadThe soft flesh of dead organisms was usually eatenorganisms was usually eaten by animals or decayed beforeby animals or decayed before it could form into a fossil.it could form into a fossil.
  5. 5. 2.2. a. Most fossils forma. Most fossils form when organismswhen organisms are buried in sedimentsare buried in sediments.. b. Sediments oftenb. Sediments often harden and changeharden and change into rockinto rock. When this happens, organisms. When this happens, organisms may be trapped in the rock. Most fossilsmay be trapped in the rock. Most fossils are found inare found in sedimentarysedimentary rocks.rocks. Copy the steps in your notes for #1 - #6 according to the diagram!
  6. 6. FOSSIL FORMATION Squid-like organism swimming in water. Animal dies and is eaten by other animals or bacteria
  7. 7. Soft tissues quickly decompose leaving the hard bones or shells behind Over time sediment builds over the top and hardens into rock
  8. 8. As the encased bones decay, minerals seep in replacing the organic material cell by cell in a process called "petrification." The void left behind may then fill with minerals making a stone replica of the organism.
  9. 9. Why are fossils seldom found inWhy are fossils seldom found in other rock types?other rock types?  Fossils are almost never found inFossils are almost never found in igneousigneous rocksrocks because magma is found deep withinbecause magma is found deep within Earth where no living things exist, and lava atEarth where no living things exist, and lava at the surface of the Earththe surface of the Earth burns/meltsburns/melts organismsorganisms before fossils can form.before fossils can form.  Fossils are rarely found inFossils are rarely found in metamorphicmetamorphic rocksrocks becausebecause heat, pressure and/orheat, pressure and/or chemical activitychemical activity that causes a rock tothat causes a rock to change, also destroys or damages fossils.change, also destroys or damages fossils.
  10. 10. c. Types of Fossilsc. Types of Fossils 1.1. CastsCasts andand moldsmolds (in(in rock)rock)
  11. 11. 2.2. ImprintsImprints – occur when leaves and feathers– occur when leaves and feathers leave an impression in soft sediment (mud) thatleave an impression in soft sediment (mud) that later hardens into rock.later hardens into rock.
  12. 12. 3.3. AmberAmber – occurs when insects are trapped and– occurs when insects are trapped and become embedded in resin (tree sap) thatbecome embedded in resin (tree sap) that hardens.hardens. [4:30][4:30]
  13. 13. 4.4. IceIce – occurs when an organism– occurs when an organism is preserved in iceis preserved in ice.[4:00].[4:00]
  14. 14. 5.5. TarTar – occurs when animals are– occurs when animals are trapped in tar pits as at the LaBreatrapped in tar pits as at the LaBrea Tar Pits of California.Tar Pits of California.
  15. 15. 6.6. PetrificationPetrification – occurs when minerals dissolved– occurs when minerals dissolved in ground water gradually replace the originalin ground water gradually replace the original tissues of plants and animals.tissues of plants and animals.
  16. 16. 7.7. Carbonaceous FilmCarbonaceous Film – occurs when the carbon– occurs when the carbon in the tissues of the organisms leave a residue ofin the tissues of the organisms leave a residue of thin carbon on sediment which then hardens intothin carbon on sediment which then hardens into rock.rock.
  17. 17. d. Interpreting Fossilsd. Interpreting Fossils 1. Fossils indicate that1. Fossils indicate that many different kindsmany different kinds of life forms existedof life forms existed at different times inat different times in EarthEarth’s history.’s history.
  18. 18. 2. When fossils are arranged according to age,2. When fossils are arranged according to age, they show thatthey show that certain living things havecertain living things have changed or evolved over timechanged or evolved over time.. Trilobites Isotelus - Ordovician Dalmantes - Silurian Calymene - Silurian Phacops - Devonian
  19. 19. 3. Fossils indicate how3. Fossils indicate how the Earththe Earth’s surface has’s surface has changedchanged. For example, fossils of marine. For example, fossils of marine organisms can be found in rocks that areorganisms can be found in rocks that are presently high above sea level.presently high above sea level. Fossil Butte •Green River Formation •Eocene (50 myrs) •Lake deposits •Excellent fossil preservation •fish, insects, reptiles, birds and mammals.
  20. 20. Phareodus •Large Carniverous fish •15 - 30 inches long
  21. 21. 4. Fossils give clues to4. Fossils give clues to EarthEarth’s past climate’s past climate
  22. 22. 5. Fossils tell about the5. Fossils tell about the appearance andappearance and activities of past life.activities of past life. For example, fossil teethFor example, fossil teeth give clues about the kind of food the animal ate.give clues about the kind of food the animal ate.
  23. 23. 4:30
  24. 24. II. Relative DatingII. Relative Dating NO! Not that kind of relative dating!!
  25. 25. A.A. Relative Age –Relative Age – thethe age of somethingage of something compared tocompared to something elsesomething else.. B.B. The GeologicThe Geologic ColumnColumn – an ideal– an ideal sequence of rocksequence of rock layers created bylayers created by combining data fromcombining data from all known rockall known rock sequences at varioussequences at various locations.locations.
  26. 26. c. Principle of Superposition –c. Principle of Superposition – In undisturbedIn undisturbed sedimentary rock layers (strata), the oldestsedimentary rock layers (strata), the oldest rock is at the bottom.rock is at the bottom. Oldest Youngest
  27. 27. D. Disturbed Rock Layers and Relative DatingD. Disturbed Rock Layers and Relative Dating 1. A fault is YOUNGER than the rock layers it cuts across. Rules of Relative Dating
  28. 28. 2. An igneous intrusion is younger than the rock layers it penetrates.
  29. 29. 3. The folding and tilting of rock layers are events that are younger than the rock layers they effect.
  30. 30. 4. Unconformity4. Unconformity  A "missing layer ofA "missing layer of rock" or a gap in therock" or a gap in the record. Simply put,record. Simply put, it is a "buriedit is a "buried erosional surface."erosional surface." .. In order for erosion to occur……. UPLIFT had to happen first to put it at the surface!!!
  31. 31. What happened here?
  32. 32. E. Rock CorrelationE. Rock Correlation
  33. 33. F. Index Fossils –F. Index Fossils – a fossil that is used to datea fossil that is used to date the rock layers in which it is foundthe rock layers in which it is found.. 1. An organism that lived during a relatively short, well- defined time span. 2. Must have a wide distribution geographically.
  34. 34. •Preservable Parts (hard parts) •Limited time in existence as a species •Widespread distribution (to correlate rocks that are far apart)
  35. 35. G. Volcanic time markers -G. Volcanic time markers - a layer ofa layer of volcanic dust covering rocks over a large areavolcanic dust covering rocks over a large area (maybe the world).(maybe the world).  When a violent eruption of a volcano occurs itWhen a violent eruption of a volcano occurs it may send dust high into the atmosphere where itmay send dust high into the atmosphere where it can spread over the entire planet. It settles outcan spread over the entire planet. It settles out of the air and forms a layer over wide regions atof the air and forms a layer over wide regions at the same time.the same time.  Asteroid impacts can have the same effect.Asteroid impacts can have the same effect. Example: the layer that marks the extinction ofExample: the layer that marks the extinction of dinosaurs has characteristics of an asteroiddinosaurs has characteristics of an asteroid impact.impact.
  36. 36. III. Geologic TimeIII. Geologic Time Up till now we have determined relative ages by:Up till now we have determined relative ages by:  Superposition andSuperposition and fossil recordfossil record  Deformation andDeformation and unconformitiesunconformities  Cross-cutting relationshipsCross-cutting relationships A.A. TheThe Geologic Time ScaleGeologic Time Scale divides Earthdivides Earth’s’s history into sections of time.history into sections of time.
  37. 37. 4:30
  38. 38. B. Geologic time began when Earth first formed about 4,600 million years ago or 4.6 billion years ago.
  39. 39. C. The units or sections of geologic time include:C. The units or sections of geologic time include: 1.1. EONEON– largest division of Earth history– largest division of Earth history Relative time scale started to be established in the 19Relative time scale started to be established in the 19thth century.century.  Hadean eonHadean eon: Establishment of core, plate tectonic system and: Establishment of core, plate tectonic system and climate (climate (3.8 – 4.6 bya3.8 – 4.6 bya))  Archean eonArchean eon: earth oldest rocks were found. Core of continents: earth oldest rocks were found. Core of continents are formed, unicellular organisms originated. (are formed, unicellular organisms originated. (2.5 – 3.8 bya2.5 – 3.8 bya))  Proterozoic eonProterozoic eon: plate tectonic and climate geosystems became: plate tectonic and climate geosystems became similar to present day. Oxygen in the atmosphere establishedsimilar to present day. Oxygen in the atmosphere established resulting in iron formations, multicellular organism developed inresulting in iron formations, multicellular organism developed in later record. (later record. (540 mya – 2.5 bya540 mya – 2.5 bya))  Phanerozoic eonPhanerozoic eon: abundant life and multicellular organisms, rich: abundant life and multicellular organisms, rich fossil record (fossil record (540 mya – present540 mya – present))
  40. 40. 2. Era – subdivisions of an eon 3. Period – subdivision of an era 4. Epoch – subdivisions of a period Phanerozoic Eon is divided into 3 eras: Paleozoic (old life) Mesozoic (middle life) Cenozoic (recent life)
  41. 41. D. The boundaries between geologic time intervalsD. The boundaries between geologic time intervals represent major changes on Earth which include:represent major changes on Earth which include: 1.1. Major extinctionsMajor extinctions – Ex: Cretaceous and– Ex: Cretaceous and Tertiary Period boundary – DinosaursTertiary Period boundary – Dinosaurs become extinctbecome extinct 2.2. Appearance of a new life formAppearance of a new life form 3.3. Major climate changesMajor climate changes –– Ex: boundaryEx: boundary between Pleistocene and Holocenebetween Pleistocene and Holocene Epochs marked by last major ice age.Epochs marked by last major ice age.
  42. 42. Soft-bodied organisms Emergence of vertebrates Major extinction ~90% of life Major Extinction ~ 50% of life
  43. 43. IV. Absolute Age –IV. Absolute Age – identifies the exactidentifies the exact date of an eventdate of an event.. A.A. RadioactivityRadioactivity – the ability of an element– the ability of an element to change spontaneously into a differentto change spontaneously into a different element byelement by losing or gaining matterlosing or gaining matter from the nucleus of an atom.from the nucleus of an atom.
  44. 44. B. Radioactive DecayB. Radioactive Decay 1.1. Radioactive or ParentRadioactive or Parent element = anelement = an atom that has an unstable nucleus thatatom that has an unstable nucleus that changes spontaneously orchanges spontaneously or “decays”.“decays”. 2.2. Decay or DaughterDecay or Daughter element = the stableelement = the stable element that is the result of theelement that is the result of the spontaneous change in a radioactivespontaneous change in a radioactive element.element.
  45. 45. 3.3. Half-life =Half-life = the time it takes for ½ of athe time it takes for ½ of a radioactive element to change into aradioactive element to change into a decay or stable element.decay or stable element. 4.4. The rate of decay (half-life) is NOTThe rate of decay (half-life) is NOT affected by any outside condition suchaffected by any outside condition such as:as: 1.1. HeatHeat 2.2. PressurePressure 3.3. Chemical actionChemical action
  46. 46. Key points of Radioactive Decay:Key points of Radioactive Decay:  A ratio between the original material (parentA ratio between the original material (parent material) and the decay product (daughtermaterial) and the decay product (daughter material) can be used to determine how manymaterial) can be used to determine how many half-lives the material has undergone.half-lives the material has undergone.  The radioisotope used should have a half - lifeThe radioisotope used should have a half - life that is around the age of the object being dated.that is around the age of the object being dated.  Ex: C14 is used for objects thousands of years oldEx: C14 is used for objects thousands of years old  C14 can be used to date back to around 50,000 years.C14 can be used to date back to around 50,000 years.
  47. 47. 5. Carbon 14 has a short half-life and is therefore used to date the remains of living things such as wood, bones, leather.
  48. 48. V. Evolutionary DevelopmentV. Evolutionary Development 1.1. SpeciesSpecies – organisms that are able to mate– organisms that are able to mate and produce offspring capable of continuingand produce offspring capable of continuing the same species.the same species. 2.2. Organic evolutionOrganic evolution – suggests that variations– suggests that variations within a species may provide some memberswithin a species may provide some members of that species with a higher probability ofof that species with a higher probability of survivalsurvival 3.3. Rock record indicates thatRock record indicates that older rockolder rock formations contain more simple and marine lifeformations contain more simple and marine life forms, while theforms, while the younger rock formationsyounger rock formations have more complex organisms.have more complex organisms.
  49. 49. Early HominidsEarly Hominids
  50. 50. Unlike Man – some organisms have changed little in their design, like sharks!

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