Geologic Time Scale for Editing.ppt
- 1. Prentice Hall EARTH SCIENCE Tarbuck Lutgens
- 3. 1. What are the things that that we need to observe in the crime scene?
- 5. The Geologic Time Scale • the time line of the History of the Earth, is based from the rock record. • Geologic time is subdivided into hierarchal intervals 1. Eon (the largest) 2. Era 3. Period 4. Epoch
- 6. • Subdivision of Geologic time is based from significant events in the Earth’s History as interpreted from the rock record.
- 7. Age of the Earth • The Earth has a very long history — 4.5 billions of years of history. • The age of the Earth is based from the radioactive isotopic dating of meteorites.
- 8. Rocks Record Earth History 12.1 Discovering Earth’s History Rocks record geological events and changing life forms of the past. We have learned that Earth is much older than anyone had previously imagined and that its surface and interior have been changed by the same geological processes that continue today.
- 9. A Brief History of Geology 12.1 Discovering Earth’s History Uniformitarianism means that the forces and processes that we observe today have been at work for a very long time.
- 10. Fossils Indicate Evolutionary Pathways: Precambrian Little direct evidence of fossils, due to lack of hard body parts. Fossil evidence include; algae, bacteria, and traces of soft body organisms. Paleozoic Era -- “Age of the Invertebrate”. Invertebrates evolved into vertebrates; First land plants evolved in the Silurian. Abundance of fishes in the Devonian which is known as the “age of the fishes”. Lung fish evolved into amphibians throughout the the Mississippian and Pennsylvanian. Amphibians evolved into reptiles in the Permian and reptiles are known as the first true land dwellers. Hard shelled eggs made this possible. Mass extinctions of invertebrates including trilobites and numerous other marine species occurred at the end of the Paleozoic Era.
- 11. Fossils Indicate Evolutionary Pathways: Mesozoic Era -- “Age of the Reptiles” Dinosaurs became dominant. First birds are seen during this time The end of the Mesozoic Era was marked by mass extinctions of reptiles including dinosaurs and numerous other species. Cenozoic Era -- “Age of the Mammals”. Mammals evolve and dominate during this time. Flowering plants are the dominant land plant. Some mammals became extinct during the late Cenozoic (11,000 years ago). These include the mastodon, mammoth, saber-tooth cat, large ground sloth, giant bison and others.
- 13. Nicholas Steno • Steno’s principles – superposition, original horizontality, and lateral continuity • Stratigraphy – the study of layered rocks.
- 14. Relative Dating—Key Principles 12.1 Discovering Earth’s History Relative dating tells us the sequence in which events occurred, not how long ago they occurred. Law of Superposition • The law of superposition states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it.
- 15. Ordering the Grand Canyon’s History
- 16. Relative Dating—Key Principles 12.1 Discovering Earth’s History Principle of Original Horizontality • The principle of original horizontality means that layers of sediment are generally deposited in a horizontal position.
- 18. Relative Dating—Key Principles 12.1 Discovering Earth’s History Principle of Cross-Cutting Relationships • The principle of cross-cutting relationships states that when a fault cuts through rock layers, or when magma intrudes other rocks and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected. Inclusions • Inclusions are rocks contained within other rocks. • Rocks containing inclusions are younger than the inclusions they contain.
- 22. Abraham Gottlob Werner • a German geologist. Werner divided the rock record into the following rock-time units (from oldest to youngest): – Primary – Secondary – Tertiary – Quaternary. • Used the Principle of Superposition extensively to establish temporal relationship among the rock units.
- 23. William Strata Smith • used fossils primarily to identify rock layers • observed that each layer or strata of sedimentary rock contain a distinct assemblage of fossils which can be used to establish equivalence (correlation) between rock units separated by long distances. Moreover • observed that these fossils succeed each other vertically in a definite order.
- 24. Charles Lyell • British Lawyer and Geologist, recognized the utility of fossils in subdividing Geologic Time on the basis of fossils. He was able to subdivide the Tertiary by examining the proportion of living vs.extinct fossils in the rocks.
- 25. Relative Dating—Key Principles 12.1 Discovering Earth’s History Unconformities • An unconformity represents a long period during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed. • An angular unconformity indicates that during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred.
- 26. Formation of an Angular Conformity
- 27. Relative Dating—Key Principles 12.1 Discovering Earth’s History Unconformities • A nonconformity is when the erosional surface separates older metamorphic or intrusive igneous rocks from younger sedimentary rocks. • A disconformity is when two sedimentary rock layers are separated by an erosional surface.
- 28. A Record of Uplift, Erosion, and Deposition
- 29. Correlation of Rock Layers 12.1 Discovering Earth’s History Correlation is establishing the equivalence of rocks of similar age in different areas.
- 30. Correlation of Strata at Three Locations
- 31. EVOLUTION OF EARTH’S HISTORY Fossils are the remains or traces of prehistoric life. They are important components of sediment and sedimentary rocks. Biostratigraphy - a sub-discipline of stratigraphy which deals with the use of fossils in correlation and establishing the relative ages of rocks. Index fossils are widespread geographically, are limited to a short span of geologic time, and occur in large numbers.
- 32. Fossils and Correlation 12.2 Fossils: Evidence of Past Life The principle of fossil succession states that fossil organisms succeed one another in a definite and determinable order. Therefore, any time period can be recognized by its fossil content. Index fossils are widespread geographically, are limited to a short span of geologic time, and occur in large numbers.
- 33. Fossil Formation 12.2 Fossils: Evidence of Past Life Interpreting Environments • Fossils can also be used to interpret and describe ancient environments.
- 34. Overlapping Ranges of Fossils
- 35. Assessment 1. the time line of the History of the Earth, is based from the rock record. 2. He is the first to recognize the correspondence of between rocks and time 3. The study of layered rocks. 4. He observed that these fossils succeed each other vertically in a definite order. 5. He observed that each layer or strata of sedimentary rock contain a distinct assemblage of fossils
- 36. 1. What are the different geologic times Scale of the Earth? 2. Enumerate the important events on the Geologic time of the Earth
- 37. The end
- 38. Fossil Formation 12.2 Fossils: Evidence of Past Life Fossils are the remains or traces of prehistoric life. They are important components of sediment and sedimentary rocks. • Some remains of organisms—such as teeth, bones, and shells—may not have been altered, or may have changed hardly at all over time. The type of fossil that is formed is determined by the conditions under which an organism died and how it was buried. Unaltered Remains
- 39. Fossil Formation 12.2 Fossils: Evidence of Past Life Altered Remains • The remains of an organism are likely to be changed over time. • Fossils often become petrified or turned to stone. • Molds and casts are another common type of fossil. • Carbonization is particularly effective in preserving leaves and delicate animals. It occurs when an organism is buried under fine sediment.
- 40. Fossil Formation 12.2 Fossils: Evidence of Past Life Indirect Evidence • Trace fossils are indirect evidence of prehistoric life. Conditions Favoring Preservation • Two conditions are important for preservation: rapid burial and the possession of hard parts.
- 42. Structure of the Time Scale 12.4 The Geologic Time Scale Based on their interpretations of the rock record, geologists have divided Earth’s 4.56-billion-year history into units that represent specific amounts of time. Taken together, these time spans make up the geologic time scale.
- 43. Structure of the Time Scale 12.4 The Geologic Time Scale Eons represent the greatest expanses of time. Eons are divided into eras. Each era is subdivided into periods. Finally, periods are divided into smaller units called epochs. There are three eras within the Phanerozoic eon: the Paleozoic, which means “ancient life,” the Mesozoic, which means “middle life,” and the Cenozoic, which means “recent life.”
- 44. Structure of the Time Scale 12.4 The Geologic Time Scale Each period within an era is characterized by somewhat less profound changes in life forms as compared with the changes that occur during an era. The periods of the Cenozoic era are divided into still smaller units called epochs, during which even less profound changes in life forms occur.
- 45. Precambrian Time 12.4 The Geologic Time Scale During Precambrian time, there were fewer life forms. These life forms are more difficult to identify and the rocks have been disturbed often.
- 46. The Geologic Time Scale
- 47. Difficulties With the Geologic Time Scale 12.4 The Geologic Time Scale A sedimentary rock may contain particles that contain radioactive isotopes, but these particles are not the same age as the rock in which they occur. The age of a particular mineral in a metamorphic rock does not necessarily represent the time when the rock was first formed. Instead, the date may indicate when the rock was metamorphosed.
- 48. Using Radiometric Methods to Help Date Sedimentary Rocks
- 49. WHAT IS A GEOLOGIC TIME SCALE? System of chronologic measurement relating to stratigraphy to time that is used by geologist and other earth scientists
- 50. INTRODUCTION TO CONCEPT: The period is the basic unit of geological time in which a single type of rock system is formed. Two or more periods comprise a geological Era. Two or more Eras form an Eon, the largest division of geologic time. Some periods are divided into epochs. The major periods in the geologic history of the Earth are (mya=million years ago):
- 52. PRECAMBRIAN Hadean Eon 4.6 to 3.9 billion years ago “Rockless Eon" - The solidifying of the Earth's continental and oceanic crusts. Archeozoic Eon (Archean) 3.9 to 2.5 billion years ago "Ancient Life" The first life forms evolve Proterozoic Eon 2.5 billion years ago to 540 mya *multi-celled, animals appear, including sponges. *Single supercontinent called Rodinia. *First multicellular life: colonial algae and soft- bodied invertebrates appear.
- 53. THE FIRST EON: HADEAN •Earth's formation by accretion from the solar nebula, 4.6 billion years ago •bombardment by meteorites •volcanism must have been severe •Earth changed from liquid to solid
- 54. THE SECOND EON: ARCHEAN •3.8 to 2.5 billion years ago •Earth cooled significantly •An atmosphere formed which lacked oxygen and an ozone layer but likely contained methane, ammonia, and other gases which would be toxic to most life on our planet today. •primordial life began to evolve: stromatolites, such as cyanobacteria (blue-green algae) and archea (bacteria that can survive in extreme conditions)
- 55. Heterocyst – Nitrogen Fixation Photosynthetic Cells Cyanobacteria
- 56. THE THIRD EON: PROTEROZOIC •started 2.5 billion years ago and ended 543 million years ago •stable land masses first appeared •oxygen build-up in the atmosphere •prokaryotic bacteria and the four eukaryotic kingdoms (plants, animals, fungi, & protists) •end of proterozoic: first soft-bodied animals (fossil evidence)
- 57. Hadean, Archean and Proterozoic Eons
- 58. Paleozoic Era
- 59. PHANEROZOIC EON Paleozoic Era: The Paleozoic is bracketed by two of the most important events in the history of animal life. 1. Multicellular animals went dramatic diversity explosion 2. Largest Mass extinction of mostly 90% of marine organisms
- 60. PALEOZOIC ERA Cambrian Period "The Age of Trilobites" 540 to 500 mya
- 61. PALEOZOIC ERA Ordovician Period 505 to 438 mya
- 62. PALEOZOIC ERA Silurian Period 438 to 408 mya
- 63. PALEOZOIC ERA Devonian Period "The Age of Fishes" 408 to 360 mya
- 64. PALEOZOIC ERA Carboniferous Mississippian Period 360 to 325 mya
- 65. PALEOZOIC ERA Carboniferous Pennyslvanian Period 325 to 280 mya
- 66. PALEOZOIC ERA Permian Period "The Age of Amphibians" 280 to 248 mya
- 67. Mesozoic Era
- 68. PHANEROZOIC EON Mesozoic Era: Many of the Old life forms had just gone extinct in the Permian Extinction, the world’s largest mass extinction. Depleted state was followed by an explosion of new life forms such as dinosaurs, mammals, birds and flowering plants
- 69. MESOZOIC ERA Triassic Period 248 to 208 mya
- 71. MESOZOIC ERA Jurassic Period 208 to 146 mya
- 73. MESOZOIC ERA Cretaceous Period 146 to 65 mya
- 77. Cenozoic Era
- 78. PHANEROZOIC EON Cenozoic Era: The most recent Era of the three major subdivisions of animal history. Also called as the Age of Mammals 65.5 million years ago to present