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Geo Chap 16 & 17

Geo Chap 16 & 17 - Chapters 16 17 Page 1 Geological...

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March 11, 2008 Chapters 16 & 17: Page 1 Geological Catastrophes Lecture: Chapters 16 & 17 I. The Great Dying A. Massive human loss by natural disasters is insignificant when compared to great dyings in fossil record B. Entire species, millions of entire species mass extinctions C. Knowledge comes through fossil record II. Fossils A. Evidence of former life B. Requisites for fossilization : 1. Possession of hard parts—shells, bones, teeth 2. Rapid burial , protecting from scavenging or disintegration C. Dinosaurs known by fossil bones, teeth and footprints 1. Abundant footprints show that some species lived in herds D. Examples: 1. Fossilized tree sap amber 2. Frozen animals (like mammoths) exposed as glaciers melt 3. Celtic miner’s body preserved for 2,300 years in salt mine collapse 4. Burial in oxygen-poor swamps or peat bogs preserves organisms, like tanning - 2,000-year-old Lindow man (below) found well preserved in a British Isles peat bog (preserving even small details) III. Early Understanding of Extinctions and Geologic Time A. 1786, French paleontologist Georges Cuvier: proved that extinction of species had occurred 1. Skeletons of mammoths demonstrably different that skeletons of elephants mammoths had gone extinct B. Observed profound changes in sedimentary record 1. Abrupt first appearances of fossils 2. Abundant fossils in overlying layers 3. Absence in higher overlying layers C. Steno’s 1669 law of superposition : 1. Younger layers of sediment are deposited on top of older layers D. William Smith, 1799: law of faunal assemblages 1. Strata of same age can be recognized by same fossils 2. Law of superposition + law of faunal assemblage law of faunal succession : a) Fossils from older (lower) rock layers are older and more different from present-day organisms than fossils from younger (higher) rock layers old forms of life have died out and new forms of life have developed 3. Geologic maps of England and Wales published in 1815 E. First geologic maps led to global movement in geology 1. Sedimentary strata from around world classified and subdivided on basis of fossil assemblages 2. Same fossils found in rocks in different areas same age rocks 3. 1841: standard geologic column based on fossil succession, relative ages
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March 11, 2008 Chapters 16 & 17: Page 2 F. 20 th century: geologic column refined with absolute ages from radioactive dating geologic timescale G. Brief History of Life 1. 3.85 billion years ago: archaea a) Found today at mid-ocean ridges, killed by oxygen b) Three branches of life – archaea, bacteria, eukarya (plants, animals) 2. 3.5 billion year ago: photosynthetic bacteria
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Geo Chap 16 & 17 - Chapters 16 17 Page 1 Geological...

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