Week3 - Historical Patterns of Global Change Geological...

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Unformatted text preview: Historical Patterns of Global Change Geological time scale is hierarchical Eon Era Period Epoch Index fossils Wide-ranging species Not restricted to microhabitats Often marine organisms planktonic, calcareous foraminiferans siliceous radiolarians (Protozoa) of the Cenozoic era chitinous colonial graptolites (Hemichordata) floating animals (Ordovician and Silurian) swimming ammonoid cephalopods (Mollusca) of Mesozoic vascular plants of Carboniferous period Theory of Continental Drift has had the largest impact on biogeography evidence is conclusive Development of Plate Tectonics Theory Lyell (mid 1800s) Antonio Snider-Pelligrini (1858) F. B. Taylor (1908 - 1910) American geologist Alfred L. Wegener meteoroligist who developed ideas of continental drift independently of Taylor while noting congruence of opposite coastlines on Atlantic Ocean; working hypothesis presented in 1912; published in 1915 Main points of Wegeners theory continental rocks fundamentally different than those of ocean floor, and are lighter & thus float on the mantel major landmasses once united into a supercontinent, Pangaea Pangaea broke into small continental plates, which moved apart Main points of Wegeners theory breakup of Pangaea began as a rift valley, which widened into an ocean midoceanic ridges mark where continents were joined distribution of major earthquake and volcanic regions, and mountain building regions are related to continental movement Main points of Wegeners theory continental blocks have retained their initial outlines, except in mountain orogeny regions joining the margins of continents lines up stratigraphic zones, fossils, and reconstructed paleoclimates rates of movement range between 0.3 and 36 m per year radioactive heating in the mantle may be the primary cause of continental movement forces of movement are gradual Opposition to the theory Involved shifting paradigm New ideas challenged in science Contained many factual errors Testing model difficult would have required much more geological and biogeographical evidence than presented Lacked a plausible mechanism Acceptance of theory took time Five decades after Wegeners proposals, sufficient evidence was gathered by geologists, paleontologists and biogeographers S. W. Carey (1955, 1958); Bullard et al (1965) demonstrated the fit of continents into Pangaea using submarine contours of continental shelves. Evidence for plate tectonics Stratigraphic Topographic features align along Wegeners proposed connections of fragmented Gondwanaland Paleoclimatic Southern Hemisphere glacial scars aligned only if Gondwanaland reconstructed Paleontological The late Paleozoic glacial deposits of southern continents are covered with Permian rocks bearing the Glossopteris flora (arborescent gymnosperms of temperate climates) - circumscribes Gondwonaland...
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Week3 - Historical Patterns of Global Change Geological...

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