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Unformatted text preview: 2/27 Glaciations and Maine Important Concepts 1) How glaciers form 2) Glacial features and interpretation 3) Hot glaciers shaped Maine's landscape Numerical Age Radioactivity Carbon14 (radioactive) o Produced in atmosphere C14, C13, and C12 mixed in atmosphere and ocean o C12 Stable = 98% o C13 Stable = <1% o C14 radioactive = .0000001% Plants and animals ingest or breath CO2 C14/C12 constant while organism is alive When organism dies, C14 amount decreases at regular rate (half-life= 5730 years). Age calculated. o C12/C14 ratio changes with time BUT... o Variation in solar radiation= variations in C14 production o Oceans reservoir time of over 4000 years o Burning of fossil fuels adds "old" carbon to atmosphere o Nuclear bombs added C14 to atmosphere o Requires calibration.... Radiocarbon years vs. calibrated years Last great Ice sheet o 22 ka= 22,000 o Laurentide Ice Sheet 1. Extent of Ice 2. Lowered World-wide Sea level Last Glacial Maximum: o World-wide (Eustatic) sea level lowered by 120 m. o Why? o Because there is only a certain amount of water on the earth Marine Inundation Sea level high-stand indicators o Fossil wood o Glaciamarine Sediment Blue Clay aka Presumpscott Fm. o Glaciomarine Deltas o Hiatella artica ...
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- Spring '08