Geologynotes#2

Geologynotes#2 - Geology notes(Wednesday February 17...

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Geology notes (Wednesday February 17) Ga=billion years Continental crust Max 3.5 – 4 Ga Avg ~ 650 Ma Fig 22.13 Caption > 3.5 Ga Archaean > 2.5 Ga Proterozoic 0.54 – 2.5 Ga Phanerozoic < 0.54 Ga Craton: stable continental crust with no tectonic activity during phanerozoic period Orogen: elongate region of continental crust Folded/faulted during continent – continent convergence I. Nature of the seafloor 1. provinces of the ocean floor fig 13.6 continental margins deep ocean basins oceanic ridges 2. continental margins a. passive continental margins not on active plate boundary (e.g., surrounding, Atlantic Ocean) features continental shelf- submerged continental crust very gentle seaward slope (long time to get to the very deep water) ~ 7.5% of modern oceans varies with sea level ex. Sea level vs continental glaciations Continental slope Narrow band Relatively steep slope : avg ~ 5 degrees 460 ft/mile covens(?) join between continental and oceanic crust continental rise seafloor slopes more gently again Avg 32 ft per mile Thick accumulations of continental sediments
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NC 16,000-23,000 ft of sediment b. Active continental margin plate boundary closely coincides with continental boundary - tectonic activity subductors zones and transform-fault margins accretionary wedge = sediments and igneous oceanic crust added to continent during convergence Fig 18.6 glacial-interglacial sea level Friday’s Notes 3. Deep Ocean Basins a. ocean trenches b. abyssal plains -deep, flat sediment buries topography fig 13.4 c. seamounts submarine volcanoes mostly extinct > 1,000,000! d. oceanic plateaus- large areas of past intense volcanism fig 13.10 fig 5.41- mantle plume and associated hot spot volcanism NEW TOPIC! III. Mater and Minerals (Chp. 3) What is earth made of? 3 ways to describe composition: 1. chemical elements (like atoms) 2. minerals (inorganic chemical compounds) 3. rocks = aggregates of minerals A. Chemistry 1. atoms -subatomic particles characterize by electrical charge and by mass protons- positive (+1) and mass of about 1 atomic mass unit (amu)***~1.66x10^-24 g neutrons- no charge and about 1 amu electron- negative (-1) and about 0.00055 amu -organization protons and neutrons are together in the nucleus (very small area- radius~10^-14m)
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nucleus is very dense electrons: “cloud” around nucleus; radius of electron clouds ~ 10^-10 m
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Geologynotes#2 - Geology notes(Wednesday February 17...

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