Dating - Dr. Sarah Cadieux PDF

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Dr. Sarah Cadieux...

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1. Ice at the poles have more negative oxygen isotopes than the values in the ocean a. The heavier one weighs out. b. It gets lighter and lighter – negative values 2. Sea level history a. Major cold periods make continental-scale sheets i. Traps large volumes of water evaporated from the oceans ii. Lowers sea level iii. Trapping ice on land iv. Ice is more negative on land v. When ice melts sea level will rise 1. Composition of ocean changes 2. Sea level rises 3. Oxygen isotopes from deep ocean sediments a. Form in ocean i. Whatever isotopic value the water is goes into the shells. ii. Record isotopic composition from when they were born iii. When the shells die they sink into the sediment 4. Milankovitch a. Eccentricity – the shape of our orbit – ellipse i. 100,000 yr cycle b. Obliquity – change of tilt c. Precession – wobbly top 5. Ice cores a. Ice – lighter during glaciers b. Dating ice i. Annual layers – building up 1. Count back in time ii. Ash 1. Ash bed – aerosols a. Date when there was a volcanic eruption c. Get a sense of temperature i. more negative as we get colder d. As you have snow build up you get rid of your air i. still have a few air bubbles 1. record atmosphere at the time the snow precipitated out 2. measure them for greenhouse gas traces 3. tells us the composition of our atmosphere e. dropstones i. tell us about past glaciations ii. like erratics – deposited in moraine sediments...