Other Questions (refer to the video lecture, your textbook, and notes): 4. Fossi

Question

Other Questions (refer to the video lecture, your textbook, and notes): 4. Fossils of foraminifera found in ocean sediments suggest that the oceans were warming during the Quaternary. There are several ways that we can use foraminifera to determine water temperature. What are they? 5. As the continental Glaciers retreated (and created floods like the Missoula Floods), the land surface that had been pushed down under the massive ice sheets began to rise back up. This is similar to how an ice cube would float back up if you pushed it into your iced tea. What is this process called? 6. Look at Figure 14-10 on page 376 of your text book. Which arca of Canada experienced the largest amount of isostatic rise? Why did this region rise more than any other portion? 7. Glaciation during the Quaternary was characterized by many retreats and advances. What earth processes have been suggested to cause ice ages?

Explanation / Answer

4. Sea level has also been inferred from the oxygen isotopic ratio measured on the calcite shells ofbenthic foraminifera. The shell 18O/16O ratio is a function of both the isotopic composition and the temperature of the water in which the foraminifera develops. Isotope oxygen-18 is a bit heavier than normal oxygen-16, and biologists had shown that the amount of each isotope that a foram takes up varies with the temperature of the water.

Variations in the water temperature inferred from oxygen isotopes from the test calcite can be used to reconstruct palaeoceanographic conditions by careful comparison of changes in oxygen isotope levels as seen in benthic forms (for bottom waters) and planktic forms(for mid to upper waters). This type of study has allowed the reconstruction of oceanic conditions during the Eocene-Oligocene, the Miocene and the Quaternary.

5. Isostasy is the movement of land mass associated with the movement of overburden pressure.

6. Incomplete information.

7. Variations in the intensity and timing of heat from the sun are the most likely cause of the glacial/interglacial cycles that is fluctuations in the amount of insolation (incoming solar radiation) are the most likely cause of large-scale changes in Earth's climate.

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