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Presentation on theme: "estrellamountain. edu/faculty/farabee/biobk/BioBookPaleo1"— Presentation transcript:

1 http://www2. estrellamountain. edu/faculty/farabee/biobk/BioBookPaleo1

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3 Light oxygen in water (H2O16) evaporates more readily that water with heavy oxygen (H2O18). Hence oceans will be relatively rich in O18  when glaciers grow and hold the precipitated O16

4 Ice core measurements Ice-core oxygenisotopic measurements from Greenland (right hand side) and from Antarctica (left hand side). The isotope measurements can be interpreted to yield the global sea surface temperatures to ~160,000 years ago (colder temperatures to the left). The two traces are consistent with each other and depict the most recent glacial period, ending ~15,000 years ago.

5 Snowball earth

6 End of glacial deposits
Figure  3. The geologists Paul Hoffman and Daniel Schrag, in Namibia, leaning on a layer of glacial sediments, among which is a large loose rock that fell to the bottom of the sea after being carried there by floating icebergs during the glacial phase. The strata is capped by a layer of carbonates sedimented after the glaciation (cap carbonates).  .harvard, edu/people/faculty/hoffman/sno wball_paper.html

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8 Figure 5.13: The development of the global climate over the past 65 million years based on deep-sea oxygen-isotope measurements in the shell of benthic foraminifera (i.e. foraminifera living at the bottom of the ocean). Theδ18O temperature scale, on the right axis, is only valid for an ice-free ocean. It therefore applies only to the time preceding the onset of large-scale glaciation in Antarctica (about 35 million years ago, see inset in the upper left corner). Figure from Zachos et al. (2008).

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11 Temperature changes are compared to the average surface temperature from 1951-1980


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