Lecture%20#2%20notes%20Geol%203950%202010%20CRStern

Lecture%20#2%20notes%20Geol%203950%202010%20CRStern -...

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Lecture #2 notes, Geology 3950, Spring 2010; CR Stern Uncertainties in interpreting the Earth’s history and understanding Earth’s dynamic activity Four main sources of uncertainty must be considered in our interpretation of the Earth’s history and our understanding of how the Earth works, the potential for future natural catastrophes, and our ability to predict and mitigate them. They include: 1) Unknown processes 2) Our short observational history of natural events 3) Analytical uncertainties in making chronological determinations and correlations of past events 4) The chaotic behavior of natural terrestrial processes Unknown processes - Good examples of the significance of unknown processes are provided by the evolution of modern concepts of the age of the Earth (see Figure 1 below). In the early 1800, three independent estimates of the age of the Earth, as being approximately 100 million years old, were made by Kelvin, Geikie and Joly. Each were incorrect because of processes that were unknown at that time, and certainly new unknown processes await discovery. 1) Joly estimated the age of the Earth from the salinity of seawater, figuring that this salinity was produced by salts added to the sea from rivers over time. The 100 million year age he determined is too young because he did not know that salt constantly is removed from seawater during interaction with the oceanic crust along mid-oceanic spreading ridges where hot seawater circulates through the oceanic crust and losses sodium and other salts.
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