Exact exerpt from Glencoe Earth Science 1997--
quote:
Uniformitarianism
Before radiometric dating was available, many people had estimated the age of Earth to be only a few thousand years old. But in the 1700's, Scottish scientist James Hutton estimated that Earth was much older. He used the principle of uniformitarianism. This principle states that Earth processes occurring today are similar to those that occurred in the past. He observed that the processes that changed the rocks and land around him were very slow, and he inferred that they had been just as slow throughout Earth's history. Hutton hypothesized that it took much longer than a few thousand years to form the layers of rock around him and to erode mountains that once towered kilometers high. John Playfair advanced Hutton's theories, but an English geologist, Sir Charles Lyell, is given the most credit for advancing uniformitarianism.
Pretty open-ended.
From Glencoe Earth Science 2002--
quote:
The principle of uniformitarianism states that the processes occurring today have been occurring since Earth formed. Only the rate, intensity, and scale with which they occur have changed.
In both texts, the PofU is talked about in a historical context to show that "As late as the turn of the nineteenth century, the majority of the world believed that Earth was only about 6000 years old." Something about Ussher, then Hutton, and finally what I quoted in the box above. The paragraph ends with an example talking about how what causes the waves of the ocean has not changed since the oceans formed. It also talks about the distribution of sediment occurring in the same way it does now. (Glencoe Earth Science 2002)
So modern geology has outgrown the need for a principle that states the obvious. OK, but we are talking about teaching not just science, but history as well. I tell the kids what the principle of uniformatarianism states and that it is pretty much a given now, but back when it was first thought of, it was a new way of thinking. I say the same things in biology when I talk about the Cell Theory. From Lucretius in 55 bce to Needham and Spallanzani in the mid-1700's to Pasteur's flasks in 1861. Uniformitarianism might sound like it is proposing that things happen uniformly throughout history, but that is not what we teach. If that makes me a lousy teacher, so be it. You have any better suggestions, Tamara?
Percy, I don't think we teach it as being part of the modern lexicon. If you want to say something about it, we talk about it when we talk about relative and radiometric dating. It is actually skimmed over with only one question on a worksheet for the students to answer--What does the principle of uniformitarianism state? I don't think we even test it!
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