Measuring the Pulse of the Earth

I am currently reading Annals of the Former World, John McPhee’s geological history of the United States. It pulls together four previously published books and then a final fifth book and includes a fascinating narrative table of contents where McPhee gives an overview of two decades of travel and writing.

I have had it on my shelf for a very long time and decided this was the year to dive in. And, I am so glad I did. McPhee was an English major who dabbled in science, especially geology. His writing is a pleasure to read. The first book, Basin and Range, is a combination of travel memoir and scientific treatise and historical outline. McPhee’s passion spills over when he tries to explain his interest in geology:

Geology was called a descriptive science, and with its pitted outwash plains and drowned rivers, its hanging tributaries and starved coastlines, it was nothing if not descriptive. I was a fountain of metaphor–of isostatic adjustments and  degraded channels, of angular unconformities, and shifting divides, of rootless mountain and bitter lakes (p. 31)

He introduces us to the early geologists, including Sherlock Holmes who despite being fictional was the first forensic geologist, interpreting bits of grit from various locales.

And, I learned that it is not just the water tides that are impacted by the moon. In fact, there are solid-earth tides: “The sea is not all that responds to the moon. Twice a day the solid earth bobs up and down, as much as a foot. That kind of force and that kind of distance are more than enough to break hard rock” (p. 21). I did not know this bit of geological trivia. While I don’t completely understand the science described here, this article describes the idea of “rock tides.” 

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