Book Month continues...
I recently read the excellent book
Reading the Rocks, by Marcia Bjornerud. I would recommend this book to anyone interested in their planet. I think it's an equally good choice for professionals and interested amateurs. The book works on several levels. It's lyrically written, with an economy of flourishes, but an ear for a good turn of phrase. She's also really keen on analogies, and that makes me like her a lot. Finally, she seems to be a kindred spirit, using geological insight as a gateway to philosophical perspective. The book is rich in detail, though broad enough in scope that it will satisfy a structural geologist, an
astronomer, or your average run-of-the-mill nature lover.
A taste of her style:
"Human consciousness is arguably the first truly novel innovation to arise since Cambrian time, in the sense that the technologies our consciousness has spawned have freed us from the limits of our own body architecture." (p. 172)
"Over more than 4 billion years, in beach sand, volcanic glass, granites, and garnet schists, the planet has unintentionally kept a rich and idiosyncratic journal of its past.... The genre varies from breathless thriller to quotidian diary; the action ranges from microbial metabolisms to mountain building." (p. 5)
Under a section subtitled "Grammar and Syntax of the Three Rock Languages," Bjornerud says, "Just as you wouldn't look to a cookbook for information on military history, you wouldn't expect a sandstone to tell you much about the Earth's interior. Sedimentary rocks are the best reference works to consult if you are interested in past conditions at the surface of the Earth - for example, ancient climates, biological activity, or the distribution of water bodies. Igneous rocks chronicle the long-term chemical evolution of the Earth and provide glimpses into processes that occur at inaccessible depths. Metamorphic rocks, born in one setting (sedimentary or igneous) and transformed as they encounter new environments, are the travel writers of the rock world, chronicling their astounding journeys through the crust." (p. 33)
I love how she gives anthropomorphic personalities to rocks. This is her great talent as a writer. Along similar lines as the quote above, she later compares mafic to felsic igneous rocks: "A mafic rock like basalt generally has tales to tell of life in the mantle, while for a felsic rock like granite, whose progenitors were themselves crustal, the mantle is a nearly forgotten ancestral homeland." (p. 43)
She has a great analogy for radioactive decay, using "parent" and "daughter" as part of the analogy itself: A "magnanimous parent who transfers half of his savings to his daughter each year on her birthday." Each year, the parent has less money, but the daughter's wealth has grown by exactly that same amount. "At any time, an external auditor could determine the age of the girl - the number of years the parent had been giving money to her - by finding the ratio of the amount in the daughter's account to the amount in the father's account." (p. 58) Clever!
She gives some great comparisons for viscosity, including glacial ice, basaltic lava, rhyolitic lava, motor oil, water at room temperature, and blood (which she helpfully reminds us is thicker than water).
Chapter 3 concludes with a great comparison between the small and the large: "...Small phenomena can wield surprising power: A trivial deviation from sphericity causes the entire planet to wobble, raindrops and tiny flaws in minerals bring down mountains, trace gases in the air govern climate, and microbes modulate the atmosphere. Perhaps the greatest challenge we face in attempting to fathom the Earth is to gain a proper sense of our own size as a human species; like spoiled children, we routinely overstimate our importance on the planet but underestimate the destructiveness of our self-absorption." (p.98)
Criticism:
- The "currently accepted geologic timescale" at the beginning of the book includes "Tertiary," with no mention of Paleogene or Neogene. Frowny face.
- She attributes John Playfair's quote about being "giddy from peering into the abyss of time" directly to James Hutton. Tragically, Hutton was never so eloquent himself.
Overall:
Highly recommended. Get it; read it.
Book Month continues...
The Greatest Show on Earth - Richard Dawkins
That's an image by Chris Waythomas of the USGS, hosted by the Alaska Volcano Observatory website. It shows a cutbank (river-eroded alluvium deposit) along Rust Slough, south of the Drift River Oil Terminal, northeast of Redoubt Volcano. The sediments exposed were deposited on March 22, 2009 by a lahar (volcanic mudflow). The lahar deposit is 2.5 m thick. When I saw this image tonight (as I was searching for another shot), I was particularly struck by the subrounded clasts of ice in the mud. Here is ice acting the part that chunks of rock usually play. Technically, ice is a mineral, and so these chunks are sedimentary clasts much like any other... But to me there's something distinctly different about seeing ice cobbles and pebbles included in a sedimentary deposit. On a planet as warm as Earth, this sort of thing isn't likely to be preserved in the geologic record. It would melt! ...And that gets me thinking about other planets and planet-like objects, like Titan. The Huygens probe took pictures of sedimentary clasts, presumably of ice, on the surface of that moon. Other cold locations could have CO2 ice ("dry ice"): That makes for the sort of rock specimen that would be really difficult to keep on your shelf as a 'deskcrop'...
