A lively introduction to current concepts in geology, pitched to the undergraduate reader but well suited to generalists as well.
Readers who learned their geology two or three decades back have a little catching up to do: The chronologies have changed, certain theories have changed and indeed the planet itself has changed, for, as Lawrence University geology professor and debut author Bjornerud notes, “the magnitude of human actions on the Earth now matches those of natural agents.” (And more: she notes that humans add 16 times more carbon dioxide to the atmosphere than do volcanoes, the next-biggest contributor to the old greenhouse effect.) Bjornerud obliges in this well-paced survey of such things as the rock cycle, thermohaline ocean circulation, and convergent evolution. Those daunted by the formidable language of geology, the stuff in which John McPhee revels, will be pleased by Bjornerud’s plain-English approach, by which, for instance, she likens the Earth to a great recycling system: “There is no natural equivalent of a landfill. Nothing is unusable waste, and nothing will last forever, at least not in any particular form.” Bjornerud covers a lot of ground, so to speak, with the result that some big-picture processes earn rather hasty treatment; pyroclastomaniacs are likely to clamor for more on volcanism, for instance, while fans of continental drift may want a little more plate tectonic action for their buck. Still, such are the shortfalls of surveys, and all the fascinating asides will spur motivated readers to dig deeper on their own. Who knew, for instance, that the oceans may once have been frozen during the period called Snowball Earth, that a little zircon chip from Australia is “the very oldest discovered object native to the Earth,” that the seas of the moon are actually big holes punched into the lunar surface by massive meteorites, and that a rock has only to be ten inches wide to qualify as a boulder?
These are the kinds of things of which naturalists’ dreams are made, and Bjornerud introduces them memorably.