A geology encyclopedia less a reference than a journey

Enlarge / An amethyst can make a good metaphor for geology as a whole.

For outsiders, geology may seem as dull as rock, with an equally opaque lexicon, but for insiders, it’s a boundless source of wonder. Various authors have used different tools to open up the dull exterior of geology to show non-geologists the sparkling wonders within: Robert Hazen used color; Jan Zalasiewicz used a pebble; and Richard Fortey used a railroad trip, for example.

Marcia Bjornerud uses words to unravel the mysteries of geology the way a video game might use gems to unlock a new level to explore. His new book is a buffet of little chapters perfect to dive in and out of, read in no particular order. Geopedia is structured like an encyclopedia in that its topics are listed alphabetically, but it is written for enjoyment rather than mere factual reference.

Bjornerud keeps the reading light even as she serves spans of time and space, and she follows each geologic “flat” with a hunter of pointers to other entrances that may be related, if only tangentially. After “Amethyst,” for example, she suggests “Kimberlite,” a diamond ore, and “Pedogenesis,” the process by which soil is made.

Geological buffet

Each chapter is its own tasting menu. Under “Amethyst” I learned that the ancient Greeks believed that amethyst crystals protected wearers from drunkenness. From there, Bjornerud jumps to the definition of a mineral, to limestone trapping atmospheric CO2, and on the atomic impurities giving color to crystals; she jumps from topic to topic like a geological Mario jumping between platforms in a video game.

The “Tully Monster” (a real creature from 310 million years ago) takes us through star wars episode ivfrom the “canteen scene” to the ongoing controversy over its place in the animal kingdom. “Oklo” links a 2 billion year old nuclear meltdown to increased oxygen in Earth’s atmosphere (your granite counter is slightly radioactive, Bjornerud mentions this in passing).

Topics include those I would expect (like Anthropocene, Discordance, Moho, etc.), but Bjornerud went out of his way to include the weird (Geophagy, anyone?) and curiosities like salt glaciers and mud volcanoes. She also unearthed words obscure even to geologists (until Geopedia, I thought a Yazoo was a synth-pop band from the 1980s).

Bites of big ideas

The book could easily have been just a frothy collection of trivia, but Bjornerud deftly nurtures the reader with meatier concepts from geology like deep time, plate tectonics, and the co-evolution of life and our planet. Subjects that could become technical are lightened by the usual analogies (fragile failure assimilated to a “knitted race”, or precipitation of uranium “like a bus full of passengers forced to disembark”, for example).

She also maintains a human connection. In “Geodynamo” we learn how Danish geophysicist Inge Lehman (a rare woman in this field at the time) identified the Earth’s inner core in 1936 thanks to a major earthquake in New Zealand. While explaining the Earth’s magnetic field, Bjornerud observes that although there is no clear evidence that magnetic field reversals cause extinctions, one today would be “debilitating” for humans. In another example, she describes a 1929 earthquake off Newfoundland that triggered a massive undersea landslide, resulting in a tsunami that killed 28 people. Severed underwater communications cables warned us of this unseen danger and provided an explanation for hitherto unexplained sediments called ‘turbidites’.

quirky gem

The tone of Geopedia is eccentric – I didn’t expect to go from “Karst” to mass executions in WWII or from “Snowball Earth” to the Norse myth of Ymir and his rock-licking cow. It can sometimes be whimsical, like when Bjornerud depicts the oldest rocks on Earth as a matriarch she dubs “Old Acasta.”

Black and white drawings by Haley Hagerman complete this quirky tone. On one page, you’ll find a rendering of a thin microscope section that looks like an abstract composition; on another is a polar bear with a sign saying “North Pole Was Here”. An intricate rendering of amethyst crystals is followed by a dog with a sparkling body of basalt.

The Bjornerud-Hagerman partnership resumes its 2018 book Respecting time: how thinking like a geologist can help save the world, which was shortlisted for the Phi Beta Kappa Prize in Science and was a finalist for the 2019 Los Angeles Times Book Prize in Science and Technology; he also won the 2019 PROSE Prize in Popular Science and Mathematics, among other accolades. Geopedia seems destined for similar praise.

Its pocket size makes it perfect as a travel companion, and its short chapters suit our depleted attention spans, making it a fun alternative to nocturnal doomscrolling or heavier non-fiction. It doesn’t matter if you’re a hardened rockhound or a geology outsider, you’ll get something worthwhile out of this little gem of a book.

Howard Lee is a freelance science writer specializing in deep-time geology and climate change. He holds a B.Sc. in Geology and M.Sc. in Remote Sensing, both from the University of London, UK. When he’s not writing, he’s probably gardening, hiking, or kayaking near his home in rural Massachusetts.

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