Strata: Stories from Deep Time

Laura Poppick. Strata: Stories from Deep Time. New York: W.W. Norton & Company, 2025. Pp 277. Endnotes, index. Cloth, $29.99.

Laura Poppick was a geology major in college and worked as a field assistant and lab technician for a year after graduation before turning her professional attention to journalism.  Nevertheless, she has not lost her fascination and love for our planet, and it shows in her writing.  The epigraph at the beginning of Strata is a quote from Rachel Carson’s The Sea Around Us, in which Carson suggests about sediments that “perhaps we can read in them all of past history.”  Strata is Robbick’s interpretation for us of what Earth scientists have come to learn about the amazing history of our planet by studying the minutia they find in the various layers of material that have been left by happenings on Earth, some tumultuous and some gradual over vast spans of time.  And in her telling, she invites us into the intimacy she feels with that long history.  Poppick sees a beauty in that history akin to the views of Earth sent back to us by the Artemis II crew on their way to the moon and back.

Strata is divided into four chapters, each about a major component of our planet’s history: Air, Ice, Mud, and Heat.  Throughout the book, we get to know both the personalities and findings of numerous Earth scientists whom Poppick has interviewed and joined for field work.  One of them is Woody Fischer, a geobiologist at Cal Tech who grew up in Minneapolis and was entranced by his first geology class in college, much as Poppick was.  He studies “how the Earth works,” by which he means the interactions and feedback loops in the Earth system consisting of atmosphere (air), lithosphere (rock), hydrosphere (water), biosphere (life), and cryosphere (ice).  For the fourth of those five components to be part of the system, there must be oxygen in the atmosphere, but it was missing when Earth history began.  One of the first big topics Poppick addresses, and which has captured much of Fischer’s attention, is the transition called the Great Oxidation Event, or Great Oxygenation Event (GOE), when things happened in Earth’s system allowing enough oxygen to be put into the atmosphere that much of it would stay there instead of immediately attaching itself to some other element (because oxygen is such a hungry element, wanting, as its atoms do, to affix themselves to atoms of other elements).

One of the great sources of information about Earth history before the GOE is Soudan iron mine at Lake Vermillion-Soudan Underground Mine State Park in northern Minnesota.  As she does throughout the book, Poppick interweaves the Earth history gleaned from the Soudan mine’s iron deposits with the more recent histories of the United States’ dispossession of the land around the mine from the Bois Forte Band of Ojibwe and with Bob Dylan’s growing up in Hibbing.

In the chapter on Ice, Poppick describes a trip she took with geologists to an area along the coast of Newfoundland (now a provincial park) where an ancient sea floor is now on the land’s surface, exposing forms left by ancient life.  Approaching the area, “We lined up our boots and sneakers mostly in silence, as if preparing to enter a sacred space.  The park only permits socked feet beyond that point to minimize scuffing.”  (p 124)  Then she stepped onto the ancient seafloor:

The hundreds of millions of years that separated us from the Ediacaran [period] beings dissolved as I traced my finger along a narrow stalk that opened into a frond that resembled seaweed swaying in a current.   My mind wished to paint it green, render it as smooth as kelp. But I batted away those urges to categorize them as quickly as they arose.  Palm pressed softly to the stalk’s edge, I accepted the invitation to imagine a version of Earth far different from our own.  A version without backbones, without hair.  Without coffee or newspapers or politics.  A version that, for some 40 million years, allowed this motley assortment of mouthless, boneless beings to reign over the kingdom of life.

The chapter on Mud is wonderful.  Before I read it, I had never been mindful of the fact that for much of Earth’s history, the land portions of Earth’s surface were rock, not what we’re used to, which meant that rain when it fell flowed directly to the ocean, making the hydrologic cycle much less complex than it is now.  Living things could affix themselves to rock, but not until the advent of mud could plants with roots evolve.  For generations, geologists were little interested in mudrock (mud that across geological time has turned to stone), focusing instead igneous rock like granite, sedimentary rock like limestone, and metamorphic rock like marble.  Now geo-scientists studying Earth’s history realize that mudrock harbors important information about earlier eras in the history of life on our planet.  And it’s not just petrified remains like bone or shell that can tell us about earlier life forms.  Paleontologists have long studied the petrified remains of plants, but conditions had to be “just right” for the remains of a plant not to decompose but rather to survive long enough to petrify.  But the “chemical ghosts” (p 164) of plants’ roots are more persistent:

The chemical traces of roots, however, are far more plentiful.  Whereas an inert object like a shell or a bone will generally only take up physical space or leave behind a physical imprint in the rock record, roots have the power to chemically manipulate the ground they grow within.  In doing so, they leave behind a more complex geologic legacy.  As they go about their daily chores of feeding and hydrating stems and leaves, roots exude cocktails of sugars and acids from their tips that change the makeup of the sediments and the underlying bedrock.  Roots also support microbial communities that leave behind visible chemical traces.

In the chapter on Heat, Poppick recounts what we now know about earlier periods when Earth’s atmosphere has warmed.  This time around, humans are causing the warming.  In the epilog, Poppick again references The Sea Around Us, wherein Rachel Carson already recognized in 1951 that Earth was warming, even though she did not know Earth history with the intimacy that we have today.

Since her passing, we have discovered more about Earth’s past than Carson could have easily imagined.  We have learned that oxygen was all but absent in the atmosphere for more than half of Earth’s existence, and that the eventual rise of this gas allowed multicellular life to evolve.  That a series of global glaciations may have helped explode and diversify that complexity into beings with eyes and lips and bones and brains.  That these complex beings lived entirely in the oceans for hundreds of millions of years, until the rise of mud on land finally ushered in the rise of floodplains where the first terrestrial communities sought refuge.  And that as those communities lushed up and warmed during the Mesozoic, hundreds of millions of years later, they generated deposits that mirror what’s to come of our future as we barrel into a warmer world.

By pushing ourselves to the edge of crisis, we have found ourselves nose to nose with our origins.  Our planet seems to be telling us to take a look back.  To remember how unlikely each of our lives is, and yet here we are.

            Poppick echoes a quote attributed to Rabbi Heschel: “Our goal should be to live life with radical amazement…. get up in the morning and look at the world in a way that takes nothing for granted,”

            I’ve quoted more of this book that I usually do in reviews, because I’ve sought to give readers a sense of how Strata conveys our intimate connections to the deep history of our beloved planet, which we now need to protect.  The beauty of Poppick’s prose instills a feeling for our wondrous planet that goes beyond love of the plants and animals with whom we are currently sharing it.

Fredric L. Quivik