Strata review: The captivating story that Earth’s ‘boring’ layered rocks tell us

Diapers
Laura Poppick (WW Norton)

The history of the earth is the history of change. The 4.5 billion years of the history of this planet transformed it from an infernal world of the magma oceans and toxic air into a temperate and habitable house covered with a diversified range of life. This arc was itself punctuated by catastrophic stops, departures and reversions while the nested biogeochemical cycles of the earth system played their roles on the most epic imaginable scene.

That we know anything about this radical story is mainly thanks to the rocks. In particular, it is thanks to the sediments which preserve in their layers an orderly order of the events which have shaped the surface. These are the strata, and the science of interpreting them is called stratigraphy.

In Strata: depth storiesThe journalist Laura Poppick offers a Breean to this subtle science of reading rocks, and the lessons he can teach us about the way the planet reacts and recovers from periods of upheaval. “It is through these lines in the stone that we can glimpse of ancient iterations of this planet and gain context for the moment we are now turning,” she writes.

There are many moments in the past of our planet which could tell a story of transformation, but Poppick focuses on four episodes, some particularly dramatic, some less known. The first explores the story of how the atmosphere has filled oxygen, a series of “whiffs”, while microorganisms began to develop photosynthesis, to the major oxidation event, which led countless species to extinction about 2.4 billion years ago.

The debates on what triggered this event gives way to the second section, on “Snowball Earth”, a period about 720 million years ago when a large part of the planet would have frozen. Another segment explores the rise of the mud and how, with the plants, he redid the continents. Then, finally, the mesozoic era dominated by dinosaurs serves as a study on how the planet behaves in a greenhouse climate due to volcanic explosions pushing the concentrations of carbon dioxide in the air several times higher than today.

For each episode, Poppick Profile the geologists who now work to unravel the many unanswered questions about what happened when and why. She also visits the key sites where the strata underlying these change stories are visible, from Newfoundland to Canada to the Australian Outback, where she worked as a geologist on the ground.

The importance of paying attention to rocks is a recurring theme. With an unusted eye, they can look commonplace, writes Poppick, but “to the formed eye, they contain physical and chemical clues, or proxies, which reveal in a remarkable detail what the planet looked like and felt when the rocks were formed”. At another time, she quotes a geologist saying: “You cannot appreciate what is special, without appreciating what is boring.”

This book is an admirable effort to make the stratigraphy not boring. He does not always succeed, and the fragmented style of Poppick meant that I sometimes lost the intrigue.

The way she compares certain transformations to changes in human origin today is also tense. For example, Poppick compares the climate of the Mesozoic greenhouse to global warming led by our programs now, but this era was so much warm than it is not really able to do it, even in the highest scenarios.

Another limitation comes from the unfinished quality of earth science itself. Some big questions that Poppick sets up – the real trigger of the land of the snowball, for example – remains without responding to answers, or are allowed to float as differences in opinion among the partisan camps. I finished reading by feeling uncertain about what we can say with certainty. But maybe this is normal for the course of geology. “Nothing is settled in stone, because our understanding of stones does not change, just like the stones themselves,” explains Poppick.

Aside from that, the book succeeds in capturing the scale of history that rocks hold. It works better when it helps us to see how the observations of “boring” rocks lead directly to information on the main transformations in the history of the earth. Such moments give us an overview of how a stratigrapher thinks when Poppick examines the outcrops otherwise forgettable, inviting us to see rocks that we meet in a new light.

“The strata are, in some ways, love letters left by an aging land,” she writes. This book is full of reasons to read their secrets.

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