The shifting sands of the Gran Desierto de Altar, a vast expanse east of the Colorado River’s former delta, offer a tangible, modern-day analogue to geological processes that shaped landscapes millions of years ago. Just as these dunes migrate inch by inch, driven by the relentless wind, ancient winds sculpted formations like the Coconino sandstone in the Grand Canyon, leaving behind diagonal striations that tell tales of prehistoric air currents from 280 million years ago. This principle, that the present offers clues to the past, forms a cornerstone of geological understanding. However, Earth’s history is not solely a narrative of gradual change; it is also punctuated by cataclysmic events, most notably the "Big Five" mass extinctions that fundamentally reshaped life and ecosystems across the globe. By delving into these ancient chapters, marked by both slow, incremental shifts and dramatic, planet-altering catastrophes, we can gain profound insights into our present circumstances and anticipate future trajectories. Understanding how geological formations, such as the sprawling Coconino sandstone, accumulated over eons, and grappling with the concept of "deep time"—the vast epochs stretching back billions of years—empowers us to better comprehend the long-term consequences of contemporary actions. Here, we explore three remarkable books that invite readers on journeys into Earth’s profound geological past.

The evocative term "deep time" was brought into wider popular consciousness by John McPhee, a celebrated writer for The New Yorker, in his seminal 1981 work, Basin and Range. For contemporary readers, the lightly updated version within his 1999 Pulitzer Prize-winning anthology, Annals of the Former World, provides an accessible entry point. Though initially published during the Reagan administration and later revised in the Clinton era, McPhee’s narratives, even with refined scientific data and evolving geological concepts, retain their captivating power. McPhee’s ambition was to illuminate the most compelling aspects of North America’s multi-billion-year history by translating the stories etched in rocks into compelling prose. He achieved this by accompanying geologists on their cross-continental expeditions, tracing their journeys along Interstate 80 from New Jersey to the dramatic landscapes of Nevada.

In the arid expanses of Utah and Nevada, McPhee intricately details the geological phenomenon of the Basin and Range Province, characterized by parallel mountain ranges separated by extensive valleys. Geologists explain to McPhee that these basins are formed by tectonic faulting, with sediments subsequently filling the resulting depressions—a simplified explanation for a process that unfolded over millions of years, a timescale significantly younger than the age of dinosaurs. McPhee delves into the forces that are actively "pulling North America to pieces" between the Rocky Mountains and the Sierra Nevada, a process not unique to the present era. His guides reveal that similar continental rifting occurred approximately 200 million years ago when the supercontinent Pangea began to fracture, ultimately leading to the formation of the Atlantic Ocean. This historical perspective prompts a thought-provoking question: might future generations witness Nevadans and Californians separated by a new ocean? McPhee’s narrative is rich with illuminating digressions, such as a visit to an abandoned silver mine in Nevada. Following a precarious road overlooking a valley that held deep spiritual significance for the Paiute people, akin to the Black Hills for the Sioux, McPhee learns about the shortsightedness of 19th-century miners who extracted the richest veins of silver, leaving potentially millions of dollars’ worth of ore discarded as waste. McPhee also artfully grapples with the sheer immensity of geologic time, observing that human perception typically spans only five generations—two ahead, two behind, with a primary focus on the present. Geologists muse with McPhee on the human capacity to measure deep time without truly grasping the scale of millions of years. McPhee’s book serves as an essential primer, an invitation to understand how geologists can "inhabit scenes that no one ever saw… archipelagos of aching beauty rising in volcanic violence to settle down quietly and then forever disappear—almost disappear."

Science journalist Laura Poppick, in her July 2025 publication, Strata: Stories from Deep Time, traverses similar historical terrain with a meticulous attention to detail that echoes McPhee’s style, yet her approach is distinct. Her book is structured around chronological themes—air, ice, mud, and heat—and woven with a reflective, meditative prose. Rocks dating back 2 to 3 billion years hold crucial evidence about the initial emergence of oxygen in Earth’s atmosphere. Poppick journeys to Minnesota to examine iron-rich rocks from a period of global anoxia, a time when oxygen was virtually absent from the atmosphere for a span equivalent to half of Earth’s existence. The composition of this ancient air set the stage for the evolution of life as we know it and underpins modern society, facilitating the formation of iron essential for everything from "steel cars and kitchen appliances and medical devices and airplanes."

Approximately 540 million years ago, the planet witnessed the Cambrian explosion, a pivotal event that saw the emergence of nearly all major animal groups present today. Paleontologists meticulously study the fossil record within rock strata to track this evolutionary radiation and the devastating losses incurred during mass extinction events. Poppick vividly recounts two of the "Big Five" mass extinctions: one occurring 250 million years ago and another roughly 50 million years later. Unlike the asteroid impact that famously ended the reign of the dinosaurs, these earlier die-offs are strongly linked to colossal volcanic eruptions in geologically sensitive regions. Poppick explains that "the magma that welled up from the mantle sat directly beneath massive reservoirs of oil, gas and coal," igniting these fossil fuels and releasing not only carbon dioxide but also toxic compounds like butanes and benzenes, alongside ozone-depleting gases. This historical account of past environmental catastrophes offers a poignant parallel to contemporary concerns about climate change, providing a framework for understanding our potentially sweltering future and pathways toward mitigation.

Climate models suggest that the seemingly endless summer of the dinosaur era was significantly warmer than today, with temperatures between 14 and 25 degrees Celsius (25 to 45 degrees Fahrenheit) higher. Poppick joins scientists on a clandestine expedition to a Wyoming site in pursuit of evidence left by the largest terrestrial animals ever to inhabit Earth: the long-necked, long-tailed sauropods, including iconic species like Diplodocus, Brontosaurus, and Apatosaurus. These scientists are less interested in the bones themselves than in understanding the environment that sustained these colossal herbivores and how that ecosystem, and its inhabitants, evolved over time. They meticulously study the Morrison Formation, a vast layer of sedimentary rock stretching from New Mexico to Montana, which has yielded more dinosaur fossils than any other formation on the continent. The deposition of these rocks spanned approximately 9 million years, offering a detailed chronicle of dinosaurian life during that period. Poppick notes the remarkable evolutionary acceleration, observing that "just twelve million years or so of evolution produced humans, gorillas and chimps from the same common ancestor." Researchers analyzing the Morrison Formation’s layers strive to understand how sauropods and other dinosaurs thrived in the Jurassic warmth, with Poppick reflecting that "as we inch closer to a clearer picture (of that time), we deepen the intimacy with which we know Earth and its capacity to withstand heat."

To truly immerse oneself in the world of the Morrison Formation, a journey into Riley Black’s February 2025 book, When the Earth Was Green, is essential. Black, a science writer and paleontologist, masterfully blends scientific data with artistic expression to evoke the sensory experience of ancient ecosystems. Each chapter unfolds as a vivid vignette, complemented by an appendix that delineates what is known, what is inferred, and what elements captured the author’s imagination. Black transports readers 150 million years into Utah’s past, moving beyond the Wyoming fossil sites Poppick explored.

In Black’s narrative, an Apatosaurus forages in a lush woodland, its diet comprising abundant horsetails and an ancient ancestor of today’s pungent ginkgo tree. The dinosaur’s elongated, muscular neck allows it to reach both high into the canopy and down to the forest floor, while its immense size offers a formidable defense against predators. Black marvels at the creature’s existence, describing it as "a testament to the strange nature of her habitat," characterized by towering conifers rising from a dense undergrowth of ferns and cycads. This rich botanical diversity was crucial for the sauropods’ extraordinary growth, illustrating what Black terms an "evolutionary dance between herbivores and plants." In her previous work, The Last Days of the Dinosaurs, Black meticulously detailed the fifth of the "Big Five" extinctions, examining its devastating impact on a timescale of seconds, minutes, hours, days, and years. In When the Earth Was Green, she shifts her focus from cataclysm to the intricate co-evolutionary relationships between ancient creatures and plants, whose intertwined stories are preserved in the fossil record.

McPhee’s writing offers a rollicking road trip through the 1970s, featuring a keen journalist and an eccentric geologist who exclaims with delight at geological wonders. While not every inside joke may land, the journey is undeniably exhilarating. Poppick invites readers into the field, joining scientific expeditions and laboratory investigations, revealing the process of scientific discovery in a surprisingly engaging manner. Black, conversely, plunges readers into almost dreamlike landscapes, painting vivid portraits of long-vanished worlds, using her imagination and expertise to make deep time palpable. Poppick wisely observes, "Our planet seems to be telling us to take a look back," and these three books serve as invaluable guides, illuminating the vastness of deep time and prompting contemplation of our place within its grand narrative.