The subtle migration of sand dunes in the Gran Desierto de Altar, east of where the Colorado River once met the Gulf of California, offers a tangible analogy for understanding geological history. These ever-shifting landscapes, shaped by wind, mirror the processes that formed ancient rock formations like the Coconino sandstone in the Grand Canyon, whose diagonal striations reveal wind patterns from 280 million years ago, illustrating the geological adage that the present is the key to the past. However, the Earth’s rock record also bears witness to immense, often global, catastrophes, most notably the "Big Five" mass extinction events that profoundly reshaped life on our planet and set the stage for all that followed. By delving into this ancient past, a tapestry woven from both gradual geological shifts and cataclysmic events, we gain invaluable insights that can illuminate our present and guide our future. Grasping the stories embedded in formations like the Coconino, deposited over vast stretches of time and across thousands of square miles, requires a shift in perspective, an embrace of what geologists term "deep time." This profound engagement with Earth’s ancient history can fundamentally alter our understanding of our current challenges and the long-term consequences of our actions. Three compelling books offer unique gateways into this geologic past, each providing a distinct lens through which to view Earth’s billions of years of evolution.

John McPhee, a celebrated writer for The New Yorker, popularized the concept of "deep time" in his seminal 1981 work, Basin and Range. This foundational text, now best experienced within the lightly updated version found in his 1999 Pulitzer Prize-winning anthology, Annals of the Former World, remains remarkably relevant. Originally published during the Reagan administration and later revised during the Clinton era, Basin and Range has seen some numerical refinements and conceptual shifts, yet its narrative power and geological insights endure. McPhee set out to explore what he considered the most captivating chapters of North America’s multi-billion-year history, aiming to convey the profound narratives that geologists decipher from the Earth’s rocky strata. His method involved accompanying geologists on their journeys across the continent, following their explorations along Interstate 80 from New Jersey to Nevada.

In the arid landscapes of Utah and Nevada, McPhee investigates the dramatic geological phenomenon of mountain ranges, known as ranges, interspersed with equally vast valleys, or basins. This characteristic pattern of "range, basin, range, basin" tells a story of tectonic forces at play. A geologist explains to McPhee that faulting created these basins, which were subsequently filled with sediments – a simplified yet evocative description of a process that, while younger than the age of dinosaurs, still unfolds over millions of years. McPhee further explores how the North American continent is actively being "pulled to pieces" in the vast region between the Rocky Mountains and the Sierra Nevada. This geological drama is not unprecedented; one of McPhee’s guides reveals that a similar rifting of the Earth occurred approximately 200 million years ago when the supercontinent Pangea began to fracture, eventually allowing the Atlantic Ocean to emerge. This historical precedent raises the intriguing question of whether future generations in Nevada might one day gaze across a new sea towards California.

McPhee’s narrative is punctuated by insightful detours, such as a visit to an abandoned silver mine in Nevada. Following a precarious road overlooking a valley that McPhee notes holds spiritual significance for the Paiute people, akin to the Black Hills for the Sioux, he learns about the nineteenth-century miners who extracted the richest silver deposits, leaving potentially millions of dollars’ worth of ore discarded as waste. These explorations often lead McPhee to contemplate the immense scale of geologic time. He observes that human perception is typically limited to about five generations – two ahead, two behind, with a strong focus on the present. Geologists, however, grapple with measuring deep time, a task that requires confronting the challenge of truly comprehending the passage of millions of years. McPhee’s book serves as an accessible primer, an introduction to the fundamental concepts of geology, and a guide to understanding how geologists can vividly reconstruct and "inhabit scenes that no one ever saw." These scenes, he writes, encompass "archipelagos of aching beauty rising in volcanic violence to settle down quietly and then forever disappear—almost disappear."

Science journalist Laura Poppick, in her book Strata: Stories from Deep Time, published in July 2025, treads similar historical ground with a comparable dedication to detail as McPhee. Yet, Poppick’s work, imbued with a meditative prose style, offers a distinct approach, organizing its narrative around chronological themes: air, ice, mud, and heat. Rocks dating back two to three billion years hold crucial clues about the initial emergence and evolution of oxygen in our atmosphere. Poppick journeys to Minnesota to examine iron-rich rocks from an era of global anoxia, a time when Earth’s atmosphere contained virtually no free oxygen. This primordial air, existing for roughly half of Earth’s history, laid the groundwork for our own existence and the development of modern life, facilitating the formation of the iron that is now integral to everything from our "steel cars and kitchen appliances and medical devices and airplanes."

The Cambrian explosion, approximately 540 million years ago, marked a pivotal moment when nearly all major animal groups alive today first appeared. Paleontologists reconstruct this evolutionary burst and the subsequent losses incurred during mass extinction events by meticulously studying fossil evidence preserved in ancient rocks. Poppick delves into two of the "Big Five" mass extinctions: one occurring 250 million years ago and another roughly 50 million years later. Unlike the famous asteroid impact that wiped out the dinosaurs, these two catastrophic die-offs appear to have been triggered by colossal volcanic eruptions in geologically unfortunate locations. Poppick explains that "the magma that welled up from the mantle sat directly beneath massive reservoirs of oil, gas and coal." As this magma ascended, it ignited these fossil fuels, releasing not only vast quantities of carbon dioxide but also toxic butanes, benzenes, and ozone-depleting gases. This historical account of past environmental devastation offers a potent parallel, potentially aiding our comprehension of a warming future and suggesting pathways toward mitigation.

Climate models suggest that the seemingly endless summer of the dinosaur era was significantly hotter than today, with temperatures between 14 and 25 degrees Celsius (25 to 45 degrees Fahrenheit) higher. Poppick accompanied scientists to a remote site in Wyoming, searching for remnants of the largest land animals ever to walk the Earth: the long-necked sauropods, such as Diplodocus, Brontosaurus, and Apatosaurus. The scientists’ focus extends beyond fossilized bones to the ancient ecosystems that supported these colossal herbivores and how they, and their inhabitants, evolved over time. They have been studying the ecological dynamics within 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 took approximately nine million years, thus preserving nine million years of dinosaurian history. Poppick emphasizes the vastness of this timescale by noting 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 strata strive to understand how sauropods and other dinosaurs thrived in the Jurassic warmth. Poppick observes 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, however, one might turn to Riley Black’s book, When the Earth Was Green, published in February 2025. A science writer and paleontologist, Black artfully blends scientific data with artistic rendering to transport readers into the sensory experience of ancient ecosystems. Each chapter unfolds as a vignette, accompanied by an appendix that details the scientific consensus, plausible hypotheses, and the author’s personal reflections, offering a comprehensive and imaginative exploration of the past.

Black’s depiction of Utah 150 million years ago eschews the direct examination of Jurassic remnants found in Wyoming, instead inviting readers on a journey through time. We follow an Apatosaurus as it forages in a sprawling woodland, consuming dense carpets of horsetails and an ancient ancestor of today’s pungent ginkgo tree. The dinosaur’s immense size and long, muscular neck allow it to reach both high into the canopy and down to the ground, providing a degree of protection from predators. "The fact that she exists at all is a testament to the strange nature of her habitat," Black writes, describing a landscape of towering conifers rising from a sea of ferns and cycads. This abundant flora, essential for sustaining such massive herbivores, illustrates what Black terms "an evolutionary dance between herbivores and plants." Black’s earlier work, The Last Days of the Dinosaurs, meticulously chronicled the fifth of the "Big Five" mass extinctions, detailing its devastating impact in granular temporal detail. In When the Earth Was Green, however, Black shifts focus from cataclysm to the intricate co-evolution of creatures and plants, illustrating how their intertwined stories are preserved as geological remnants.

McPhee’s writing style evokes a road trip through the American West in the 1970s, accompanied by a witty journalist and an eccentric geologist whose exclamations of "Shazam!" punctuate the discovery of remarkable rock formations. While not every inside joke may be immediately apparent, the journey itself is exhilarating. Poppick’s approach immerses readers in deep time by bringing them along on field trips, involving them in scientific research, and guiding them through laboratories, revealing the engaging process of scientific discovery. Black, conversely, transports readers into dreamlike landscapes with her vivid descriptions of long-vanished worlds, employing her imagination and scientific knowledge to foster a visceral experience of deep time. As Poppick aptly observes, "Our planet seems to be telling us to take a look back." Each of these books serves as a profound guide, leading us through the immensity of geologic time and prompting us to contemplate our place within this grand, ancient narrative.