Notes from Deep Time A Journey Through Our Past and Future Worlds

Deep time is, to me, one of the most awe-inspiring concepts to come out of the earth sciences. Getting to grips with the incomprehensibly vast stretches of time over which geological processes play out is not easy. We are, in the words of geologist Marcia Bjornerud, naturally chronophobic. In Notes from Deep Time, author Helen Gordon presents a diverse and fascinating collection of essay-length chapters that give 16 different answers to the question: "What do we talk about when we talk about deep time?" This is one of those books whose title is very appropriate.

For Gordon, a chance encounter with an outdoor information board during a walk on the North Downs near London ignites her interest in deep time. Before long, she is visiting museums and interviewing earth scientists and palaeontologists. Notes from Deep Time is thus very relatable to a general audience who, like Gordon, are not geologists. A few of the 16 chapters in this book have previously been published, but most are new. She has organised them around three topics: geology, extinct life, and the intersection of deep time with human affairs. Having introduced the concept of deep time and how the age of the Earth was slowly uncovered, she delves into palaeoclimatology, stratigraphy, plate tectonics, earthquakes, volcanic eruptions, dinosaurs, the Anthropocene, palaeoart, urban geology, nuclear waste, etc.

One enjoyable aspect is that Gordon brings in new perspectives, even for topics I was familiar with. When discussing ice cores, she explains the work of pioneer Willi Dansgaard and his discovery of rapid climatic changes subsequently named Dansgaard-Oeschger events. Initially eyed suspiciously by scientists, the idea was soon enough corroborated by evidence from pollen records and ocean sediments. Her discussion of dinosaurs is equally novel, and appropriately titled "what we talk about when we talk about dinosaurs". She asks why children are so fascinated by them, how fossil dig sites have changed over time, how the palaeontological community is torn over the trade in fossils, and how the story of their extinction forms "an irresistible backdrop onto which to project our own fears of climate change and contemporary apocalypse" (p. 196), something explored further in Sepkoski's Catastrophic Thinking. When visiting a dinosaur trackway in Utah, she reminds the reader that it is easy to lose sight of the beasts themselves. "Bombarded with plastic figurines and dinosaur memes, familiarity stops me really seeing a dinosaur. [...] Touching the edges of one of the theropod's lozenge-shaped toes, 150 million years almost dissolve in the hot desert air. There really were dinosaurs here. For a moment that fact becomes amazing once again" (p. 198-199).

I furthermore appreciated how Gordon pays attention to the subtleties and technicalities of topics. In two chapters she takes a surprisingly deep yet accessible dive into stratigraphy. In 2018, a terrible ruckus broke out when some stratigraphers proposed subdividing our current epoch, the Holocene, into three new ages, the most recent one being called the Meghalayan. Partially this was because others are still working on the stratigraphical case for the Anthropocene. She listens to the arguments put forth by both proponents and opponents of these concepts. She goes into a similar level of nuanced detail when discussing colour as deduced from exceptionally well-preserved fossils. The focus has so far been on melanosomes and the pigment melanin, but Gordon also interviews Maria McNamara who is looking at carotenoid pigmentation and structural colours. These discoveries allow palaeoartists to make more true-to-life reconstructions. An open-hearted conversation with palaeoartist Robert Nicholls touches on his Psittacosaurus model, the importance of thorough background research, and his frank opinion that most dinosaur art that gets published is "regurgitated nonsense" (p. 214). And while I had read about the plans for long-term underground storage of nuclear waste in Finland in Macfarlane's Underland, Gordon adds an interesting discussion on the challenges of designing warning signs for distant future generations to stay away from such repositories.

Some chapters touched on, for me, completely novel subjects. There is a chapter on chalk, one of the least appreciated rock types amongst geologists. Here, she accompanies a team making a new map of the chalk formations underlying parts of Britain. She discusses the primitive fossil trees found in Gilboa in the US, and their unusual mode of growth. Another chapter focuses on the difficulty of predicting earthquakes and volcanic eruptions, and highlights that part of the problem is the loss of hard-won knowledge and experience when scientists retire. And she opened my eyes to the phenomenon of urban geology, the idea that the materials used in buildings, especially older ones, can reveal more about local geology.

What makes this wide-ranging collection of deep-time musings so captivating is Gordon's language and sharp observations. She talks to the Geological Society's librarian who highlights commonalities between poetry and geology: both involve "building worlds in your mind and presenting them to others using descriptive language" (p. 8). When we discuss history, we merrily skip over thousands and millions of years. As Gordon puts it beautifully: "if the human brain naturally compresses the past, then the scientists working with deep time are in the business of decompression" (p. 22). When explaining how the theory of plate tectonics came together, she of course pays homage to Alfred Wegener but cleverly points out that "you can tell the story of plate tectonics in many different ways" (p. 75), depending on whose contributions you focus on. And why, of all the proposed new stratigraphical units, has the Anthropocene taken such hold of the popular imagination? Gordon's answer is that science has been in the business of knocking humans off their pedestal for several centuries. "Considered one way, then, the Anthropocene concept puts humans back at the centre of the world [...] and at some level we can't help finding that attractive – even if the price for that return is environmental disaster" (p. 244). The only thing I felt was missing from this book were illustrations and photos; many of the places and phenomena described here would have benefited from some.

Notes from Deep Time is a fantastic dive into the deep past of our planet that engages with deep time on many levels. Readers will find at least some, if not many chapters that will thoroughly captivate them and induce that most rare of sensations: "temporal vertigo" (p. 1).