When Google Earth first launched in 2001, I, like many others, found myself poring over satellite imagery. Identifying familiar and unfamiliar landmarks always brought a certain thrill, and spotting craters was part of that. But to properly map impact structures, you need a better dataset. The stunningly produced Terrestrial Impact Structures is a large-format atlas that maps all currently accepted ones, plus some likely candidates, and makes for an instant must-have reference work for any geology or astronomy library.
Terrestrial Impact Structures: The TanDEM-X Atlas (2-volume set), written by Manfred Gottwald, Thomas Kenkmann, and Wolf Uwe Reimold, published by Verlag Dr. Friedrich Pfeil in November 2020 (hardback, 608 pages)
This atlas is, furthermore, a beautiful example of one field of scientific enquiry playing off another. The TanDEM-X in the subtitle refers to the German satellite mission that, during six years, collected the precise planetary-wide elevation data that is the bedrock of this atlas. To be clear, this book was obviously not the reason these satellites were put in orbit. But, once gathered, such data can have many uses and scientists can apply to get access to it, which is exactly what these three authors did.
Next to introducing the satellite mission and the principles behind radar remote sensing (specifically synthetic aperture radar interferometry), the six chapters in the 33-page introductory section provide very readable overviews of asteroid and comet formation, a blow-by-blow analysis of the first seconds and minutes following a typical hypervelocity impact, and the geological traces these leave. This last one is a particularly important chapter. After all, how do you determine if a crater resulted from volcanism, tectonics, or an impact? Especially when you keep in mind that ancient craters are modified over time by erosion, sediment deposition, and tectonic deformation. The answer is that the forces unleashed by an impact are unlike any other geological process on our planet and modify rocks in a unique way, something known as shock metamorphism. Thus, features such as shatter cones, microscopic planar and feather fractures, and specific lithologies—impact breccias, impact melt rock, and (micro)tektites—are important diagnostic criteria.
The atlas forms the bulk of this book. Volume 1 covers Africa, North & Central America, and South America, while volume 2 deals with Asia, Australia, and Europe. It seems no impact structures have been located in Antarctica yet. The authors draw on the widely respected and accepted Earth Impact Database, hosted and maintained by the Planetary and Space Science Center at the University of New Brunswick in Canada. This contains 190 structures to which the authors add another 18 recent ones that are confirmed according to shock metamorphism criteria.
“[T]he descriptions are as revealing as the maps themselves. Many of these structures are either eroded beyond obvious recognition or were buried following impact.”
Each entry contains a full-page topographical map, coloured to show elevation, with a legend detailing longitude and latitude, the structure’s diameter, and the currently accepted age estimate. For craters that are clearly visible on the surface, additional satellite imagery is included, while for those that have been well researched the authors include geological maps or cross-sections (redrawn from earlier publications), field photos of characteristic rock outcrops, or photos of diagnostic rock samples showing traces of shock metamorphism.
Short fact sheets, written by either Kenkmann or Reimold, detail the geological setting of the impact location, the topology and age of the crater as far as known, and the history of its discovery. A short separate section gives tips on how to reach the location, ranging from “take exit so-and-so” to “requires permits / extensive expedition planning / a helicopter”. Finally, there is a list of selected references that are a goldmine in themselves, pointing to non-English publications, proceedings, and unpublished master’s theses. Mercifully, these are also compiled at the end of volume 2 in one large bibliography, together with a six-page glossary, lists of chemical elements and abbreviations, and two separate indices, one cartographic and one general. The geologic timescale is included at the end of each volume. This is thus a fully self-contained reference work.
Next to famous impact structures such as Meteor Crater or Chicxulub, there are those treated in e.g. Springer’s Impact Studies series; Virginia’s Chesapeake Bay, Russia’s Puchezh–Katunki, or Norway’s awesomely named Mjølnir. But the majority will be little known outside the impact geology research community. This is where the descriptions are as revealing as the maps themselves. Many of these structures are either eroded beyond obvious recognition or were buried following impact, leaving no visible traces at the surface. Some were revealed when aerial surveys showed magnetic or gravitational anomalies, while others were discovered by companies prospecting for minerals or hydrocarbons. Further fascinating insights are the now obsolete history of explaining these structures in a uniformitarian framework as the result of cryptovolcanism or cryptoexplosions, rather than accepting catastrophist explanations. The authors are particularly mindful to highlight the rationale behind disagreements on age or size estimates. Their rigour also shows in their decision to relegate some structures, widely accepted in the community but still in need of further work to close the case, to a separate “further confirmation required” section at the end of each continent’s chapter.
“I am very pleased the authors worked with a publisher who cares about quality. [This] is a beautiful work consisting of two over-sized volumes produced by traditional offset printing”
It would be tempting to call this work unprecedented, and it is certainly a step up from Paul Hodge’s 1994 Meteorite Craters and Impact Structures of the Earth that contained 139 entries. But there is one potential fly in the ointment: the publication last year by Springer of the Encyclopedic Atlas of Terrestrial Impact Craters that draws on the same Earth Impact Database. That atlas is based on the Italian COSMO–SkyMed mission, which also used synthetic aperture radar operating in the X-band. From what I can deduce, though, that mission did not rely on an interferometry setup with two satellites flying in tandem and did not yield elevational data.
Not having read it, I cannot speak for the quality of the scholarship of that book, though I can speak for the print quality. In my daytime job, I handle Springer books on an almost daily basis and, like the vast majority of their publications, this is a print-on-demand book. Their printing process is wholly unsatisfactory for visual books such as atlases, resulting in desaturated and grainy colour images (pretty much as if they were printed on your home inkjet printer). I am very pleased, therefore, that the authors of the book under review worked with a publisher who cares about quality. Terrestrial Impact Structures is a beautiful work consisting of two over-sized volumes measuring 24.5 × 32.6 cm in a very handsome slipcase, 
produced by traditional offset printing on thick, slightly glossy, high-quality paper stock. And all that at a lower price. In case you were in doubt which to choose, this, here, is the book to go for.
Terrestrial Impact Structures is a feast for the eyes that is a mandatory reference work for any professional or amateur geology or astronomy library. If you are on the fence, I will let you in on one last detail. The acknowledgements mention that the printing costs were in part covered by two of the authors. I might be proven wrong, but I have a suspicion that once this book sells out, it will not be reprinted and will quickly become highly sought after.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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Volcanoes are some of the most awe-inspiring natural spectacles on our planet. There is much more to them, though, than the stereotypical image of a conical fire-spitting mountain, and I have been keen to learn more. As I searched for serious introductory books on volcanology, this was one title that kept coming up. But wait, why is a biologist reviewing geology textbooks?
Volcanoes, written by the late Peter Francis and Clive Oppenheimer, published by Oxford University Press in December 2003 (paperback, 521 pages)
A short preamble seems in place. My choice to study biology went at the expense of geology, although the latter topic continued to fascinate me. Two decades later, my job exposes me to many fascinating-sounding but advanced-level earth science books. I have since started to make inroads into this field for the sheer joy of expanding my knowledge. And thus I found myself eyeing up the new book Volcanotectonics. Yet, as I recently rediscovered, there is still a gap between having covered the essentials of geology and diving headlong into an advanced topic. Hoping to bridge that gap, I turned to Francis & Oppenheimer’s Volcanoes.
The first edition of this book was published in 1993 and authored by volcanology professor Peter Francis. When he passed away in 1999, his former PhD student Clive Oppenheimer, now a professor of volcanology in his own right, took it upon him to revise the text and bring it up to date for this second edition, published in 2003. Francis’s desire was to write a book to be read rather than consulted. Volcanoes is thus less of a textbook than you might think: there are no chapter summaries or student exercises. What you will find is a logical flow of chapters detailing the inner workings of volcanoes, glued together by the fascinating stories of past eruptions and, occasionally, Francis’s trademark humour, lampooning the field of volcanology.
“Volcanoes is […] less of a textbook than you might think: there are no chapter summaries or student exercises. What you will find is a logical flow of chapters detailing the inner workings of volcanoes, glued together by the fascinating stories of past eruptions […]”
Volcanoes starts with very primordial questions. Where do the heat and the rocks that drive volcanism come from? This introduces you to planetary formation and the radioactive decay of isotopes. In case you were expecting to start with plate tectonics, that is the next subject to be tackled. This explains the difference between volcanoes at plate margins where the oceanic crust is either formed or destroyed, and the minority occurring far from margins, such as the volcanic islands of Hawai’i.
Chapters four to twelve form, to my mind, the nuts-and-bolts section of this book, going into all the glorious and gory details of an eruption from beginning to end. This covers everything from formation and movement of magma; different eruption styles; types of lava; eruption columns and the deposits of ash and pyroclastic rocks they leave behind; pyroclastic density currents, debris avalanches, and mudflows or lahars—and their deposits; the different landscape forms left after eruptions, including types of volcanoes and how they erode, and the landscape depressions known as calderas; super-eruptions; and, finally, the common but hard-to-observe phenomenon of underwater volcanism.
The last four chapters cover closely allied topics: volcanoes in the solar system; the effects of recent eruptions on climate and the palaeoclimatological evidence of older ones; and, new to this edition, two chapters on monitoring of volcanoes, and assessing and managing the risks they pose.
“I was fascinated by some of the technicalities. For example by […] the physics behind eruption columns and the interplay with the wind, and how to deduce eruption intensity from them […]”
Two aspects, I thought, make this book very enjoyable to read. First, it broaches subjects without overwhelming you. When it talks of magma, it mentions the physics of gas bubble formation and growth (vesiculation), and the flow of liquid rock (rheology) without smothering you in detail. It will list different eruption styles (Hawaiian, Strombolian, Vulcanian, Plinian, etc.) and lavas (andesitic, dacitic, rhyolitic, etc.) while highlighting the arbitrary nature of such classifications, as these things exist on a continuum. And where formulas are given, for instance in the chapter on eruption columns, it is to demonstrate principles rather than go deep into the mathematics. If you are so inclined, each chapter comes with recommended sources and literature references for further research.
The authors explain terminology as they go, supported by many photos and diagrams. I would have liked a glossary—lacking that, I occasionally had to grab my dictionary to jog my mind. Even so, I was fascinated by some of the technicalities. For example by the distinction between central vent and large-scale fissure eruptions. By the underground movement of magma and intrusion of dikes. By the physics behind eruption columns and the interplay with the wind, and how to deduce eruption intensity from them. By the detective work that uses palaeoenvironmental records such as tree rings, and the extent and thickness of deposits to reconstruct eruptions for which there is no eyewitness testimony. Or by what makes pyroclastic density currents so terrifyingly destructive.
The second aspect that makes Volcanoes very readable is that this is not a theoretical treatise with hypothetical scenarios. Explanations are given by means of real-world examples of past eruptions. Four classic ones are introduced early on (Vesuvius, Krakatau, Mount Pelée, and Mount St. Helens), but plenty of others are recounted throughout. This includes those familiar from popular accounts (e.g. Tambora, Laki, and Toba), technical books (e.g. Pinatubo and the Soufrière Hills volcano), and those only known to volcanologists and victims (e.g. El Chichón and Nevado del Ruiz). You will learn as much about these eruptions as about what we learned from them.
“Having read the book cover to cover, there remains one important question that is difficult for me to answer. Given its publication date, how up to date is it? And is it time for a new edition?”
Having read the book cover to cover, there remains one important question that is difficult for me to answer. Given its publication date, how up to date is it? And is it time for a new edition? Technological advances and new space missions have revealed much more about extraterrestrial volcanoes—this book was published before the Opportunity and Curiosity rovers started trundling over the surface of Mars, for example. But what about volcanism here on earth? Recent eruptions have probably taught us new lessons (2010 tongue-twister Eyjafjallajökull no doubt revealing more about ash clouds), but not being a student of earth sciences, this is a hard question for me to answer. The only other more recent book I could think of was The Encyclopedia of Volcanoes, published in a second edition in 2015. But at over 1400 pages this can hardly be called an introductory textbook.
I decided to contact Clive Oppenheimer who kindly replied that there have not been any paradigmatic shifts in volcanology since then, but he did mention, in addition, the 2010 Merapi eruption, and highlighted new technology such as synchrotron radiation sources for fine-scale chemical analysis of volcanic rocks. Additionally, he pointed out Volcanoes: Global Perspectives (2022) as a recent textbook. And a third edition? It is not yet in the making, though he hopes to get around to it when time allows.
So, in sum, if you are looking for a good introductory volcanology textbook, I found this one both enjoyable and accessible. I came away feeling I understood much more about volcanoes. Bring on Volcanotectonics.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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After I reviewed Joy McCann’s book Wild Sea I became fascinated with the three-dimensional nature of ocean currents. She captivated my imagination with her vivid description of the formation of bodies of heavy, cold water plunging into the abyss around Antarctica. So when Cambridge University Press announced this textbook it seemed like the perfect opportunity to dive deeper into this topic.
Ocean Circulation in Three Dimensions, written by Barry A. Klinger and Thomas W.N. Haine, published by Cambridge University Press in March 2019 (hardback, 470 pages)
Both authors are oceanographers that actively teach courses on ocean circulation, so the material and exercises presented here have been field-tested on undergraduate students. Their preface contains suggestions for teachers on how to build a two-semester course out of this book, while a useful table indicates which chapters to read before others. This thoughtful level of organisation characterises the book as a whole. The three dimensions of ocean circulation are also applied figuratively, with each chapter divided into three sections: observations of ocean movements, concepts to explain these observations, and theory to quantify and apply these concepts.
The first two chapters review the foundations of physical oceanography you need to be familiar with, of which three pillars stand out. First are the physical characteristics of the ocean, specifically the importance of temperature and salinity, but also the influence of Earth’s rotation, which affects ocean circulation through the Coriolis force. Second is how oceanographers gather their data: via submerged sensors attached to stationary or moving platforms, or via satellites. With so much of oceanography now done using computers and remotely collected data sets, it is easy to forget where your data come from. It is equally easy to forget their limitations, which feeds into the third foundational pillar: mathematical models.
The oceans are enormous and largely inaccessible, and datasets are often limited in either time or space. You can collect long time series in one location, or you can cover more ground but only collect snapshots. Satellites and remote sensing have advanced the field tremendously, but these time series are relatively recent, often have some limitation on spatial resolution or on how deep they can probe the ocean, and are of limited duration: satellites only last so long and new space missions require continued funding. As such, physical oceanography, and therefore this book, rely heavily on numerical models to fill in the gaps and make predictions.
“A useful table indicates which chapters to read before others. This thoughtful level of organisation characterises the book as a whole […] with each chapter divided into three sections”
Having explained these basics, Klinger & Haine first consider the upper ocean, then the deep ocean, and finally the unique circulation patterns at the planet’s poles. What these chapters reveal is the beautiful complexity and diversity of circulation mechanisms. I will attempt a brief summary – with advance apologies if I oversimplify or butcher concepts given my limited background knowledge.
So, at the surface, wind drives the formation of gyres (frequently mentioned in news reports on plastic pollution and oceanic garbage patches). But rather than centrally located whirlpools, the Earth’s rotation causes them to be offset to the west, leading to powerful western boundary currents hugging the coasts of various continents. The constant churning of wind and waves turns the top layer of the ocean into a mixed layer with a relatively uniform vertical profile of temperature, salinity, and density. Gyre circulation at depth differs from the surface. As you descend, pressure rises and circulation patterns slow down and weaken, building up vertical shear. At the equator, currents differ again, with converging and diverging surface flows dominating, leading to upwelling and downwelling through so-called Ekman suction and pumping, transporting water vertically. Here, the three-dimensional character of ocean circulation comes to the fore, with surface and subsurface waters flowing in different directions.
An interlude, chapter 7, talks about meanders, eddies, and small-scale mixing processes. The authors then complete the circulation picture by looking at polar overturning cells where water sinks into the abyss, moves at depth over long distances, and wells up again near the equator. This is where the topography of the ocean bottom comes into play, with sills and marginal seas having an influence. Because of the position of the continents, the world’s oceans have several north-south corridors such as the Atlantic, where the direction of flow is along lines of longitude or meridians, hence this is called meridional overturning.
“The oceans are enormous and largely inaccessible, and datasets are often limited in either time or space. […] As such, physical oceanography, and therefore this book, rely heavily on numerical models […]”
The planet’s poles deserve special attention. The main reason is that the South Pole with its raging Antarctic Circumpolar Current connects to and interacts with all of Earth’s major ocean basins. This involves all the processes discussed so far. Together with the difficulty of gathering data here, this is still aqua incognita, so to speak: many questions remain and many details are sketchy. The other reason why the poles deserve attention is that they are, well, polar opposites. While the South Pole is an isolated landmass surrounded by water, the North Pole is a land-locked ocean partially covered with sea ice. Narrow passages such as the Bering Strait and the Barents Sea Opening are the only connection to global ocean circulation.
I found the observation and concept sections of each chapter reasonably accessible, and some of the illustrations particularly helpful, though I would have liked a glossary. Klinger & Haine define important terms, but I had to go back repeatedly to look up basic concepts such as geostrophic flow that remained abstract to me. As far as the book’s level is concerned then, this is an advanced-level text – personally, I would have benefitted from first reading an introductory oceanography textbook. Students will want to tackle this book in a classroom setting, especially once it gets to the theoretical sections. I read through these only to discover mathematical operators that I didn’t even know existed. One of the endorsements printed on the book mentions the option of self-study, though my impression is that this is the preserve of advanced students and professional oceanographers who are both familiar and comfortable with the mathematics and modelling used here.
“The planet’s poles deserve special attention […] the Southern Pole with its raging Antarctic Circumpolar Current connects to and interacts with all of Earth’s major ocean basins.”
The above is, of course, not a criticism of the book, but is good to know going in. Minor suggestions for improvements would be aforementioned glossary. Similarly, an online module with animations to help visualise movements and dynamic processes (such as was included with the CUP textbook Structural Geology) would be nifty, though I recognize the time, skill, and effort involved in creating these. No, what I really felt was missing was a final integrative chapter bringing together all the concepts that have been treated separately up to that point. Clearly, different modes of circulation dominate in different parts of the oceans, and at different times, but none of them occurs in isolation. So, what, ultimately, does ocean circulation in three dimensions look like? A short ocean-by-ocean walkthrough would have been instructive. That said, I certainly would not suggest ditching the current last chapter. Here, Klinger & Haine briefly explore the link between ocean circulation and the global climate, palaeoclimatology, and the possibility of abrupt climate change.
Ocean Circulation in Three Dimensions is one of the first books I know of to tackle this topic head-on. The authors explore competing models and explanations and are mindful to highlight that this is forever work-in-progress. Nevertheless, as an overview of our current state of knowledge, this book will be a valuable reference work for professionals. Similarly, the book’s structure and plentiful exercises make it a useful textbook for students, though they will probably need a classroom or graduate course setting to get the most out of it.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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or Like Antarctica, Greenland is one of those places that exerts an irresistible pull on my imagination. As journalist, historian and The New York Times Magazine feature writer Jon Gertner makes clear in The Ice at the End of the World, I am not alone. This solidly researched reportage chronicles both the early explorers venturing onto Greenland’s ice sheet and shows the reasons it plays a starring role in research on climate change. Some books ought to come with a warning about how binge-read-worthy they are. This is one of them.
The Ice at the End of the World: An Epic Journey Into Greenland’s Buried Past and Our Perilous Future, written by Jon Gertner, published in Europe by Icon Books in September 2019 (hardback, 421 pages)
Split into two parts, “Explorations” and “Investigations”, the book starts with what Gertner calls the waning days of the age of exploration. The names of those who tried to reach our planet’s poles have gone down in the annals of history, but the men who ventured onto Greenland’s ice sheet have largely been lost to memory: Norwegian explorer Fridtjof Nansen, the first European to trek across the ice sheet below the Arctic circle from East to West in 1888. The American Robert Peary, who made a gruelling round trip at Greenland’s northernmost end in 1891-92. The Greenland-born Dane Knud Rasmussen and Norwegian Peter Freuchen who explored the same area as Peary did some two decades later, but with an eye towards ethnographical research amongst the local Inuit.
Although these men were celebrities in their time, and, like Charles Darwin and Alfred Russel Wallace, wrote large books about their travels, I had not heard of them before. Some of their books were never translated into English, and there have been no biographies written about them in recent decades, if at all. Gertner has thus dug into original sources in libraries and research institutes to retell the stories of these men and the brave souls who joined them on their expeditions, for these journeys were not solitary affairs. These are amazing stories of brutal physical and mental hardships: freezing temperatures, fierce winds, snowblindness, crushing monotony and boredom, fingers and toes lost to frostbite, and sometimes death. But also stories of raw beauty and poetic rapture at the scale and grandeur of nature. Greenland does this to you, and Gertner gratefully mines their writings for inspiring words.
“These are amazing stories of brutal physical and mental hardships […] but also stories of raw beauty and poetic rapture at the scale and grandeur of nature. Greenland does this to you.”
The only name that did ring a bell was Alfred Wegener, the German meteorologist and geophysicist who fathered the idea of continental drift. But that will be my fascination with the captivating history of the reluctant acceptance of his ideas , and the fact that there are recent biographies on him (see Ending in Ice and the exceptionally thorough Alfred Wegener). Gertner nimbly side-steps the continental drift story and maintains a tight focus on Wegener and Johan Peter Koch’s first ice sheet crossing in 1913, and Wegener’s later return to set up a research base in the middle of the Greenland ice sheet in the early 1930s. A successful undertaking for which he tragically paid with his life, freezing to death on a return trip.
From here, Gertner jumps forward in time a few decades. Whereas early expeditions had scientific aims, they were as much about exploration and often sheer survival, so early findings were both exploratory and limited. Gertner highlights the role of French explorer Paul-Émile Victor who brought his experience in the US Air Force, testing and developing survival equipment, to bear on polar research. As frequently happens, technology developed by the military often finds a second life in science. The development of more reliable heavy-duty motorised vehicles removed the need for death-defying expeditions by human or dog-pulled sledges. This was the start of the drilling of ice cores and saw the discipline of glaciology bloom.
“A particularly eye-opening chapter is that of Thule Air Base […] The sheer amount of manpower, material, and money that the US threw at this project was staggering.”
A particularly eye-opening chapter is that of Thule Air Base that the US Department of Defense established in 1951 in northern Greenland at the start of the Cold War. This story was only touched upon in Cold Rush, but it explains America’s continued interest in Greenland. Trump has not been the first US president trying to purchase Greenland from Denmark. And it is a bizarre story. The sheer amount of manpower, material, and money that the US threw at this project was staggering. Victor cleverly piggy-backed on the army’s presence and funding to undertake scientific research. Their departure as the Cold War wound down complicated financing further research to understand Greenland’s role in climate change.
This second part of the book revolves primarily around the drilling for ice cores and the research that has allowed scientists to deduce past temperature, CO2 levels, and other palaeoclimatological variables. Gertner combines first-hand reportage during repeated visits to Greenland, numerous interviews, and careful reading of scientific papers to tell a thrilling narrative. Especially the shock discovery of evidence for abrupt climate change in the deep past takes centre-stage here. Initially, this was thought to be noise in the data, but then it was confirmed when subsequent ice cores showed the same signal, again and again.
“the shock discovery of evidence for abrupt climate change in the deep past [was] initially thought to be noise in the data, but then it was confirmed when subsequent ice cores showed the same signal, again and again.”
Gertner does a good job here introducing the physical basis of climate change, the long history of research on it, and some of the technical details of methods currently in use (isotope analysis, mass spectrometry, remote sensing with satellites, and the gravimetric analyses by NASA’s GRACE mission). But what he makes especially clear is that there is nothing alarmist about climate scientists’ concerns regarding melting ice sheets, calving glaciers, and the threat of tipping points beyond which changes could rapidly accelerate.
Gertner has spent years on this book, and The Ice at the End of the World stands out for the depth and thoroughness of its research. The 300-page narrative maintains a tight focus on its subject. It is accompanied by 70 pages of often very interesting notes where Gertner acknowledges which diversions are beyond the scope of this book, a section called “further sources” including a long list of interviews conducted and oral histories consulted, and a selected bibliography. But above all, the book is gripping. The memorable cast of historical characters, the pioneering research under challenging circumstances, the unusual settings – it has resulted in a book that I just could not put down.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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“Archaeology from Space: How the Future Shapes Our Past“, written by Sarah Parcak, published by Henry Holt in July 2019 (hardback, 286 pages)
I first touched on this topic in my review of Tropical Forests in Prehistory, History, and Modernity, which mentioned the use of LiDAR (Light Detection And Ranging) to reveal the scope of jungle ruins. You will have been hard-pressed to miss these findings making news headlines. The rationale behind remote sensing is simple, says Parcak: Where do you begin? Given that, at the surface, many archaeological sites are covered under either sand, jungle, or modern infrastructure, how do you know what lurks beneath? And how do you even begin to decide where to dig? You would be surprised what you can see from the air.
Ever since we had cameras, hot air balloons, and the first aeroplanes, aerial photography became a thing. More concerted efforts came in the 1950s with the development of infrared technology and the spy satellite programmes of the Cold War, and in the ’60s with NASA launching satellites. But space archaeology had to wait until technological developments allowed for high-resolution images. That moment arrived in the 2000s and everything has gone a bit crazy since then.
The central part of Archaeology from Space is a mind-blowing tour of archaeological digs where remote sensing was involved. Parcak is an Egyptologist by training but has also worked on sites in, amongst others, Iceland, The Shetland Islands, Italy, and Newfoundland. And she provides an overview of some of the most spectacular finds others have made.
“The rationale behind remote sensing is simple, says Parcak: […] how do you even begin to decide where to dig? You would be surprised what you can see from the air.”
It is hard to overstate the significance of this technology. Take Tanis, a well-known site in Egypt. Where two centuries of work on the ground have focused on temples, tombs, and pyramids, Parcak inspected satellite images that revealed the whole city! Work on Easter Island, meanwhile, is overturning the long-held assumption that the Polynesians caused their own demise by cutting down their forests. Instead, introduced diseases by European explorers are to blame (see also The Statues that Walked: Unraveling the Mystery of Easter Island). And the use of LiDAR in the Maya Biosphere Reserve in Central America has to date mapped more than 60,000 buildings (a finding Parcak calls insane). Particularly memorable is the story of archaeologist Arlen Chase, who found more ancient Maya sites in one night of feverishly inspecting satellite imagery than he had in 30 years working in the jungle. Probably the most important topic she tackles is wide-scale looting. In an era where online platforms such as eBay feed through to many potential buyers, there is scope for a massive black market. But here, too, satellite imagery has a role to play.
Despite the potential of this technology, Parcak is quick to recognise its limitations. Every potentially interesting site you identify needs to be ground-truthed with fieldwork. Even for a trained eye, it is easy to make mistakes, dismissing sites that are worthwhile or chasing phantoms that turn out to be false positives. With disarming honesty, Parcak tells of some of her biggest howlers. In the process, she reveals just what is involved in overseeing an excavation.
Midway the book she takes an unexpected step back from remote sensing. She combines the fictionalised life story of a woman in ancient Egypt with what we know about the transition of its Old Kingdom to its Middle Kingdom about 2200-2000 BC. This is Parcak’s home turf and her knowledgeable account is interesting, but I could not help but feel it broke the flow of the book a bit. Her next piece of fiction – picturing how an archaeologist in 2119 might go about things, complete with swarms of nano-drones and other futuristic archaeotech – is a relevant exercise in imagination, however.
“archaeology now faces the same problem as genomics and astronomy: big data. It has never been easier to acquire more information than you could hope to process in several lifetimes.”
See, archaeology now faces the same problem as e.g. genomics and astronomy that routinely reel in data by the tera- and petabytes: big data. It has never been easier to acquire more information than you could hope to process in several lifetimes. For the first time, we actually have tools to get to grips with the scale of what remains to be discovered. The estimated guesses Parcak gives are mind-boggling, but she revels in impossible odds. She is a dreamer, and I mean that in the best possible sense of the word. Technology is developing at a break-neck pace, allowing things we could not have imagined a few decades ago. Does anyone else remember that article where X-ray imaging was used to read charred papyrus sheets that were too fragile to unroll? Exactly. Suddenly her speculations on hyperspectral imaging and machine learning do not sound that implausible anymore.
And there is one other avenue Parcak has already bravely explored: crowdsourcing. She tells how, having won the million-dollar TED prize in 2016, she founded GlobalXplorer. This online, citizen-science platform allows anyone with an internet connection to help out locating sites of archaeological interest on satellite imagery. The response to the opening campaign was overwhelming and revealed many new and genuinely interesting sites. But Parcak dreams big. This is the woman who would have us map the entire world in the next ten years using this approach. What a hero.
One reviewer faulted the book for not talking enough about the technical details. Given that Parcak has authored the textbook Satellite Remote Sensing for Archaeology that gives you all the technical details you could want, this book is not the place for that. Even so, she explains why and how underground structures show up in satellite imagery (plant growth can be affected by what is buried underground, leading to visible crop marks), goes into some detail about hyperspectral imaging, and explains how seasonality and weather can influence your results.
“Harrison Ford might be too old to inspire a new generation of archaeologists as Indiana Jones, but he can safely pass his fedora on to Sarah Parcak.”
It is true that Parcak sometimes goes off-script to talk about things close to her heart. Next to her chapter about historical Egypt, one chapter discusses the underrepresentation of women in archaeology. Seems like a very understandable and important diversion to me. I admit that I found some of her jokes borderline silly (they probably work wonderfully as one-liners in a presentation), but I had a lot of fun reading this book.
Archaeology from Space is a remarkably inspiring book, full of wonder and hope, buoyed by Parcak’s boundless enthusiasm and love for her profession. Harrison Ford might be too old to inspire a new generation of archaeologists as Indiana Jones, but he can safely pass his fedora on to Sarah Parcak.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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