by Paul Braterman
Timefulness: How thinking like a geologist can help save the world, Marcia Bjornerud, Princeton University Press, 2018/2020, pp 208, sale price $8.84/£7.00 through publisher
There are many excellent overviews for the general reader of how life on Earth has changed over time (see, for a recent example, Neil Shubin’s Some Assembly Required, which I reviewed here recently). The history of the Earth itself has not been so well served, and Timefulness: How Thinking Like a Geologist Can Help Save the World, by Marcia Bjornerud, Professor of Geology and environmental Sciences at Lawrence University, is a welcome and timely addition to this badly under-represented genre.[1] The book is beautifully written, in plain language, with complex ideas explained with great simplicity and the use of strikingly appropriate verbal imagery. Behind this transparency of language lies a deep love and knowledge of her subject. The book should appeal to anyone looking for an overview of the Earth as the abode of life, or a perspective on our place in time, and how recklessly we are compressing the tempo of natural change.
The author presents her book as an argument for what she calls timefulness, the perception of ourselves as living in and constrained by time, of time itself as having both extension and texture, of the acceptance of our own mortality, and of our own responsibilities. This she sees as severely lacking in our society. We expect people to know something about distances on the map, but not about the timescale of the events that have shaped the Earth, as if what happened before we were born and what will happen after we die did not really exist. We have an economic system that (at least in normal times) depends on the expectation of continued growth, although if maintained over a very brief interval of geological or even historical time, such growth is clearly unsustainable.[2] Consumerism, rather than conservation, is regarded as good citizenship.
Geology itself, seen as a historical science, is regarded by academic snobs as low in the intellectual pecking order, even though, as I have myself argued elsewhere, historical science is not only as intellectually engaging as rule-seeking science, but more likely, when the two come into conflict, to be correct. Its lessons are also more likely to point to a sustainable solutions for our most pressing problems. For lack of a timeful perspective, we reduce complex ecological problems to simple engineering conundrums, and pursue policies involving Earth-changing activity as if there were no tomorrow. Tellingly, one of Bjornerud’s examples is the fact that there is serious discussion [3] of mitigating the effects of climate change by releasing sulphuric acid haze into the stratosphere, although geological precedent shows that in a matter of years this haze would become ineffectual through droplet coalescence, and trap us on a treadmill of supplementation, with unforeseeable consequences.
The book begins with some reflections on the author’s visits to Svarlbad, a place that does not belong in any official time zone, leading on to the introductory chapter, a plea for a sense of the depth of time, its texture, and changing rhythms, and how this has played out by making Earth what it is. This is what she refers to as timefulness. Next we have chapters on our emerging awareness from the late 18th century onwards of the age of the Earth and its successive transformations; our current understanding of the forces that have shaped the continents and thrust up and worn down the mountains; how Earth’s atmosphere has changed over time and how it is changing today; the dramatic change in pace produced by human activity; and the changes in perception that she sees as necessary in order for us to manage this. Such change is also necessary if we are to appreciate the full richness of our own existence as creatures in time. There are three appendices; a simplified geologic timescale, listing the different periods we now recognize from the formation of the Earth to the present and some of their salient features; the lifespans of Earth phenomena and length of natural cycles, from 500 million years for the assemblage and breakup of supercontinents, to months for the migration of air masses across the Indian and Pacific oceans, to 24 hours (in the Archaean 18 hours) for the Earth’s rotation; and the causes and consequences of seven major crises in Earth’s history, from the end of Snowball Earth around 570 million years before present (Mybp) to the tumultuous changes, for such they are, of the Anthropocene. Tacked onto the end of the 2020 paperback edition of the book are a number of thought-provoking discussion questions, which would further enhance the value of the book either as supplementary material for academic courses (the author tells me that some of her colleagues are using the book in this way), or as material for book reading clubs.
The popular view of geological time, which scales it down to 24 hours and then fits humanity’s existence into the last fraction of a second before midnight, is useless. It ignores our deep roots in time (complex living cells, on this scale, would appear at 6 AM), and, chillingly, it regards our present situation as finality. Besides, it misses the point. As the author puts it, “Focusing simply on the age of the Earth is like describing a symphony in terms of its total measure count. Without time, a symphony is a heap of sounds; the durations of notes and recurrence of themes give it shape…[T]he grandeur of Earth’s story lies in the gradually unfolding, interwoven rhythms of its many movements.”
There is a small group who devote much trouble and indeed some scientific expertise to misrepresenting the geological record and denying the reality of deep time. The motivation is invariably religious; in extreme cases, pursuit of biblical literalism, but more generally the denial of sufficient time for life to have diversified through the natural processes of evolution. This case was put forward most strongly by Lord Kelvin, who in the late 19th century argued that all sources of energy then known would have sufficed only to fuel the Sun’s output for some 20 million years, far less than required for Darwin’s newly minted theory of evolution. Kelvin was of course completely correct, and the source of the missing energy (conversion of action to helium in the solar interior) was not identified until the 1920s.
One major theme of the book is uniformitarianism, an idea that which dates back explicitly to Charles Lyell in the early 19th century, and implicitly to James Hutton in the 1780s. This was opposed to catastrophism, the idea that the Earth had been altered by a succession of sudden and violent episodes. The basic idea of uniformitarianism is that we can understand the ancient Earth by reference to the same processes that are at work today. Here I think we need to make a number of distinctions, depending on exactly what kind of uniformity we are discussing. Firstly, there is uniformity of natural laws, regarded by creationists as an arbitrary assumption, but in reality deeply confirmed by observation. The oldest rocks obey the same laws of chemistry as minerals being formed right now, and the atomic absorption lines in starlight from the most distant galaxies that we can observe are an exact match to those that we measure in today’s laboratories, although that light must have set out on its journey more than 7 billion years before the Earth itself came into being. Then there is uniformity of process, and I find it deeply moving that we can see raindrop marks and mud cracks, matching those I find in my back garden, in sediments a billion years old. Finally, often linked to uniformitarianism, there is Lyell’s assumption of uniformity of rate, or gradualism, inherited by Darwin in his doctrine of slow evolutionary change, and that is quite another matter.
TH Huxley, in his 1869 address to the British Geological Society, pronounced the death of the controversy between uniformitarianism and catastrophism. It does however linger on, in the propaganda of creationists, who have an obvious vested interest here. The reality, of course, is that sometimes things happen quite fast, sometimes much more slowly, and one of the themes of the book is that time does not simply have extent, but texture. Not only duration, but process.
The author relates changes in geological opinion to the overall mood of the times. Hutton, a member of the Scottish Enlightenment, took it for granted that the Earth was fitted for indefinite human habitation, and indeed used that assumption as his starting point. Lyell, with an early Victorian belief in steady rational progress, explicitly adopted a gradualist uniformitarianism. In the atomic age, however, scientists were more ready to consider cataclysmic causes, as in the Alvarez’ invocation of an asteroid impact to explain the sudden extinction of the dinosaurs.[4] Her case is further strengthened if we mention here that such impacts had already been invoked as a cause of mass extinction by Harold Urey, the leading geochemist of his time, in a Nature article in 1973, and that Urey was among those expressing concerns about the possible effects of nuclear warfare on the planet in the popular press as early as 1946.
Bjornerud describes how our ideas about the age of the Earth have developed over the past 2 ½ centuries. Hutton invoked deep time, and by the early 1800s it was possible to match sediments according to the particular kinds of fossil that they contained. Sediments could be placed in order, since generally speaking younger sediments lie on top of older ones, giving the familiar geological column of relative time. Our knowledge of the actual ages rests on radiometric dating, now over a century old. This method is particularly applicable to igneous rocks, especially basalt intrusions and radioactive ash, which occur interspersed throughout sediments worldwide. The book gives an excellent account of the principles that lie behind the method, including the clearest exposition that I have seen of such complex topics as argon-argon and lead-lead dating, and the use of the latter to determine the total age of the Earth.
Next comes a description of how mapping of the seafloor led from the late 1940s onwards to the discovery of mid-ocean ridges, and how the demonstration of matched patterns of magnetisation on either side of these ridges led to the acceptance of the concept of ocean floor spreading. This spreading can now be measured directly by GPS, and takes place at a rate of around 1 cm a year in the Atlantic, but several times that speed in the Pacific. If ocean floor is spreading at one location, it must be disappearing at another, and there are indeed deep subduction trenches on either side of the Pacific. There, material is forced downwards underneath the landmasses of East Asia and America, giving rise to the Pacific’s ring of volcanoes and earthquake zones. Over the past few decades, we have developed an understanding of plate tectonics, in which continental crust is carried as a passenger on the ocean crust, while that crust streams outwards from where it is formed at midocean ridges, and disappears in subduction zones. It is the collision between blocks of continental crust that causes mountain building. Over a few hundred million years, the individual continents move together, but eventually, when they have done so, heat trapped beneath the continental crust leads to local stretching and rifting, and eventually breakup. The ultimate driver here is the Earth’s heat, a combination of the heat left over since its formation, and that generated ever since by radioactive decay. This gives rise to convection currents in the magma, a stiff material that can nonetheless flow over geological time, and that liquefies when pressure is relieved to give flowing lava at ridges and volcanoes.
There are a few minor (and largely interrelated) historical oversimplifications in Bjornerud’s account of these discoveries. Like many authors, she says that Hutton inferred deep cycles of time from what he saw at Siccar Point, when in reality (see below) he had derived his theory from almost religious principles, and then used it as the framework to explain his observations. She gives Arthur Holmes, for whom I have enormous admiration, too much credit in one regard and too little in another. She describes his research from 1908 on as the earliest use of radiometric dating, although Bertram Boltwood, acting on a suggestion from Ernest Rutherford, had published, in 1907, radiometric dates going back as far as 2200 million years before present. [5] Rutherford, indeed, correctly described a Cambrian rock, on the basis of radiometric dating, as being 500 million years old, on the occasion of his 1904 famous confrontation with Kelvin. She also correctly states that Holmes had realise the importance of convective heat transfer from the mantle, but seems unaware that by the 1930s he had linked this to continental drift, and accepted the corollary of ocean trench subduction, thus anticipating much of what we now call plate tectonics.[6] Like US-based geologists in general, she goes on to regard the development of plate tectonics in the 1960s as an intellectual revolution, unaware that British and European geologists were quietly amused at the Americans’ failure to realise that they were merely playing catchup.[7] She does indeed mention Wegener’s concept of continental drift, but describes the idea as anathema within British, as well as American, geological circles, although Holmes appeals to the concept repeatedly.
The author describes the processes of mountain building, erosion, and evolutionary adaptation as being in general remarkably well matched, despite being driven by different forces. Here I have a problem following her, because these processes are quite closely coupled. Thus erosion is faster on the steep science of newly formed mountains, and the mountain-raising process itself is responsive to removal of mass by erosion. It is true that most of the time evolution is plenty fast enough to respond to changing conditions, and can indeed speed up greatly following a change in circumstances. Examples of this are the Ediacaran/Cambrian “explosion”, and the rapid emergence of new families of birds and mammals following the extinction of the dinosaurs. However, the matching of geological and biological rates of change cannot be taken for granted. There have been multiple crises for living things in the Earth’s history (the “great extinctions”, and many smaller episodes), and indeed the dangers of mismatch provide one of the main themes of this book.
Evolution is adaptation to the environment, and as they evolve living things can follow alterations provided they are given enough time. However, as the author puts it “they suffered spectacularly whenever their environments, and especially the atmosphere, changed too fast.” The implications are clear, and spelt out repeatedly in the book. One recurrent argument used by opponents of greenhouse gas control is that climates have changed throughout Earth’s history. But the opponents of action draw exactly the wrong conclusion from this history, and time after time such change, when over-rapid, has been disastrous. In a mass extinction, to use Bjornerud’s metaphor, the scalpel of natural selection is transformed into a machete, with entire branches of the tree of life being brutally removed.
There have been five major mass extinctions, including the end-Permian extinction 250 million years ago, by far the most severe, and all of these have involved rapid changes in the composition of the atmosphere through volcanic activity, combined with the acidification of the oceans, which also developed oxygen-starved dead zones. Replace “volcanic activity” by human activity, and the danger we are in is all too obvious.
The atmosphere in particular is notoriously vulnerable to human activity, such as greenhouse gas emissions which in turn increase planetary temperatures. The author saw this for herself on her first visit to Svarlbad, where she discovered that the glaciers were considerably up-valley from the positions shown in maps from the 1930s, and was shocked to see how much more had changed when she we visited the area 20 years later, with both glaciers and sea ice having dramatically retreated.
The speed and insensitivity with which human activity is changing the face of the Earth is completely unprecedented, and the author illustrates it with an anecdote from her own training. This involved the class exploring an unusual volcanic formation (a pegmatite gem pocket) that had formed over a billion years ago, leaving beautiful crystals embedded in the walls of a cavern recently exposed by mining activity. She decided to collect one unusual specimen, a beautiful 3 inch long crystal of tourmaline, tapped with her hammer, and smashed it. Immediately, she was horrified by what she and her classmates were doing, destroying in a moment of greed an object of beauty older than the mountains. This, for her, is a parable for current human activity, unprecedented in its scale, and destined to cast long shadows into the future.
For almost 20 years, geologists have been discussing whether our present age deserves its own geological label, the Anthropocene. There are five obvious ways in which human activity has more than doubled the rate of geological processes; erosion, sealevel rise, ocean acidification, extinction rates (now amplifying to well over 1000 fold the normal background rate), and carbon dioxide emissions (exceeding volcanic emissions by a factor of 100). To these one might add phosphorus and nitrogen run-off, producing anoxic dead zones in lakes and coastal waters, and the harnessing to human needs of one quarter of all photosynthetic activity on land. I would add to this list our material impact, from plastic waste to paved parking lots to buildings. There is no precedent for such rapid change, and what guidance we can obtain from the historical and geological record is not comforting.
The recurrent Ice Ages that started around 2 ½ million years ago were driven by changes in the amount of sunlight reaching the Earth, as the result of small variations in its orbit. The effect of this original driving force is roughly doubled by positive feedback loops, such as increase in water vapour (itself a greenhouse gas), and loss of reflective ice, during warm periods. Other positive feedback loops, which could come into play very quickly, include more rapid decomposition of organic material around the edges of glaciers, and, very frighteningly, the release of methane, an extremely potent greenhouse gas, from the solid methane hydrates that form at the edge of the permafrost. Such loops cannot but amplify the direct influence of our carbon dioxide emissions as a driver. Feedback influences on increases and decreases in temperature are not symmetrical, and lead to a sawtoothed pattern, with rapid rises and far slower falls. Thus repairing the damage caused by a rise in temperature would take considerably more time than inflicting it.
There are no easy answers. It is often claimed that the change in the past few years from coal as the main fossil fuel, to oil, and then to gas, mitigates the CO2 problem, but unfortunately the reality is that oil and gas extraction release methane into the atmosphere, since neither the wells nor the pipelines can be perfectly sealed. There is much talk of CO2 capture, but extracting carbon dioxide from flue gas is expensive, and there is no good answer to the question of what should be done with it. The reaction of carbon dioxide with silicate rocks does remove it from the atmosphere, but the process is far too slow to be of any use to us. There is the idea of using biomass as fuel, but this is energy expensive, leads to further CO2 emissions from the soil, and uses up on land that would otherwise be growing food. Then there is the idea of adding sulphur dioxide to the stratosphere, where it would slowly be converted to sulphuric acid haze, scattering light. As mentioned earlier, this has obvious problems. Repeated dosing would be necessary. The treatment would do nothing about ocean acidification, and would indeed add to it as the haze was washed out. And there would be no escape from the treadmill, because failure to replenish the haze would lead to a rapid spike in temperature.
In Doing Good Better, William MacAskill points out that market forces pay no attention at all to the interests of future generations, since future generations are not yet making spending decisions. Nor, I would add, do they vote. Yet, as this book points out, we do indeed value the future. Consider how much of our activity would suddenly be rendered pointless if we thought that our generation was going to be the last. (As I wrote those words, I suddenly remembered that there are millions of Americans who believe that this may well be the case, and that the whole of physical reality can be compressed into just over 6000 years.)
What, then, is to be done? Bjornerud points to the work of artists, listing, among other examples, a short story collection to be published 100 years from now on paper pulped from the wood of trees just planted, and a 10,000 year clock powered by temperature changes that will adjust itself by checking the position of the Sun. She also points out the self-defeating efforts of Silicon Valley billionaires, building themselves disaster-proof bunkers. How many generations are those supposed to last, should they ever become relevant? And what is going on in the heads of people who imagine that anything of lasting value can be achieved by terraforming Mars?
Next she draws the contrast between the seven-generation perspective of the Iroquois, and the business oriented policies of her home state of Wisconsin, which has undone 40 years’ worth of science-based environmental laws within months. Native American tribes have pooled their expertise to mount informed opposition to this trend, pointing out the governmental responsibility for protecting the environment, and the book points out the irony of the tribes, so long the victims of the actions of the American government, now trying to save America from itself.
We need a change in perspective, typified, the author suggests, by Kurt Vonnegut’s suggestion that we appoint a Cabinet-level Secretary of the Future, overseeing the realignment of policies and taxation to protect the interests of our grandchildren. A carbon tax is one obvious suggestion. Education, ideally, would convey a more truthful sense of the past, so that we can recognise the deep roots of poverty and class-based discrimination. (It is interesting here to consider how the Black Lives Matter movement is compelling the Western world to re-evaluate its complacent historical narratives.) Geology would be a capstone subject in the curriculum, and we would understand our own temporal position woven into its narratives. In this way, people might come to see evolution as strengthening, rather than threatening, the sense we have of ourselves. We need, here she quotes Aldo Leopold, to start “thinking like a mountain.”
I found it interesting to compare Bjornerud’s perspective with Hutton’s. Hutton, in his 1785 Dissertation Concerning the System of the Earth, its Duration, and Stability, writes that “An endeavour is then made to support the theory by an argument of a moral nature, drawn from the consideration of a final cause [emphasis added].” Here the reference is to Aristotle’s theory of causation, with “final cause” embodying the idea of purpose. He goes on to argue that from the products of erosion, “the foundation is laid for future continents, in order to support the system of this living world”, and out from his theory “an argument may be established for wisdom and benevolence to be perceived in nature.” For Hutton, as a member of the Scottish Enlightenment, observation confirms his assumption that nature is benevolent, and works to maintain indefinitely an Earth suited to human habitation. He sees purposefulness, and intelligent design, as built into its workings, although the modern Intelligent Design movement conspicuously fails to invoke him as an ally. For Bjornerud, as a contemporary natural scientist, the interrelationship between the Earth itself, and the forms of life that have evolved and are evolving on it, is far more subtle and interesting. Life has reshaped the face of the Earth, and the Earth has its own deep rhythms that constrain what is possible for life, but there is no foresight involved in any of these processes. There are no guaranteed happy endings. Nature is wonderful, but it is not a source of moral purpose. That has to come from us.
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1] I would however mention here David Montgomery’s The Rocks Don’t Lie, written, like the excellent multi-authored Grand Canyon, Monument to an Ancient Earth, with an eye to refuting Young Earth creationism, Don Prothero’s The Story of the Earth in 25 Rocks, and Bjornerud’s own earlier Reading the Rocks.
2] Thus 3% annual economic growth, which economists might suggest as a desirable target, corresponds to almost 20-fold growth over a century, which seems barely plausible, and 7 trillion fold growth over a millennium, which is clearly absurd. We cannot build a society on such a basis.
3] Involving even such eminent individuals as the Nobel prizewinner Paul Crutzen, whose contributions to atmospheric science are cited in the text more than once.
4] Pedantically speaking, non-avian dinosaurs.
5] Bertram B. Boltwood, American Journal of Science, XXIII, (134),1907, p77. The paper is titled Ultimate disintegration products of the radioactive elements; Part II, Disintegration products of uranium, which may explain why it is not better known.
6] Arthur C. Holmes, summary at Geol. Mag., 65, 236 (1928); full account at Trans. Geol. Soc. Glasgow, 18, 559 – 606 (1931). Holmes’ suggestion here was that spreading generally took place underneath or outwards from the continental crust, driven by local buildups of heat.
7] See e.g. Martin J.S. Rudwick, Earth’s Deep History, University of Chicago Press, 2014, p. 258.
8] USGCRP Chapter 3 2017 Figure 3.1 panel 2, Figure 3.3 panel 5.