Timefulness
Page 3
of Young- Earthers— have droned on about the unimaginable
slowness of geologic processes, and the idea that geologic
changes accrue only over immense periods of time. Moreover,
geologic textbooks invariably point out (almost gleefully) that
if the 4.5 billion- year story of the Earth is scaled to a 24- hour
day, all of human history would transpire in the last fraction of
a second before midnight. But this is a wrongheaded, and even
irresponsible, way to understand our place in Time. For one
thing, it suggests a degree of insignificance and disempower-
ment that not only is psychologically alienating but also allows
us to ignore the magnitude of our effects on the planet in that
quarter second. And it denies our deep roots and permanent
entanglement with Earth’s history; our specific clan may not
have shown up until just before the clock struck 12:00, but our
A Call for Timefulness 17
extended family of living organisms has been around since at
least 6 a.m. Finally, the analogy implies, apocalyptically, that
there is no future— what happens after midnight?
A M AT T E R O F T I M E
While we humans may never completely stop worrying about
time and learn to love it (to borrow a turn of phrase from
Dr. Strange love), perhaps we can find some middle ground be-
tween chronophobia and chronophilia, and develop the habit
of timefulness— a clear- eyed view of our place in Time, both
the past that came long before us and the future that will elapse
without us.
Timefulness includes a feeling for distances and proximities
in the geography of deep time. 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.
Similarly, the grandeur of Earth’s story lies in the gradually
unfolding, interwoven rhythms of its many movements, with
short motifs scampering over tones that resonate across the en-
tire span of the planet’s history. We are learning that the tempo
of many geologic processes is not quite as larghissimo as once
thought; mountains grow at rates that can now be measured
in real time, and the quickening pace of the climate system is
surprising even those who have studied it for decades.
Still, I am comforted by the knowledge that we live on a
very old, durable planet, not an immature, untested, and pos-
sibly fragile one. And my daily experience as an earthling is
enriched by an awareness of the lingering presence of so many
previous versions and denizens of this place. Understanding the
reasons for the morphology of a particular landscape is similar
18 Ch a pter 1
to the rush of insight one has upon learning the etymology of
an ordinary word. A window is opened, illuminating a distant
yet recognizable past— almost like remembering something
long forgotten. This enchants the world with layers of mean-
ing and changes the way we perceive our place in it. Although
we may fervently wish to deny time for reasons of vanity, exis-
tential angst, or intellectual snobbery, we diminish ourselves
by denouncing our temporality. Bewitching as the fantasy of
timelessness may be, there is far deeper and more mysterious
beauty in timefulness.
A S H O R T L O O K A H E A D
I’ve written this book in the belief (possibly naïve) that if more
people understood our shared history and destiny as Earth-
dwellers, we might treat each other, and the planet, better. At
a time when the world appears more deeply divided than ever
by religious dogmas and political animosities, there would
seem to be little hope of finding a common philosophy or list
of principles that might bring all factions to the table for honest
discourse about increasingly intractable environmental, social,
and economic problems.
But the communal heritage of geology may yet allow us to
reframe our thinking about these issues in a fresh new way. In
fact, natural scientists already serve as a kind of impromptu in-
ternational diplomatic corps who demonstrate that it is possible
for people from developed and developing countries, socialist
and capitalist regimes, theocracies and democracies to co-
operate, debate, disagree, and move toward consensus, unified
by the fact that we are all citizens of a planet whose tectonic,
hydrologic, and atmospheric habits ignore national boundaries.
Maybe, just maybe, the Earth itself, with its immensely deep
A Call for Timefulness 19
history can provide a politically neutral narrative from which
all nations may agree to take counsel.
In the chapters that follow, I hope to convey the mind-
altering sense of time and planetary evolution that permeates
geologic thinking. It may not be possible to grasp fully the im-
mensity of geologic time, but one can at least develop some
feeling for its proportions. I once had a math professor who
was fond of reminding the class that “there are many sizes and
shapes of infinity.” Something similar can be said about geo-
logic time, which though not actually infinite is effectively so
from a human perspective. But there are different depths in
the seas of Deep Time— from the shallows of the last Ice Age
to the abyss of the Archean. Chapter 2 tells the story of how
geologists mapped the ocean of time, first qualitatively using
the fossil record, then with increasing quantitative precision
through the phenomenon of natural radioactivity. (This is the
most technical material in the book; if isotope geochemistry
just isn’t your thing, you can skip the details and move on with-
out guilt or loss of continuity). The geologic timescale is an
underappreciated collaborative intellectual achievement, and
still a work in progress. A simplified version of the timescale is
provided for reference in appendix I.
Chapter 3 is about the intrinsic rhythms of the solid earth—
the paces of tectonics and landscape evolution, and how a
geologic perspective requires us to abandon any belief in the
permanence of topographic features. Geologic processes may
be slow, but they are not beyond our perception. And one
of the most important insights to emerge from “clocking the
Earth” is that the rates of disparate natural processes, from the
growth of mountains, to erosion, to evolutionary adaptation—
each powered by different motive forces— are remarkably well
matched. The durations, rates, and recurrence intervals of
20 Ch a pter 1
various geologic phenomena are summarized in several tables
in appendix II.
Chapter 4 is about the evolution of the atmosphere and the
rates of change in its composition during environmental up-
heavals and mass extinctions in geologic history. A recurrent
theme is that long periods of planetary stability have ended
abruptly in the past when rates of environm
ental change out-
paced the biosphere’s capacity to adapt (and in only one case
can we lay the blame on a meteorite). Appendix III compares
the causes and consequences of eight great environmental
crises in Earth’s history, including changes unfolding now.
Chapter 5 begins with the discovery of the Ice Age (the Pleis-
tocene) in the nineteenth century and explains how modern
understanding of climate change gradually emerged from that.
The Pleistocene was not simply an interval of constant cold,
but more than 2 million years of climate variability. It was the
transition into the climatically stable Holocene 10,000 years ago
that allowed the emergence of modern human civilization. This
is sobering in light of current rates of environmental change,
which are virtually unprecedented in geologic time— the basis
for the argument that we are now in a new geologic epoch, the
Anthropocene.
The final chapter looks to the geologic future and outlines
ideas for building a more robust, enlightened, time- literate
society that is able to make decisions on intergenerational
timescales. This requires only a shift in perception. For many in
North America, the 2017 total solar eclipse was a trans formative
experience, a fleeting vision of our place in the cosmos. Simi-
larly, geologic observation provides a view of the strange and
scintillating world of Time we dwell in but cannot ordinarily
see. Even a glimpse can alter one’s experience of being alive
on Earth.
C H A P T E R 2
A N AT L A S O F T I M E
Although we are mere sojourners on the surface of the planet, chained to a
mere point in space, enduring but for a moment of time, the human mind
is not only enabled to number worlds beyond the unassisted ken of mortal
eye, but to trace the events of indefinite ages before the creation of our race.
— C H A R L E S LY E L L , P R I N C I P L E S O F G E O LO GY , 1 8 3 0
T H I N K I N G L I K E A R O C K
Like many geologists, I stumbled into the discipline more or
less by accident. Geoscience is not present or prioritized in
most U.S. high school curricula in the same way that physics,
chemistry, and biology are, and as a result, there are few stu-
dents who enter university aware of geology as a mature aca-
demic field with its own lively intellectual culture. As a first- year
college student with a proclivity for the humanities, I enrolled
in an introductory geology course mainly to fulfill a science
requirement. My expectations were rather low; it was “rocks
for jocks.” The weekly field trips would at least be a chance to
get off campus. To my surprise, I found that geology demanded
a type of whole- brain thinking I hadn’t encountered before. It
creatively appropriated ideas from physics and chemistry for
the investigation of unruly volcanoes and oceans and ice sheets.
It applied scholarly habits one associates with the study of lit-
erature and the arts— the practice of close reading, sensitivity
to allusion and analogy, capacity for spatial visualization— to
the examination of rocks. Its particular form of inferential logic
demanded mental versatility and a vigorous but disciplined
22 Ch a pter 2
imagination. And its explanatory power was vast; it was noth-
ing less than the etymology of the world. I was hooked.
An apt way to describe how geologists perceive rocks and
landscapes is the metaphor of a palimpsest— the term used by
medieval scholars to describe a parchment that was used more
than once, with old ink scraped off to allow a new document to be
inscribed. Invariably, the erasure was imperfect, and vestiges of
the earlier text survived. These remnants can be read using x- rays
and various illumination techniques, and in some cases are the
only sources of very ancient documents (including several of the
most important writings of Archimedes). In the same way, every-
where on Earth, traces of earlier epochs persist in the contours of
landforms and the rocks beneath, even as new chapters are being
written. The discipline of geology is akin to an optical device for
seeing the Earth text in all its dimensions. To think geologically
is to hold in the mind’s eye not only what is visible at the surface
but also present in the subsurface, what has been and will be.
Other disciplines, especially cosmology, astrophysics, and
evolutionary biology, are concerned with Deep Time ( John
McPhee’s evocative phrase for the prehistorical, prearcheo-
logical past1), but geology is unique in having direct access to
tangible objects that witnessed it. Geology is not concerned
with the nature of time per se but rather with its unmatched
powers of transformation. In documenting the evidence for
earlier versions of the world, geologists were the first to develop
an instinct for the immensity of planetary time, even though
they had no way of measuring it until the twentieth century.
H O W T H E E A R T H G O T O L D ( T H E N A L O T YO U N G E R )
Among the sciences, geology is something of a late bloomer.
The motions of the planets were explained in the seventeenth
An atlas of time 23
century, the laws of thermodynamics and electromagnetism
were worked out in the nineteenth, and the secrets of the atom
were known in the early twentieth, all before we knew the age
of the Earth or had any clear idea about its planetary- scale
behavior. This does not mean geologists have been dullards
but rather that Earth has been an elusive subject to study—
simultaneously too near and too far away to get into clear view.
When other sciences were making great strides toward describ-
ing nature using telescopes, microscopes, beakers, and bell jars,
Earth could neither be viewed through one lens nor reduced
to a laboratory- sized experiment. Also, interpreting the Earth
has always been deeply entangled with our self- perception as
humans and our cherished stories about our relationship to the
rest of creation. No wonder it is difficult to step back and see
things in clear perspective.
More than any other scientific discipline, geology requires
prodigious powers of visualization and openness to bold in-
ductive inferences. How, for example, could someone in the
eighteenth century begin to answer the question, How old is
the Earth? In the Western world, most people had no reason
to challenge the 6,000 years or so implied in the Bible (in 1654,
the archbishop of the Church of Ireland, James Ussher, with
astonishing precision, had calculated the date of the creation:
Sunday, 23 October 4004 BC). When I ask twenty- first century
students how they would go about answering this question on
their own, setting aside religious preconceptions and the 4.5
billion- year figure they have been told, they usually say some-
thing like, “Well, find the oldest rocks and figure out how old
they are,” and then realize this is no answer— how does one
&n
bsp; know which rocks are oldest, and how does one go about de-
termining their age? One needs the whole edifice of modern
geology even to begin. So it is truly extraordinary that in 1789, a
24 Ch a pter 2
Scottish physician, gentleman farmer, and natural philosopher
had the insight to see the vastness of geologic time in an outcrop
on the coast near Dunbar.2
At a blustery cape called Siccar Point, Hutton noted a discon-
tinuity between two sequences of sedimentary rocks, a surface
dividing a lower sequence in which the layers were nearly ver-
tical, from an upper one with the layers closer to the expected
horizontal (see figure 2). Many people had seen this promontory
before; anyone in a boat would have been careful to steer clear
of it to avoid being caught in the waves that crash on the rocks.
Hutton, however, was able to see the rocks not merely as a nav-
igational hazard but as a vivid record of vanished landscapes.
He made two astoundingly perceptive interpretive leaps. First,
he recognized that the underlying vertical rocks represented a
former mountain range where marine strata had been tilted by
crustal upheaval. Second, he understood that the surface that
truncated them represented an erosional interval long enough
to wear down the mountains, and that the overlying rocks were
sediments that had accumulated on top of their ruins.
Based on his estimate of the rate of erosion on his own land,
Hutton asserted that the discontinuity— now called an angular
unconformity— represented an unfathomably long interval of
time, essentially infinite compared with the biblically ordained
age of the Earth. In this simple but revolutionary calculation,
Hutton broke with the prevailing belief that Earth’s present and
past were governed by different regimes, that a violent past of
cataclysms like Noah’s flood had given way to the unchanging
world of the present. Under the assumption that the Earth was
only a few thousand years old, deeply eroded valleys and thick
piles of sedimentary rock could be explained only by large-
magnitude catastrophic events. Hutton replaced this worldview
with the foundational idea of geology: uniformitarianism— the
An atlas of time 25
F I G U R E 2 . Hutton’s unconformity at Siccar Point, Scotland