(Roughly) Daily

Posts Tagged ‘geology

“Over the long term, symbiosis is more useful than parasitism. More fun, too.”*…

Blue-green formations of malachite form in copper deposits near the surface as they weather. But they could only arise after life raised atmospheric oxygen levels, starting about 2.5 billion years ago.

There are many more varieties of minerals on earth than previously believed– and about half of them formed as parts or byproducts of living things…

The impact of Earth’s geology on life is easy to see, with organisms adapting to environments as different as deserts, mountains, forests, and oceans. The full impact of life on geology, however, can be easy to miss.

A comprehensive new survey of our planet’s minerals now corrects that omission. Among its findings is evidence that about half of all mineral diversity is the direct or indirect result of living things and their byproducts. It’s a discovery that could provide valuable insights to scientists piecing together Earth’s complex geological history—and also to those searching for evidence of life beyond this world.

In a pair of papers published on July 1, 2022 in American Mineralogist, researchers Robert HazenShaunna Morrison and their collaborators outline a new taxonomic system for classifying minerals, one that places importance on precisely how minerals form, not just how they look. In so doing, their system acknowledges how Earth’s geological development and the evolution of life influence each other.

Their new taxonomy, based on an algorithmic analysis of thousands of scientific papers, recognizes more than 10,500 different types of minerals. That’s almost twice as many as the roughly 5,800 mineral “species” in the classic taxonomy of the International Mineralogical Association, which focuses strictly on a mineral’s crystalline structure and chemical makeup.

Morrison and Hazen also identified 57 processes that individually or in combination created all known minerals. These processes included various types of weathering, chemical precipitations, metamorphic transformation inside the mantle, lightning strikes, radiation, oxidation, massive impacts during Earth’s formation, and even condensations in interstellar space before the planet formed. They confirmed that the biggest single factor in mineral diversity on Earth is water, which through a variety of chemical and physical processes helps to generate more than 80 percent of minerals.

But they also found that life is a key player: One-third of all mineral kinds form exclusively as parts or byproducts of living things—such as bits of bones, teeth, coral, and kidney stones (which are all rich in mineral content) or feces, wood, microbial mats, and other organic materials that over geologic time can absorb elements from their surroundings and transform into something more like rock. Thousands of minerals are shaped by life’s activity in other ways, such as germanium compounds that form in industrial coal fires. Including substances created through interactions with byproducts of life, such as the oxygen produced in photosynthesis, life’s fingerprints are on about half of all minerals.

But they also found that life is a key player: One-third of all mineral kinds form exclusively as parts or byproducts of living things—such as bits of bones, teeth, coral, and kidney stones (which are all rich in mineral content) or feces, wood, microbial mats, and other organic materials that over geologic time can absorb elements from their surroundings and transform into something more like rock. Thousands of minerals are shaped by life’s activity in other ways, such as germanium compounds that form in industrial coal fires. Including substances created through interactions with byproducts of life, such as the oxygen produced in photosynthesis, life’s fingerprints are on about half of all minerals.

Historically, scientists “have artificially drawn a line between what is geochemistry and what is biochemistry,” said Nita Sahai, a biomineralization specialist at the University of Akron in Ohio who was not involved in the new research. In reality, the boundary between animal, vegetable, and mineral is much more fluid.

A new origins-based system for classifying minerals reveals the huge geochemical imprint that life has left on Earth. It could help us identify other worlds with life too: “Life Helps Make Almost Half of All Minerals on Earth,” from @jojofoshosho0 in @QuantaMagazine.

Larry Wall


As we muse on minerals, we might send systemic birthday greetings to Thomas Samuel Kuhn; he was born on this date in 1922.  A physicist, historian, and philosopher of science, Kuhn believed that scientific knowledge didn’t advance in a linear, continuous way, but via periodic “paradigm shifts.”  Karl Popper had approached the same territory in his development of the principle of “falsification” (to paraphrase, a theory isn’t false until it’s proven true; it’s true until it’s proven false).  But while Popper worked as a logician, Kuhn worked as a historian.  His 1962 book The Structure of Scientific Revolutions made his case; and while he had– and has— his detractors, Kuhn’s work has been deeply influential in both academic and popular circles (indeed, the phrase “paradigm shift” has become an English-language staple).

“What man sees depends both upon what he looks at and also upon what his previous visual-conception experience has taught him to see.”

Thomas S. Kuhn, The Structure of Scientific Revolutions


“The commonality between science and art is in trying to see profoundly – to develop strategies of seeing and showing”*…

Working with her scientist husband, Orra Hitchcock produced illustrations on bolts of linen that manifest original knowledge about extinction, stratigraphy, and their evidentiary features in the surrounding landscape– and trained eager young students to recognize and describe geological and natural-historical phenomena…

After meeting and falling in love with Edward Hitchcock, her employer at Massachusetts’ Deerfield Academy, Orra (née White) married him in 1821, beginning a lifetime of professional collaboration while raising a family amid piles of rocks and research tomes. Highly trained, white, and wealthy, she was far from an oddity in nineteenth-century education. Like many other women of her class, Hitchcock received extensive instruction in the arts and sciences, making a name by working alongside, not beneath, a man who had easier access to academic opportunities. Variously lauded as “an anomaly” and “the most remarkable” of their era, her scientific illustrations have rarely been considered on their own terms — admired for the natural historical and religious knowledge they contain — without being made an exemplar of the broader category of “women’s work”.

Moving to Amherst when Edward was appointed Professor of Chemistry and Natural History, the couple embarked on a decades-long exploration of the Connecticut River Valley’s botany and geology. While Edward lectured to eager young students about the principles of nature, from the depths of oceans to the granite veins of the earth, Orra produced more than sixty hand-colored scientific illustrations on poster-sized linen swaths designed to be hung on classroom walls.

Ranging from extinct mammals like Megatherium (a genus of giant ground sloth [below]) through lithic strata to fossilized footprints, the collection is striking for its modern abstraction, anticipating the later works of George Maw. Although some of Hitchcock’s geological illustrations seem far from “accurate” in their specificity (or lack thereof), her devotion to clear and concise visual communication bespeaks a deep-seated understanding of complex scientific principles…

An appreciation: “Orra White Hitchcock’s Scientific Illustrations for the Classroom (1828–40),” from @PublicDomainRev.

* Edward Tufte


As we picture it, we might send sharply-observant birthday greetings to Cecilia Helena Payne-Gaposchkin; she was born on this date in 1900.  An astrophysicist and astronomer, she was the first– in her Radcliffe (Harvard) PhD thesis in 1927– to apply the laws of atomic physics to the study of the temperature and density of stellar bodies: the first to conclude that hydrogen and helium are the two most common elements in the universe and the first to suggest that the Sun is primarily (99%) composed of hydrogen.  During the 1920s, the accepted explanation of the Sun’s composition was a calculation of around 65% iron and 35% hydrogen.  Her thesis adviser, astronomer Henry Norris Russell, reached a similar conclusion via his own observations several years later, and (while he made brief mention of Payne’s work) was for a time credited with the discovery.  But in 1947, astronomer Fred Hoyle confirmed her original claim.

She spent her entire career at Harvard.  In 1956 she became the first woman to be promoted to full professor from within the faculty at Harvard’s Faculty of Arts and Sciences. Later, with her appointment to the Chair of the Department of Astronomy, she also became the first woman to head a department at Harvard.

Her students included Helen Sawyer Hogg, Joseph AshbrookPaul W. Hodge, and Frank Drake (the creator of the Drake Equation)– all of whom made important contributions to astronomy.


“For himself (and only for a short time) a man may postpone enlightenment in what he ought to know, but to renounce it for posterity is to injure and trample on the rights of mankind”*…

A (small) part of the mechanism of The Clock of the Long Now [source]

The 10,000-year clock is neither a ‘frightening’ ‘distraction,’ as its critics scorn, nor the ‘admirable objective’ its fans claim. It’s something else — a monument to long-term thinking that can unlock a deeper and more thoughtful spirit of interpretive patience. Vincent Ialenti considers The Clock of the Long Now

… Stonehenge was not (to our knowledge) created with the intent of drawing people to think about the far future. However, like the clock, it can also relay a few relatively coherent messages across time. Its monolithic slabs were designed to align with the summer solstice’s sunrise and the winter solstice’s sunset. The clock was likewise designed to synchronize each day at solar noon.

As a result, the architectures of both can exhibit, for future societies, evidence of deliberate human-astronomical calibration. These features could, when encountered by successive generations, foster an ongoing awareness of humanity’s enduring attunement to the heavens. This could serve as a transgenerational reminder that, in the deeper time horizons of the universe, all of us humans are, ultimately, contemporaries — living and dying by the same star.

Long Now’s atmosphere of unhinged creativity and unapologetic eco-pragmatism provided a near-constant drip of bold, stimulating, outside-the-box ideas. There is, to my knowledge, no better setting for pondering the planetary challenges of climate adaptation, nuclear weapons risk and sociopolitical division we will all need to face in the years ahead.

If [Clock designer Danny] Hillis’ clock is a monument to this, then surely it stands for something important. Yet to appreciate why, one must first commit to approaching all timebound commentaries on the clock — including this one — with a patient, non-tempocentric, interpretive ambivalence. Five thousand years from now, after all, it may well be captivating millions, just as Stonehenge does today. What’s certain is that neither its designers nor its critics will live to find out.

The Long Now Foundation (@longnow) and its monumental incitement to take the long view: “Keeping Time Into The Great Beyond,” from @vincent_ialenti in @NoemaMag.

* Immanuel Kant, An Answer to the Question: What Is Enlightenment?


As we resolve to be good ancestors, we might spare a thought for another long-term thinker, Pierre Teilhard de Chardin; he died on this date in 1955.  A Jesuit theologian, philosopher, geologist, and paleontologist, he conceived the idea of the Omega Point (a maximum level of complexity and consciousness towards which he believed the universe was evolving) and developed Vladimir Vernadsky‘s concept of noosphere.  Teilhard took part in the discovery of Peking Man, and wrote on the reconciliation of faith and evolutionary theory.  His thinking on both these fronts was censored during his lifetime by the Catholic Church (in particular for its implications for “original sin”); but in 2009, they lifted their ban.


“Appearances are a glimpse of the unseen”

A shower of comets rains down on Earth while violent volcanic eruptions billow up from below. Both events may follow our planet’s passage through dark matter concentrated in the Milky Way’s plane and help to trigger extinction events.

Are we on the verge of understanding the upheavals that have shaped the earth?

Do geologists dream of a final theory? Most people would say that plate tectonics already serves as geology’s overarching idea. The discovery of plate tectonics 50 years ago was one of the great scientific achievements of the 20th century, but is the theory complete? I think not. Plate tectonics describes Earth’s present geology in terms of the geometry and interactions of its surface plates. Geologists can extrapolate plate motions both back in time and into the future, but they cannot yet derive the behavior and history of plate tectonics from first principles.

Although scientists can interpret the history through the lens of what they see today, an important question remains: Why did geologic events — such as hot-spot volcanism, the breakup of continents, fluctuations in seafloor spreading, tectonic episodes, and sea-level oscillations — occur exactly when and where they did? Are they random, or do they follow some sort of a pattern in time or space?

A complete theory of Earth should explain geologic activity in the spatial domain, as plate tectonics does quite well for the present (once you incorporate hot spots), but also in the time and frequency domains. Recent findings suggest to me that geology may be on the threshold of a new theory that seeks to explain Earth’s geologic activity in time and space in the context of its astronomical surroundings.

The solar system oscillates with respect to the midplane of the disk-shaped Milky Way Galaxy with a period of about 60 million years. The Sun’s family passes through this plane twice each period, or once every 30 million years or so. The solar system behaves like a horse on a carousel — as we go around the disk-shaped galaxy, we bob up and down through the disk, passing through its densest part roughly every 30 million years.

Surely, it is too much of a coincidence that the cycle found in mass extinctions and impact craters should turn out to be one of the fundamental periods of our galaxy. The idea seemed almost too pretty to be wrong. But people searching for cycles have been fooled before, and we still had to answer the question: How does this cycle of movement lead to periodic perturbations of the Oort Cloud comets?

The idea of a roughly 30 million-year rhythm in geologic events has a long history in the geological literature. In the early 20th century, W.A. Grabau, an expert on sedimentary strata, proposed that tectonic activity and mountain building drove periodic fluctuations in sea level with an approximately 30 million-year cycle. In the 1920s, noted British geologist Arthur Holmes, armed with a few age determinations from radioactive decay, saw a similar 30 million-year cycle in Earth’s geologic activity…

If the cycles are real, what could be driving these long-term changes in volcanism, tectonics, sea level, and climate at such regular, if widely spaced, intervals? At first, I thought that the periodic energetic impacts might somehow be affecting deep-seated geological processes. I suggested in a short note in the journal Nature that large impacts might so deeply excavate and fracture the crust — to depths in excess of 10 miles (16 km) — that the sudden release of pressure in the upper mantle would result in large-scale melting. This would lead to the production of massive flood-basalt lavas, which would cover the crater and possibly create a mantle hot spot at the site of the impact. Hot spots could lead to continental breakup, which can cause increased tectonics and changes in ocean-floor spreading rates, and in turn cause global sea levels to fluctuate. Unfortunately, no known terrestrial impact structure has a clear association with volcanism, although some volcanic outpourings on Mars seem to be located along radial and concentric fractures related to large impacts.

The potential key to resolving this geological conundrum may come from outer space. Remember that Randall and Reece suggested that Earth passes through a thin disk of dark matter concentrated along the Milky Way’s midplane every 30 million years or so. Astrophysicist Lawrence Krauss and Nobel Prize-winning physicist Frank Wilczek of Harvard University, and independently Katherine Freese, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, proposed that Earth could capture dark matter particles that would accumulate in the planet’s core. The number of dark matter particles could grow large enough so that they would undergo mutual annihilation, producing prodigious amounts of heat in Earth’s interior.

A 1998 paper in the journal Astroparticle Physics (which I am sure few geologists ever read) provided a potential missing link. Indian astrophysicists Asfar Abbas and Samar Abbas (father and son, respectively) at Utkal University also were interested in dark matter and its interactions with our planet. They calculated the amount of energy released by the annihilation of dark matter captured by Earth during its passage through a dense clump of this material. They found that mutual destruction among the particles could produce an amount of heat 500 times greater than Earth’s normal heat flow, and much greater than the estimated power required in Earth’s core to generate the planet’s magnetic field. Putting together the predicted 30 million-year periodicity in encounters with dark matter with the effects of Earth capturing this unstable matter produces a plausible hypothesis for the origin of regular pulses of geologic activity.

Excess heat from the planet’s core can raise the temperature at the base of the mantle. Such a pulse of heat might create a mantle plume, a rising column of hot mantle rock with a broad head and narrow tail. When these rising plumes penetrate Earth’s crust, they create hot spots, initiate flood-basalt eruptions, and commonly lead to continental fracturing and the beginning of a new episode of seafloor spreading. The new source of periodic heating by dark matter in our planet’s interior could lead to periodic outbreaks of mantle-plume activity and changes in convection patterns in Earth’s core and mantle, which could affect global tectonics, volcanism, geomagnetic field reversals, and climate, such as our planet has experienced in the past.

These geologic events could lead to environmental changes that might be enough to cause extinction events on their own. A correlation of some extinctions with times of massive volcanic outpourings of lava supports this view. This new hypothesis links geologic events on Earth with the structure and dynamics of the Milky Way Galaxy.

It is still too early to tell if the ingredients of this hypothesis will withstand further examination and testing. Of course, correlations among geologic events can occur even if they are not part of a periodic pattern, and long-term geological cycles may exist apart from any external cosmic connections. The virtue of the galactic explanation for terrestrial periodicity lies in its universality — because all stars in the galaxy’s disk, many of which harbor planets, undergo a similar oscillation about the galactic midplane — and in its linkage of biological and geological evolution on Earth, and perhaps in other solar systems, to the great cycles of our galaxy.

Dark matter’s shadowy effect on Earth“: Earth’s periodic passage through the galaxy’s disk could initiate a series of events that ultimately lead to geological cataclysms and mass extinctions. From Michael Rapino (@mrr1_michael)

For very different angle on the evolution of the earth, the wonderful Walter Murch: “Why Birds Can Fly Over Mount Everest.”

* Anaxagoras


As we dig deep, we might spare a thought for Harlow Shapley; he died on this date in 1972. An astronomer known as “the Modern Copernicus,” he did important work first at the Mt. Wilson Observatory, and then as head of the Harvard College Observatory. He boldly and correctly proclaimed that the globulars outline the Galaxy, and that the Galaxy is far larger than was generally believed and centered thousands of light years away in the direction of Sagittarius: he discovered the center of our Galaxy, and our position within it.


“Everything is in motion. Everything flows.”*…

(Roughly) Daily has looked at the related theories of plate tectonics and continental drift before (e.g., here and here). They are relatively young: proposed in the early twentieth century by Alfred Wegener, they weren’t widely accepted until 1960 or so. Now they’re fundamental– and allowing scientists to reconstruct the earth’s past. To wit, this animation looking at the Earth’s tectonic plate movement from 1 ga (geological time for 1 billion years ago) to the present-day (the video starts at time 1,000 ma [1,000 million years ago], and moves at the rate of about 25 million years every second)…

From Earthbyte

Here’s a even more ambitious project, looking back 3.3 billion years:

More on plate tectonics and the supercontinents that it formed (and unformed) at Visual Capitalist.

* William Hazlitt


As we buckle up, we might recall that in the very late 50s, the Ohio Art Company– which had been pursuing a pair of business: toys (e.g., windmills and a climbing monkey) and custom metal lithography products for food container and specialty premium markets– found a way to merge the two.  It acquired the rights to French electrician André Cassagnes‘ L’Écran Magique (The Magic Screen)– a drawing toy that allowed users to spin knobs to create line drawings, which could be erased by by turning the device upside down and shaking it. Ohio Art renamed it the Etch A Sketch, and introduced it in this date in 1960.

At its launch, which was near the peak of the Baby Boom, the Etch A Sketch was priced at $2.99 (equivalent to $26 in 2020); the company sold 600,000 units that year … and went on to sell over 100 million units and to earn a place in the National Toy Hall of Fame.


Written by (Roughly) Daily

July 12, 2021 at 1:00 am

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