Tag Archives: geology

How do nanoscale crystals make volcanoes explode?

This research may have the answer as to why a supposedly peaceful volcano will suddenly explode violently. From a September 24, 2020 University of Bayreuth press release (also on EurekAlert),

Tiny crystals, ten thousand times thinner than a human hair, can cause explosive volcanic eruptions. This surprising connection has recently been discovered by a German-British research team led by Dr. Danilo Di Genova from the Bavarian Research Institute of Experimental Geochemistry & Geophysics (BGI) at the University of Bayreuth. The crystals increase the viscosity of the underground magma. As a result, a build-up of rising gases occurs. The continuously rising pressure finally discharges in massive eruptions. The scientists present the results of their nanogeoscientific research in the journal “Science Advances“.

“Exactly what causes the sudden and violent eruption of apparently peaceful volcanoes has always been a mystery in geology research. Nanogeoscience research has now allowed us to find an explanation. Tiny crystal grains containing mostly iron, silicon, and aluminium are the first link in a chain of cause and effect that can end in catastrophe for people living in the vicinity of a volcano. The most powerful volcanic eruption in human history was Mount Tambora in Indonesia in 1815”, says Dr. Danilo Di Genova. For the recently published study, he worked closely with scientists from the University of Bristol, the Clausthal University of Technology, and two European synchrotron radiation facilities.

Because of their diameter of a few nanometres, the crystals are also known as nanolites. Using spectroscopic and electron microscopy methods, the researchers have detected traces of these particles, invisible to the eye, in the ashes of active volcanoes. In the BGI’s laboratory, they were then able to describe these crystals and finally to demonstrate how they influence the properties of volcanic magma. The investigations focused on magma of low silicon oxide content cooling to form basalt on the earth’s surface after a volcanic eruption. Low silica magma is known for its low viscosity: It forms a thin lava that flows quickly and easily. The situation is different, however, if it contains a large number of nanolites. This makes the magma viscous – and far less permeable to gases rising from the earth’s interior. Instead of continuously escaping from the volcanic cone, the gases in the depths of the volcano become trapped in the hot magma. As a result, the magma is subjected to increasing pressure until it is finally ejected explosively from the volcano.

“Constant light plumes of smoke above a volcanic cone need not necessarily be interpreted as a sign of an imminent dangerous eruption. Conversely, however, the inactivity of apparently peaceful volcanoes can be deceptive. Rock analyses, written and archaeological sources suggest, for example, that people in the vicinity of Vesuvius were surprised by an extremely violent eruption of the volcano in 79 AD. Numerous fatalities and severe damage to buildings were the result”, says Di Genova. In his further research, the Bayreuth scientist hopes to use high-pressure facilites and computer simulation to model the geochemical processes that lead to such unexpected violent eruptions. The aim is to better understand these processes and thus also to reduce the risks for the population in the vicinity of volcanoes.

The researchers have included a nanocrystal image to illustrate their work,

Caption: A transmission electron microscopy image of a nano crystal (ca 25 nm in diameter) in a basaltic magma from Mt. Etna (Italy). The nano crystal is enriched in iron (Fe) and it was produced in a laboratory during at BGI. Credit Image: Nobuyoshi Miyajima.

Here’s a link to and a citation for the paper,

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions by Danilo Di Genova, Richard A. Brooker, Heidy M. Mader, James W. E. Drewitt, Alessandro Longo, Joachim Deubener, Daniel R. Neuville, Sara Fanara, Olga Shebanova, Simone Anzellini, Fabio Arzilli, Emily C. Bamber, Louis Hennet, Giuseppe La Spina and Nobuyoshi Miyajima. Science Advances DOI: 10.1126/sciadv.abb0413 Vol. 6, no. 39, eabb0413 Published: 23 Sep 2020

This paper appears to be open access.

“The earth is mostly made of cubes,” said Plato in 5th Century BCE. Turns out, he was right!

Theories from mathematics, physics, and geology have been used to demonstrate that the earth’s basic shape is, roughly speaking, a cube. From a July 20, 2020 news item on ScienceDaily,

Plato, the Greek philosopher who lived in the 5th century B.C.E. [before the common era], believed that the universe was made of five types of matter: earth, air, fire, water, and cosmos. Each was described with a particular geometry, a platonic shape. For earth, that shape was the cube.

Science has steadily moved beyond Plato’s conjectures, looking instead to the atom as the building block of the universe. Yet Plato seems to have been onto something, researchers have found.

In a new paper in the Proceedings of the National Academy of Sciences [PNAS], a team from the University of Pennsylvania, Budapest University of Technology and Economics, and University of Debrecen [Hungary] uses math, geology, and physics to demonstrate that the average shape of rocks on Earth is a cube.

A July 17, 2020 University of Pennsylvania news release (also on EurekAlert but dated July 20, 2020), which originated the news item, goes on to describe the work as “mind-blowing,”

“Plato is widely recognized as the first person to develop the concept of an atom [Maybe not, scroll down to find the subhead “Leucippus and Democritus”], the idea that matter is composed of some indivisible component at the smallest scale,” says Douglas Jerolmack, a geophysicist in Penn’s School of Arts & Sciences’ Department of Earth and Environmental Science and the School of Engineering and Applied Science’s Department of Mechanical Engineering and Applied Mechanics. “But that understanding was only conceptual; nothing about our modern understanding of atoms derives from what Plato told us.

“The interesting thing here is that what we find with rock, or earth, is that there is more than a conceptual lineage back to Plato. It turns out that Plato’s conception about the element earth being made up of cubes is, literally, the statistical average model for real earth. And that is just mind-blowing.”

The group’s finding began with geometric models developed by mathematician Gábor Domokos of the Budapest University of Technology and Economics, whose work predicted that natural rocks would fragment into cubic shapes.

“This paper is the result of three years of serious thinking and work, but it comes back to one core idea,” says Domokos. “If you take a three-dimensional polyhedral shape, slice it randomly into two fragments and then slice these fragments again and again, you get a vast number of different polyhedral shapes. But in an average sense, the resulting shape of the fragments is a cube.”

Domokos pulled two Hungarian theoretical physicists into the loop: Ferenc Kun, an expert on fragmentation, and János Török, an expert on statistical and computational models. After discussing the potential of the discovery, Jerolmack says, the Hungarian researchers took their finding to Jerolmack to work together on the geophysical questions; in other words, “How does nature let this happen?”

“When we took this to Doug, he said, ‘This is either a mistake, or this is big,'” Domokos recalls. “We worked backward to understand the physics that results in these shapes.”

Fundamentally, the question they answered is what shapes are created when rocks break into pieces. Remarkably, they found that the core mathematical conjecture unites geological processes not only on Earth but around the solar system as well.

“Fragmentation is this ubiquitous process that is grinding down planetary materials,” Jerolmack says. “The solar system is littered with ice and rocks that are ceaselessly smashing apart. This work gives us a signature of that process that we’ve never seen before.”

Part of this understanding is that the components that break out of a formerly solid object must fit together without any gaps, like a dropped dish on the verge of breaking. As it turns out, the only one of the so-called platonic forms–polyhedra with sides of equal length–that fit together without gaps are cubes.

“One thing we’ve speculated in our group is that, quite possibly Plato looked at a rock outcrop and after processing or analyzing the image subconsciously in his mind, he conjectured that the average shape is something like a cube,” Jerolmack says.

“Plato was very sensitive to geometry,” Domokos adds. According to lore, the phrase “Let no one ignorant of geometry enter” was engraved at the door to Plato’s Academy. “His intuitions, backed by his broad thinking about science, may have led him to this idea about cubes,” says Domokos.

To test whether their mathematical models held true in nature, the team measured a wide variety of rocks, hundreds that they collected and thousands more from previously collected datasets. No matter whether the rocks had naturally weathered from a large outcropping or been dynamited out by humans, the team found a good fit to the cubic average.

However, special rock formations exist that appear to break the cubic “rule.” The Giant’s Causeway in Northern Ireland, with its soaring vertical columns, is one example, formed by the unusual process of cooling basalt. These formations, though rare, are still encompassed by the team’s mathematical conception of fragmentation; they are just explained by out-of-the-ordinary processes at work.

“The world is a messy place,” says Jerolmack. “Nine times out of 10, if a rock gets pulled apart or squeezed or sheared–and usually these forces are happening together–you end up with fragments which are, on average, cubic shapes. It’s only if you have a very special stress condition that you get something else. The earth just doesn’t do this often.”

The researchers also explored fragmentation in two dimensions, or on thin surfaces that function as two-dimensional shapes, with a depth that is significantly smaller than the width and length. There, the fracture patterns are different, though the central concept of splitting polygons and arriving at predictable average shapes still holds.

“It turns out in two dimensions you’re about equally likely to get either a rectangle or a hexagon in nature,” Jerolmack says. “They’re not true hexagons, but they’re the statistical equivalent in a geometric sense. You can think of it like paint cracking; a force is acting to pull the paint apart equally from different sides, creating a hexagonal shape when it cracks.”

In nature, examples of these two-dimensional fracture patterns can be found in ice sheets, drying mud, or even the earth’s crust, the depth of which is far outstripped by its lateral extent, allowing it to function as a de facto two-dimensional material. It was previously known that the earth’s crust fractured in this way, but the group’s observations support the idea that the fragmentation pattern results from plate tectonics.

Identifying these patterns in rock may help in predicting phenomenon such as rock fall hazards or the likelihood and location of fluid flows, such as oil or water, in rocks.

For the researchers, finding what appears to be a fundamental rule of nature emerging from millennia-old insights has been an intense but satisfying experience.

“There are a lot of sand grains, pebbles, and asteroids out there, and all of them evolve by chipping in a universal manner,” says Domokos, who is also co-inventor of the Gömböc, the first known convex shape with the minimal number–just two–of static balance points. Chipping by collisions gradually eliminates balance points, but shapes stop short of becoming a Gömböc; the latter appears as an unattainable end point of this natural process.

The current result shows that the starting point may be a similarly iconic geometric shape: the cube with its 26 balance points. “The fact that pure geometry provides these brackets for a ubiquitous natural process, gives me happiness,” he says.

“When you pick up a rock in nature, it’s not a perfect cube, but each one is a kind of statistical shadow of a cube,” adds Jerolmack. “It calls to mind Plato’s allegory of the cave. He posited an idealized form that was essential for understanding the universe, but all we see are distorted shadows of that perfect form.”

The human capacity for imagination, in this case linking ideas about geometry and mathematics from the 5th Century BCE to modern physics and geology and to the solar system, astounds and astonishes me. As for Jerolmack’s comment that Plato (428/427 or 424/423 – 348/347 BC) was the first to develop the concept of an atom, not everyone agrees.

Leucippus and Democritus

It may not ever be possible to determine who was the first to theorize/philosophize about atoms but there is relatively general agreement that Leucippus (5th cent.BCE) and his successor, Democritus (c. 460 – c. 370 BC) were among the first. Here’s more about Ancient Atomism and its origins from the Stanford Encyclopedia of Philosphy,

Leucippus (5th c. BCE) is the earliest figure whose commitment to atomism is well attested. He is usually credited with inventing atomism. According to a passing remark by the geographer Strabo, Posidonius (1st c. BCE Stoic philosopher) reported that ancient Greek atomism can be traced back to a figure known as Moschus or Mochus of Sidon, who lived at the time of the Trojan wars. This report was given credence in the seventeenth century: the Cambridge Platonist Henry More traced the origins of ancient atomism back, via Pythagoras and Moschus, to Moses. This theologically motivated view does not seem to claim much historical evidence, however.

Leucippus and Democritus are widely regarded as the first atomists [emphasis mine] in the Greek tradition. Little is known about Leucippus, while the ideas of his student Democritus—who is said to have taken over and systematized his teacher’s theory—are known from a large number of reports. These ancient atomists theorized that the two fundamental and oppositely characterized constituents of the natural world are indivisible bodies—atoms—and void. The latter is described simply as nothing, or the negation of body. Atoms are by their nature intrinsically unchangeable; they can only move about in the void and combine into different clusters. Since the atoms are separated by void, they cannot fuse, but must rather bounce off one another when they collide. Because all macroscopic objects are in fact combinations of atoms, everything in the macroscopic world is subject to change, as their constituent atoms shift or move away. Thus, while the atoms themselves persist through all time, everything in the world of our experience is transitory and subject to dissolution.

Although the Greek term atomos is most commonly associated with the philosophical system developed by Leucippus and Democritus, involving solid and impenetrable bodies, Plato’s [emphasis mine] Timaeus presents a different kind of physical theory based on indivisibles. The dialogue elaborates an account of the world wherein the four different basic kinds of matter—earth, air, fire, and water—are regular solids composed from plane figures: isoceles and scalene right-angled triangles. Because the same triangles can form into different regular solids, the theory thus explains how some of the elements can transform into one another, as was widely believed.

As you can see from the excerpt, they are guessing as to the source for atomism and thee are different kinds of atomism and Plato staked his own atomistic territory.

The paper

Here’s a link to and a citation for the paper followed by a statement of significance and the paper’s abstract,

Plato’s cube and the natural geometry of fragmentation by Gábor Domokos, Douglas J. Jerolmack, Ferenc Kun, and János Török. PNAS DOI: https://doi.org/10.1073/pnas.2001037117 First published July 17, 2020

This paper is behind a paywall.

Now for the Significance and the Abstract,

We live on and among the by-products of fragmentation, from nanoparticles to rock falls to glaciers to continents. Understanding and taming fragmentation is central to assessing natural hazards and extracting resources, and even for landing probes safely on other planetary bodies. In this study, we draw inspiration from an unlikely and ancient source: Plato, who proposed that the element Earth is made of cubes because they may be tightly packed together. We demonstrate that this idea is essentially correct: Appropriately averaged properties of most natural 3D fragments reproduce the topological cube. We use mechanical and geometric models to explain the ubiquity of Plato’s cube in fragmentation and to uniquely map distinct fragment patterns to their formative stress conditions.

Plato envisioned Earth’s building blocks as cubes, a shape rarely found in nature. The solar system is littered, however, with distorted polyhedra—shards of rock and ice produced by ubiquitous fragmentation. We apply the theory of convex mosaics to show that the average geometry of natural two-dimensional (2D) fragments, from mud cracks to Earth’s tectonic plates, has two attractors: “Platonic” quadrangles and “Voronoi” hexagons. In three dimensions (3D), the Platonic attractor is dominant: Remarkably, the average shape of natural rock fragments is cuboid. When viewed through the lens of convex mosaics, natural fragments are indeed geometric shadows of Plato’s forms. Simulations show that generic binary breakup drives all mosaics toward the Platonic attractor, explaining the ubiquity of cuboid averages. Deviations from binary fracture produce more exotic patterns that are genetically linked to the formative stress field. We compute the universal pattern generator establishing this link, for 2D and 3D fragmentation.

Fascinating, eh?

13,000 year old nanodiamonds and a scientific controversy about extinction

It took scientists from several countries and institutions seven years to reply to criticism of their 2007 theory which posited that a comet exploded over the earth’s surface roughly 13,000 years ago causing mass extinctions and leaving nano-sized diamonds in a layer of the earth’s crust. From a Sept. 1, 2014 news item on Azonano,

Tiny diamonds invisible to human eyes but confirmed by a powerful microscope at the University of Oregon are shining new light on the idea proposed in 2007 that a cosmic event — an exploding comet above North America — sparked catastrophic climate change 12,800 years ago.

In a paper appearing online ahead of print in the Journal of Geology, scientists from 21 universities in six countries report the definitive presence of nanodiamonds at some 32 sites in 11 countries on three continents in layers of darkened soil at the Earth’s Younger Dryas boundary.

The scientists have provided a map showing the areas with nanodiamonds,

The solid line defines the current known limits of the Younger Dryas Boundary field of cosmic-impact proxies, spanning 50 million square kilometers. [downloaded from http://www.news.ucsb.edu/2014/014368/nanodiamonds-are-forever#sthash.FtKG6WwS.dpuf]

The solid line defines the current known limits of the Younger Dryas Boundary field of cosmic-impact proxies, spanning 50 million square kilometers. [downloaded from http://www.news.ucsb.edu/2014/014368/nanodiamonds-are-forever#sthash.FtKG6WwS.dpuf]

 An Aug. 28,, 2014 University of Oregon news release, which originated the Azonano news item, describes the findings and the controversy,

The boundary layer is widespread, the researchers found. The miniscule diamonds, which often form during large impact events, are abundant along with cosmic impact spherules, high-temperature melt-glass, fullerenes, grape-like clusters of soot, charcoal, carbon spherules, glasslike carbon, heium-3, iridium, osmium, platinum, nickel and cobalt.

The combination of components is similar to that found in soils connected with the 1908 in-air explosion of a comet over Siberia and those found in the Cretaceous-Tertiary Boundary (KTB) layer that formed 65 million years ago when a comet or asteroid struck off Mexico and wiped out dinosaurs worldwide.

In the Oct. 9, 2007, issue of Proceedings of the National Academy of Sciences, a 26-member team from 16 institutions proposed that a cosmic impact event set off a 1,300-year-long cold spell known as the Younger Dryas. Prehistoric Clovis culture was fragmented, and widespread extinctions occurred across North America. Former UO researcher Douglas Kennett, a co-author of the new paper and now at Pennsylvania State University, was a member of the original study.

In that [2007] paper and in a series of subsequent studies, reports of nanodiamond-rich soils were documented at numerous sites. However, numerous critics refuted the findings, holding to a long-running theory that over-hunting sparked the extinctions and that the suspected nanodiamonds had been formed by wildfires, volcanism or occasional meteoritic debris, rather than a cosmic event.

The University of Oregon news release goes on to provide a rejoinder from a co-author of both the 2007 paper and the 2014 paper. as well as. a discussion of how the scientists gathered their evidence,

The glassy and metallic materials in the YDB layers would have formed at temperatures in excess of 2,200 degrees Celsius and could not have resulted from the alternative scenarios, said co-author James Kennett, professor emeritus at the University of California, Santa Barbara, in a news release. He also was on the team that originally proposed a comet-based event.

In the new paper, researchers slightly revised the date of the theorized cosmic event and cited six examples of independent research that have found consistent peaks in the creation of the nanodiamonds that match their hypothesis.

“The evidence presented in this paper rejects the alternate hypotheses and settles the debate about the existence of the nanodiamonds,” said the paper’s corresponding author Allen West of GeoScience Consulting of Dewey, Arizona. “We provide the first comprehensive review of the state of the debate and about YDB nanodiamonds deposited across three continents.”

West worked in close consultation with researchers at the various labs that conducted the independent testing, including with co-author Joshua J. Razink, operator and instrument manager since 2011 of the UO’s state-of-the-art high-resolution transmission electron microscope (HR-TEM) in the Center for Advanced Materials Characterization in Oregon (CAMCOR).

Razink was provided with samples previously cited in many of the earlier studies, as well as untested soil samples delivered from multiple new sites. The samples were placed onto grids and analyzed thoroughly, he said.

“These diamonds are incredibly small, on the order of a few nanometers and are invisible to the human eye and even to an optical microscope,” Razink said. “For reference, if you took a meter stick and cut it into one billion pieces, each of those pieces is one nanometer. The only way to really get definitive characterization that these are diamonds is to use tools like the transmission electron microscope. It helps us to rule out that the samples are not graphene or copper. Our findings say these samples are nanodiamonds.”

In addition to the HR-TEM done at the UO, researchers also used standard TEM, electron energy loss spectroscopy (EELS), energy-dispersive X-ray spectroscopy (EDS), selected area diffraction (SAD), fast Fourier transform (FFT) algorithms, and energy-filtered transmission electron microscopy (EFTEM).

“The chemical processing methods described in the paper,” Razink said, “lay out with great detail the methodology that one needs to go through in order to prepare their samples and identify these diamonds.”

The University of California at Santa Barbara (UCSB) produced an Aug. 28, 2014 news release about this work and while there is repetition, there is additional information such as a lede describing some of what was made extinct,

Most of North America’s megafauna — mastodons, short-faced bears, giant ground sloths, saber-toothed cats and American camels and horses — disappeared close to 13,000 years ago at the end of the Pleistocene period. …

An Aug. 27, 2014 news item (scroll down to the end) on ScienceDaily provides a link and a citation to the latest paper.

Worlds in the making at FACT in Liverpool

It’s quite the week for finding art/science/technology projects in the UK. This time I’ve found the Worlds in the Making exhibition at FACT (from their About page),

FACT (Foundation for Art and Creative Technology) has been leading the UK video, film and new media arts scene for 20 years with groundbreaking exhibitions, education and research projects. The organisation aims to pioneer new forms of artistic and social interaction with individuals and communities.

Frank Swain’s July 1, 2011 article about the exhibition  for The Guardian notes,

Artist duo Semiconductor launch a major exhibition at the Fact [sic] gallery in Liverpool on Friday [July 1, 2011] portraying the subterranean, primeval world of geology.

“We’re really interested in the material nature of the world around us – in what the natural building blocks are of the visible physical world, and how we create an understanding of them,” says Ruth Jarman, one half of British artist duo Semiconductor [Joe Gerhardt is the other half].

One of the works on display features an audio representation of gems being created in the Earth’s subterranean depths. I think they’ve included the sound in their video preview of the show,

As for Swain’s (aka @sciencepunk on Twitter) provocative closing question,

Worlds in the Making is certainly art, but does it do anything for science? Can artists like Jarman and Gerhardt inspire wonder in the same way Brian Cox [BBC science presenter/programme host] does?

I think one of the answers is that there are many ways to inspire wonder and that artists such as Semiconductor and presenters such as Brian Cox can co-exist inspiring wonder each in their unique fashion. Thank you to Frank Swain for asking the question in such a way as to expose a false dichotomy.

FACT was last mentioned here in my October 1, 2009 posting.