Strange Sounds


Airbursts: An underappreciated hazard

A paper published in March of 2021 in the journal Science Advances reports on the discovery of evidence for a large airburst type impact within the SØr Rondane Mountains, Queen Maud Land, East Antarctica. The report bears the names of a 15-member international team that did the research. The lead author was M. Van Ginneken with the Belgian Geological Survey. In the first sentence of the abstract to the article the authors support something I have been saying for literally decades: "Large airbursts, the most frequent hazardous impact events, are estimated to occur orders of magnitude more frequently than crater-forming impacts."

This fact is confirmed simply because airbursts don't leave impact craters. In this case the fingerprints of the event took the form of condensation spherules resulting from "a touchdown event, in which a projectile vapor jet interacts with the Antarctic ice sheet." The authors go on to explain that "Finding evidence of these low-altitude meteoritic events thus remains critical to understanding the impact history of Earth and estimating hazardous effects of asteroid impacts." They further report that "In recent years, meteoritic ablation debris resulting from airburst events have been found in three different locations of Antarctica. The material . . . all appears to have been produced during a Tunguska-like airburst event 480 thousand years (ka) ago."

With respect to their research, they say: "Here, we present the discovery of extraterrestrial particles formed during a significantly larger event recovered on . . . Queen Maud Land, East Antarctica. The characteristic features of the recovered particles attest to an unusual type of touchdown event, intermediate between an airburst and a crater-forming impact, during which the high-velocity vapor jet produced by the total disruption of an asteroid reached the Antarctic ice sheet." This event was estimated by the team to have occurred about 430 thousand years ago.

The authors provide some critical perspective on the effects of these type of impacts:

"The impact hazards resulting form the atmospheric entry of an asteroid that are currently being addressed by impact mitigation programs depend mainly on whether the impactor reaches the ground or is entirely disrupted in the atmosphere (i.e., airburst). For small-to medium-sized impactors (50- to 150-m diameter) producing airbursts, the main hazard is limited to blast effects resulting in strong overpressures over areas of up to 100,000 km2 wide. [38,600 sq miles] Thermal radiation may also result in fires over an area of 10 to 1000 km2 wide. . . . in addition to shockwaves and thermal radiation covering the aforementioned areas, these events are potentially destructive over a large area, corresponding to the area of interaction between the hot jet and the ground. The authors point out that such an event over Antarctica would inject ice crystals and impact dust into the upper atmosphere but would not directly affect human activity. However, they explain that "if a touchdown impact event takes place above a densely populated area, this would result in millions of casualties and severe damages over distances of up to hundreds of kilometers."

Now comes a new report in Earth and Planetary Science Letters on the discovery of evidence for yet another airburst event over Antarctica. The 11-member team responsible for the report is comprised of geologists, astrophysicists, and archaeologists from the U.S., the United Kingdom, Belgium, Russia, Japan, France and Italy.


Large ingenous events, cosmic impacts and crises in the history of life

© Randall Carlson Newsletter - March 2024
Last month, in the February 2024 issue of the Kosmographia Newsletter I reported on new research correlating a series of large-scale igneous events which produced the Central Atlantic Magmatic Province (CAMP) and the Siberian Traps with mass extinction episodes. On February 8 another paper was published in the journal Global and Planetary Change which further supports correlations between mass extinction episodes with gigantic volcanic eruptions and catastrophic cosmic impacts. The lead author of the paper is Michael Rampino, who has for decades been in the forefront of researching catastrophic events in Earth history. I have been following his work since the early 1980s and hold him in high regard as a scientist who is willing to think outside established paradigms of Earth history. The abstract to the paper begins:

"We find that Large Igneous Province (LIP) volcanism, mostly continental flood basalts (CFBs), along with the largest extraterrestrial impacts show significant correlations with mass-extinction events in the Phanerozoic geologic record. The ages of the 6 major marine mass extinctions (≥ 40% extinction of genera) of the last 541 MY ̶ the end-Ordovician (~444 Ma), late Devonian (~ 372 Ma), end-Guadalupian (~259 Ma), end-Permian (~ 252 Ma), end-Triassic (~201 Ma), and end-Cretaceous (66 Ma) extinctions are significantly correlated with high-quality U — Pb zircon and 40Ar/39Ar ages of 6 continental flood basalts (CFBs) ̶ the Cape St. Mary's, Viluy, Emeishan, Siberian, CAMP, and the Deccan Basalts.

U — Pb zircon dating (Uranium-lead) is a widely used method for dating metamorphic rocks typically employing a thermal ionization mass spectrometer. Zircon is used because it includes uranium and thorium atoms in its crystalline structure when forming but rejects lead, so any lead found in a zircon crystal is radiogenic, meaning it results from radioactive decay. Argon dating can measure Argon isotopes from a single mineral grain. The ratio of Argon 40 to Argon 39 yields the age of the sample.

The extinctions listed above are considered to be major events in the history of life on Earth. A number of less severe extinctions have taken place, although these events are somewhat more difficult to discern in the geologic/palaeontologic record. Nevertheless, a correlation can be discerned between these extinctions and both volcanic eruptions and cosmic impact.

Bizarro Earth

Geologists unravel plate tectonic chain reaction

A plate tectonic chain reaction.
© Utrecht UniversityA plate tectonic chain reaction.
Geologists at Utrecht University are working hard to unravel the secrets of plate tectonics, the mechanism that continuously shapes Earth's crust and is causing earthquakes and volcanic eruptions. This time, another mystery has been dissected. In the Earth's geological past, there were 'short' periods of a few million years during which many tectonic plates around the world suddenly changed their speed and direction. What caused these abrupt changes in plate movements? Earlier research showed that changes in movement between two plates can result from continental collisions or rising mantle plumes. But could such collisions or mantle plumes set off a global chain reaction? Now geologists have succeeded in finding evidence that supports this. "With this discovery, we are able to better understand the driving forces behind plate movements, and thus processes such as mountain formation or volcanism."

This paper, published in Nature Geoscience, was a collaboration between geoscientists from Utrecht University, Australian National University, and Ben-Gurion University of the Negev. To test their hypothesis, the researchers asked themselves the following question: did the formation of a new subduction zone north of Arabia that was triggered by a mantle plume that caused a super volcano near Madagascar ~100 million years ago set off a chain reaction? Utrecht professor of plate tectonics and paleogeography Douwe van Hinsbergen, geologist, former Utrecht PhD student and first author Derya Gürer, and geophysicist Roi Granot, analysed the consequences step by step. "If our hypothesis is correct, the new subduction zone that formed north of Arabia should have caused forces that accelerated, and rotated the African Plate in the 10 million years after subduction initiation. However, to analyse this, we had to solve a major problem," says Gürer.


Geomythology looks to ancient stories for hints of scientific truth

Everyone loves a good story, especially if it's based on something true.

Consider the Greek legend of the Titanomachy, in which the Olympian gods, led by Zeus, vanquish the previous generation of immortals, the Titans. As recounted by the Greek poet Hesiod, this conflict makes for a thrilling tale - and it may preserve kernels of truth.

The eruption around 1650 B.C. of the Thera volcano could have inspired Hesiod's narrative. More powerful than Krakatoa, this ancient cataclysm in the southern Aegean Sea would have been witnessed by anyone living within hundreds of miles of the blast.

Thera Volcano
© Steve Jurvetson, CC BYThe massive eruption of the Thera volcano more than 3,500 years ago left behind a hollowed out island, today known as Santorini.
Historian of science Mott Greene argues that key moments from the Titanomachy map on to the eruption's "signature." For example, Hesiod notes that loud rumbles emanated from the ground as the armies clashed; seismologists now know that harmonic tremors - small earthquakes that sometimes precede eruptions - often produce similar sounds. And the impression of the sky - "wide Heaven" - shaking during the battle could have been inspired by shock waves in the air caused by the volcanic explosion. Hence, the Titanomachy may represent the creative misreading of a natural event.

In 2021 I published the first textbook in the field, Geomythology: How Common Stories Reflect Earth Events. As the book demonstrates, researchers in both the sciences and the humanities practice geomythology. In fact, geomythology's hybrid nature may help to bridge the gap between the two cultures. And despite its orientation toward the past, geomythology might also provide powerful resources for meeting environmental challenges in the future.


Twelfth century literature and space-age data help map 3,000 years of auroras

Researchers from National Institute of Polar Research and the Institute of Statistical Mathematics published maps indicating how the auroral zone has moved over the last three millennia.
Auroras over the Centuries
© National Institute of Polar ResearchReconstructed auroral zone in 2010 AD (left) and 1200 AD (right).
"The Poetic Edda", an Old Norse collection of poems believed to have been most likely drawn up between 1000 and 1100 AD, contains the gods and giants of ancient Scandinavian lore but lacks perhaps the most magical of real phenomena — auroras. A century later, another Old Norse text, called "The King's Mirror", describes auroras over modern-day Greenland. Around the same time, auroras were witnessed across Japan, including written records of red and white curtain-like lights just north of Kyoto.

Why the discrepancy? Researchers set out to better understand the auroral zone and its movement over the last 3,000 years in an effort to predict how it might change in the future. The team published maps indicating how the auroral zone has moved over the last three millennia on Aug. 20 in the Journal of Space Weather and Space Climate.

"The accurate knowledge of the auroral zone over the past 3,000 years — via worldwide old witness record of auroras, including those even from low-latitude Japan — helps us understand the extreme magnetic storms," said first author Ryuho Kataoka, associate professor at the National Institute of Polar Research.


Cooling atmosphere: Sun halos, sun pillars spotted in sky over central Pennsylvania

Sun halos and sun pillars are created from ice crystals in the sky refracting sun light, but the both look different and can form at different times of the day.
Sun pillar in Pennsylvania
© Erin
Sun halos are created when sunlight or moonlight is reflecting off ice crystals in the sky. These crystals will then form a halo around the sun. Most of the ice crystals are found in cirrus clouds or cirrostratus clouds. It usually forms a white circle or even sometimes you will see rainbow colors in the halo.


Ancient conch makes music for the first time in 17,000 years

Drawing of Ancient Conch
© Carole Fritz et al. 2021 / drawing: Gilles ToselloReconstruction of the instrument being played. In the background, a red dotted buffalo decorates the walls of the Marsoulas Cave; similar motifs decorate the instrument.
How old-fashioned is your taste in music? Researchers have recreated notes from a 17,000-year-old conch shell, found in a cave in southern France.

Discovered in the Marsoulas Cave, just north of the Pyrenees mountains, in 1931, the shell was initially thought to be a drinking cup. But a more detailed analysis, published today in the journal Science Advances, showed that the shell had been subtly modified by humans to attach a mouthpiece and use as a musical instrument.

The researchers enlisted the help of a musicologist specialising in wind instruments, who played the instrument in a recording studio. With the mouthpiece of the shell protected to avoid damage to the artefact, the musicologist blew air through the shell in a similar manner to playing trumpet or trombone, which allowed the shell to vibrate at its natural resonance and produce notes. Three distinct tones were recorded, which were similar to the modern notes C, D and C sharp.


Analysis of gravitational-wave data leads to wealth of discoveries

Black Hole Merger
© LIGO/T. PyleAn illustration showing the merger of two black holes and the gravitational waves that ripple outward as the black holes spiral toward each other.
A global network of scientists has completed the first major analysis of gravitational wave data, providing exciting insights into some of the most exotic objects in the Universe.

"We are announcing the discovery of 44 confirmed black hole mergers, which is a more than a four-fold increase in the number of previously known gravitational-wave signals," says Shanika Galaudage from Australia's Monash University, who was part of the research team.

"With so many black holes to study, we can start to answer deep questions about how these systems came to merge."

It's been just five years since physicists shook the scientific world with the long-sought-after detection of gravitational waves. This Nobel Prize-winning feat recorded the ripples in spacetime created by a colossal crash between two orbiting black holes - a phenomenon first predicted by Einstein's theory of general relativity.

Since then, detections have generally been announced one by one. But now, as detectors such as the LIGO and Virgo observatories improve, observations have exploded.

"Gravitational-wave astronomy is revolutionary - revealing to us the hidden lives of black holes and neutron stars," says Christopher Berry, co-author and astrophysicist from the University of Glasgow. "In just five years we have gone from not knowing that binary black holes exist to having a catalogue of over 40."

These new detections create a diverse family portrait of black hole binaries, showing that they are stranger and more common than thought, as well as illuminating their origins.

Cloud Lightning

Red sprites captured in slow motion over Sverdlovsk Oblast, Russia in August

Red sprites captured over the Sverdlovsk oblast in the summer of 2020. The abundance of nighttime thunderstorms this season has made it possible to capture this rare phenomenon in great detail:

00:00 - sprite №1 close-up, real time
00:10 - sprite №1 close-up, speed is slowed down 2 times
00:13 - sprite №1 close-up, speed is slowed down 5 times
00:19 - sprite №1, stack of frames
00:27 - sprite №2 close-up, real time
00:29 - sprite №2 close-up, speed slowed 2 times
00:35 - sprite №2 close-up, speed is 5 times slower
00:39 - sprite №2, stack of frames
00:48 - sprite №3, real time
00:52 - sprite №3 close-up, speed slowed 2 times
00:56 - sprite №3 close-up, speed slowed down 5 times
01:00 - sprite №3, stack of frames


Weakening of Earth's magnetic field probed

Earth’s magnetic field
© Aubert et al./IPGP/CNRS Photo libraryA simulation of the Earth’s magnetic field.
Geophysicists have been puzzling over a gradual weakening of the Earth's magnetic field in an area stretching from Africa to South America, which has resulted in technical disturbances in satellites orbiting Earth.

Scientists have resorted to data from the European Space Agency's (ESA) Swarm constellation to probe the disturbing weakening of Earth's magnetic field in the area known as the "South Atlantic Anomaly".

Jurgen Matzka, from the German Research Centre for Geosciences, and a team of experts from the Swarm Data, Innovation and Science Cluster (DISC) have been using data from ESA's Swarm satellite constellation to identify and measure the different magnetic signals that comprise Earth's magnetic field.
"The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously. We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth's core driving these changes," said Matzka.