Posts Tagged ‘volcano’
“Appearances are a glimpse of the unseen”
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.
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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?
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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
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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.
“Gentlemen, you can’t fight in here! This is the War Room!”*
In “Dr. Strangelove Dr. Strangelove,” Kristan Horton imitates the glorious satirical film Dr. Strangelove, using common household objects to re-create the world created by Kubrick—silverware become an airplane, plastic and coffee grounds become the sky…
The sublime, recreated with the mundane: “Dr. Strangelove Dr. Strangelove,” via the ever-illuminating The Morning News.
See also the “3-D Rooms Project.”
* Peter Sellers as President Merkin Muffley, one of three roles he played in Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb, produced, directed, and co-written (with Terry Southern, very loosely based on a novel by Peter George) by Stanley Kubrick
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As we ride it down, we might recall that it was on this date in 1883 that the volcano at Krakatoa (Krakatau) erupted with full force. The sound was heard over 2,000 miles away (that’s over 7.5% of the earth’s surface– the equivalent of an explosion in New York City being heard in San Francisco); tsunamis caused by the great blast killed 36,000 people in Java and Sumatra.
But there was another sense in which Krakatoa was importantly “the sound heard ’round the world”: While news of Lincoln’s assassination (only 18 years earlier) had taken almost two weeks to reach London, Europe and the U.S. knew of Krakatoa in about four hours. In the years between 1865 and 1883, there had been three interrelated developments: the global spread of the telegraph, the invention of Morse Code, and the establishment of Reuter’s news agency… and the world had become much smaller. (C.F., Tom Standage’s marvelous The Victorian Internet for the details– both remarkable and altogether resonant with today.)
As big as the explosion was, it was not the biggest in history: experts suggest that Santorini’s eruption in 1628 BCE was three times as powerful.
“You have to be in the right place at the right time. Or the wrong place at the wrong time, depending on your perspective”*…
Hailstones are balls (or spikes, or flattish pancakes) of frozen precipitation that measure at least 0.2 inches across, according to the National Oceanic and Atmospheric Administration’s Severe Storms Laboratory. Several other types of smaller frozen precipitation are known as “ice pellets,” reports the National Snow & Ice Data Center, and may take the form of graupel (soft balls of water droplets clinging to a snow crystal and looking like Styrofoam) or sleet (essentially icy raindrops). In the sky, either of these can serve as an “embryo,” the little nucleus around which a hailstone can grow. The longer a fledgling hailstone stays lofted in a thunderstorm’s fierce updraft, the bigger it gets. Beyond that minimum 0.2-inch threshold, there are a few finer distinctions between hailstones, thrown around by researchers and sometimes forecasters at the National Weather Service. “Severe” hail has a maximum dimension of one inch or more, “significantly severe” stones are larger than two inches, and “giant” hail is bigger than four inches.
“Giant” sounds pretty big, but this crop of researchers didn’t think it seemed quite big enough. A hailstone of more than four inches is “certainly very large,” says Matthew Kumjian, a meteorologist at Penn State University and lead author of the paper. But, he adds, while stones of that size are rare, “they are not exceptional.” Hailstones bigger than four inches are reported 30 to 40 times a year in the United States alone, he says. Stones larger than six inches, though, are few and far between. Kumjian’s co-author, graduate student Rachel Gutierrez, combed through reports and found about 10 confirmed instances in the last 10 or 15 years, mostly in the U.S. (There were a handful of unconfirmed reports in Australia, Africa, and Asia, but photos or official measurements were missing.)
The researchers suspect that there are probably more of these spectacularly sized hailstones dropping down across the country, but they’re likely going unnoticed. When measuring hail, time is of the essence: Hailstones vanish fairly quickly, especially in hot or humid conditions, or if they shatter on impact; even large ones with cushioned falls might be overlooked. The most severe hailstorms in the United States are in the Great Plains, Kumjian says, where people are spread fairly far apart…
They’re huge; they’re rare; and they’re melting all the time: “The Slippery Problem of Measuring Enormous Hunks of Hail.”
* Matthew Kumjian, a meteorologist at Penn State University, on measuring hailstones
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As we check the weather, we might recall that it was on this date in 1883 that the volcano on the Indonesian island of Krakatoa began to release huge plumes of steam and ash. Roughly three months later, on August 27, it erupted in earnest– with a sound so loud that it circled the earth four times. (As big as the explosion was, it was not the biggest in history: experts suggest that Santorini’s eruption in 1628 BCE was three times as powerful.)
“A volcano may be considered as a cannon of immense size”*…
On August 27, 1883, the Earth let out a noise louder than any it has made since.
It was 10:02 a.m. local time when the sound emerged from the island of Krakatoa, which sits between Java and Sumatra in Indonesia. It was heard 1,300 miles away in the Andaman and Nicobar islands (“extraordinary sounds were heard, as of guns firing”); 2,000 miles away in New Guinea and Western Australia (“a series of loud reports, resembling those of artillery in a north-westerly direction”); and even 3,000 miles away in the Indian Ocean island of Rodrigues, near Mauritius (“coming from the eastward, like the distant roar of heavy guns.”). In all, it was heard by people in over 50 different geographical locations, together spanning an area covering a thirteenth of the globe.
Think, for a moment, just how crazy this is. If you’re in Boston and someone tells you that they heard a sound coming from New York City, you’re probably going to give them a funny look. But Boston is a mere 200 miles from New York. What we’re talking about here is like being in Boston and clearly hearing a noise coming from Dublin, Ireland. Traveling at the speed of sound (766 miles or 1,233 kilometers per hour), it takes a noise about four hours to cover that distance. This is the most distant sound that has ever been heard in recorded history…
More at “The Sound So Loud That It Circled the Earth Four Times.”
(And for a consideration of “the noise beneath the noise,” check out “The Noise at the Bottom of the Universe.”)
* Oliver Goldsmith, Goldsmith’s Miscellaneous Works (1841), 90
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As we Bring the Noise, we might that it was on this date in 2013 that the eruption of Ecuador’s Tungurahua volcano sent a massive plume of ash, stones, and vapor soaring more than eight miles into the sky above the Andes.
Pyrocumulus clouds soaring high above the Andes due to the eruption of Ecuador’s Tungurahua volcano
Out of harm’s way?…
The online real-estate service Trulia has crunched federal-disaster data to create a series of local maps and a collection of national maps showing the worst cities to live in for weatherphobes and quake-haters – stay out of California metropolises if you fear having your home burnt down, for instance, and Oklahoma City is a terrible place to hunker if you don’t want EF-4 twisters knocking at your door. The Trulia team warns:
Most metros were high risk for at least one of the five natural disasters [hurricanes, tornadoes, floods, forest fires and earthquakes], even though no metro area is high risk for everything. Earthquakes and wildfires tend to go hand-in-hand, with California and other parts of the West at high risk for both. Hurricanes and flooding also tend to strike the same places, particularly in Florida and along the Gulf Coast. Tornadoes affect much of the south-central U.S. What parts of the country are left? Not the Northeast coastal cities, which – as we all know after Hurricane Sandy – face hurricane and flood risk. Instead, the metros at medium-to-low risk for all five disasters span Ohio (Cleveland, Akron, and Dayton), upstate New York (Syracuse and Buffalo), and other parts of the Northeast and Midwest, away from the coasts…
Where should one head to avoid the next great storm? Here are the top 10 large housing markets in America that are most removed from “nature’s wrath,” according to the company’s risk assessment (the prices refer to the average home-asking price per square foot):
- Syracuse, New York* ($89)
- Cleveland ($80)
- Akron, Ohio ($81)
- Buffalo ($93)
- Bethesda-Rockville-Frederick, Maryland ($174)
- Dayton, Ohio ($72)
- Allentown, Pennsylvania-New Jersey ($109)
- Chicago ($113)
- Denver ($129)
- Warren-Troy-Farmington Hills, Michigan ($94)
* Syracuse: Trulia says the “data on flood risk, which comes from the Federal Emergency Management Agency [FEMA], is incomplete for Syracuse and for several other metros not on the ten lower-risk list.”
Read the whole story at “These U.S. Cities Are the Safest Refuges From Natural Disasters“; and explore the Trulia maps here.
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As we dream of Oz, we might recall that it was on this date in 1834 that Mt. Vesuvius erupted. Again.
Vesuvius famously erupted in 79 CE, destroying Pompeii and Herculaneum; but the volcano had erupted many times before, and has again, many times since.
The last major eruption was in March 1944. It destroyed the villages of San Sebastiano al Vesuvio, Massa di Somma, Ottaviano, and part of San Giorgio a Cremano. At the time of the eruption, the United States Army Air Forces 340th Bombardment Group was based at Pompeii Airfield near Terzigno, Italy, just a few kilometers from the eastern base of the mountain. Tephra (rock fragments ejected by the eruption) and hot ash damaged the fuselages, the engines, the Plexiglas windshields, and the gun turrets of the 340th’s B-25 Mitchell bombers; estimates were that 78 to 88 aircraft were completely destroyed.
Vesuvius from Portici by Joseph Wright of Derby
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