воскресенье, 8 октября 2017 г.

Сергей Конча. КОНЦЕПЦИЯ ПРОИСХОЖДЕНИЯ ИНДОЕВРОПЕЙЦЕВ...


Сергей Конча. КОНЦЕПЦИЯ ПРОИСХОЖДЕНИЯ ИНДОЕВРОПЕЙЦЕВ Т.В.ГАМКРЕЛИДЗЕ И В.В.ИВАНОВА (критический этюд) . 23.06.2015.
Предлагаемая вниманию читателей статья была написана более десяти лет назад, но так и не была опубликована. Сборник работ, для которого она предназначалась, по некоторым причинам, не увидел свет, а позже рассматриваемая проблематика перестала мне казаться актуальной. От коллег-археологов обычно приходилось слышать что-то вроде: «Нет никакого смысла углубляться в разбор и критику гипотезы Т.В.Гамкрелидзе — В.В.Иванова, ведь и так понятно, что их концепция прародины неверна». Лингвисты, с которыми доводилось об этом говорить, рассуждали примерно так: авторы, без сомнения, высококлассные специалисты, что же касается археологической части (т. е., по сути, всех исторических импликаций, которые представляли для меня главный интерес), то оценивать её они некомпетентны. Т. е. выходило, что концепция вроде бы как и есть, она весьма известна и даже авторитетна, но говорить о ней незачем, полемизировать, в сущности, не с чем.
Просматривая дискуссии по индоевропейской проблеме на сайте «Генофонд.рф» и обнаружив несколько прямых отсылок к ближневосточной прародине и именно, как мне показалось, в том варианте, который предложили Т.В.Гамкрелидзе и Вяч. Вс.Иванов, я вспомнил об этой так и неопубликованной статье. Мне подумалось, что в споре между сторонниками южного и северного векторов индоевропейских миграций изложенные в ней соображения окажутся нелишними.
В статье предпринята попытка показать, как не следует, по моему мнению, подходить к решению проблемы прародины и древнейших миграций индоевропейцев. Хотя статья получилась острополемической, местами даже злой, я ни в коей мере не ставил целью преуменьшить заслуги таких замечательных исследователей как Т.В.Гамкрелидзе и Вяч. Вс.Иванов или каким-то образом бросить тень на их имена. С Тамазом Валериановичем Гамкрелидзе мне посчастливилось познакомиться в 2000 году на конференции в Оулу, в Финляндии и тогда между нами завязалась интересная (и вполне дружеская) дискуссия по поводу ближневосточной концепции, продолжением которой в какой-то мере и явились изложенные в статье положения.
Минимально обновив эту работу, предлагаю её вниманию уважаемых читателей.
Скачать статью в PDF по ссылке
http://xn--c1acc6aafa1c.xn--p1ai/?page_id=3952


astronomyblog: Vela Pulsar The star of this movie is the Vela…


astronomyblog:



Vela Pulsar


The star of this movie is the Vela pulsar, a neutron star that was formed when a massive star collapsed. The Vela pulsar is about 1,000 light years from Earth, spans about 12 miles in diameter, and makes over 11 complete rotations every second, faster than a helicopter rotor. As the pulsar whips around, it spews out a jet of charged particles that race out along the pulsar’s rotation axis at about 70% of the speed of light. In this still image from the movie, the location of the pulsar and the 0.7-light-year-long jet are labeled.


Credit: NASA, Chandra, CXC, Univ of Toronto, M.Durant et al



Astronomy & Astrophysics


livias:+ only the knife knows what goes inside the heart of a…


livias:



+ only the knife knows what goes inside the heart of a pumpkin + 



СИЛЬНЫЙ ВЕТЕР В ЧАЙКОВСКОМ (ПЕРМСКИЙ КРАЙ)Сильный ветер, с...








СИЛЬНЫЙ ВЕТЕР В ЧАЙКОВСКОМ (ПЕРМСКИЙ КРАЙ)


Сильный ветер, с порывами до 20 м/c, ломал в городе Чайковский деревья, остановки общественного транспорта и рекламные щиты. С местной детской спортивной школы ветер сорвал крышу и откинул ее на рядом расположенную трансформаторную подстанцию. По словам местных жителей, крышу только недавно уложили. Поврежденными оказались некоторые машины и другие объекты.По счастливой случайности пострадавших нет.


Туманное утро сегодня в Брянске….











Туманное утро сегодня в Брянске.


Research rethinks the evolutionary importance of variability in a population



It’s been long thought that variability within a population is key to population’s growth and survival but new research questions that assumption.











Research rethinks the evolutionary importance of variability in a population
Researchers find that low cellular growth rate variability leads to an increase in population growth 
in single-cell organisms [Credit: Harvard University]

Ariel Amir, Assistant Professor in Applied Mathematics at the Harvard John A. Paulson School of Engineering and Applied Sciences, and Jie Lin, the George Carrier Postdoctoral Fellow in Applied Mathematics, found that in an unchanging environment, variability can actually lower population growth in single-cell organisms.


“For decades, researchers have been looking at the wrong indicator to understand population growth rate in single-cell organisms in fixed environments,” said Amir. “Researchers took for granted that variability in the time between a cell’s birth and division was key to measuring population growth rate but we found that the evolutionary pressures on variability within a population are much more nuanced than previously thought.”


This insight is important for characterizing the fitness of a population, which is useful, for instance, in understanding how bacteria respond to antibiotics. The research is published in Cell Systems.


Variability in single-cell organisms is characterized by differences in generation time — the time from birth to division — and differences in cell biomass growth rate. Seminal research in the 1950s found that variations in generation time — the time it takes from birth to division — leads to a larger population growth rate when the environment is unchanging. However, researchers had assumed that generation time was random and independent from mother to daughter cell.


But we now know that’s not the case. In 2014 and 2015, Amir and his team demonstrated that cell volume and interdivision time is correlated across generations, and quantified these correlations. If a mother cell grows for a longer duration than average, for example, then a daughter cell would have to grow for a time shorter than average to compensate.


“No matter how small these correlations are, they profoundly change the result of how variability changes population growth,” said Lin.


Lin and Amir found that variability in the single-cell biomass growth rate — not generation time — impacts population size. As a result, low cellular growth rate variability leads to an increase in population growth.


“Evolutionarily, if you want to optimize your population growth rate, you want to minimize your cell growth rate variability,” Amir said. “We found that generation time fluctuations don’t matter. You can have divisions that vary wildly. As long as your biomass always increases at the same rate, your population will continue to grow at the same rate. Similarly, the details of the mechanism controlling cell size doesn’t matter — as long as it exists — which is the difference between our analysis and previous work.”


This can be seen experimentally as well. The researchers observed that growth rate fluctuations in E. coli are smaller than fluctuations in generation time — in some cases 6 percent growth rate variability compared to 20 to 30 percent variability in generation time — and that the population growth rate was consistent with the theoretical predictions.


“This shows that cells size control has to be taken into account in population growth and these subtle correlations that a priori might appear to be innocuous are actually really important,” said Amir.


Author: Leah Burrows | Source: Harvard John A. Paulson School of Engineering and Applied Sciences [October 04, 2017]




TANN




An unexpected phenomenon observed in merger of galaxy clusters



An international team of astronomers led by Francesco de Gasperin (Leiden University, the Netherlands) has witnessed an unexpected phenomenon in a merger of a two clusters of galaxies. The astronomers discovered a gas trail that slowly extinguished, but then lit up again. It is unclear where the energy for the rejuvenation of this trail comes from. The researchers publish their findings in Science Advances.











An unexpected phenomenon observed in merger of galaxy clusters
A galaxy (in orange) moves to the left and leaves a gas trail. The trail seems to extinguish slowly, but lightens 
up again near the second, white-yellow galaxy. Most white dots in the image are complete galaxies 
[Credit: Leiden University]

The astronomers investigated Abell 1033. This is a cluster of galaxies consisting of two smaller clusters that are in the process of merging. Abell 1033 is located in the northern constellation of Leo Minor (near Ursa Major). Clusters of galaxies are the largest structures in the universe. They can contain hundreds to thousands of galaxies similar to our Milky Way. Smaller clusters can merge together to form a larger cluster.


The astronomers observed that an individual galaxy in Abell 1033 leaves a trail of gas as it traveled through the cluster. On astronomical scale, such a trail resembles the trail of colored smoke behind a stunt plane.


The astronomers had expected that the gas trail, like the ones behind a stunt plane, would slowly fade and eventually disappear. To their astonishment they saw that the end of the gas trail was brighter than the middle.


“This was totally unexpected,” says Francesco de Gasperin, the first author of the research paper that is published in Science Advances. “As these clouds of electrons radiate away their energy over time, they should become fainter and disappear. Instead, in this case, after more than a hundred million years, the trail of electrons is glowing brightly.”


There is no precise explanation for this phenomenon, yet. It seems that the trail brightens near the center of the cluster of galaxies. De Gasperin: “Part of the energy released in the merger event must have been transferred to rejuvenate the cloud of electrons.”


The research on merging clusters of galaxies is complicated because astronomers only see a snapshot of a process that takes billions of years to complete. In addition to that, the telescopes that are needed for the investigation must receive signals at extremely low frequencies.


The astronomers combined data from the Indian Giant Metrewave Radio Telescope and LOFAR, the Low Frequency Array. LOFAR was designed and built by the Dutch research institute ASTRON. The telescope consists of thousands of antennas spread across eight countries. The heart of LOFAR is in Drenthe in the north-east of the Netherlands.


“It’s like being among the last explorers. As soon as we move in uncharted territories, or in this case at unexplored frequencies, our universe is still full of surprises,” says De Gasperin. “And this is just a first step. Much is still to be done to understand the complexity of galaxy clusters, and find what is lurking at low radio frequencies”


Source: Leiden University [October 05, 2017]





TANN




New NASA study shows moon once had an atmosphere



A new study shows that an atmosphere was produced around the ancient Moon, 3 to 4 billion years ago, when intense volcanic eruptions spewed gases above the surface faster than they could escape to space. The study was published in Earth and Planetary Science Letters.











New NASA study shows moon once had an atmosphere
Artistic impression of the Moon, looking over the Imbrium Basin, with lavas erupting, venting gases, 
and producing a visible atmosphere [Credit: NASA, MSFC]

When one looks up at the Moon, dark surfaces of volcanic basalt can be easily seen to fill large impact basins. Those seas of basalt, known as maria, erupted while the interior of the Moon was still hot and generating magmatic plumes that sometimes breached the lunar surface and flowed for hundreds of kilometers. Analyses of Apollo samples indicate those magmas carried gas components, such as carbon monoxide, the ingredients for water, sulfur, and other volatile species.


In new work, Dr. Debra H. Needham, Research Scientist of NASA Marshall Space Flight Center, and Dr. David A. Kring, Senior Staff Scientist, at the Lunar and Planetary Institute, calculated the amounts of gases that rose from the erupting lavas as they flowed over the surface and showed that those gases accumulated around the Moon to form a transient atmosphere. The atmosphere was thickest during the peak in volcanic activity about 3.5 billion years ago and, when created, would have persisted for about 70 million years before being lost to space.











New NASA study shows moon once had an atmosphere
Map of basaltic lavas that emitted gases on the lunar nearside 
[Credit: Debra Needham]

The two largest pulses of gases were produced when lava seas filled the Serenitatis and Imbrium basins about 3.8 and 3.5 billion years ago, respectively. The margins of those lava seas were explored by astronauts of the Apollo 15 and 17 missions, who collected samples that not only provided the ages of the eruptions, but also contained evidence of the gases produced from the erupting lunar lavas.


This new picture of the Moon has important implications for future exploration. The analysis of Needham and Kring quantifies a source of volatiles that may have been trapped from the atmosphere into cold, permanently shadowed regions near the lunar poles and, thus, may provide a source of ice suitable for a sustained lunar exploration program. Volatiles trapped in icy deposits could provide air and fuel for astronauts conducting lunar surface operations and, potentially, for missions beyond the Moon.


Over the past decade, the search for volatiles within the Moon and on the surface of the Moon has intensified. Those volatiles may hold clues about the material that accreted to form the Earth and Moon and, thus, our planetary origins. The volatiles may also provide the in-situ resources needed for sustained lunar surface activities that may follow the development of NASA’s new Orion crew vehicle and a Gateway structure that may orbit the Moon. In addition, robotic assets, like NASA’s Resource Prospector, are being developed to explore the nature and distribution of volatile deposits that might be suitable for scientific analysis and recovery. Based on the new results of Needham and Kring, those assets may be recovering ice that is partially composed of volatiles erupted from volcanic fissures over 3 billion years ago.


Source: Lunar and Planetary Institute, Universities Space Research Association [October 05, 2017]





TANN




Встреча зимы и осени. Шерегеш, Кемеровская область.(Октябрь...


Встреча зимы и осени. Шерегеш, Кемеровская область.(Октябрь 2017)


Ураган “Нэйт” в Билокси ( Миссисипи, США, 7-8.10.2017)…










Ураган “Нэйт” в Билокси ( Миссисипи, США, 7-8.10.2017)


giflounge: Very Relaxing…


giflounge:



Very Relaxing…



GIFs Зацикленные ГИФ


mypubliclands: Get ready to #FindYourWay!The countdown is on!…





mypubliclands:



Get ready to #FindYourWay!


The countdown is on!  We are gearing up to celebrate the 50th anniversaries of the Wild and Scenic Rivers Act and National Trails System Act in October 2018.


In February of 1965, President Lyndon B. Johnson called for a National System of Trails. Secretary of the Interior Stewart Udall called on the Bureau of Outdoor Recreation to take the lead in developing a trail system study. A steering committee conducted the study with representatives from the Bureau of Outdoor Recreation, the National Park Service, the U.S. Forest Service, and the Bureau of Land Management.


For the BLM, Eldon F. Holmes, Chief, Recreational Staff, participated on the committee. The collaborative interagency work resulted in a 1966 report entitled “Trails for America.” The report contained an early version of the National Trails System Act.  


Today, the National Trails System is larger than the Interstate Highway System in length, and includes 11 National Scenic Trails, 19 National Historic Trails, and over 1,500 National Recreation Trails. Within the National Trails System, the BLM manages public lands along 6,000 miles of 18 congressionally designated trails in 15 States as National Conservation Lands and multiple National Recreation Trails.



bijoux-et-mineraux: Fluorite and Quartz – Okoruso Mine,…


bijoux-et-mineraux:



Fluorite and Quartz – Okoruso Mine, Otjiwarongo District, Namibia      



thalassarche:Reddish Egret, white morph (Egretta rufescens) …


thalassarche:



Reddish Egret, white morph (Egretta rufescens) – photo by Dennis Adair



Шкваловый ворот на Родосе ( Греция, 8.10.2017)…


Шкваловый ворот на Родосе ( Греция, 8.10.2017)


Первый снег в общине Нова-Варош ( Сербия, 7.10.2017)…


Первый снег в общине Нова-Варош ( Сербия, 7.10.2017)


Вячеслав Всеволодович Ива́нов — выдающийся русский...

Вячеслав Всеволодович Ива́нов — выдающийся русский лингвист, академик АН СССР и РАН, профессор Калифорнийского университета, директор Института мировой культуры МГУ, директор Русской антропологической школы РГГУ. Его исследования посвящены исторической и сравнительной лингвистике, психолингвистике, семиотике, математической лингвистике, литературоведению, истории культуры, антропологии.


Viral Geovandalism This image comes from Goblin Valley State…


Viral Geovandalism


This image comes from Goblin Valley State Park in Utah. It shows formations known as, well, Goblins –mushroom-shaped rock structures, some of which can be several meters high.


These types of structures are formed from differential erosion. These are sedimentary rocks – shown by the layering in the photo. The upper layers are stronger and more resistant to erosion, the lower layers are less resistant. When the strong layers crack, water is able to move through that layer, travel downward, and erode the lower layer. The upper layer stays put while the lower layers erode, leaving these mushroom shapes standing until finally so much erosion occurs that they collapse.

Dynjandi falls in Iceland’s Westfjords





Dynjandi falls in Iceland’s Westfjords


brendon_wainwright 🌿 This is Nerina Kloof – Jonkershoek 🌿 The…





brendon_wainwright 🌿 This is Nerina Kloof – Jonkershoek 🌿 The most tranquil fern-forest jungle 🌿 I’ve ever found myself in, we spent a few minutes here enjoying the sound of water, birds and nature at its finest! Oh, we also brewed some coffee ☕️ to go with it! 🌿💚


Genome analysis of early plant lineage sheds light on how plants learned to thrive on land



Though it’s found around the world, it’s easy to overlook the common liverwort — the plant can fit in the palm of one’s hand and appears to be composed of flat, overlapping leaves. Despite their unprepossessing appearance, these plants without roots or vascular tissues for nutrient transport are living links to the transition from the algae that found its way out of the ocean to the established multitude of land plants.











Genome analysis of early plant lineage sheds light on how plants learned to thrive on land
Marchantia polymorpha thallus in the vegetative form. Cup-shaped structures on the surface are gemma cups (cupules), 
reproductive organs producing asexual propagules (gemmae). The image complements a Cell paper in which an 
international team that included researchers at the U.S. Department of Energy Joint Genome Institute analyzed the 
genome sequence of the common liverwort (Marchantia polymorpha) to identify genes and gene families that were 
deemed crucial to plant evolution and have been conserved over millions of years and across plant lineages 
[Credit: Shohei Yamaoka, Kyoto University]

As reported in Cell, an international team including researchers at the U.S. Department of Energy Joint Genome Institute (DOE JGI), a DOE Office of Science User Facility, analyzed the genome sequence of the common liverwort (Marchantia polymorpha) to identify genes and gene families that were deemed crucial to plant evolution and have been conserved over millions of years and across plant lineages. The work was led by researchers at Monash University in Australia, and at Kyoto University and Kindai University in Japan.


“Early plants like the liverwort are what set the world up for land plants. Without them, we wouldn’t have plants more than two feet from the ocean and freshwater,” said DOE JGI Plant Program head Jeremy Schmutz. “In going back to liverworts, we find genes shared with grasses that are candidate genes for crops for biofuel generation. Land plants began with same parts present in Marchantia today so the changes are all due to factors such as evolution, polyploidy, gene exchange and rounds of selection. We want to know what genes do and we do this by translating function across genomes using conserved sequences. Smaller genomes with less complexity — such as those in a basal or early plant model like liverwort — give us the ability to identify ancestral genes for a gene or gene family. We identify gene function in a plant and determine how this gene works, and then we identify other genes by understanding the evolutionary history of gene or gene family across the history of plants.”


The genome sequencing and annotation was done through the DOE JGI’s Community Science Program, and allows for genomic comparisons with other early plant lineages sequenced and analyzed by the DOE JGI: the spikemoss Selaginella moellendorffi and the moss Physcomitrella patens. One of the most important biochemical pathways concerns production of the hormone auxin, which is critical for regulating plant growth and development. The team identified a minimal but complete pathway for auxin biosynthesis in the liverwort. Another finding suggests that the genes encoding enzymes producing “sunscreen” that allowed early plants to tolerate ultraviolet light may have been transferred from ancient soil microbes.


One of the team’s most important findings concern plant cell wall development. The variety of genes encoding enzymes for plant cell wall development found in Marchantia emphasizes the importance of plant cell walls for the transition to land plants. The team identified early lignin biosynthesis genes similar to those in Physcomitrella. While they identified genes involved in plasmodesmata formation (plasmodesmata are membrane channels involved in nutrient and signal molecule transfers) a pathway that is involved in cell division, they also found that liverworts retain the vestiges of cell division pathways predating land plant-specific pathway.


Another important finding involves water retention and distribution. Early plants had to develop strategies for dealing with drought and desiccation, and many of these same strategies are still employed by modern plants. Abscisic acid is a plant stress hormone that regulates when a plant goes dormant when water is in short supply. The team found homologous genes for abscisic acid biosynthesis, and were also able to identify when specific receptors became critical to land plant families.


Schmutz pointed out that through the Community Science Program, the DOE JGI’s exploration of plant evolutionary history is expanding, leading to the development of a comparative genomics framework, including those from early plant lineages like the liverwort, that benefits the plant research community at large. “The more we accumulate this information in early plant lineages, the easier it is to transfer plant function across plant phylogeny and compare plant families to see the radiation of these genes. We’ll be focusing quite a bit more on the basal lineages of plants to get at the evolutionary history and position of genes. If we can understand the origin of these genes then we can understand historical function. Having multiple species allows us to do more and show more than what we can with just one genome.”


By learning the original functions of genes, elucidated from the genomes of earlier, simpler, plants and cells, scientists can more easily solve for the functions of related genes seen in more complex plants that may help address DOE missions in bioenergy and environmental processes.


Source: DOE/Joint Genome Institute [October 05, 2017]




TANN




Magma chambers of supervolcanoes have sponge-like structure



Supervolcanoes are superlative in every respect. The eruption of the Toba caldera in modern-day Indonesia approximately 74,000 years ago was so powerful that it led to a period of global cooling and, possibly, a drastic fall in the population of humankind. Around 2.1 million years ago, the first of three eruptions of the Yellowstone supervolcano in the USA formed a crater with an area of 50 x 80 kilometres. Approximately 2,800 cubic kilometres of material were ejected in the process — around 10 to 20 times as much as in the 1815 eruption of Mount Tambora in Indonesia. Even this relatively small eruption, considered the largest in recent times, produced effects that could be felt around the world.











Magma chambers of supervolcanoes have sponge-like structure
The Wheeler Monument, Colorado, USA, is a classic example of volcanic deposits formed by a super eruption 
[Credit: Dave Minkel, flickr]

However, supervolcanoes are difficult to study and therefore continue to baffle researchers to this day. For example, scientists agree that there must be a chamber of magma at a depth of a few kilometres in the Earth’s crust, containing material that escapes during an eruption. However, the experts do not agree on the form and consistency of such a reservoir.


Swimming pool vs solidified block


Some geologists assume that calderas, as supervolcano craters are known, sit on top of a gigantic reservoir of liquid magma embedded in the Earth’s crust. The mantle supplies this reservoir with material and heat, and a supervolcano of this kind can erupt explosively at any time.


Others deem it more plausible that the magma chamber has cooled down completely and solidified, and that it is only made liquid by a massive influx of heat from the mantle. Only then can an eruption take place.


“Probably neither theory is correct,” says Olivier Bachmann, Professor of Volcanology at ETH Zurich. Bachmann and his group have published two articles in the journal Nature Geoscience, in which they demonstrate that the truth may lie somewhere between these two extremes.


The truth somewhere in the middle?


“The magma chamber of a supervolcano does not resemble a pot of soup that can boil over at any time and at the slightest provocation,” Bachmann explains. Similarly, he says it is wrong to assume that the magma has cooled down to form a completely solidified body, as reactivating a body of this kind would require an enormous influx of heat within a very short time. In addition, volatile substances such as water and CO2 would escape from the body during cooling and solidification. However, these substances are essential for an eruption as they serve to build up the corresponding pressure in the magma chamber.











Magma chambers of supervolcanoes have sponge-like structure
This is how volcanic researchers imagine the magma chamber under a supervolcano 
[Credit: Bachmann & Huber, American Mineralogist, 2016]

Taking the supervolcano eruption of the “Kneeling Nun Tuff” in New Mexico as an example, studies by Bachmann’s doctoral student Dawid Szymanowski demonstrated that a supervolcano’s magma chamber contains a mixture of liquid and crystalline — that is, solidified — magma. More than 40 to 50 percent of the reservoir is present in crystalline form. In the ETH researcher’s view, the chambers may exhibit a sponge-like texture, with a mesh structure of crystallised rock and pores containing molten material — crystal mush, as Szymanowski calls it.


Rare minerals as data-loggers


This mush is likely to remain in the magma chamber for a very long time before being hurled to the surface. Szymanowski derives this conclusion from the analysis of zircon and titanite, two trace minerals that are present in the magma. Zircon is the crystalline material of the oldest known rock samples on Earth — some crystals found in Australia are approximately 4.4 billion years old.


Zircon and titanite crystals record not only the time at which they were formed but also the temperature during their formation, as this temperature influences the incorporation of chemical elements into the crystal lattice. After crystal formation, the chemical composition of these minerals in a magma chamber remains essentially unchanged even if the conditions in the magma chamber change significantly.


By analysing the age and chemical composition of zircon and titanite crystals from different rocks in the laboratory, the researchers obtain information about how a magma chamber’s temperature has changed over time. The eruption brings these two minerals up to the surface, where they can be found in corresponding rock strata.


From these analyses, the volcanologists from ETH concluded that the temperature in the magma chamber that fed the Kneeling Nun Tuff eruption must have remained between 680 and 730 degrees Clesius for over half a million years. From the minerals, the researchers could determine that it took the supervolcano a very long time to become fully “charged” and to reach the point of eruption.


Numerical model supports mineral analyses


The mineral analyses are also supported by a computer model created by Ozge Karakas, a postdoc in Bachmann’s group. This model was published in June — also in the journal Nature Geoscience — and describes a system made up of a magma chamber in the upper crust that is connected with further chambers in the lower crust.











Magma chambers of supervolcanoes have sponge-like structure
Zirconium crystals under the microscope: These minerals log the temperature of a magma chamber 
that prevailed during their crystalization [Credit: Dawid Szymanowski Dawid/ETH Zurich]

Hot “source” magma forms in the mantle at a temperature of approximately 1,200 degrees before rising through cracks and chimneys into the upper crust. Once there, it forms a reservoir, which cools down and partially crystallises but can survive as a crystal mush for hundreds of thousands of years.


Using the model, the scientists were able to show that the formation of a permanent reservoir in the upper crust does not require gigantic quantities of material from the mantle in short periods of time. “The conditions in the upper crust are not suitable for collecting and storing that much material very quickly,” says Karakas. Nevertheless, the geologist says that the reservoir does need a connection with magma in the lower mantle in order to ensure the transport of heat, and she emphasises that, until now, researchers had not included the lower crust in their considerations. “Without it, however, there would be no supervolcanoes.”


Very rare events


Both the model and the mineral analyses therefore point to the idea that supervolcanoes form and mature over very long periods of time, and that they can only erupt at intervals of tens of thousands of years. “The magma is primarily preserved as a type of crystalline, sponge-like structure. And it must always be reactivated by an influx of heat before it can erupt,” says Olivier Bachmann, summing up the findings.


It is not possible to predict when the next supervolcano eruption is about to occur based on the new findings, as the system is not yet understood in sufficient detail. However, mechanisms of growth and reactivation of giant magma reservoirs become clearer, and that may help to better assess the reawakening signs of those systems in the future. “In any case — and fortunately for us — a supervolcano eruption is a very rare event,” says Bachmann.


Author: Peter Rüegg | Source: ETH Zurich [October 05, 2017]




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