This simplified hydrology model shows the subsurface of Oklahoma. The Arbuckle Group is the area where most wastewater is injected. This layer allows fluid to move easily to distant areas. The added water causes stress as it travels and can cause earthquakes when it encounters pre-existing faults. Credit: University of Oklahoma
University of Oklahoma Mewbourne College of Earth and Energy assistant professor Xiaowei Chen and a group of geoscientists from Arizona State University and the University of California, Berkeley, have created a model to forecast induced earthquake activity from the disposal of wastewater after oil and gas production.
“In this region of the country, for every barrel of oil produced from the ground, usually between eight and nine barrels of water are also extracted from many wells,” said Chen.
The large amount of water leads to a problem for oil producers — what to do with it?
Also called brine, this wastewater contains salt, minerals and trace amounts of oil, making it unusable for consumption or agricultural purposes and cost-prohibitive to treat. It is disposed of by injecting it back into the earth, deep into porous rock formations.
Wastewater injection can cause earthquakes, explained Chen, and while most of the recent earthquakes in Oklahoma have been small, several have been in excess of 3.0 on the Richter scale.
Chen and a team of researchers, led by Guang Zhai and Manoochehr Shirzaei from ASU, and Michael Manga from UC Berkeley, set out to find a way to make induced earthquakes in Oklahoma predictable and small.
Their method, explained Chen, was to “create a model that correlates injected wastewater volume with stress changes on nearby faults and the number of earthquakes in that area.”
Finding the Formula
Forecasting the amount of seismic activity from wastewater injection is difficult because it involves accounting for numerous variables:
How easily brine can move through the rock in a given region
Where and how much brine is injected
The regional stress on those faults
The presence of existing geological faults
The team tackled each issue.
Chen and her fellow researchers studied subsurface hydrology parameters — how fast fluid moves within porous rocks and how quickly introduced fluid changes the stress in the subsurface basement. This is important because the subsurface basement is the location of Oklahoma’s induced earthquakes.
While the ASU team used satellite data to determine subsurface hydrology parameters, Chen focused on space and time distributions of earthquakes, and determined hydrology parameters by looking at how fast earthquakes move away from injection zones. By comparing both sets of data, researchers further increased the accuracy of their model.
As it turns out, the Arbuckle Group, a sedimentary layer that sits on top of the subsurface basement deep within the earth, is especially permeable, allowing brine, and therefor earthquakes, to easily spread.
“When we inject brine into the Arbuckle Group at a depth of 1-3 kilometers, it can transport through the porous rocks, modifying stresses and causing earthquakes on basement faults,” said Chen.
Next, researchers can plug in the amount of fluid into the model. By adding the volume of fluid injected in a particular area into their model, they can determine the stress it will place on that region as it spreads.
With the brine variables accounted for, researchers then added information about pre-existing faults into regional calculations. The more researchers know about a particular area, the more accurate the data will be.
“If we are going to operate in an area where we don’t have any prior seismicity, it will be a little challenging to forecast accurately,” said Chen. “But by operating in a new area and taking real-time parameters, operators and researchers should be able to forecast future behavior.”
Results
Chen hopes that by following the results of the models she helped create, oil operators in the state can create new protocols for how much wastewater to inject and where.
This could help prevent large induced earthquakes in Oklahoma. Chen does not believe forthcoming protocols will end induced seismicity altogether, but rather will help cap earthquake size and rate with restricted injection control. This method can forecast future induced seismicity.
Chen foresees a protocol similar to tornado watches — a window of time where Oklahomans are warned they may feel minor tremors in a region of the state.
According to Chen, this is an area where the close working ties between geoscientists and petroleum engineers will need to be even stronger. So far, her research has garnered interest from both geoscientists and petroleum engineers in industry and academia.
Reference:
Guang Zhai, Manoochehr Shirzaei, Michael Manga, Xiaowei Chen. Pore-pressure diffusion, enhanced by poroelastic stresses, controls induced seismicity in Oklahoma. Proceedings of the National Academy of Sciences, 2019; 116 (33): 16228 DOI: 10.1073/pnas.1819225116
A fossilized mantle of a vampyropod, a relative to the vampire squid. The ink sacis the raised structure in the center, and muscles have a striated appearance. Credit: Rowan Martindale/The University of Texas at Austin Jackson School of Geosciences.
Some of the world’s most exquisite fossil beds were formed millions of years ago during time periods when the Earth’s oceans were largely without oxygen.
That association has led paleontologists to believe that the world’s best-preserved fossil collections come from choked oceans. But research led by The University of Texas at Austin has found that while low oxygen environments set the stage, it takes a breath of air to catalyze the fossilization process.
“The traditional thinking about these exceptionally preserved fossil sites is wrong,” said lead author Drew Muscente. “It is not the absence of oxygen that allows them to be preserved and fossilized. It is the presence of oxygen under the right circumstances.”
The research was published in the journal PALAIOS on November 5.
Muscente conducted the research during a postdoctoral research fellowship at the UT Jackson School of Geosciences. He is currently an assistant professor at Cornell College in Mount Vernon, Iowa. The research co-authors are Jackson School Assistant Professor Rowan Martindale, Jackson School undergraduate students Brooke Bogan and Abby Creighton and University of Missouri Associate Professor James Schiffbauer.
The best-preserved fossil deposits are called “Konservat-lagerstätten.” They are rare and scientifically valuable because they preserve soft tissues along with hard ones — which in turn, preserves a greater variety of life from ancient ecosystems.
“When you look at lagerstätten, what’s so interesting about them is everybody is there,” said Bogan. “You get a more complete picture of the animal and the environment, and those living in it.”
The research examined the fossilization history of an exceptional fossil site located at Ya Ha Tinda Ranch in Canada’s Banff National Park. The site, which Martindale described in a 2017 paper, is known for its cache of delicate marine specimens from the Early Jurassic — such as lobsters and vampire squids with their ink sacks still intact — preserved in slabs of black shale.
During the time of fossilization, about 183 million years ago, high global temperatures sapped oxygen from the oceans. To determine if the fossils did indeed form in an oxygen-deprived environment, the team analyzed minerals in the fossils. Since different minerals form under different chemical conditions, the research could determine if oxygen was present or not.
“The cool thing about this work is that we can now understand the modes of formation of these different minerals as this organism fossilizes,” Martindale said. “A particular pathway can tell you about the oxygen conditions.”
The analysis involved using a scanning electron microscope to detect the mineral makeup.
“You pick points of interest that you think might tell you something about the composition,” said Creighton, who analyzed a number of specimens. “From there you can correlate to the specific minerals.”
The workup revealed that the vast majority of the fossils are made of apatite — a phosphate-based mineral that needs oxygen to form. However, the research also found that the climatic conditions of a low-oxygen environment helped set the stage for fossilization once oxygen became available.
That’s because periods of low ocean oxygen are linked to high global temperatures that raise sea levels and erode rock, which is a rich source of phosphate to help form fossils. If the low oxygen environment persisted, this sediment would simply release its phosphate into the ocean. But with oxygen around, the phosphate stays in the sediment where it could start the fossilization process.
Muscente said that the apatite fossils of Ya Ha Tinda point to this mechanism.
The research team does not know the source of the oxygen. But Muscente wasn’t surprised to find evidence for it because the organisms that were fossilized would have needed to breathe oxygen when they were alive.
The researchers plan to continue their work by analyzing specimens from exceptional fossil sites in Germany and the United Kingdom that were preserved around the same time as the Ya Ha Tinda specimens and compare their fossilization histories.
Reference:
A.D. MUSCENTE, ROWAN C. MARTINDALE, JAMES D. SCHIFFBAUER, ABBY L. CREIGHTON, BROOKE A. BOGAN. TAPHONOMY OF THE LOWER JURASSIC KONSERVAT-LAGERSTÄTTE AT YA HA TINDA (ALBERTA, CANADA) AND ITS SIGNIFICANCE FOR EXCEPTIONAL FOSSIL PRESERVATION DURING OCEANIC ANOXIC EVENTS. PALAIOS, 2019; 34 (11): 515 DOI: 10.2110/palo.2019.050
Extremophiles, such as the thermophiles that give the microbial mats such vivid colors in the hot springs in Yellowstone National Park, are a hot topic of study amongst astrobiologists in the UK. IMAGE CREDIT: JIM PEACO/NATIONAL PARK SERVICE.
Mapping the bonds and vibrational modes of molecules containing sulfur isotopes is helping to shed light on the chemical reactions that took place in Earth’s atmosphere during the Archean era, before the atmosphere became oxygenated about 2.5 billion years ago.
The Archean is a geological eon that lasted from 4 billion years to 2.5 billion years ago. It saw the emergence of the first life on Earth, but these microbes were anaerobic, meaning they did not breath oxygen. In fact, during this time, Earth’s atmosphere did not contain any molecular oxygen. Instead, the atmosphere was rich with the likes of carbon and, particularly, sulfur.
The sulfur in the Archean Earth’s atmosphere was emitted by volcanic activity, and through a process called mass independent fractionation, sulfur’s various isotopes (sulfur atoms containing the same number of protons but different numbers of neutrons) became enriched in a manner that does not correlate with their mass. Evidence that this occurred is found in surface deposits dating back to the Archean, and it was these sulfur isotopes, as part of molecules such as hydrogen sulfide (H2S) and sulfur dioxide (SO2), which microbes metabolized, releasing oxygen in the process and beginning the process of oxygenating Earth’s atmosphere—a development referred to as the Great Oxygenation Event.
Because sulfur is quickly oxidized in an oxygen-rich environment, and then removed from the atmosphere by precipitation and run-off into the ocean, the sulfur chemistry of early Archean life was phased out and lost to time. However, by understanding the mass independent fractionation process, it should be possible to learn more about the atmosphere of the pre-oxygenated Earth and the conditions in which the first life on Earth lived.
The process behind the mass independent fractionation of sulfur remains uncertain, but the two most popular hypotheses are either photolysis (the breaking apart of molecules) by ultraviolet light from the Sun, or reactions between elemental sulfur. “However, the actual phenomenon, reaction or mechanism is still to be identified,” says Dmitri Babikov, a Professor of Physical Chemistry and Molecular Physics at Marquette University in Milwaukee, Wisconsin.
Sulfur’s molecular bonds
Babikov, along with his Marquette colleagues Igor Gayday and Alexander Teplukhin, have published a new paper in the journal Molecular Physics that explores some of the molecular bonds of a sulfur-4 (S4) molecule, and how these bonds affect the vibrational modes of the molecule, which in turn may influence the mass independent fractionation process.
They identified a second, previously unknown, bond that joins together S2 molecules (containing two sulfur atoms) to form S4. “This second bond holds the molecule tight in a [trapezoid-shaped] arrangement and does not allow easy rotation of the two S2 molecules within S4,” says Babikov. In turn, this arrangement of sulfur atoms then determines how they move as the S4 molecule vibrates.
The vibrational states, or frequencies, of the S4 molecule are determined by both the shape of the molecule’s ‘potential energy surface,” which describes the energy of the isotopes in the trapezoid arrangement of the S4 molecule, and how chemical reactions change the potential energy of that system. Not only do the number of vibrational modes, involving stretching and compression of the bonds between the S2 molecules, have a bearing on the reaction rate, but they could also be sensitive to a given isotope, which could help identify the chemical reaction behind mass independent fractionation. “But at this point this is still a hypothesis,” says Babikov.
A better understanding of the role of mass independent fractionation in the sulfur chemistry of Archean Earth not only gives us a picture of the environment on Earth before oxygenation, but it also tells us about the potential biosignatures a similar environment on an exoplanet could create.
“[Sulfur isotopes] could potentially serve as a signature of the environment that created life on Earth,” says Babikov. However, he says, our current level of telescopic technology means it would be very difficult to determine the isotopic composition of an exoplanet’s atmosphere to the required level of detail.
The study, “Computational analysis of vibrational modes in tetra-sulfur using dimensionally reduced potential energy surface,” was published in the journal Molecular Physics. The work was supported in part by NASAAstrobiology through the Exobiology Program.
Reference:
Igor Gayday et al. Computational analysis of vibrational modes in tetra-sulfur using dimensionally reduced potential energy surface, Molecular Physics (2019). DOI: 10.1080/00268976.2019.1574038
The season that an earthquake occurs could affect the extent of ground failure and destruction that the event brings, according to a new look at two historical earthquakes that occurred about 100 years ago near Almaty, Kazakhstan.
In a paper published in Seismological Research Letters, researchers conclude that the June 1887 magnitude 7.3 Verny earthquake and the nearby January 1911 magnitude 7.8 Kemin earthquake likely produced similar shaking. However, the 1911 earthquake caused significantly more ground failure, probably due to a shallow frozen ground layer that was present during the winter months.
The frozen layer may have inhibited the drainage of pore-pressure excess through the surface during the earthquake, causing liquefaction at depth. In effect, the frozen layer extending about one meter below the surface “was a sealant layer that was not allowing the pore pressure to diffuse,” explained Stefano Parolai, a co-author of the paper at the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale in Italy.
The findings suggest seismologists should incorporate potential seasonal differences in soil characteristics “as they are making probabilistic liquefaction or ground failure assessments,” added co-author Denis Sandron, also at the Istituto Nazionale.
The effect of frozen ground on ground deformation is already calculated for some types of infrastructure such as oil pipelines in Alaska, but Parolai said the Kazakhstan study shows the importance of considering these effects in urban areas as well, especially when it can become a seasonal effect.
The Verny (Verny is the former name of Almaty) earthquake destroyed nearly all of the town’s adobe buildings and killed 300 people in 1887. The Kemin earthquake, which took place about 40 kilometers from Verny, caused a surprising amount of widespread ground failure and destruction and 390 deaths.
Parolai and his colleagues reviewed historical records of the two earthquakes as part of a larger project studying site effects and seismic risk in central Asia led by the GFZ German Research Centre for Geosciences. The two Almaty earthquakes, including their secondary effects such as landslides, “were very well documented by expeditions of the Mining Department of Russia and the Russian Mining Society at the time,” Parolai said.
The differences in ground failure between the two earthquakes were perplexing to the researchers. The fact that the two earthquakes had taken place at different times of year prompted Sandron and his colleagues to consider whether frozen ground might have been a factor in ground failure, as previous researchers had noted for the 1964 magnitude 9.2 Great Alaska earthquake.
To explore this idea, the research team created computer simulations of the earthquakes using different models of the soil profile that would affect the velocity of seismic waves passing through them, along with temperature data (more than 100 years of temperature recordings exist for Almaty) to determine whether it would be likely to have a frozen layer of ground at shallow depth during January.
One of the other challenges, said co-author Rami Alshembari ,formerly of the International Centre for Theoretical Physics in Italy and currently at the University of Exeter in the United Kingdom, was finding a way to include appropriate strong motion data recordings in the simulations, since “of course there were no digital recordings of these two earthquakes. We had to choose the most reasonable and robust studies for input of strong motion,” finally settling on data taken from the 1999 magnitude 7.6 Chi-Chi earthquake in Taiwan, appropriately modified, as being most similar to the Almaty earthquakes.
Models that included a one-meter deep frozen layer as a seal against pore pressure draining were the best fit for the ground failure seen in the Kemin earthquake, they concluded. Although the researchers suspected that a frozen layer could be the culprit, Parolai said they were surprised by the strength of the effect.
The findings suggest that other seismologists should consider seasonality in their site effect studies, he noted. “Even in materials where we would not expect this effect, due to local conditions and temperatures it could happen.”
“Without this good documentation, probably we would not have noticed this effect,” said Parolai. “This is telling us that good data taken in the past can be very precious in 100 years.”
Reference:
Rami Alshembari et al. Seasonality in Site Response: An Example from Two Historical Earthquakes in Kazakhstan. Seismological Research Letters (2019) doi.org/10.1785/0220190114
Left panel: Map of the upper section of the Aragón River. The locations of the CANF seismic station and the A271 gauge station are shown using red and yellow stars. Digital elevation model is provided by the Instituto Geográfico Nacional with a 25 m resolution (http://www.ign.es/ign/layoutIn/modeloDigitalTerreno.do). Coordinates are labeled in km (Universal Mercator projection). Right panel: Blow up map and pictures showing the morphology of the river channel in the vicinity of the recording site. Yellow dots show the location of each picture, all of them taken upstream
A team of researchers at Institute of Earth Sciences Jaume Almera of the Spanish National research Council (ICTJA-CSIC) have analysed the seismic signals generated by the variations in water flow of the Aragón river (Central Pyrenees) due to the snow melting in its upper basin. In the study, which has been published recently in the journal PLOS ONE, the researchers describe how they have been able to identify the different snowmelt episodes from the temporal variation patterns in the seismic data.
The authors of the study have used the data recorded from 2013 to 2016 with a seismometer located in the Laboratorio Subterráneo de Canfranc (LSC) in the Central Spanish Pyrenees, at about 400 m of the Aragón river channel.
The researchers calculated the daily spectrograms from the available data sets registered by the seismic broad band station. Spectrograms are graphics where the energy of the signal is represented in function of the frequency.
“During the snowmelt episodes we have been able to identify seismic signals with a characteristic spectrogram which allowed us to differentiate them from other seismic sources that were present in the background of the record”, explains Jordi Díaz, researcher at ICTJA-CIC and first author of the study.
Afterwards, the researchers designed an algorithm to make a hierarchical classification of the signal spectra, aimed to find common patterns. In this way, they could identify the days with snowmelt episodes as well as the intensity of these processes.
The researchers analysed the spectrograms to conclude that, in general, the snowmelt episodes are concentrated along the months of April and May. In some particular cases, such as in 2013, the researchers were even able to identify river rises derived from snowmelt at the beginning of July.
“Our results show a great variability among the different studied years, which is due to the variations in the atmospheric parameters like temperature, heat and precipitations.”, explains Jordi Díaz.
The authors have shown that the seismic data can be used to make automatic daily estimates of snowmelt intensity. The rise in river flow due to snowmelt has a daily cycle that starts at the beginning of the afternoon, after a few hours of insolation. According to this study, when the snow fusion intensity ranges between weak and moderate, the rise in flow features a sensible reduction towards the end of the night hours. During the most intense snowmelt episodes, the river flow is more stable along the day, but is still more intense during the afternoon.
“Under good circumstances, that is, with low noise level caused by human activities, seismic records can be a useful tool to study and monitor this kind of hydrological phenomena in the long-term scale and can contribute, for instance, to understand the outcomes of Climate Change”, concludes Jordi Díaz.
Reference:
Díaz, J., Sánchez-Pastor, P., Ruiz, M. (2019) Hierarchical classifcation of snowmelt episodes i the Pyrenees using seismic data. PLOS ONE. 14(10):e0223644. DOI: 10.1371/journal.pone.0223644
Peaty sedimentary archive from a palm swamp collected with a Russian corer. (Image:Encarni Montoya)
“Mauritia flexuosa” is the most widespread plant in the Orinoco Delta, in north-western Venezuela. This has not always been the case in the past. This palm, locally known as “moriche”, started its domination over the vegetal community of the area 3000 years ago, according to a new research that has reconstructed for the first time the ecological dynamics and evolution of the Orinoco’s Delta for the last 6200 years. The authors of the study, which has been published in Quaternary Science Reviews, have been able to identify 3 different periods characterized by different types of vegetation.
“With this research we have seen the importance of both local and superregional natural drivers in the vegetation dynamics”, says Encarni Montoya, researcher at Institute of Earth Sciences Jaume Almera of the Spanish National Research Council (ICTJA-CSIC) and lead author of the study.
Researchers extracted a 141 cm-long sediment core from a swamp near “caño Tigre”. The sediment samples were analysed by means of paleomagnetic techniques, X Ray diffraction, and stable isotope analysis.
Moreover, scientists analysed pollen samples from the recovered sediment core to know the vegetation type that existed in the area throughout the studied period. A radiocarbon analysis was carried out to date exactly the different layers of the sediments. Charcoal particles were also analysed as a proxy to obtain information about the fires occurred in the region, from which obtain clues about human settlement periods.
researchers notes that, although forested during the last 6200 years, the composition of the forest of the region have greatly varied through the time. Thanks to the fossil pollen samples found in the sediments, researchers could identify three well-distinguished periods depending on the different vegetal species that populated the delta.
According to the study, the first vegetal community, the oldest odf the register, was a mixed rainforest with coastal elements. This community was replaced 5400 years ago by a more inland-mixed-swamp forest community, a shift probably related with the progress of the coastline as a consequence of the sea level stabilization after the deglaciation.
Finally, 3000 years ago, the current vegetal community was established: a swamp dominated by “Mauritia flexuosa” palm”, during a wide unstable climatic period under the influence of the El Niño–Southern Oscillation (ENSO).
The indigenous Warao culture calls “Mauritia flexuosa” “The tree of life”, highlighting the importance of this palm for this human community that live dispersed in an intricate labyrinth of river channels and creeks of the Orinoco Delta.
“Processes like the sea level rise after the last glaciation or the frequency and intensity of climatic phenomena like the ENSO are crucial in determining the type of vegetation that establishes or persists in a new community”, notes Montoya, who is currently professor at University of Liverpool.
According to Encarni Montoya, this research shows “how fast the vegetal community of the delta has responded to the environmental changes throughout the last 6200 years, a process of special interest to understand the possibly future scenery marked by global change”.
“Coastal systems, and specially the deltas are especially vulnerable to the climate changes due to its proximity to the sea”, explains Encarni Montoya. “Given the variety of factors that may disrupt in this areas, the studies about the behaviour and dynamics of the ecosystem are fundamental”, adds the researcher who hopes that this work “awakes the interest of the scientific community and the society for this so magnificent area which is still unknown and which is currently facing some human induced threats, like oil prospection and extraction activities”.
The Orinoco is one of the largest rivers of South America and it discharges into the Atlantic Ocean in the North East of Venezuela, where it forms a big delta shaped by hundreds of little rivers and channels (called “caños”).
Reference:
Montoya, E., Pedra-Méndez, J., García-Falcó, E., Gómez-Paccard, M., Giralt, S., Vegas-Vilarrúbia, T., W. Stauffer, F., Rull, V. (2019) Long-term vegetation dynamics of a tropical megadelta: Mid-Holocene palaeoecology of the Orinoco Delta (NE Venezuela). Quaternary Science Reviews. Volume 221, 105874, DOI: 10.1016/j.quascirev.2019.105874.
An ore is a natural occurrence of rock or sediment which contains enough minerals with economically important elements, typically metals, that can be extracted from the deposit economically. The ores are extracted by mining for a profit from the earth; they are then refined (often by smelting) in order to extract the valuable elements.
The ore quality, and density of a rock or metal ore, as well as its occurrence type, can directly affect the ore mining costs. It is therefore necessary to weigh the extraction cost against the metal value contained in the rock to determine which ore can be processed and which ore is too low a grade to be worth mining.
Metal ores are generally oxides, sulfides, silicates, or native metals (such as native copper) not commonly concentrated in the crust of the Earth, or noble metals (normally not forming compounds) such as gold. To remove the elements of interest from the waste material and the ore crystals, the ores must be extracted. A variety of geological processes form ore bodies. The formation of the ore process is called the genesis of the ore.
Classification of Ore Minerals
Ore Mineral deposits are categorized according to different criteria that have been established through the study of economic geology or mineral genesis. Typical are the classifications below.
Hydrothermal epigenetic deposits
Mesothermal lode gold deposits, typified by the Golden Mile, Kalgoorlie
Archaean conglomerate hosted gold-uranium deposits, typified by Elliot Lake, Ontario,
Canada and Witwatersrand, South Africa
Carlin–type gold deposits, including;
Epithermal stockwork vein deposits
Granite related hydrothermal
IOCG or iron oxide copper gold deposits, typified by the supergiant Olympic Dam Cu-Au-U deposit
Intrusive-related copper-gold +/- (tin-tungsten), typified by the Tombstone, Arizona deposits
Hydromagmatic magnetite iron ore deposits and skarns
Skarn ore deposits of copper, lead, zinc, tungsten, etcetera
Magmatic deposits
Magmatic nickel-copper-iron-PGE deposits including
– Cumulate vanadiferous or platinum-bearing magnetite or chromite
– Cumulate hard-rock titanium (ilmenite) deposits
– Komatiite hosted Ni-Cu-PGE deposits
– Subvolcanic feeder subtype, typified by Noril’sk-Talnakh and the Thompson Belt, Canada
– Intrusive-related Ni-Cu-PGE, typified by Voisey’s Bay, Canada and Jinchuan, China
Lateritic nickel ore deposits, examples include Goro and Acoje, (Philippines) and Ravensthorpe, Western Australia.
Volcanic-related deposits
Volcanic hosted massive sulfide (VHMS) Cu-Pb-Zn including;
Examples include Teutonic Bore and Golden Grove, Western Australia
– Besshi type
– Kuroko type
Metamorphically reworked deposits
Podiform serpentinite-hosted paramagmatic iron oxide-chromite deposits, typified by Savage River, Tasmania iron ore, Coobina chromite deposit
Broken Hill Type Pb-Zn-Ag, considered to be a class of reworked SEDEX deposits
Carbonatite-alkaline igneous related
Phosphorus-tantalite-vermiculite (Phalaborwa South Africa)
Rare earth elements – Mount Weld, Australia and Bayan Obo, Mongolia
Diatreme hosted diamond in kimberlite, lamproite or lamprophyre
Sedimentary deposits
Banded iron formation iron ore deposits, including
– Channel-iron deposits or pisolite type iron ore
Heavy mineral sands ore deposits and other sand dune hosted deposits
Alluvial gold, diamond, tin, platinum or black sand deposits
Alluvial oxide zinc deposit type: sole example Skorpion Zinc
Sedimentary hydrothermal deposits
SEDEX
– Lead-zinc-silver, typified by Red Dog, McArthur River, Mount Isa, etc.
– Stratiform arkose-hosted and shale-hosted copper, typified by the Zambian copperbelt.
– Stratiform tungsten, typified by the Erzgebirge deposits, Czechoslovakia
– Exhalative spilite-chert hosted gold deposits
Mississippi valley type (MVT) zinc-lead deposits
Hematite iron ore deposits of altered banded iron formation
Astrobleme-related ores
Sudbury Basin nickel and copper, Ontario, Canada
Ore Extraction
The basic extraction of ore deposits follows these steps:
Prospecting or exploration to find and then define the extent and value of ore where it is located (“ore body”)
Conduct resource estimation to mathematically estimate the size and grade of the deposit
Conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work.
Conduct a feasibility study to evaluate the financial viability, technical and financial risks and robustness of the project and make a decision as whether to develop or walk away from a proposed mine project. This includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability, marketability and payability of the ore concentrates, engineering, milling and infrastructure costs, finance and equity requirements and a cradle to grave analysis of the possible mine, from the initial excavation all the way through to reclamation.
Development to create access to an ore body and building of mine plant and equipment
The operation of the mine in an active sense
Reclamation to make land where a mine had been suitable for future use
Examples of Ore Minerals
Acanthite (cooled polymorph of Argentite): Ag2S for production of silver
Barite: BaSO4
Bauxite Al(OH)3 and AlOOH, dried to Al2O3 for production of aluminium
Beryl: Be3Al2(SiO3)6
Bornite: Cu5FeS4
Cassiterite: SnO2
Chalcocite: Cu2S for production of copper
Chalcopyrite: CuFeS2
Chromite: (Fe, Mg)Cr2O4 for production of chromium
Cinnabar: HgS for production of mercury
Cobaltite: (Co, Fe)AsS
Columbite-Tantalite or Coltan: (Fe, Mn)(Nb, Ta)2O6
Researchers at the The University of Western Australia have uncovered evidence of a new type of fossilization that may explain how some of Earth’s oldest microfossils formed and might even help scientists detect evidence of past life on other planets.
Microfossils provide important clues about the early history of life on Earth, however some mystery still surrounds how they were preserved.
It generally thought that many of the oldest microfossils formed when silica grew on their cell walls encasing the microorganism. When the microorganism died, their cells rapidly decayed, leaving behind only traces of carbon in a hollow cavity that molded the shape of the organism.
The scientists worked on the 340-million-year-old Red Dog zinc-lead deposit in northern Alaska, and found the carbon filling of semi-hollow microfossils was not derived from the original organism but from migrated oil.
UWA Professor Birger Rasmussen from the School of Earth Sciences said the team found that oil infiltration of silica-entombed bacteria was responsible for producing the structures, which resembled many of the oldest microfossils preserved in the rock record.
“Using high-resolution electron microscopes, we found microfossils located around oil-carrying fractures were black and filled by a thin film of carbon,” Professor Rasmussen said.
“In contrast, microfossils between the fractures contained little or no internal carbon and were virtually invisible.”
Professor Rasmussen said the formation of carbon-rich microfossils around fractures suggested oil moving through the cracks in the rock had seeped into the semi-hollow molds left after the bacteria died.
“What we have found is a new process of fossilization.” Professor Rasmussen said.
“We are now looking at rock samples from other localities to examine what role oil might have played in the preservation of microfossils on the early Earth.
“The results may have implications for how we assess whether ancient microstructures are signs of life on early Earth and how we might detect biosignatures on Mars and other rocky planets.”
The research was jointly carried out by Professor Birger Rasmussen and Dr. Janet Muhling at The University of Western Australia and is published in the journal Geology.
Fossilised 20 centimetre long hand claw of theropod discovered at Eric the West site on Victoria’s Otway Coast. Credit: Stephen Poropat/Museums Victoria
Swinburne and Museums Victoria have announced the discovery of several theropod bones, including a 20 centimeter long hand claw, from the Otway Coast of Victoria.
The bones were found in the Eumeralla Formation, a geological deposit that is approximately 107 million years old.
Fossils of theropods—the group of dinosaurs that includes such famous predators as Tyrannosaurus and Velociraptor, as well as modern birds—are relatively rare in Australia. The new Victorian specimens were discovered at a site known as “Eric the Red West’ on the Otway Coast between 2011 and 2017, by volunteers working on Dinosaur Dreaming team’s annual digs.
These digs are held each February and are coordinated by husband and wife paleontologists, Swinburne’s Professor Patricia Vickers-Rich and Dr. Thomas Rich from Museums Victoria.
Previously, the Eric the Red West site had produced the skeleton of Diluvicursor pickeringi, a unique species of ornithopod dinosaur that was described and named in 2018.
The new theropod fossils were found isolated rather than as part of a skeleton. This is because they were carried some distance from where the theropods died by ancient, deep, fast-flowing rivers. These rivers snaked through the then-narrow rift valley (now Bass Strait) that opened as Australia and Tasmania separated during the Early Cretaceous period, more than 110 million years ago.
Victorian bones resemble bones from western Queensland
Many of the theropod bones found at the Eric the Red West site are from a group of theropods called megaraptorids. Intriguingly, they look almost identical to those of the Australian megaraptorid theropod Australovenator wintonensis from western Queensland.
Australovenator lived around ten million years after—and thousands of kilometers further north than—the Victorian megaraptorid. This suggests that megaraptorid theropods roamed over a large part of Australia and for a long period of time.
The research on the new Victorian theropod remains was led by Swinburne’s Dr. Stephen Poropat as part of a postdoctoral research fellowship in vertebrate palaeontology.
According to Dr. Poropat, who has conducted research on Australian dinosaurs for several years, the presence of megaraptorid theropods in Victoria that are nearly indistinguishable from Australovenator—but older than it by around ten million years—is unusual.
“The similarities between the Victorian megaraptorid remains and Australovenator are striking,” Dr. Poropat says.
“If we had found these theropod bones in Queensland, we would probably have called them Australovenator wintonensis. But they’re from Victoria, which prompts the question: “Could one dinosaur species exist for more than ten million years, across eastern Australia?” Maybe.”
Australovenator lived in Queensland around 95 million years ago, alongside several species of long-necked sauropod dinosaur (like Diamantinasaurus matildae and Savannasaurus elliottorum). However, the 107 million year-old rocks of western Victoria that produced the new theropod bones have not yielded a single scrap of sauropod bone.
“This is important, because it tells us that Australian megaraptorid theropods weren’t entirely dependent on sauropods for food,” says Dr. Poropat.
“We find megaraptorid teeth with sauropod carcasses in central Queensland all the time, but they seem to have been doing just fine in Victoria where sauropods seem to have been absent.”
So were megaraptorid theropods relying on another food source in Victoria? Dr. Poropat thinks so. “Adult sauropods were many times heavier than adult megaraptorids, so attacking them would have been dangerous. What we do know is that another group of plant-eating dinosaurs—the ornithopods—were abundant in Victoria (based on bones) and in central Queensland (based on footprints).
“Although ornithopods might have been ideal meals for megaraptorids in both regions, Queensland’s megaraptorids had another food choice—sauropod steaks! Whether they were fresh or on rotting carcasses, they would have been a pretty tempting item to have on the menu!”
The new theropod bones are held at Melbourne Museum. Another field trip to the Eric the Red West site is planned for November 2019. Dr. Poropat hopes that more megaraptorid bones might yet be found there.
The scientific paper describing the new fossils was published on Thursday 10 October in the Journal of Vertebrate Paleontology.
Reference:
Stephen F. Poropat et al. New megaraptorid (Dinosauria: Theropoda) remains from the Lower Cretaceous Eumeralla Formation of Cape Otway, Victoria, Australia, Journal of Vertebrate Paleontology (2019). DOI: 10.1080/02724634.2019.1666273
Images of the numerical solution at the moment when a supercontinent (left, in purplish grey) begins to break up. In the image on the left, the modelled fictional planet looks much like the Earth: its surface and mantle move spontaneously, at speeds close to those observed on Earth. The distribution of the plates (some of which are large, while many are small) is also similar, as is the topography: red hues represent shallow regions of the ocean (ridges), while blue indicates the deep seafloor. The deepest blue areas correspond to subduction trenches (where a plate is sinking into the mantle). The continents are shown in translucent white (and therefore appear purplish grey).The image on the right shows warm currents (plumes) rising from the bottom of the mantle. Credit: Nicolas Coltice
Do tectonic plates move because of motion in the Earth’s mantle, or is the mantle driven by the movement of the plates? Or could it be that this question is ill-posed? This is the point of view adopted by scientists at the École Normale Supérieure — PSL, the CNRS and the University of Rome 3, who regard the plates and the mantle as belonging to a single system. According to their simulations, published in Science Advances on October 30, 2019, it is mainly the surface that drives the mantle, although the dynamic balance between the two changes over supercontinent cycles.
Which forces drive tectonic plates? This has remained an open question ever since the advent of plate tectonic theory 50 years ago. Do the cold edges of plates slowly sinking into the Earth’s mantle at subduction zones cause the motion observed at the Earth’s surface? Or alternatively, does the mantle, with its convection currents, drive the plates? For geologists, this is rather like the problem of the chicken and the egg: the mantle apparently causes the plates to move, while they in turn drive the mantle…
To shed light on the forces at work, scientists from the Geology Laboratory of the École Normale Supérieure (CNRS/ENS — PSL), the Institute of Earth Sciences (CNRS/Universities Grenoble Alpes and Savoie Mont Blanc/IRD/Ifsttar) and the University of Rome 3 treated the solid Earth as a single indivisible system and carried out the most comprehensive modelling to date of the evolution of a fictional planet very similar to the Earth. The scientists first had to find the appropriate parameters, and then spend some nine months solving a set of equations with a supercomputer, reconstructing the evolution of the planet over a period of 1.5 billion years.
Using this model, the team showed that two thirds of the Earth’s surface moves faster than the underlying mantle, in other words it is the surface that drags the interior, while the roles are reversed for the remaining third. This balance of forces changes over geological time, especially for the continents. The latter are mainly dragged by deep motion within the mantle during the construction phases of a supercontinent, as in the ongoing collision between India and Asia: in such cases, the motion observed at the surface can provide information about the dynamics of the deep mantle. Conversely, when a supercontinent breaks up, the motion is mainly driven by that of the plates as they sink down into the mantle.
The computation contains a wealth of data that remains largely unexploited. The data obtained could help us to understand how mid-ocean ridges form and disappear, how subduction is triggered, or what determines the location of the plumes that cause vast volcanic outpourings.
As part of MISTI-India, Megan Guenther, a junior in EAPS, records field notes about the landscape of the Kohistan-Ladakh region of the Himalayas in northern India. Credit: Craig Martin
According to Craig Martin, deciphering Earth’s geologic past is like an ant climbing over a car crash. “You’ve got to work out how the car crash happened, how fast the cars were going, at what angle they impacted,” explains Martin, a graduate student at MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “You’re just a tiny ant wandering over this massive chaos,” he adds.
The crash site Martin is investigating is the Himalayas, a 1,400-mile mountain range that rose when the Indian and Eurasian tectonic plates scrunched together. “The mainstream idea is: There was Eurasia; there was India; and they collided 50 million years ago,” says Oliver Jagoutz, an associate professor in EAPS and Martin’s advisor. “We think it was much more complicated than that, because it’s always more complicated.”
Detective work at 11,000 feet
Eighty million years ago, India and Eurasia were 4,000 miles apart, separated by an ancient body of water that geologists call the Neotethys Ocean, but Jagoutz believes there was more than just seawater between the two. He’s not alone. Many geologists agree on the existence of an arc of volcanic islands that formed on the boundary of a smaller tectonic plate, similar to the Mariana Islands in the Pacific Ocean. However, there is debate on whether these islands first collided with the Eurasian plate to the north or the Indian plate to the south. Jagoutz’s hypothesis is the latter. “If I’m right, the arc sits near the equator. If the others are right, the fragments should be 20 degrees north,” he explains. “That’s how simple it is.” But it can mean a world of difference in terms of explaining the paleoclimate—not just in the Himalayas, but globally as well.
To test this hypothesis, Jagoutz and Martin turned to paleomagnetism. Some rock minerals, such as magnetite, contain iron and act as tiny bar magnets, orienting their magnetization along Earth’s magnetic field. At the Equator, magnetite in newly formed rocks will be magnetized parallel to the ground but the further north or south it is, the more inclined the magnetization will be. “We can measure, essentially, the latitude that a rock was formed at,” explains Martin.
If you were to take a slice of the Kohistan-Ladakh region of the Himalayas in northern India, you would see a succession of rock layers representing the India plate and the Eurasia plate, with the volcanic island arc sandwiched in between. “That’s why Ladakh is a really cool place to go to, because you can walk though this whole collision,” says Martin.
In summer 2018, Martin and Jade Fischer, a junior double-majoring in EAPS and physics, spent six weeks in Ladakh collecting samples from the volcanic rocks. Back at MIT, Martin measured the paleomagnetic signature of these rocks, and his results placed the Kohistan-Ladakh arc right at the equator, in agreement with Jagoutz’s theory.
A magnetic collaboration
Megan Guenther, a junior in EAPS, first heard about the opportunity to do field work in Ladakh when Martin gave a presentation about his research in her structural geology class last fall. “At the end, he told us he was probably going again and to let him know if we were interested,” Guenther explains. “I emailed him an hour later.”
Guenther had been looking for a chance to gain more field experience. She works on the compositions of lunar glasses with Tim Grove, the Robert R. Shrock Professor of Earth and Planetary Sciences, where the research takes place entirely in the lab. “You can’t really do field work on the moon,” she jokes.
This past summer, Guenther and Martin spent six weeks in Ladakh collecting rock samples from the Eurasian plate to prove that this was not also further south, mapping the region and doing structural analyses. Both Guenther and Martin were supported by MIT International Science and Technology Initiatives (MISTI) and the MISTI Global Seed Fund.
MISTI and Jagoutz go back a long time, with MISTI funding class excursions, department field trips, and a number of Jagoutz’s students. “MISTI-India has been good to us,” he says. “They financed the workshop where we came up with the whole concept of this work.” And, says Jagoutz, the students really love the experience. “They get influenced by it, and a lot of people chose their career paths after it,” says Jagoutz. “Ultimately, that’s what MISTI is all about: an experience that tells students they want to get into science.”
For Guenther, the trip was an essential part of her education as a geologist. “I feel much more confident as a field geologist, which is exactly what I wanted,” she says. It also impressed on her the titanic scale of geology. “The scale of everything is so crazy,” says Guenther. “You’re already at 11,000 feet, minimum, the whole time, and then these huge mountains tower above that.”
By solving the story of the collision that resulted in the Himalayas, Jagoutz and his team also shed light on its global implications. Large-scale collisions, Jagoutz explains, don’t just have local effects, and in the case of the Himalayas they can also explain some of Earth’s past glaciation events. “That’s the good thing about geology: the dimensions,” says Jagoutz. “You look at a magnetite crystal in a rock, and it tells you how global cooling works.”
A controversial theory that suggests an extraterrestrial body crashing to Earth almost 13,000 years ago caused the extinction of many large animals and a probable population decline in early humans is gaining traction from research sites around the world.
The Younger Dryas Impact Hypothesis, controversial from the time it was presented in 2007, proposes that an asteroid or comet hit the Earth about 12,800 years ago causing a period of extreme cooling that contributed to extinctions of more than 35 species of megafauna including giant sloths, sabre-tooth cats, mastodons and mammoths. It also coincides with a serious decline in early human populations such as the Clovis culture and is believed to have caused massive wildfires that could have blocked sunlight, causing an “impact winter” near the end of the Pleistocene Epoch.
In a new study published this week in Scientific Reports, a publication of Nature, UofSC archaeologist Christopher Moore and 16 colleagues present further evidence of a cosmic impact based on research done at White Pond near Elgin, South Carolina. The study builds on similar findings of platinum spikes — an element associated with cosmic objects like asteroids or comets — in North America, Europe, western Asia and recently in Chile and South Africa.
“We continue to find evidence and expand geographically. There have been numerous papers that have come out in the past couple of years with similar data from other sites that almost universally support the notion that there was an extraterrestrial impact or comet airburst that caused the Younger Dryas climate event,” Moore says.
Moore also was lead author on a previous paper documenting sites in North America where platinum spikes have been found and a co-author on several other papers that document elevated levels of platinum in archaeological sites, including Pilauco, Chile — the first discovery of evidence in the Southern Hemisphere.
“First, we thought it was a North American event, and then there was evidence in Europe and elsewhere that it was a Northern Hemisphere event. And now with the research in Chile and South Africa, it looks like it was probably a global event,” he says.
In addition, a team of researchers found unusually high concentrations of platinum and iridium in outwash sediments from a recently discovered crater in Greenland that could have been the impact point. Although the crater hasn’t been precisely dated yet, Moore says the possibility is good that it could be the “smoking gun” that scientists have been looking for to confirm a cosmic event. Additionally, data from South America and elsewhere suggests the event may have actually included multiple impacts and airbursts over the entire globe.
While the brief return to ice-age conditions during the Younger Dryas period has been well-documented, the reasons for it and the decline of human populations and animals have remained unclear. The impact hypothesis was proposed as a possible trigger for these abrupt climate changes that lasted about 1,400 years.
The Younger Dryas event gets its name from a wildflower, Dryas octopetala, which can tolerate cold conditions and suddenly became common in parts of Europe 12,800 years ago. The Younger Dryas Impact Hypothesis became controversial, Moore says, because the all-encompassing theory that a cosmic impact triggered cascading events leading to extinctions was viewed as improbable by some scientists.
“It was bold in the sense that it was trying to answer a lot of really tough questions that people have been grappling with for a long time in a single blow,” he says, adding that some researchers continue to be critical.
The conventional view has been that the failure of glacial ice dams allowed a massive release of freshwater into the north Atlantic, affecting oceanic circulation and causing the Earth to plunge into a cold climate. The Younger Dryas hypothesis simply claims that the cosmic impact was the trigger for the meltwater pulse into the oceans.
In research at White Pond in South Carolina, Moore and his colleagues used a core barrel to extract sediment samples from underneath the pond. The samples, dated to the beginning of the Younger Dryas with radiocarbon, contain a large platinum anomaly, consistent with findings from other sites, Moore says. A large soot anomaly also was found in cores from the site, indicating regional large-scale wildfires in the same time interval.
In addition, fungal spores associated with the dung of large herbivores were found to decrease at the beginning of the Younger Dryas period, suggesting a decline in ice-age megafauna beginning at the time of the impact.
“We speculate that the impact contributed to the extinction, but it wasn’t the only cause. Over hunting by humans almost certainly contributed, too, as did climate change,” Moore says. “Some of these animals survived after the event, in some cases for centuries. But from the spore data at White Pond and elsewhere, it looks like some of them went extinct at the beginning of the Younger Dryas, probably as a result of the environmental disruption caused by impact-related wildfires and climate change.”
Additional evidence found at other sites in support of an extraterrestrial impact includes the discovery of meltglass, microscopic spherical particles and nanodiamonds, indicating enough heat and pressure was present to fuse materials on the Earth’s surface. Another indicator is the presence of iridium, an element associated with cosmic objects, that scientists also found in the rock layers dated 65 million years ago from an impact that caused dinosaur extinction.
While no one knows for certain why the Clovis people and iconic ice-age beasts disappeared, research by Moore and others is providing important clues as evidence builds in support of the Younger Dryas Impact Hypothesis.
“Those are big debates that have been going on for a long time,” Moore says. “These kinds of things in science sometimes take a really long time to gain widespread acceptance. That was true for the dinosaur extinction when the idea was proposed that an impact had killed them. It was the same thing with plate tectonics. But now those ideas are completely established science.”
Reference:
Christopher R. Moore, Mark J. Brooks, Albert C. Goodyear, Terry A. Ferguson, Angelina G. Perrotti, Siddhartha Mitra, Ashlyn M. Listecki, Bailey C. King, David J. Mallinson, Chad S. Lane, Joshua D. Kapp, Allen West, David L. Carlson, Wendy S. Wolbach, Theodore R. Them, M. Scott Harris, Sean Pyne-O’Donnell. Sediment Cores from White Pond, South Carolina, contain a Platinum Anomaly, Pyrogenic Carbon Peak, and Coprophilous Spore Decline at 12.8 ka. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-019-51552-8
Brittany Erickson, an assistant professor in the Department of Computer and Information Science who studies geophysics and is a colleague of UO’s Leif Karlstrom, peers into the Halema’uma’u lava lake on Hawai’i’s Kiīlauea volcano. Credit: University of Oregon
“We’re Barely Listening to the U.S.’s Most Dangerous Volcanoes,” read the headline on a recent story in the New York Times, pointing to the dismal state of volcano monitoring in the Pacific Northwest.
UO earth scientist Leif Karlstrom believes that same headline could also be interpreted literally — he wants to teach others about volcanoes through an ambitious initiative he calls the Volcano Listening Project that seeks to express and understand volcanic data through sound.
As Karlstrom explains, the human brain has evolved to react to and interpret a world full of sounds. This is a practical survival skill when faced with the sound of a falling tree or an approaching city bus, and sound through music can be a compelling window into human emotion.
“Most people regularly listen to music, but rarely do we think of sound as a means of interpreting scientific data,” Karlstrom said. “My goal is to bring volcanoes — safely! — into public spaces, exploring complex scientific data in surprising and hopefully interesting ways.”
The project is part of Karlstrom’s Career Award from the National Science Foundation, which he received in spring 2019 and includes a five-year plan to further develop his Volcanic Listening Project to generate sounds from data recorded at erupting volcanoes. He will use this so-called “sonified” data to inform scientific interpretations, as well as to make and perform music.
A professor in the Department of Earth Sciences, Karlstrom characterizes his research as “fluid and solid mechanics applied to volcanoes and glaciers.” When a volcano erupts, Karlstrom says, scientists record ever-increasing amounts of information, which can include photographic or video imagery, gas emissions, deformation of the ground, subsurface earthquakes and chemical compositions of erupted lavas.
Karlstrom and his collaborators have developed computer programs that translate these volcanic data into sound, at which point Karlstrom puts on his music hat to examine the results. As a lifelong musician, he earned a degree in violin performance from the UO and has been playing professionally for nearly 20 years.
After earning his doctorate in earth and planetary science at the University of California, Berkeley, he helped start a number of groups in the San Francisco Bay Area. These include the band Front Country in 2012, now a full-time group based out of Nashville that tours internationally, and the duo Small Town Therapy.
For Karlstrom, combining scientific research with music doesn’t often happen, but with this new project he has found a pairing that he says makes sense.
“Sound provides emotional experiences as well as an intuitive way to grapple with the scientific goals of understanding patterns and peering through noisy data,” Karlstrom said, adding that he hopes to use these contrasting, biologically hardwired relationships to teach people about volcano science.
“Millions of people are affected by volcanoes and the hazards associated with them,” Karlstrom said. “We are exploring new ways to engage with awe-inspiring parts of the natural word, which operate on scales that are well outside the normal human experience. ”
Karlstrom will continue to build out his Volcano Listening Project to include learning materials for those interested in data sonification and visualization. He will also promote musical composition and performance based on volcanic data.
The first iteration of the Volcano Listening Project features a collaboration between Portland-based visual artist Zack Marlow-McCarthy and Karlstrom’s group Small Town Therapy. It includes the track “Hotel Kilauea” from their 2019 record. A merging of art and science, the track is a blend of acoustic instruments mixed with computer-generated sounds from data collected at Kilauea volcano in Hawaii between the years 2000-10.
‘Hotel Kilauea’ is UO earth scientist Leif Karlstrom’s multimedia work, which depicts 10 years of data collected at Hawaii’s Kilauea volcano, compressed into a little more than three minutes. Raw data associated with ground deformation and gas emissions are ‘sonified,’ then used as the basis for musical improvisation.
Computer sounds were used as the basis for free improvisation of the data by Karlstrom and three other musicians who formed an ensemble of two violins, guitar and upright bass. The performance follows in the footsteps of free jazz exemplified by artists like John Zorn or Ornette Coleman, known for their ability to stretch the conventional use of tempo, rhythm, and harmony and perform in a completely improvised manner.
“The challenge (of free improvisation) is, can you make art if there are no rules?” Karlstrom said. “Can you make it up on the spot? Is it still musical or is it just noise?”
The video released along with Hotel Kilauea is based both on the data and on musical performance. It animates the transformation of a volcano over time with an abstract touch, much as the music provides an abstract interpretation of the raw volcanic data. A detailed listener’s guide for the track is available on the project website.
Karlstrom is working on installations of the Volcano Listening Project that will debut nationally over the coming years, starting with the Centennial Theater at the American Geophysical Union Fall Meeting in San Francisco in December.
He also hopes that others will latch on to volcano music, which he views as a steppingstone for creating new ways to engage the public around science.
“Science is a creative enterprise, just like music,” Karlstrom said. “I am hoping that the Volcanic Listening Project can help generate new knowledge about volcanoes as well as compelling new art.”
Photograph of the traces analyzed: : Megalosauripus transjuranicus (A) y Jurabrontes transjuranicus (B). Credit: Matteo Belvedere et al.
Dinosaur footprints found in several European countries, very similar to others in Morocco, suggest that they could have been dispersed between the two continents by land masses separated by a shallow sea more than 145 million years ago.
At the end of the Jurassic, as a consequence of the defragmentation of the Pangaea supercontinent, the countries that now form Europe were part of an archipelago surrounded by a shallow sea. In its interior, the Iberian Peninsula was located in the southernmost part, on the continent of Laurasia (which included present-day North America and Eurasia), but near Gondwana, the continent to the south.
Large predators strolled through these lands and their footprints have been found on different continents. Thus, for example, ichnites and bones of allosaurs and stegosaurs have been found in both North America and Portugal, suggesting that both territories were connected in some way.
In a new study, published in the Journal of African Earth Sciences, a team of European scientists, with Spanish participation, has now recognized two types of dinosaur footprints related to large Jurassic predators in today’s Switzerland, Portugal, Spain (which belonged to Laurasia) and Morocco (which was in Gondwana).
The marks, called Megalosauripus transjuranicus and Jurabrontes curtedulensis, belonged to carnivorous theropods similar to Tyrannosaurus rex. “On the one hand, we have identified a type of large and slender footprints with a size of 30-50 cm and, on the other hand, other gigantic and robust footprints measuring more than 50 cm,” as Diego Castanera, from the Miquel Crusafont Catalan Institute of Palaeontology (ICP) of the Autonomous University of Barcelona and co-author of the work, has explained to SINC.
Shallow water trails
In order to distinguish the types of footprints, the team used a novel software called DigTrace, which made it possible to virtually compare the fossilized footprints. “We can’t determine with certainty what animal left a particular footstep since different related dinosaurs could leave very similar footprints,” says Castanera.
However, this study confirms that the differences between the two groups of footprints identified are important enough for their originators to be different but closely related dinosaurs.
Scientists thus suggest that they probably belonged to Allosaurus and Torvosaurus, since their remains have been found in the Upper Jurassic of Portugal, indicating the presence of two super-predators in the terrestrial ecosystems of the late Jurassic.
To confirm these data, the group of researchers stresses that more studies are needed, especially to answer an important question: how did the dinosaurs pass between Laurasia and Gondwana? “The answer is problematic because geological studies indicate that there was a deep sea between the two continents,” stresses the scientist.
The presence of the same species in such distant places forces scientists to propose dispersal routes between continents during the Mesozoic, the time during which dinosaurs lived. These large animals were thus able to move between Africa and Europe on land masses with short emersion periods and through southern Italy and the Balkans or through Iberia (what is nowadays the Iberian Peninsula).
Reference:
Matteo Belvedere et al, Late Jurassic globetrotters compared: A closer look at large and giant theropod tracks of North Africa and Europe, Journal of African Earth Sciences (2019). DOI: 10.1016/j.jafrearsci.2019.103547
California is one of the richest states in mineral diversity.
Not unexpectedly, it has a good reputation when it comes to activities related to gold mining, but not only that; it is also home to a number of gemstone mines. Most of these mines are situated in the California southern region.
Locations of some of these gemstone mines:
Himalaya Mine, Mesa Grande District, California.
The Himalaya Tourmaline Mine is located near Santa Ysabel, CA at Lake Henshaw in the beautiful Mesa Grande is the best place for gem hunting in california. We offer a fun gem and crystal dig to the public. Visit our dig at Lake Henshaw Resort where you will dig and screen through ore from the world famous Himalaya Mine. Many minerals can be found including pink and green tourmaline, black tourmaline, quartz crystals, spessertine garnet, lepidolite, clevelandite, and a variety of others. Keep all you find.
Where are we located? Lake Henshaw 26439 Hwy 76, Santa Ysabel, CA 92070
When are we open? Open Thursday through Sunday 10am – 3pm. Reservations are not necessary.
Also, Mondays by reservation available
Cost: Adult Dig $75, youth 13 years old to 15 years old half price ($37.50), children 12 years old and under are free with paying adult. Additional children $20.
Discounts: Senior and active military rate $60. Rain day $10 off if it rains more than 75% of the day.
Adult Group Rates: Groups 20+ $50 per person, 10+ people $5 off
Children Group Rates: $20 per child, 12 and under
What to Bring: Sun hat or rain gear, muddy shoes, maybe some rubber gloves, tooth brush, baggie for your crystals and a small bucket, or bin, for specimens. Tissue paper for wrapping your crystals and specimens.
Accommodations: Lake Henshaw Resort Cabins, RV parking, and camping. Call 760-782-3501. Also in Julian (25 miles away) there are several hotels including the historic Gold Rush Hotel. And, there’s a casino, Rincon, I believe it is called.
Gold Prospecting Adventures, LLC has built a solid reputation throughout California’s Gold Country as the best of the best for gem hunting in california. We are the leading professionals in gold prospecting and gold rush history. That’s because we’ve spent the last 40 years perfecting our techniques, improving our knowledge, and tailoring our programs to meet the needs of the thousands of guests who visit our camp each year. Our guides, dressed in period costume, receive special training to insure that every individual enjoys a remarkably genuine and comprehensive gold rush experience. No other gold prospecting company can stake that claim!
We know (and will share) the real secrets of successful prospecting. And the gold is here, participants have taken out over 300 ounces of gold from the one hole at our Jimtown 1849 Gold Mining Camp.
Whether you are a family looking for a fun and interesing way to spend a few hours on your way to Yosemite, a real adventurer, seeking the true secrets to successful prospecting, or a group organize, planning your next tour. we have the trip for you.
Be our guest, come to Jamestown, live the adventure and take home some gold.
A visit to the Oceanview Mine allows you a unique view of the only actively working underground mine in the world famous Pala Gem mining district and a chance to find your own gems—tourmalines, kunzites, morganites and more so it is one of best places for gem hunting in california. Screen the dump piles of material we take out of our mine and find the gems we’ve missed—and we miss a lot! You get to keep everything you find at no extra charge; the standard dig fee allows you to keep all you find and you can take home one 5-gallon bucket of rocks that you have screened and washed. Guests also get a jeep tour of Chief Mountain where you can see all of the currently active mines and prospects, as well as views of the famous Pala Chief, Tourmaline Queen and other historic mines.
We’ve taken care of everything you need. We provide you with screens, water, buckets and shovels–and most importantly, a big pile of gem-rich dirt and gravel taken from our mines! After a brief training session, you have four hours to work the pile, looking for your gems. You get to keep everything you find at no extra charge; the standard dig fee allows you to keep all you find. In addition, you can take home one 5-gallon bucket of rocks that you have screened and washed if you want to more carefully sort through them at home. Guests also get a jeep tour of Chief Mountain where you can see all of the currently active mines and prospects, as well as views of the famous Pala Chief, Tourmaline Queen and other historic mines.
Location: 37304 Magee Rd, Pala, CA 92059 What You Might Find: Tourmaline (black, watermelon, and green), Kunzite, Aquamarine, Morganite, Lepidolite, Quartz, & more! Cost: Adults – $75 each) // 5-11 years old – $60 each // 4 and under are free
Opal Hill Mine, Mule Mountains District, Riverside Co., California.
Opal Hill, located in eastern California near the border of Arizona, is known for its beautiful opal eggs, quartz crystals, and wonderful fire agates so it is one of the best places for gem hunting in california. Sometimes called Coon Hollow, this site is located deep in the Mule Mountains not far from Palo Verde, CA.
To reach the site from Interstate 10, take Wiley Well Road exit and head south for approx. 17 miles, just past the BLM Coon Hollow Campround. Turn left on the small gravel road (high clearance vehicle recommended) at the Opal Hill Mine sign and drive east for another couple of miles to the mine site, which is located on the right.
Opal Hill has a long known history of quality fire agate production, having produced many wonderful gemstones over the years. The old original Opal Hill mining claim used to offers a pay to mine service during the cooler fall, winter and spring months (December 2015 Note: The mine has a new owner and it is unknown if it is any longer open to the public).
Location From Interstate 10, take Wiley Well Exit and head south on the graded dirt road for 11.86 miles. A dirt road leads to the claim; it’s no longer marked. (If you pass the entrance to the Coon Hollow Campground going south you’ve missed the road.) Go east on the cut off road and travel for a about 2.3 miles on the rough dirt and rocky road. A high clearance 4×4 vehicle is needed to navigate the last mile of rocky road to the mine. GPS 33°27’08.0″N 114°51’53.5″W
Gems of Pala, Magee Rd, Pala, California
Gems of Pala is a locally owned and operated business. Our owners Blue Sheppard and his wife Shannon are onsite to personally greet you. Blue has over 52 years of experience with gems and minerals. to share with you. We pride ourselves on quality pricing and superior customer service and especially for being the #1 choice in San Diego County for a true family mining adventure.
Gems of Pala gives you the educational experience and excitement of mining for precious gems from a real mine. Enjoy the thrill of searching for gems just like the miners of the 1800’s. You will be provided with all the tools of a gem hunter as well as a demonstration. No reservations required, except for large groups!
Location: 35940 Magee Rd, Pala, CA 92059 What You Might Find: Quartz, Lepidolite, Kunzite, Morganite, Tourmaline Cost: Gem Buckets that you dig from our pile are $30.00 each. Pre-Dug Gem Bags are $50.00 each. All Cash Only.
California State Gem Mine, Los Gatos Creek Rd, Coalinga, California
Here’s your chance to come find the state gemstone of California, Benitoite
A prospector, James Couch, was grubstaked by Roderick Dallas, and in February, 1907, and on his way to investigate some intriguing outcrops, found a small area littered with blue crystals which he thought might be blue sapphires. He collected several and rushed back to Coalinga. A claim was placed which was named the Dallas Gem mine. Dr. George Louderback, a professor of mineralogy at the University of California, Berkeley, was provided some of the stones. Dr. Louderback soon realized that they were not sapphires or spinel as some thought, but a new mineral not known to science. In July 1907 he published an article, naming the new mineral benitoite, named after San Benito County. The black mineral associated with the benitoite was initially called ‘carlosite’, named after the nearby San Carlos peak. However, he later discovered that this mineral was neptunite which had been discovered in Greenland in 1893.
When word got out of the new discovery, several people, including Dr. George Kunz from Tiffany’s of New York, rushed to the site to secure an exclusive marketing agreement with the miners. Mr. G. Eacret, of Shreve and Company in San Francisco won the marketing rights.
The mine owner, Mr. R.W. Dallas, built a mine camp and immediately expanded mining operations. The mine produced benitoite from an open cut in the hillside, as well as a short underground tunnel pushed into an outcrop of benitoite-bearing material called blueschist. For about 5 years, the blueschist layer yielded thousands of excellent gemstones.
Location: The Historic Old Road Camp – 48242 Los Gatos Rd. Coalinga, CA 93210 What You Might Find: Benitoite (the state gemstone) Cost: Adults – $70 person // 12 and younger – $20
Stewart Mine, Pala Mining District, San Diego County, California
Location: Tourmaline Queen Mountain (Pala Mtn; Queen Mtn), Pala, Pala Mining District, San Diego County, California, USA
In the world of treasures, few precious and desirable things can ever exceed the pink tourmaline of Pala, California it is one of best places for gem hunting in california. Gem quality natural pink tourmaline is five times as rare as gem diamond and more than ten times as valuable as gold in its pure form. Tourmaline is harder than quartz (Mohs 7.253), is highly refractive when cut, and produces exquisite gemstones.
The Stewart Mine will always be one of the great classic locations for mineralogists. The Stewart produces the world’s finest natural pink tourmaline, both for mineral specimens that spotlight the world’s museums and. also, for gemstones that highlight the World jewelry industry, but especially for the fabulous blue-capped rubellite specimens that hallmark Pala as the very crest of the best in tourmaline over the whole planet.
Tourmaline Queen Mine, Pala, Pala Mining District, San Diego County, California
Location: Tourmaline Queen Mountain (Pala Mtn; Queen Mtn), Pala, Pala Mining District, San Diego County, California, USA
For over a century the Tourmaline Queen mine near Pala, California has been known for large and beautiful crystals of tourmaline and morganite beryl, it is amazing place for gem hunting in california. The extraordinary blue-capped pink elbaites recovered in 1972 remain among the most famous mineral specimens of any kind ever found in California, and are surely the finest tourmalines ever recovered in North America. Here is the story behind this great locality, which today is once again producing fine specimens.
The Tourmaline Queen Mine located in Pala, San Diego County, California, has always inspired mineral collectors, high graders and geologists. It was originally claimed by Frank Salmons and Associates in March, 1903. Exploratory work yielded some 80 pounds of gem tourmaline. The Queen immediately became the leading producer of tourmaline in the Pala district during the period 1904 through 1914. With the collapse of the major Chinese market for tourmaline, due to the 1911 overthrow of the Imperial government, the mines soon became uneconomical. From about 1914 to 1971, the Queen was worked intermittently by high graders, with limited success.
Pala Properties International, Inc., became involved in the Pala mining district when Ed Swoboda purchased the Stewart Lithia, Tourmaline Queen and Pala Chief Mines. We had been mining the Stewart with mild success since 1968, when we decided that it was time to make the switch up the hill to the Tourmaline Queen. Originally our idea in mining the Stewart was to set up basic operations, learn the gem mining trade, and then move up to the Queen which we were sure was more promising. However, with the discovery of the famed lost tourmaline adit and initial production of a few fine tourmaline crystals, we overstayed these original plans. But without increased production, economics forced us to make the necessary move up the mountain.
Vredefort Dome, Free State, South Africa. Credit: NASA
The Largest Verified Impact Crater on Earth
The Vredefort crater is the largest certified impact crater on Earth. In the present Free State Province of South Africa, what remains of it is more than 300 kilometers (190 mi) from when it was created.
It is named after the town of Vredefort, near its center. Although the crater itself has long been worn away, it is known as the Vredefort Dome or Vredefort impact structure that the remaining geological structures at its core are.
It is estimated that the crater is 2,023 billion years old (± 4 million years old), with an impact in the Paleoproterozoic period. It’s the Earth’s second oldest known crater.
In 2005, the Vredefort Dome was added to the list of UNESCO World Heritage sites for its geologic interest.
Where is the world’s oldest meteorite impact crater?
The Vredefort crater located in South Africa.
How big is the Vredefort crater?
The Vredefort Impact Crater is the largest asteroid impact site with an estimated initial diameter of 300 kilometers that still has visible evidence on Earth’s surface.
Who discovered the Vredefort crater?
Twenty years ago, the now professor of Western Earth Sciences first visited the core of the Vredefort impact crater in South Africa, discovering what he claimed to be some of the last remnants of a magma sea formed in a 300-kilometer-wide crater more than 2 billion years ago.
Vredefort crater Formation and structure
It is believed that the asteroid that struck Vredefort was one of the largest ever to hit Earth (at least since the Hadean Eon about four billion years ago), thought to be about 10–15 km in diameter (6.2–9.3 mi).
The main crater is measured to have a diameter of about 300 km (190 mi) but has been eroded. It would have been wider than the Sudbury Basin of 250 km (160 mi) and the Chicxulub crater of 180 km (110 mi). The resulting formation, the “Vredefort Dome,” consists of a small ring of 70 km (43 mi) in diameter of hills and is the remnants of a dome formed after the collision by the stone recovery below the impact site.
It is estimated that the age of the crater is 2 02 300 billion years (± 4 million years). It is the second-oldest known crater on Earth, slightly less than 300 million years younger than the Suavjärvi crater in Russia. In contrast, the effect of the Sudbury Basin is about 10% older (at 1,849 billion years).
The dome in the center of the crater was originally thought to have been created by a volcanic eruption, but in the mid-1990s, evidence showed that it was the site of a major bolide strike, as telltale shatter cones were found in the bed of the nearby Vaal River.
The crater site is one of the few craters on Earth that have multiple rings, though they are the most prominent in the solar system. Valhalla crater on Jupiter’s moon, Callisto is perhaps the most prominent example. There is also Earth’s Sun. The most multi-ring craters on Earth have been destroyed by geological processes, such as erosion and tectonic plates.
In 250 million years between 950 and 700 million years before the Vredefort impact, the effects warped Witwatersrand Basin.
The overlying lavas of Ventersdorp and Transvaal Supergroup were also skewed by the formation of the 300-km (190.000 mi) crater between 700 and 80 million years prior to the meteorite strike. The rocks are now partially clustered around the crater centre, with the youngest rocks of the Witwatersrand forming a half-circle of 25 miles. The Witwatersrand rocks contain multiple layers (e.g. quartzites and banded ironstones) of sediments that have been very strong, erosion prone, and form the prominent arc of hills in satellite picture above to the Northwest. Follow the rocks of the Witwatersrand, the lava of Ghaap Dolomites and the Pretoria Subgroup, which together form a 25-to-30-kilometer (16 to 19 mi) chain, follow at a distance of about 35 km from the middle and the Transvaal Subgroup, consisting of a small gang of the rocks of the Dolomites and of the Dolomites and Pretorias.
The order of the rocks is reversed from approximately halfway through the Pretoria subgroup of rocks around the crater centre. The Ghaap Dolomite band resurfaces from the middle at 60 km (37 mi), to the outer direction of where the crater rim used to be, followed by the Ventersdorp Lava arch, after which the Witwatersrand rocks are now a broken outcrop arc at 80-120 km (50 and 75 mi) from the core. The Johannesburg group is the most famous one because it was here that gold was discovered in 1886. It is thus possible that if it had not been for the Vredefort impact this gold would never have been discovered.
Maps of the Siljan impact structure and study locations. a Map of Sweden with the Siljan area indicated. b Geological map of the Siljan impact structure with locations of the cored boreholes and the quarry sampled for mineral coatings indicated, along with the sedimentary units in the crater depression, towns, lakes (white) and roads (black lines). Gas compositions exist from boreholes VM2 and VM5 (located adjacent to VM2). Credit: Nature Communications, 2019
Fractured rocks of impact craters have been suggested to host deep microbial communities on Earth, and potentially other terrestrial planets, yet direct evidence remains elusive. In a new study published in Nature Communications, a team of researchers shows that the largest impact crater in Europe, the Siljan impact structure, Sweden, has hosted long-term deep microbial activity.
Life thrives deep beneath our feet in a vast but underexplored environment coined the deep biosphere. Colonization of these deep environments—on Earth and potentially on other Earth-like planets—may have been sparked by meteorite impacts. Such violent events provide both space to microbial communities due to intense fracturing, and heat that drives fluid circulation favorable for deep ecosystems. Especially on planetary bodies that otherwise are geologically dead, such systems may have served as rare havens for life with considerable astrobiological implications.
At the scenic site of Siljan, in the heart of Sweden, an impressive impact structure of >50 km diameter formed almost 400 million years ago. Previous well-known drilling attempts for deep natural gas are now renewed, and from these newly retrieved drill cores, a team of researchers have found widespread evidence of deep ancient life.
Henrik Drake, of the Linnaeus University, Sweden, and lead author of the study, explains the discovery: “We examined the intensively fractured rock at significant depth in the crater and noted tiny crystals of calcium carbonate and sulphide in the fractures. When we analyzed the chemical composition within these crystals it became clear to us that they formed following microbial activity. Specifically, the relative abundance of different isotopes of carbon and sulfur within these minerals tells us that microorganisms that produce and consume the greenhouse gas methane have been present, and also microbes that reduce sulfate into sulfide. These are isotopic fingerprints for ancient life.”
Nick Roberts at the British Geological Survey, and co-author of the study, tells more about how the timing of the microbial activity could be estimated: “We applied newly developed radioisotopic dating techniques to the tiny calcite crystals formed following microbial methane cycling, and could determine that they formed in the interval 80 to 22 million years ago. This marks long-term ancient microbial activity in the impact crater, but also that the microbes lived up to 300 million years after the impact. Our study shows that detailed multi-method investigations are needed to understand the link between the impact and the colonization,” Henrik Drake continues. “At Siljan we see that the crater is colonized but that it has mainly occurred when conditions, such as temperature, became more favorable than at the impact event. The impact structure itself, with a ring zone of down-faulted Paleozoic sediments, has been optimal for deep colonization, because organics and hydrocarbons from shales have migrated throughout the fractured crater and have acted as energy sources for the deep microbial communities.”
Christine Heim, of University of Göttingen, Germany, co-author adds: “The preserved organic molecules that we could detect within the minerals give us additional evidence both for microbial activity in the crater, as we find molecules specific to certain microorganisms, but also for microbial biodegradation of shale-derived hydrocarbons, ultimately leading to production of secondary microbial methane at depth.”
“Detailed understanding of microbial colonization of impact craters has wide-ranging astrobiological implications. The methodology that we present should be optimal to provide spatiotemporal constraints for ancient microbial methane formation and utilization in other impact crater systems, such as the methane emitting craters on Mars,” Magnus Ivarsson, Swedish Museum of Natural History, a co-author of the study, adds.
Henrik Drake summarizes: “Our findings indeed confirm that impact craters are favorable microbial habitats on Earth and perhaps beyond.”
Reference:
Drake et al., Timing and origin of natural gas accumulation in the Siljan impact structure, Sweden, Nature Communications, 2019 DOI: 10.1038/s41467-019-12728-y
Much of our modern technology relies on the use of rare earth elements (REEs), and a key to finding more of them is to understand the processes that concentrate them in the Earth’s crust. In the ancient Bergslagen ore province of central Sweden lies a zone of Bastnäs-type rare earth element deposits, and in a new study, scientists from Uppsala University and the Geological Survey of Sweden (SGU) show how these deposits originally formed.
The increasing demand for REEs in a wide range of modern high-tech applications, including applications vital to achieving “fossil-free” transportation and energy production, has triggered a worldwide effort to discover new sources of these critical metals and therefore also a need to better understand how they formed. The Bastnäs-type REE deposits in the Bergslagen ore province in south central Sweden were the first hard-rock ores ever to be mined for REEs and played a key role in the original discovery of several rare earth elements (including cerium and lanthanum) and REE minerals (such as the mineral bastnäsite; see photo). These Palaeoproterozoic, skarn-hosted magnetite-REE deposits represent a large-scale (>100 km) feature of high-grade REE concentrations, the “REE line’ in Bergslagen, south central Sweden. An improved understanding of their origin could help to guide exploration for this type of REE mineralization here and elsewhere to secure the future supply of these critical commodities.
To unravel the formation of Bastnäs-type REE deposits, robust constraints on the nature of ore-forming processes and fluids were needed. To address this, a research team from Uppsala University, the Geological Survey of Sweden (SGU) and the University of Cape Town collected mineral oxygen and carbon isotope data from ten of the classic central Swedish Bastnäs-type deposits to assess their mode of origin. The results have now been published in Scientific Reports.
The new isotope data allowed the team to perform numerical models that, combined with existing geological observations, imply an origin in a sub-seafloor, shallow-marine back-arc setting where high-temperature magmatic fluids reacted with pre-existing limestone layers. The drastic changes in chemical environment experienced by the fluids during their interaction with the limestone led to localized skarn formation and magnetite-REE mineral precipitation. These results advance the long-standing debate on the origin of the Bastnäs-type REE deposits and provide new insights into geological processes that have the potential to produce high-grade REE mineralization.
Reference:
Fredrik Sahlström et al. Interaction between high-temperature magmatic fluids and limestone explains ‘Bastnäs-type’ REE deposits in central Sweden, Scientific Reports (2019). DOI: 10.1038/s41598-019-49321-8
Note: The above post is reprinted from materials provided by Uppsala University.
A new paper from scientists at The University of Manchester has discovered why some volcanic eruptions are more explosive than others.
Basaltic eruptions are the most common form of volcanic eruption, and for the most part, they involve relatively tame magma activity. Occasionally, however, the magma activity results in highly explosive and hazardous eruptions. The latter are known as Plinian eruptions, after the Ancient Roman writer who described the eruption of Mt Vesuvius in 79AD.
A new paper, “Magma fragmentation in highly explosive basaltic eruptions induced by rapid crystallization”, published in the journal Nature Geoscience, proposes an explanation for this discrepancy. When magma is rapidly expelled from a volcano, it undergoes rapid cooling. This induces the formation of crystals, resulting in a sudden increase in the viscosity of the magma. In turn, this produces magma fragmentation, creating a highly explosive eruption.
Dr. Fabio Arzilli, from The University of Manchester, and his colleagues discovered this process using a combination of numerical modeling and in situ and ex situ experiments. They also observed natural samples from previous highly explosive basaltic eruptions, such as the 1886 Tarawera eruption in New Zealand. The work was carried out with partners at the Oxfordshire-based Diamond Light Source.
Dr. Arzilli said; “We found that, under certain conditions consistent with highly explosive eruptions, crystallization can occur within a couple of minutes during magma ascent.”
Previous research into magma crystallization had led volcanologists to believe it occurred too slowly to be responsible for highly explosive eruptions.
Commenting on the findings of the paper, Dr. Arzilli said; “Our results imply that all basaltic systems on Earth have the potential to produce powerful explosive eruptions.”
He continued; “This has important implications for the volcanic hazard and risk, on not only the regional, but also the global scale. Indeed, Icelandic eruptions are recognized as one of the highest priority risks in the National Risk Register of Civil Emergencies for the UK population.”
Reference:
Fabio Arzilli et al. Magma fragmentation in highly explosive basaltic eruptions induced by rapid crystallization, Nature Geoscience (2019). DOI: 10.1038/s41561-019-0468-6
Ampyx priscus in linear formation (Moroccan Lower Ordovician Fezouata Shale). Credit: Jean Vannier, Laboratoire de Geologie de Lyon: Terre, Planètes, Environnement (CNRS / ENS de Lyon / Université Claude Bernard Lyon 1)
Ever felt like you’ve been queuing forever?
Scientists say fossils found in Morocco suggest the practice of forming orderly lines may date back 480 million years and could have had evolutionary advantages.
Their study, published Thursday in the journal Scientific Reports, describes groups of blind trilobites—known as Ampyx—all facing in the same direction, apparently maintaining contact via their long rearward spines.
The researchers from France, Switzerland and Morocco analyzed the fossils and concluded that the tiny trilobites, which look similar to modern horseshoe crabs, probably intentionally formed a queue as they swarmed along the prehistoric sea floor.
“Given the scale of the patterns seen, this consistent linearity and directionality is unlikely to be the result of passive transportation or accumulation by currents,” they said.
Jean Vannier, a researcher at the University of Lyon, France, who co-authored the study, said possible reasons for this group behavior include environmental stresses or reproduction.
Similar behavior is also found in modern-day members of the extended family of arthropods that trilobites belonged to, such as caterpillars, ants and lobsters, who band together for protection or to find mates.
“Living and moving in groups seems to have rapidly represented an evolutionary advantage among ancient animals,” Vannier said.
Lucy McCobb, a paleontologist at the National Museum Wales who wasn’t involved in the study, said that while similar ‘conga lines’ of fossilized Ampyx have been reported before, the researchers behind the study had built “a very strong case for the intentional lining up of the trilobites in response to some cue.”
“These fossils give us a wonderfully vivid glimpse into the lives of these very ancient but clearly sophisticated creatures,” she said.
Vannier said the findings support the idea that collective behavior like forming lines emerged around the same time or shortly after animals first developed sophisticated nervous systems and sensory organs. He and fellow researchers said re-examining 520 million-year-old fossils of shrimp-like creatures found in China could offer evidence that such behavior began even earlier.
