This is an illustration of the Guadalupian extinction. Credit: Wits University
An international team led by researchers from the Evolutionary Studies Institute (ESI) at the University of the Witwatersrand, Johannesburg, has obtained an age from rocks of the Great Karoo that shed light on the timing of a mass extinction event that occurred around 260 million years ago.
This led to the disappearance of a diverse group of early mammal-like reptiles called dinocephalians, which were the largest land-living animals of the time.
The project was led by Dr Michael Day, a postdoctoral fellow at Wits University, and the findings are contained in paper, titled: When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa, published today, 8 July 2015, in the latest issue of the Royal Society’s biological journal, Proceedings of the Royal Society B.
The Karoo is very rich in fossils of terrestrial animals from the Permian and Triassic geological periods, which makes it one of the few places to study extinction events on land during this time. As a result South Africa’s Karoo region provides not only a historical record of biological change over a period of Earth’s history but also a means to test theories of evolutionary processes over long stretches of time.
By collecting fossils in the Eastern, Western and Northern Cape Provinces the team was able to show that around 74-80% of species became extinct along with the dinocephalians in a geologically short period of time.
The new date was obtained by high precision analyses of the relative abundance of uranium and lead in small zircon crystals from a volcanic ash layer close to this extinction horizon in the Karoo.
This provides a means of linking the South African fossil record with the fossil record in the rest of the world. In particular, it helps correlate the Karoo with the global marine record, which also records an extinction event around 260 million years ago.
“A mid-Permian extinction event on land has been known for some time but was suspected to have occurred earlier than those in the marine realm. The new date suggests that one event may have affected marine and terrestrial environments at the same time, which could mean its impact was greater than we thought,” says Day.
The mid-Permian extinction occurred near the end of what geologists call the Guadalupian epoch that extended from 272.3 to around 259.1 million years ago. It pre-dated the massive and much more famous end-Permian mass extinction event by 8 million years.
“The South African Karoo rocks host the richest record of middle Permian land-living vertebrate animals. This dataset, the culmination of 30 years of fossil collecting and diligent stratigraphic recording of the information, for the first time provides robust fossil and radioisotopic data to support the occurrence of this extinction event on land,” says Day.
“The exact age of the marine extinctions remains uncertain,” says Jahandar Ramezani of Massachusetts Institute of Technology and who was responsible for dating the rocks, “but this new date from terrestrial deposits of the Karoo, supported by palaeontological evidence, represents an important step towards a better understanding of the mid-Permian extinction and its effect on terrestrial faunas.”
Reference:
Michael O. Day, Jahandar Ramezani, Samuel A. Bowring, Peter M. Sadler, Douglas H. Erwin, Fernando Abdala, Bruce S. Rubidge. When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa. Proceedings of the Royal Society B, 2015 DOI: 10.1098/rspb.2015.0834
A marrellomorph arthropod, probably belonging to the genus Furca. c. Credit: Peter Van Roy
Some of the oldest marine animals on the planet, including armoured worm-like forms and giant, lobster like sea creatures, survived millions of years longer than previously thought, according to a spectacularly preserved fossil formation from southeastern Morocco.
The Lower Fezouata formation has been revealing exciting discoveries about life in the Ordovician — around 485 — 444 million years ago — since its discovery just five years ago.
‘The Fezouata is extraordinarily significant’ says Professor Derek Briggs of Yale University, co-author of a study published today in the Journal of the Geological Society. ‘Animals typical of the Cambrian are still present in rocks 20 million years younger, which means there must be a cryptic record in between, which is not preserved.’
Over 160 genera have already been documented from the Fezouata, with much more expected to be found. They include animals which would have looked perfectly at home during the Cambrian: armoured lobopodians — worm like creatures with spines on their backs and short, stubby legs, and anomalocaridids — huge segmented animals with remarkable feeding limbs, which are some of the largest marine creatures of the time.
As well as demonstrating the longevity of fauna thought to have been extinct millions of years previously, the Fezouata proves that other creatures evolved far earlier than previously thought.
‘Horseshoe crabs, for example, turn out to be at least 20 million years older than we thought. The formation demonstrates how important exceptionally preserved fossils are to our understanding of major evolutionary events in deep time’ says Peter Van Roy, also of Yale, who first recognised the scientific importance of the Fezouata fauna and is lead author of the study, part of a project funded by the National Science Foundation.
The spectacular preservation, which includes detailed soft parts and organisms over 2 metres in length, is thanks to the fine grained, muddy sediments in which the organisms were preserved.
‘These are special rocks’ says Professor Briggs. ‘Some of the organisms are enormous — several metres in length. With such exceptional preservation, in a fully marine exposure, we can develop a reasonably full picture of what marine life looked like in the Ordovician.’
The discoveries suggest the ‘Great Ordovician Biodiversification Event’ — an explosion in diversity throughout the earlier part of the Ordovician period — may have been a continuation of the Cambrian explosion.
‘There is much more to learn from the Fezouata’ says Professor Briggs. ‘Why do we not see more assemblages like this in the Ordovician? What ecological changes happened at the Cambro-Ordovician interval? Are the Cambrian Explosion and the Great Ordovician Biodiversification Event separate, or phases of the same event?’
The paper, published online today, marks the start of a themed series of ‘Review focus’ articles for the Journal of the Geological Society, centring on sites of exceptional fossil preservation spanning Earth’s history. All papers in the series will be available for free download, and further ‘Review focus’ themes are planned.
‘The purpose of these articles is to present a distilled, forward looking review of a topic’, says the series editor Professor Philip Donoghue. ‘We decided to start with a thematic series on fossil Lagerstätten since these deposits are fundamental archives of evolutionary history.’
‘By making the papers freely available, it is hoped they will interest a wide range of readers, from undergraduates, to specialists in the field, to members of the public.’
Reference:
Van Roy, P., Briggs, D.E.G. & Gaines R.R. The Fezouata fossils of Morocco; an extraordinary record of marine life in the Early Ordovician. Journal of the Geological Society, July 8, 2015 DOI: 10.1144/jgs2015-017
This is a photograph of the geological section across the Matuyama-Brunhes boundary in Chiba Prefecture, Japan. (a) Overview of the Chiba section. (b) and (c) Detail of a volcanic ash layer (Byk-E) just below the MBB in the Chiba section. The length of the ruler (b) and diameter of the coin (c) are 1.25 m and 2 cm, respectively. Credit: NIPR/Ibaraki University/JAMSTEC
Earth’s magnetic field periodically reverses such that the north magnetic pole becomes the south magnetic pole. The latest reversal is called by geologists the Matuyama-Brunhes boundary (MBB), and occurred approximately 780,000 years ago. The MBB is extremely important for calibrating the ages of rocks and the timing of events that occurred in the geological past; however, the exact age of this event has been imprecise because of uncertainties in the dating methods that have been used.
A team of researchers based in Japan and Canada have obtained an improved age for the MBB. The team studied volcanic ash that was deposited immediately before the MBB. This volcanic ash contains small crystals called zircons. Some of these crystals formed at the same time as the ash; thus, radiometric dating of these zircons using the uranium-lead method provided the exact age of the ash. To verify their findings, the researchers also used a different method to date sedimentary rock from the same place that was formed at the time of the MBB. The combined results demonstrate that the age of the MBB is 770.2 ± 7.3 thousand years ago. The research has been published in the journal Geology.
Dr. Yusuke Suganuma of the National Institute of Polar Research, Tokyo, who is the lead author on the paper, commented: “This study is the first direct comparison of radiometric dating, dating of sediments, and the geomagnetic reversal for the Matuyama-Brunhes boundary. Our work contributes calibrating the geological time scale, and will be extremely important in future studies of the events that occurred at this time.”
Reference:
Y. Suganuma, M. Okada, K. Horie, H. Kaiden, M. Takehara, R. Senda, J.-I. Kimura, K. Kawamura, Y. Haneda, O. Kazaoka, M. J. Head. Age of Matuyama-Brunhes boundary constrained by U-Pb zircon dating of a widespread tephra. Geology, 2015; 43 (6): 491 DOI: 10.1130/G36625.1
Although global concentration of greenhouse gases in the atmosphere has continuously increased over the past decade, the mean global surface temperature has not followed the same path. A team of international reseachers, KIT scientists among them, have now found an explanation for this slowing down in global warming: the incoming solar radiation in the years 2008-2011 was twice as much reflected by volcanic aerosol particles in the lowest part of the stratosphere than previously thought. The team presents their study in Nature Communications.
For the lowest part of the stratosphere – i. e. the layer between 10 and 16 kilometres – little information was available so far, but now the international IAGOS-CARIBIC climate project combined with satellite observations from the CALIPSO lidar provided new essential information. According to the study, the cooling effect due to volcanic eruptions was clearly underestimated by climate models used for the last Intergovernmental Panel on Climate Change (IPCC) report. Led by the University of Lund, Sweden, and supported by the NASA Langley Research Center, USA, and the Royal Netherlands Meteorological Institute, three major German atmospheric research institutes were also involved: the Max Planck Institute for Chemistry in Mainz (MPI-C), the Leibniz Institute for Tropospheric Research in Leipzig (TROPOS) and the Karlsruhe Institute of Technology (KIT). Since more frequent volcanic eruptions and the subsequent cooling effect are only temporary the rise of Earths’ temperature will speed up again. The reason is the still continuously increasing greenhouse gas concentration, the scientists say.
In the first decade of the 21st century the average surface temperature over the northern mid-latitude continents did increase only slightly. This effect can be now explained by the new study on volcanic aerosol particles in the atmosphere reported here. The study uses data from the tropopause region up to 35 km altitude, where the former is found between 8 km (poles) and 17 km (equator) altitude. The tropopause region is a transition layer between the underlying wet weather layer with its clouds (troposphere) and the dry and cloud-free layer above (stratosphere). “Overall our results emphasize that even smaller volcanic eruptions are more important for the Earth´s climate than expected”, summarize CARIBIC coordinators Dr. Carl Brenninkmeijer, MPI-C, and Dr. Andreas Zahn, KIT. The IAGOS-CARIBIC observatory was coordinated and operated by the MPI-C until the end of 2014, since then by the KIT.
To collect their data the team combined two different experimental approaches: sampling and in situ measurements made by IAGOS-CARIBIC together with observations from the CALIPSO satellite. In the IAGOS-CARIBIC observatory trace gases and aerosol particles in the tropopause region are measured since 1997. A modified air-freight container is loaded once per month for four intercontinental flights into a modified Airbus A340-600 of Lufthansa. Altogether about 100 trace gas and aerosol parameters are measured in situ at 9-12 km altitude as well as in dedicated European research laboratories after flight. TROPOS in Leipzig is responsible for the in situ aerosol particle measurements in this unique project. KIT runs 5 of the 15 installed instruments, also the one for ozone. Collected particles are analyzed at the University of Lund, Sweden, using an ion beam accelerator for measuring the amount of particulate sulfur. When comparing this particulate sulfur concentration to the in situ measured ozone concentration this ratio is usually quite constant at cruise altitude. However, volcanic eruptions increase the amount of particulate sulfur and thus the ratio becomes an indicator of volcanic eruption influencing the tropopause region. “The ratio of particulate sulfur to ozone from the CARIBIC measurements clearly demonstrates the strong influence from volcanism on the tropopause region”, report Dr. Sandra M. Andersson and Professor Bengt G. Martinsson of the University of Lund, who are the lead authors.
The second method is based on satellite observations. The Cloud-Aerosol Lidar and Pathfinder Satellite Observation (CALIPSO) mission, a collaboration between the National Aeronautics and Space Administration (NASA) in the US and the Centre National d’Etude Spatiale (CNES) in France, has provided unprecedented view on aerosol and cloud layers in the atmosphere. Until recently, the data had only been scrutinized above 15 km, namely where volcanic aerosol are known to affect our climate for a long time. Now also aeorosol particles of the lowermost stratosphere have been taken into account for calculating the radiative balance of the atmosphere, to evaluate the impact of smaller volcanic eruptions on the climate.
The influence from volcanic eruptions on the stratosphere was small in the northern hemisphere between 1999 and 2002. However, strong signals of volcanic aerosol particles were observed between 2005 and 2012. In particular three eruptions stand out: the Kasatochi in August 2008 (USA), the Sarychev in June 2009 (Russia), and the Nabro in June 2011 (Eritrea). Each of the three eruptions injected more than one megaton sulfur dioxide (SO2) into the atmosphere. “Virtually all volcanic eruptions reaching the stratosphere lead to more particles there, as they bring in sulfur dioxide, which is converted to sulfate particles”, explains Dr. Markus Hermann of TROPOS, who conducts the in situ particle measurements in CARIBIC.
Whether a volcanic eruption has a global climate impact or not depends on several factors. There is the amount of volcanic sulfur dioxide as well as the injection height. But also the latitude of the eruption is important: As the air flow in northern hemispheric stratosphere is largely disconnected from the southern hemisphere, only volcanic eruptions near the equator can effectively distribute the emitted material over both hemispheres. As in the Tambora eruption on the Indonesian Island Sumbawa 200 years ago. This eruption led to such a strong global cooling that the year 1816 was called “year without summer”, including worldwide crop failures and famines. Also the Krakatau eruption 1883 on Indonesia or the Pinatubo 1991 on the Philippines led to noticeable cooling. The present study now indicates that “the cooling effect of volcanic eruptions was underestimated in the past, because the lowest part of the stratosphere was mostly not considered. Interestingly our results show that the effect also depends on the season. The eruptions investigated by us had their strongest impact in late summer when the incoming solar radiation is still strong”, explains Dr. Sandra M. Andersson.
Reference:
“Significant radiative impact of volcanic aerosol in the lowermost stratosphere.” Nature Communications, DOI: 10.1038/ncomms8692
The tiny fossil sponge was just 1.2 millimeters in width, seen here in a high-resolution scanning electron microscope image. Credit: Zongjun Yin/Nanjing Institute of Geology and Palaeontology
Researchers have unearthed a fossil of a sponge, no bigger than a grain of sand, that existed 60 million years earlier than many expected.
This is the first time paleontologists have found a convincing fossil sponge specimen that predates the Cambrian explosion—a 20-million-year phenomenon, beginning about 542 million years ago, when most major types of animal life appear.
New tools could allow scientists to discover other fossils that significantly predate the start of the Cambrian explosion, according to David Bottjer, professor of earth sciences, biological sciences and environmental studies and co-author of a study announcing the finding of the sponge in the Proceedings of the National Academy of Sciences.
“It’s easier to look at large fossils that don’t require high-tech instruments,” Bottjer said. “We’re analyzing very tiny things that require sophisticated microscopy, and we’re really just starting to look at this kind of evidence.”
Though some evidence, including molecular clocks, has already pointed to sponges evolving earlier, this fossil shows that the Cambrian explosion might not be a period when a large number of new traits emerged, but a period when a large number of fossils could be preserved, as animals during the Cambrian grew larger and gained skeletons.
“This specimen is of an animal that had already evolved a number of fundamental sponge traits,” Bottjer said. “It implies that by the time this animal was living, most of the developmental genes for sponges had evolved.”
This raises the possibility that some aspects of early animals’ evolution, a good deal of which happened during the Cambrian explosion, happened even more gradually.
With an international team of colleagues, Bottjer discovered that the millimeter-wide, 600-million-year-old fossil has characteristics that many thought emerged in sponges only 540 million years ago.
“Fundamental traits in sponges were not suddenly appearing in the Cambrian Period, which is when many think these traits were evolving, but many million years earlier,” Bottjer said. “To reveal these types of findings, you have to use pretty high-tech approaches and work with the best people around the world.”
Very old rocks
Since 1999, Bottjer has worked with a team of researchers from the Nanjing Institute of Geology and Palaeontology (Chinese Academy of Sciences) and the California Institute of Technology, as well as the European Synchrotron Radiation Facility in Grenoble, France.
Team members in China dissolved several 600 million-year-old rocks, which are regularly mined for Chinese agricultural fertilizer from the Doushantuo rock formation in southwestern China’s Guizhou Province. They then used a gentle acid bath to reveal tiny fossils made of calcium phosphate and a Scanning Electron Microscope (SEM) to determine which of those fossils were preserved well enough to merit analysis with the synchrotron.
“The preservation in these Doushantuo rocks is extremely fine—and you can even see individual cells with the SEM,” Bottjer said. “Once a specimen worthy of further study is found, synchrotron microscopy is used to create very, very detailed images of the fossil in two and three dimensions. From these images we are then able to see what types of animals these fossils represent.”
Future study lies in the relatively new field of paleogenomics, which analyzes the evolutionary history of genes to determine when individual genes first appeared. Bottjer said many of the genes operating in sponges 600 million years ago are the same genes that other animals have, including humans.
“These organisms don’t have all the bells and whistles that modern creatures do,” Bottjer said. “But this particular fossil has enough complexity that we can say we hadn’t been dating the early evolution of animal traits properly.”
A) Skull of the therapsid Pristerodon; B) Image obtained from neutron tomographic data. Credit: Image courtesy of the author.
A recent study by means of neutron tomography revealed that some forerunners of mammals were already able to hear airborne sound, because these animals already possessed an eardrum at the lower jaw, an impedance-matching middle ear and a small cochlea.
Most land animals can only hear sound from the air via a specialised area for sound reception – the eardrum. Furthermore, the middle ear consisting of three ear ossicles, the malleus, incus and stapes, amplifies sound impulses from the eardrum, and the cochlea is responsible for transforming a wide range of sound frequencies into nerve impulses for the brain.
In contrast, early land-living tetrapods were originally unable to hear airborne sound, because they evolved from aquatic ancestors. Instead, it seems likely that they could only detect seismic sound from the ground with the mandible, like some modern snakes. Until recently, it was unresolved whether the forerunners of mammals, the therapsids, already possessed an eardrum and an impedance-matching middle ear to hear sound from the air or not.
Interestingly, it was discovered almost 200 years ago that the mammalian ear ossicles are the homologues of the the articular and quadrate, the bones that form the jaw articulation in reptiles and in the forerunners of mammals. In early mammalian evolution, a new jaw articulation evolved and these bones were separated from the skull and the mandible and only served for hearing. Therefore, it was uncertain if therapsids were already able to hear airborne sound. If so, their massive jaw articulation must have had a dual function – to withstand the forces from feeding and to conduct weak sound impulses to the inner ear.
To shed light on this problem, Michael Laaß from the University of Duisburg-Essen investigated a ca. 260 million years old skull of the therapsid Pristerodon from the Karoo Basin of South Africa by means of neutron tomography. The experiments were conducted at the Swiss spallation neutron source SINQ, Paul Scherrer Institute in Switzerland, and were supported through the NMI3 Access Programme.
As stated by Laaß “Neutron tomography was well suited to investigate the skull because neutrons were able to penetrate this fossil very well and produce a good contrast between the fossil bones and the matrix.” This investigation revealed the earliest evidence of a cochlea in a far relative of mammals. Moreover, it was possible to reconstruct the ear virtually in 3D and to reconstruct the function of the middle ear. Interestingly, the latter was able to amplify sound and to conduct weak sound impulses from the mandible to the inner ear if the jaw musculature was relaxed.
Furthermore, the postcranial anatomy of Pristerodon suggests that this animal already had a more upright posture than other therapsids. As a consequence, the lower jaw was usually not in contact with the ground and hearing of seismic sound was impossible. This might be the reason why Pristerodon evolved an airborne-sound-sensitive ear, because this was necessary to detect predators or to communicate with conspecifics.
Reference:
Laaß, Michael. 2015. “The origins of the cochlea and impedance matching hearing in synapsids.” Acta Palaeontologica Polonica. DOI: 10.4202/app.00140.2014
A rare earth element (REE) or rare earth metal (REM), as defined by IUPAC, is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Scandium and yttrium are considered rare earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties.
Despite their name, rare earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth’s crust, with cerium being the 25th most abundant element at 68 parts per million, or as abundant as copper. However, because of their geochemical properties, rare earth elements are typically dispersed and not often found concentrated as rare earth minerals in economically exploitable ore deposits. It was the very scarcity of these minerals (previously called “earths”) that led to the term “rare earth”. The first such mineral discovered was gadolinite, a mineral composed of cerium, yttrium, iron, silicon and other elements. This mineral was extracted from a mine in the village of Ytterby in Sweden; four of the rare earth elements bear names derived from this single location.
Discovery and early history
Rare earth elements became known to the world with the discovery of the black mineral “Ytterbite” (renamed to Gadolinite in 1800) by Lieutenant Carl Axel Arrhenius in 1787, at a quarry in the village of Ytterby, Sweden.
Arrhenius’s “ytterbite” reached Johan Gadolin, a Royal Academy of Turku professor, and his analysis yielded an unknown oxide (earth) that he called yttria. Anders Gustav Ekeberg isolated beryllium from the gadolinite but failed to recognize other elements that the ore contained. After this discovery in 1794 a mineral from Bastnäs near Riddarhyttan, Sweden, which was believed to be an iron–tungsten mineral, was re-examined by Jöns Jacob Berzelius and Wilhelm Hisinger. In 1803 they obtained a white oxide and called it ceria. Martin Heinrich Klaproth independently discovered the same oxide and called it ochroia.
Thus by 1803 there were two known rare earth elements, yttrium and cerium, although it took another 30 years for researchers to determine that other elements were contained in the two ores ceria and yttria (the similarity of the rare earth metals’ chemical properties made their separation difficult).
In 1839 Carl Gustav Mosander, an assistant of Berzelius, separated ceria by heating the nitrate and dissolving the product in nitric acid. He called the oxide of the soluble salt lanthana. It took him three more years to separate the lanthana further into didymia and pure lanthana. Didymia, although not further separable by Mosander’s techniques, was a mixture of oxides.
In 1842 Mosander also separated the yttria into three oxides: pure yttria, terbia and erbia (all the names are derived from the town name “Ytterby”). The earth giving pink salts he called terbium; the one that yielded yellow peroxide he called erbium.
So in 1842 the number of known rare earth elements had reached six: yttrium, cerium, lanthanum, didymium, erbium and terbium.
Nils Johan Berlin and Marc Delafontaine tried also to separate the crude yttria and found the same substances that Mosander obtained, but Berlin named (1860) the substance giving pink salts erbium and Delafontaine named the substance with the yellow peroxide terbium. This confusion led to several false claims of new elements, such as the mosandrium of J. Lawrence Smith, or the philippium and decipium of Delafontaine.
Origin
Rare earth elements, except scandium, are heavier than iron and thus are produced by supernova nucleosynthesis or the s-process in asymptotic giant branch stars. In nature, spontaneous fission of uranium-238 produces trace amounts of radioactive promethium, but most promethium is synthetically produced in nuclear reactors.
Rare earth elements change through time in small quantities (ppm, parts per million), so their proportion can be used for geochronology and dating fossils.
Geological distribution
Rare earth cerium is actually the 25th most abundant element in Earth’s crust, having 68 parts per million (about as common as copper). Only the highly unstable and radioactive promethium “rare earth” is quite scarce.
The rare earth elements are often found together. The longest-lived isotope of promethium has a half life of 17.7 years, so the element exists in nature in only negligible amounts (approximately 572 g in the entire Earth’s crust). Promethium is one of the two elements that do not have stable (non-radioactive) isotopes and are followed by (i.e. with higher atomic number) stable elements (the other being technetium).
Due to lanthanide contraction, yttrium, which is trivalent, is of similar ionic size as dysprosium and its lanthanide neighbors. Due to the relatively gradual decrease in ionic size with increasing atomic number, the rare earth elements have always been difficult to separate. Even with eons of geological time, geochemical separation of the lanthanides has only rarely progressed much farther than a broad separation between light versus heavy lanthanides, otherwise known as the cerium and yttrium earths. This geochemical divide is reflected in the first two rare earths that were discovered, yttria in 1794 and ceria in 1803. As originally found, each comprised the entire mixture of the associated earths. Rare earth minerals, as found, usually are dominated by one group or the other, depending on which size range best fits the structural lattice.
Thus, among the anhydrous rare earth phosphates, it is the tetragonal mineral xenotime that incorporates yttrium and the yttrium earths, whereas the monoclinic monazite phase incorporates cerium and the cerium earths preferentially. The smaller size of the yttrium group allows it a greater solid solubility in the rock-forming minerals that comprise Earth’s mantle, and thus yttrium and the yttrium earths show less enrichment in Earth’s crust relative to chondritic abundance, than does cerium and the cerium earths. This has economic consequences: large ore bodies of the cerium earths are known around the world, and are being exploited. Corresponding orebodies for yttrium tend to be rarer, smaller, and less concentrated. Most of the current supply of yttrium originates in the “ion absorption clay” ores of Southern China. Some versions provide concentrates containing about 65% yttrium oxide, with the heavy lanthanides being present in ratios reflecting the Oddo-Harkins rule: even-numbered heavy lanthanides at abundances of about 5% each, and odd-numbered lanthanides at abundances of about 1% each. Similar compositions are found in xenotime or gadolinite.
Well-known minerals containing yttrium include gadolinite, xenotime, samarskite, euxenite, fergusonite, yttrotantalite, yttrotungstite, yttrofluorite (a variety of fluorite), thalenite, yttrialite. Small amounts occur in zircon, which derives its typical yellow fluorescence from some of the accompanying heavy lanthanides. The zirconium mineral eudialyte, such as is found in southern Greenland, contains small but potentially useful amounts of yttrium. Of the above yttrium minerals, most played a part in providing research quantities of lanthanides during the discovery days. Xenotime is occasionally recovered as a byproduct of heavy sand processing, but is not as abundant as the similarly recovered monazite (which typically contains a few percent of yttrium). Uranium ores from Ontario have occasionally yielded yttrium as a byproduct.
Well-known minerals containing cerium and the light lanthanides include bastnäsite, monazite, allanite, loparite, ancylite, parisite, lanthanite, chevkinite, cerite, stillwellite, britholite, fluocerite, and cerianite. Monazite (marine sands from Brazil, India, or Australia; rock from South Africa), bastnäsite (from Mountain Pass, California, or several localities in China), and loparite (Kola Peninsula, Russia) have been the principal ores of cerium and the light lanthanides.
In 2011, Yasuhiro Kato, a geologist at the University of Tokyo who led a study of Pacific Ocean seabed mud, published results indicating the mud could hold rich concentrations of rare earth minerals. The deposits, studied at 78 sites, came from “[h]ot plumes from hydrothermal vents pull[ing] these materials out of seawater and deposit[ing] them on the seafloor, bit by bit, over tens of millions of years. One square patch of metal-rich mud 2.3 kilometers wide might contain enough rare earths to meet most of the global demand for a year, Japanese geologists report July 3 in Nature Geoscience.” “I believe that rare earth resources undersea are much more promising than on-land resources,” said Kato. “[C]oncentrations of rare earths were comparable to those found in clays mined in China. Some deposits contained twice as much heavy rare earths such as dysprosium, a component of magnets in hybrid car motors.”
Global rare earth production
Until 1948, most of the world’s rare earths were sourced from placer sand deposits in India and Brazil. Through the 1950s, South Africa took the status as the world’s rare earth source, after large veins of rare earth bearing monazite were discovered there. Through the 1960s until the 1980s, the Mountain Pass rare earth mine in California was the leading producer. Today, the Indian and South African deposits still produce some rare earth concentrates, but they are dwarfed by the scale of Chinese production. In 2010, China produced over 95% of the world’s rare earth supply, mostly in Inner Mongolia, although it had only 37% of proven reserves; the latter number has been reported to be only 23% in 2012. All of the world’s heavy rare earths (such as dysprosium) come from Chinese rare earth sources such as the polymetallic Bayan Obo deposit. In 2010, the United States Geological Survey (USGS) released a study that found that the United States had 13 million metric tons of rare earth elements.
New demand has recently strained supply, and there is growing concern that the world may soon face a shortage of the rare earths. In several years from 2009 worldwide demand for rare earth elements is expected to exceed supply by 40,000 tonnes annually unless major new sources are developed.
Global rare earth element production from 1950 through 2000, colored to indicate source. (1 kt=106 kg) Credit: BMacZero
Rare earth pricing
Rare earth elements are not exchange-traded in the same way that precious (for instance, gold and silver) or non-ferrous metals (such as nickel, tin, copper, and aluminium) are. Instead they are sold on the private market, which makes their prices difficult to monitor and track. The 17 elements are not usually sold in their pure form, but instead are distributed in mixtures of varying purity, e.g. “Neodymium metal ≥ 99%”. As such, pricing can vary based on the quantity and quality required by the end user’s application.
Oil sands, Tar sands or, more technically, bituminous sands, are a type of unconventional petroleum deposit.
Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of sand, clay, and water, saturated with a dense and extremely viscous form of petroleum technically referred to as bitumen (or colloquially tar due to its similar appearance, odour, and colour). Natural bitumen deposits are reported in many countries, but in particular are found in extremely large quantities in Canada. Other large reserves are located in Kazakhstan and Russia. The estimated worldwide deposits of oil are more than 2 trillion barrels (320 billion cubic metres); the estimates include deposits that have not been discovered. Proven reserves of bitumen contain approximately 100 billion barrels, and total natural bitumen reserves are estimated at 249.67 Gbbl (39.694×109 m3) worldwide, of which 176.8 Gbbl (28.11×109 m3), or 70.8%, are in Alberta, Canada.
Oil sands reserves have only recently been considered to be part of the world’s oil reserves, as higher oil prices and new technology enable profitable extraction and processing. Oil produced from bitumen sands is often referred to as unconventional oil or crude bitumen, to distinguish it from liquid hydrocarbons produced from traditional oil wells.
The crude bitumen contained in the Canadian oil sands is described by the National Energy Board of Canada as “a highly viscous mixture of hydrocarbons heavier than pentanes which, in its natural state, is not usually recoverable at a commercial rate through a well because it is too thick to flow.” Crude bitumen is a thick, sticky form of crude oil, so heavy and viscous (thick) that it will not flow unless heated or diluted with lighter hydrocarbons such as light crude oil or natural-gas condensate. At room temperature, it is much like cold molasses. The World Energy Council (WEC) defines natural bitumen as “oil having a viscosity greater than 10,000 centipoise under reservoir conditions and an API gravity of less than 10° API”. The Orinoco Belt in Venezuela is sometimes described as oil sands, but these deposits are non-bituminous, falling instead into the category of heavy or extra-heavy oil due to their lower viscosity. Natural bitumen and extra-heavy oil differ in the degree by which they have been degraded from the original conventional oils by bacteria. According to the WEC, extra-heavy oil has “a gravity of less than 10° API and a reservoir viscosity of no more than 10,000 centipoise”.
Tar sandstone from the Monterey Formation of Miocene age (10 to 12 million years old), of southern California, USA. Credit: James St. John
According to the study ordered by the Government of Alberta and conducted by Jacobs Engineering Group, emissions from oil-sand crude are 12% higher than from conventional oil.
History
The exploitation of bituminous deposits and seeps dates back to Paleolithic times. The earliest known use of bitumen was by Neanderthals, some 40,000 years ago. Bitumen has been found adhering to stone tools used by Neanderthals at sites in Syria. After the arrival of Homo sapiens, humans used bitumen for construction of buildings and waterproofing of reed boats, among other uses. In ancient Egypt, the use of bitumen was important in preparing Egyptian mummies.
In ancient times, bitumen was primarily a Mesopotamian commodity used by the Sumerians and Babylonians, although it was also found in the Levant and Persia. The area along the Tigris and Euphrates rivers was littered with hundreds of pure bitumen seepages. The Mesopotamians used the bitumen for waterproofing boats and buildings. In Europe, they were extensively mined near the French city of Pechelbronn, where the vapour separation process was in use in 1742.
Nomenclature
The name tar sands was applied to bituminous sands in the late 19th and early 20th century. People who saw the bituminous sands during this period were familiar with the large amounts of tar residue produced in urban areas as a by-product of the manufacture of coal gas for urban heating and lighting. The word “tar” to describe these natural bitumen deposits is really a misnomer, since, chemically speaking, tar is a human-made substance produced by the destructive distillation of organic material, usually coal.
Since then, coal gas has almost completely been replaced by natural gas as a fuel, and coal tar as a material for paving roads has been replaced by the petroleum product asphalt. Naturally occurring bitumen is chemically more similar to asphalt than to coal tar, and the term oil sands (or oilsands) is more commonly used by industry in the producing areas than tar sands because synthetic oil is manufactured from the bitumen, and due to the feeling that the terminology of tar sands is less politically acceptable to the public. Oil sands are now an alternative to conventional crude oil.
Early explorers
In Canada, the First Nation peoples had used bitumen from seeps along the Athabasca and Clearwater Rivers to waterproof their birch bark canoes from early prehistoric times. The Canadian oil sands first became known to Europeans in 1719 when a Cree native named Wa-Pa-Su brought a sample to Hudsons Bay Company fur trader Henry Kelsey, who commented on it in his journals. Fur trader Peter Pond paddled down the Clearwater River to Athabasca in 1778, saw the deposits and wrote of “springs of bitumen that flow along the ground.” In 1787, fur trader and explorer Alexander MacKenzie on his way to the Arctic Ocean saw the Athabasca oil sands, and commented, “At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance.”
Geology
The world’s largest oil sands are in Venezuela and Canada. The geology of the deposits in the two countries is generally rather similar. They are vast heavy oil, extra-heavy oil, and/or bitumen deposits with oil heavier than 20°API, found largely in unconsolidated sandstones with similar properties. “Unconsolidated” in this context means that the sands have high porosity, no significant cohesion, and a tensile strength close to zero. The sands are saturated with oil which has prevented them from consolidating into hard sandstone.
Major deposits
There are numerous deposits of oil sands in the world, but the biggest and most important are in Canada and Venezuela, with lesser deposits in Kazakhstan and Russia. The total volume of non-conventional oil in the oil sands of these countries exceeds the reserves of conventional oil in all other countries combined. Vast deposits of bitumen – over 350 billion cubic metres (2.2 trillion barrels) of oil in place – exist in the Canadian provinces of Alberta and Saskatchewan. If only 30% of this oil could be extracted, it could supply the entire needs of North America for over 100 years. These deposits represent plentiful oil, but not cheap oil. They require advanced technology to extract the oil and transport it to oil refineries.
Most of the Canadian oil sands are in three major deposits in northern Alberta. They are the Athabasca-Wabiskaw oil sands of north northeastern Alberta, the Cold Lake deposits of east northeastern Alberta, and the Peace River deposits of northwestern Alberta. Between them, they cover over 140,000 square kilometres (54,000 sq mi)—an area larger than England—and contain approximately 1.75 Tbbl (280×109 m3) of crude bitumen in them. About 10% of the oil in place, or 173 Gbbl (27.5×109 m3), is estimated by the government of Alberta to be recoverable at current prices, using current technology, which amounts to 97% of Canadian oil reserves and 75% of total North American petroleum reserves. Although the Athabasca deposit is the only one in the world which has areas shallow enough to mine from the surface, all three Alberta areas are suitable for production using in-situ methods, such as cyclic steam stimulation (CSS) and steam assisted gravity drainage (SAGD).
Production
Bituminous sands are a major source of unconventional oil, although only Canada has a large-scale commercial oil sands industry. In 2006, bitumen production in Canada averaged 1.25 Mbbl/d (200,000 m3/d) through 81 oil sands projects. 44% of Canadian oil production in 2007 was from oil sands. This proportion is expected to increase in coming decades as bitumen production grows while conventional oil production declines, although due to the 2008 economic downturn work on new projects has been deferred. Petroleum is not produced from oil sands on a significant level in other countries.
Methods of extraction
Except for a fraction of the extra-heavy oil or bitumen which can be extracted by conventional oil well technology, oil sands must be produced by strip mining or the oil made to flow into wells using sophisticated in-situ techniques. These methods usually use more water and require larger amounts of energy than conventional oil extraction. While much of Canada’s oil sands are being produced using open-pit mining, approximately 90% of Canadian oil sands and all of Venezuela’s oil sands are too far below the surface to use surface mining.
Primary production
Conventional crude oil is normally extracted from the ground by drilling oil wells into a petroleum reservoir, allowing oil to flow into them under natural reservoir pressures, although artificial lift and techniques such as horizontal drilling, water flooding and gas injection are often required to maintain production. When primary production is used in the Venezuelan oil sands, where the extra-heavy oil is about 50 degrees Celsius, the typical oil recovery rates are about 8-12%. Canadian oil sands are much colder and more biodegraded, so bitumen recovery rates are usually only about 5-6%. Historically, primary recovery was used in the more fluid areas of Canadian oil sands. However, it recovered only a small fraction of the oil in place, so it not often used today.
Surface mining
The Athabasca oil sands are the only major oil sands deposits which are shallow enough to surface mine. In the Athabasca sands there are very large amounts of bitumen covered by little overburden, making surface mining the most efficient method of extracting it. The overburden consists of water-laden muskeg (peat bog) over top of clay and barren sand. The oil sands themselves are typically 40 to 60 metres (130 to 200 ft) thick deposits of crude bitumen embedded in unconsolidated sandstone, sitting on top of flat limestone rock. Since Great Canadian Oil Sands (now Suncor Energy) started operation of the first large-scale oil sands mine in 1967, bitumen has been extracted on a commercial scale and the volume has grown at a steady rate ever since.
A large number of oil sands mines are currently in operation and more are in the stages of approval or development. The Syncrude Canada mine was the second to open in 1978, Shell Canada opened its Muskeg River mine (Albian Sands) in 2003 and Canadian Natural Resources Ltd (CNRL) opened its Horizon Oil Sands project in 2009. Newer mines include Shell Canada’s Jackpine mine, Imperial Oil’s Kearl Oil Sands Project, the Synenco Energy (now owned by Total S.A.) Northern Lights mine, and Suncor’s Fort Hills mine.
Oil sands tailings ponds
Oil sands tailings ponds are engineered dam and dyke systems that contain salts, suspended solids and other dissolvable chemical compounds such as acids, benzene, hydrocarbons residual bitumen, fine silts (mature fine tails MFT), and water. Large volumes of tailings are a byproduct of surface mining of the oil sands and managing these tailings is one of the most difficult environmental challenges facing the oil sands industry. The Government of Alberta reported in 2013 that tailings ponds in the Alberta oil sands covered an area of about 77 square kilometres (30 sq mi). The Syncrude Tailings Dam or Mildred Lake Settling Basin (MLSB) is an embankment dam that is, by volume of construction material, the largest earth structure in the world in 2001.
Cold Heavy Oil Production with Sand (CHOPS)
Some years ago Canadian oil companies discovered that if they removed the sand filters from heavy oil wells and produced as much sand as possible with the oil, production rates improved significantly. This technique became known as Cold Heavy Oil Production with Sand (CHOPS). Further research disclosed that pumping out sand opened “wormholes” in the sand formation which allowed more oil to reach the wellbore. The advantage of this method is better production rates and recovery (around 10% versus 5-6% with sand filters in place) and the disadvantage that disposing of the produced sand is a problem. A novel way to do this was spreading it on rural roads, which rural governments liked because the oily sand reduced dust and the oil companies did their road maintenance for them. However, governments have become concerned about the large volume and composition of oil spread on roads. so in recent years disposing of oily sand in underground salt caverns has become more common.
Cyclic Steam Stimulation (CSS)
The use of steam injection to recover heavy oil has been in use in the oil fields of California since the 1950s. The cyclic steam stimulation (CSS) “huff-and-puff” method is now widely used in heavy oil production world-wide due to its quick early production rates; however recovery factors are relatively low (10-40% of oil in place) compared to SAGD (60-70% of OIP).
CSS has been in use by Imperial Oil at Cold Lake since 1985 and is also used by Canadian Natural Resources at Primrose and Wolf Lake and by Shell Canada at Peace River. In this method, the well is put through cycles of steam injection, soak, and oil production. First, steam is injected into a well at a temperature of 300 to 340 degrees Celsius for a period of weeks to months; then, the well is allowed to sit for days to weeks to allow heat to soak into the formation; and, later, the hot oil is pumped out of the well for a period of weeks or months. Once the production rate falls off, the well is put through another cycle of injection, soak and production. This process is repeated until the cost of injecting steam becomes higher than the money made from producing oil.
Steam Assisted Gravity Drainage (SAGD)
Steam assisted gravity drainage was developed in the 1980s by the Alberta Oil Sands Technology and Research Authority and fortuitously coincided with improvements in directional drilling technology that made it quick and inexpensive to do by the mid 1990s. In SAGD, two horizontal wells are drilled in the oil sands, one at the bottom of the formation and another about 5 metres above it. These wells are typically drilled in groups off central pads and can extend for miles in all directions. In each well pair, steam is injected into the upper well, the heat melts the bitumen, which allows it to flow into the lower well, where it is pumped to the surface.
SAGD has proved to be a major breakthrough in production technology since it is cheaper than CSS, allows very high oil production rates, and recovers up to 60% of the oil in place. Because of its economic feasibility and applicability to a vast area of oil sands, this method alone quadrupled North American oil reserves and allowed Canada to move to second place in world oil reserves after Saudi Arabia. Most major Canadian oil companies now have SAGD projects in production or under construction in Alberta’s oil sands areas and in Wyoming. Examples include Japan Canada Oil Sands Ltd’s (JACOS) project, Suncor’s Firebag project, Nexen’s Long Lake project, Suncor’s (formerly Petro-Canada’s) MacKay River project, Husky Energy’s Tucker Lake and Sunrise projects, Shell Canada’s Peace River project, Cenovus Energy’s Foster Creek and Christina Lake developments, ConocoPhillips’ Surmont project, Devon Canada’s Jackfish project, and Derek Oil & Gas’s LAK Ranch project. Alberta’s OSUM Corp has combined proven underground mining technology with SAGD to enable higher recovery rates by running wells underground from within the oil sands deposit, thus also reducing energy requirements compared to traditional SAGD. This particular technology application is in its testing phase.
Vapor Extraction (VAPEX)
Several methods use solvents, instead of steam, to separate bitumen from sand. Some solvent extraction methods may work better in in situ production and other in mining. Solvent can be beneficial if it produces more oil while requiring less energy to produce steam.
Vapor Extraction Process (VAPEX) is an in situ technology, similar to SAGD. Instead of steam, hydrocarbon solvents are injected into an upper well to dilute bitumen and enables the diluted bitumen to flow into a lower well. It has the advantage of much better energy efficiency over steam injection, and it does some partial upgrading of bitumen to oil right in the formation. The process has attracted attention from oil companies, who are experimenting with it.
The above methods are not mutually exclusive. It is becoming common for wells to be put through one CSS injection-soak-production cycle to condition the formation prior to going to SAGD production, and companies are experimenting with combining VAPEX with SAGD to improve recovery rates and lower energy costs.
Toe to Heel Air Injection (THAI)
This is a very new and experimental method that combines a vertical air injection well with a horizontal production well. The process ignites oil in the reservoir and creates a vertical wall of fire moving from the “toe” of the horizontal well toward the “heel”, which burns the heavier oil components and upgrades some of the heavy bitumen into lighter oil right in the formation. Historically fireflood projects have not worked out well because of difficulty in controlling the flame front and a propensity to set the producing wells on fire. However, some oil companies feel the THAI method will be more controllable and practical, and have the advantage of not requiring energy to create steam.
Advocates of this method of extraction state that it uses less freshwater, produces 50% less greenhouse gases, and has a smaller footprint than other production techniques.
Petrobank Energy and Resources has reported encouraging results from their test wells in Alberta, with production rates of up to 400 bbl/d (64 m3/d) per well, and the oil upgraded from 8 to 12 API degrees. The company hopes to get a further 7-degree upgrade from its CAPRI (controlled atmospheric pressure resin infusion) system, which pulls the oil through a catalyst lining the lower pipe.
After several years of production in situ, it has become clear that current THAI methods do not work as planned. Amid steady drops in production from their THAI wells at Kerrobert, Petrobank has written down the value of their THAI patents and the reserves at the facility to zero. They have plans to experiment with a new configuration they call “multi-THAI,” involving adding more air injection wells.
Combustion Overhead Gravity Drainage (COGD)
This is an experimental method that employs a number of vertical air injection wells above a horizontal production well located at the base of the bitumen pay zone. An initial Steam Cycle similar to CSS is used to prepare the bitumen for ignition and mobility. Following that cycle, air is injected into the vertical wells, igniting the upper bitumen and mobilizing (through heating) the lower bitumen to flow into the production well. It is expected that COGD will result in water savings of 80% compared to SAGD
Economics
The world’s largest deposits of bitumen are in Canada, although Venezuela’s deposits of extra-heavy crude oil are even bigger. Canada has vast energy resources of all types and its oil and natural gas resource base is large enough to meet Canadian needs for generations. Abundant hydroelectric resources account for the majority of Canada’s electricity production and very little electricity is produced from oil. Since Canada will have more than enough energy to meet its growing needs, the excess oil production from its oil sands will probably go to export. The major importing country will probably continue to be the United States, although there is increasing demand for oil, particularly heavy oil, from growing in Asian countries such as China and India.
Canada has abundant resources of bitumen and crude oil, with an estimated remaining ultimate potential of 54 billion cubic metres (340 billion barrels). Of this, oil sands bitumen accounts for 90 per cent. Alberta currently accounts for all of Canada’s bitumen resources. Resources become reserves only after it is proven that economic recovery can be achieved. At current prices using current technology, Canada has remaining oil reserves of 27 billion m3 (170 billion bbls), with 98 per cent of this attributed to oil sands bitumen. This puts its reserves in third place in the world behind Venezuela and Saudi Arabia.
A University of Tokyo research group has discovered slow-moving low-frequency tremors which occur at the shallow subduction plate boundary in Hyuga-nada, off east Kyushu. This indicates the possibility that the plate boundary in the vicinity of the Nankai Trough is slipping episodically and slowly (over days or weeks) without inducing a strong seismic wave.
It was thought that the shallow part of the plate boundary was completely “uncoupled,” being able to slowly slip relative to the neighboring plate. However, after the 2011 Great East Japan Earthquake, it was discovered that is not entirely correct, and it is very important, in particular in the Nankai Trough, an area in which a major earthquake is expected, to understand the coupling state of the plate boundary. Hyuga-nada is located off east Kyushu in the western part of the Nankai Trough, a highly seismically active area in which M7-class interplate earthquakes occur every few decades, but interplate slip at the shallow plate boundary in this region is insufficiently understood.
A research group comprising Project Researcher Yusuke Yamashita, Assistant Professor Tomoaki Yamada, Professor Masanao Shinohara and Professor Kazushige Obara at the University of Tokyo Earthquake Research Institute and researchers at Kyushu University, Kagoshima University, Nagasaki University, and the National Research Institute for Earth Science and Disaster Prevention, carried out ocean bottom seismological observation using 12 ocean bottom seismometers installed on the seafloor of Hyuga-nada from April to July 2013. The research group discovered migrating (moving) shallow low-frequency tremors which are thought to be triggered by slow episodic slipping (slow slip event) at the shallow plate boundary. The shallow tremors had similar migration properties to deep low-frequency tremors that occur at the deep subducting plate interface, and that they also occurred synchronized in time and space with shallow very-low-frequency tremors that also thought to be triggered by slow slip events. These observations indicate that episodic slow slip events are probably occurring at the shallow plate boundary in the vicinity of the Nankai Trough.
After the 2011 Great East Japan Earthquake, a fundamental review of the shallow plate boundary interface is required. These new findings provide important insight into slip behavior at a shallow plate boundary and will improve understanding and modeling of subduction megathrust earthquakes and tsunamis in the future.
This research was published in the journal Science on May 8, 2015.
Reference:
Y. Yamashita, H. Yakiwara, Y. Asano, H. Shimizu, K. Uchida, S. Hirano, K. Umakoshi, H. Miyamachi, M. Nakamoto, M. Fukui, M. Kamizono, H. Kanehara, T. Yamada, M. Shinohara, K. Obara. Migrating tremor off southern Kyushu as evidence for slow slip of a shallow subduction interface. Science, 2015; 348 (6235): 676 DOI: 10.1126/science.aaa4242
Chinese government researchers are using chickens, fish and toads to try to predict earthquakes, media reports
Chinese government researchers are using chickens, fish and toads to try to predict earthquakes, media reported.
The seismological bureau in the eastern city of Nanjing has transformed seven animal farms into seismic stations, the China Daily newspaper reported last week.
Breeders on the farms are asked to update the bureau about the behaviour of the animals twice a day, the report said.
Possible abnormal behaviour which could indicate imminent earthquakes includes chickens flying atop trees, fish leaping out of water or toads moving in a group, it added.
Nanjing plans to recruit seven more farms into the scheme this year, it said. Facilities need to house more than three species to be eligible.
But some animal keepers seemed reluctant to become involved.
“Our zoo is not being transformed into a monitor station because the animals will display abnormal behaviour when they are teased by visitors,” the report quoted a local zookeeper as saying.
Using animals predict earthquakes is not new in China. State-run media said last year that the central city of Nanchang was using dogs to predict tremors.
China is regularly hit by seismic incidents, with hundreds of thousands killed in major disasters in the past. Three people died in the latest fatal earthquake last week, in the far western region of Xinjiang.
Note: The above post is reprinted from materials provided by AFP.
Ikenna Nlebedim and fellow scientists at the Critical Materials Institute have developed a new recycling method for recovering rare earths from manufacturing waste. Credit: Image courtesy of Ames Laboratory
A new recycling method developed by scientists at the Critical Materials Institute, a U.S. Department of Energy Innovation Hub led by the Ames Laboratory, recovers valuable rare-earth magnetic material from manufacturing waste and creates useful magnets out of it. Efficient waste-recovery methods for rare-earth metals are one way to reduce demand for these limited mined resources.
The process, which inexpensively processes and directly reuses samarium-cobalt waste powders as raw material, can be used to create polymer-bonded magnets that are comparable in performance to commercial bonded magnets made from new materials. It can also be used to make sintered magnets (formed by pressure compaction and heat).
The grinding and cutting processes used to manufacture magnets produces waste metal powders and filings, called swarf. When swarf contains costly rare-earth materials like samarium, neodymium, and dysprosium, materials recovery is important.
Early on, the CMI research team’s goal was to find an efficient method of separating and recovering the rare-earth metals for reuse. But CMI scientist Ikenna Nlebedim said he and co-inventor Bill McCallum wanted to push further. “We decided to see if there is a possibility of reusing the swarf itself for magnet manufacturing,” he said. “We wanted to see if we could save that extra step of metals separation, because it’s not just an extra step, it’s an expensive and time consuming one.”
The initial results of the process produced magnets with a magnetic strength (maximum energy product) of approximately 11 MGOe (megagauss-oersteds), a property that the team believes they can improve by optimizing the process.
“If we can optimize the process, this magnet will fit very well in a performance gap that exists between the non-rare-earth magnets and rare-earth magnets,” Nlebedim said. The product may be a more cost-effective choice for some applications, reducing the need for more expensive neodymium-iron-boron magnets.
Nlebedim said the researchers continue to explore other possibilities for the technology as well, including the production of sintered samarium-cobalt magnets, a material with more economic value than bonded magnets. Nlebedim said the process also accomplishes its original goal of separating rare-earth metals, when necessary.
“I think the beauty of this process is that it has direct value to manufacturers of magnets,” said Nlebedim. “They recover their own swarf directly and recycle it themselves. Because it is not recovered from post-consumer products, manufacturers retain quality control of the composition of their materials and can be confident of the grade of their product. From a profit standpoint, this process is very strategically placed to benefit them.”
This is Nanipora kamurai found in Zamami Island Okinawa, Japan. Credit: Yu Miyazaki; CC-BY 4.0
Research conducted in Okinawa, Japan, by graduate student Yu Miyazaki and associate professor James Davis Reimer from the University of the Ryukyus has found a very unusual new species of octocoral from a shallow coral reef in Okinawa, Japan. The new species can be considered a “living fossil,” and is related in many ways to the unusual blue coral. The study was published in the open access journal ZooKeys.
Unlike scleractinians, most octocorals lack a hard skeleton, and therefore many have the common name “soft coral.” One exception is the endangered genus Heliopora, known as blue coral, which is found in tropical locations in the Pacific Ocean.
Blue coral forms a massive skeleton of aragonite calcium-carbonate. Due to this unique feature, blue corals have long been placed within their own special order inside the octocorals.
This new species, named Nanipora kamurai, also has an aragonite calcium-carbonate skeleton, and molecular analyses show the two groups are most closely related to each other among all octocorals. As fossils show that blue coral and their relatives were globally distributed during the Cretaceous period (XX-XXX mya), Heliopora and this new species can be considered “living fossils.”
In the past, another octocoral species with an aragonite skeleton, Epiphaxum, was discovered in 1977. Since 1977, several recent and fossil Epiphaxum specimens from the deep sea have been recorded. Although this new species seems to be morphologically close to Epiphaxum, it is classified in a separate genus inside the same family (Lithotelestidae) due to many structural differences.
Perhaps most surprisingly, Nanipora kamurai was found from a very shallow coral reef of <1 m depth. “Most living fossils from the ocean seem to come from deeper, more stable environments” stated Miyazaki, “suggesting that there are important discoveries on coral reefs even in shallow areas still awaiting us.”
“The diverse and pristine reefs of Zamami Island, which was recently included in a new national park, need to be investigated even more,” he added.
The discovery of this species undoubtedly will give new insight on octocoral taxonomy.
Reference:
Yu Miyazaki, James D. Reimer. A new genus and species of octocoral with aragonite calcium-carbonate skeleton (Octocorallia, Helioporacea) from Okinawa, Japan. ZooKeys, 2015; 511: 1 DOI: 10.3897/zookeys.511.9432
The brain hidden inside the oldest known Old World monkey skull has been visualized for the first time. The ancient monkey, known as Victoriapithecus, first made headlines in 1997 when its 15 million-year-old skull was discovered on an island in Kenya’s Lake Victoria. Now, thanks to high-resolution X-ray imaging, researchers have peered inside its cranial cavity and created a three-dimensional computer model of what the animal’s brain likely looked like. Its tiny but remarkably wrinkled brain supports the idea that brain complexity can evolve before brain size in the primate family tree. The creature’s fossilized skull is now part of the permanent collection of the National Museums of Kenya in Nairobi. Credit: Photo courtesy of Fred Spoor of the Max Planck Institute for Evolutionary Anthropology
The brain hidden inside the oldest known Old World monkey skull has been visualized for the first time. The creature’s tiny but remarkably wrinkled brain supports the idea that brain complexity can evolve before brain size in the primate family tree.
The ancient monkey, known scientifically as Victoriapithecus, first made headlines in 1997 when its fossilized skull was discovered on an island in Kenya’s Lake Victoria, where it lived 15 million years ago.
Now, thanks to high-resolution X-ray imaging, researchers have peered inside its cranial cavity and created a three-dimensional computer model of what the animal’s brain likely looked like.
Micro-CT scans of the creature’s skull show that Victoriapithecus had a tiny brain relative to its body.
Co-authors Fred Spoor of the Max Planck Institute for Evolutionary Anthropology and Lauren Gonzales of Duke University calculated its brain volume to be about 36 cubic centimeters, which is less than half the volume of monkeys of the same body size living today.
If similar-sized monkeys have brains the size of oranges, the brain of this particular male was more akin to a plum.
“When Lauren finished analyzing the scans she called me and said, ‘You won’t believe what the brain looks like,'” said co-author Brenda Benefit of New Mexico State University, who first discovered the skull with NMSU co-author Monte McCrossin.
Despite its puny proportions, the animal’s brain was surprisingly complex.
The CT scans revealed numerous distinctive wrinkles and folds, and the olfactory bulb — the part of the brain used to perceive and analyze smells — was three times larger than expected.
“It probably had a better sense of smell than many monkeys and apes living today,” Gonzales said. “In living higher primates you find the opposite: the brain is very big, and the olfactory bulb is very small, presumably because as their vision got better their sense of smell got worse.”
“But instead of a tradeoff between smell and sight, Victoriapithecus might have retained both capabilities,” Gonzales said.
The findings, published in the July 3 issue of Nature Communications, are important because they offer new clues to how primate brains changed over time, and during a period from which there are very few fossils.
“This is the oldest skull researchers have found for Old World monkeys, so it’s one of the only clues we have to their early brain evolution,” Benefit said.
In the absence of fossil evidence, previous researchers have disagreed over whether primate brains got bigger first, and then more folded and complex, or vice versa.
“In the part of the primate family tree that includes apes and humans, the thinking is that brains got bigger and then they get more folded and complex,” Gonzales said. “But this study is some of the hardest proof that in monkeys, the order of events was reversed — complexity came first and bigger brains came later.”
The findings also lend support to claims that the small brain of the human ancestor Homo floresiensis, whose 18,000-year-old skull was discovered on a remote Indonesian island in 2003, isn’t as remarkable as it might seem. In spite of their pint-sized brains, Homo floresiensis was able to make fire and use stone tools to kill and butcher large animals.
“Brain size and brain complexity can evolve independently; they don’t have to evolve together at the same time,” Benefit said.
The work was funded by the Max Planck Society and University College London. The skull was originally discovered with support from the National Science foundation (9505778).
Video
Reference:
Lauren A. Gonzales, Brenda R. Benefit, Monte L. McCrossin, Fred Spoor. Cerebral complexity preceded enlarged brain size and reduced olfactory bulbs in Old World monkeys. Nature Communications, 2015; 6: 7580 DOI: 10.1038/ncomms8580
Royal BC Museum in Victoria (Canada) Credit: Flying Puffin
The first comprehensive analysis of the woolly mammoth genome reveals extensive genetic changes that allowed mammoths to adapt to life in the arctic. Mammoth genes that differed from their counterparts in elephants played roles in skin and hair development, fat metabolism, insulin signaling and numerous other traits. Genes linked to physical traits such as skull shape, small ears and short tails were also identified. As a test of function, a mammoth gene involved in temperature sensation was resurrected in the laboratory and its protein product characterized.
The study, published in Cell Reports on July 2, sheds light on the evolutionary biology of these extinct giants.
“This is by far the most comprehensive study to look at the genetic changes that make a woolly mammoth a woolly mammoth,” said study author Vincent Lynch, PhD, assistant professor of human genetics at the University of Chicago. “They are an excellent model to understand how morphological evolution works, because mammoths are so closely related to living elephants, which have none of the traits they had.”
Woolly mammoths last roamed the frigid tundra steppes of northern Asia, Europe and North America roughly 10,000 years ago. Well-studied due to the abundance of skeletons, frozen carcasses and depictions in prehistoric art, woolly mammoths possessed long, coarse fur, a thick layer of subcutaneous fat, small ears and tails and a brown-fat deposit behind the neck which may have functioned similar to a camel hump. Previous efforts to sequence preserved mammoth DNA were error-prone or yielded insights into only a limited number of genes.
To thoroughly characterize mammoth-specific genes and their functions, Lynch and his colleagues deep sequenced the genomes of two woolly mammoths and three Asian elephants — the closest living relative of the mammoth. They then compared these genomes against each other and against the genome of African elephants, a slightly more distant evolutionary cousin to both mammoths and Asian elephants.
The team identified roughly 1.4 million genetic variants unique to woolly mammoths. These caused changes to the proteins produced by around 1,600 genes, including 26 that lost function and one that was duplicated. To infer the functional effects of these differences, they ran multiple computational analyses, including comparisons to massive databases of known gene functions and of mice in which genes are artificially deactivated.
Genes with mammoth-specific changes were most strongly linked to fat metabolism (including brown fat regulation), insulin signaling, skin and hair development (including genes associated with lighter hair color), temperature sensation and circadian clock biology — all of which would have been important for adapting to the extreme cold and dramatic seasonal variations in day length in the Arctic. The team also identified genes associated with the mammoth body plan, such as skull shape, small ears and short tails.
Of particular interest was the group of genes responsible for temperature sensation, which also play roles in hair growth and fat storage. The team used ancestral sequence reconstruction techniques to “resurrect” the mammoth version of one of these genes, TRPV3. When transplanted into human cells in the laboratory, the mammoth TRPV3 gene produced a protein that is less responsive to heat than an ancestral elephant version of the gene. This result is supported by observations in mice that have TRPV3 artificially silenced. These mice prefer colder environments than normal mice and have wavier hair.
Although the functions of these genes match well with the environment in which woolly mammoths were known to live, Lynch warns that it is not direct proof of their effects in live mammoths. The regulation of gene expression, for example, is extremely difficult to study through the genome alone.
“We can’t know with absolute certainty the effects of these genes unless someone resurrects a complete woolly mammoth, but we can try to infer by doing experiments in the laboratory,” he said. Lynch and his colleagues are now identifying candidates for other mammoth genes to functionally test as well as planning experiments to study mammoth proteins in elephant cells.
While his efforts are targeted toward understanding the molecular basis of evolution, Lynch acknowledges that the high-quality sequencing and analysis of woolly mammoth genomes can serve as a functional blueprint for efforts to “de-extinct” the mammoth.
“Eventually we’ll be technically able to do it. But the question is: if you’re technically able to do something, should you do it?” he said. “I personally think no. Mammoths are extinct and the environment in which they lived has changed. There are many animals on the edge of extinction that we should be helping instead.”
Reference:
Vincent J. Lynch, Oscar C. Bedoya-Reina, Aakrosh Ratan, Michael Sulak, Daniela I. Drautz-Moses, George H. Perry, Webb Miller, Stephan C. Schuster. Elephantid Genomes Reveal the Molecular Bases of Woolly Mammoth Adaptations to the Arctic. Cell Reports, 2015 DOI: 10.1016/j.celrep.2015.06.027
Graphic shows how the combination of hill-slope erosion and precipitation-generated runoff over geological time create a landscape of orderly ridges and valleys. Credit: Courtesy of Joshua Roering
University of Oregon geologists have seen ridges and valleys form in real time and — even though the work was a fast-forwarded operation done in a laboratory setting — they now have an idea of how climate change may impact landscapes.
On a basic-science front, the findings, which appear in the July 3 issue of the journal Science, provide a long-sought answer to why some landscape features appear so orderly, with distinct and evenly spaced valleys and ridges.
Picture the Painted Hills near John Day, Oregon, the Colorado Plateau, the badlands of Montana and South Dakota, and even portions of the Coastal Range between Eugene and Florence, Oregon. These watersheds are masterpieces that nature has formed over geological timescales, said the UO’s Joshua J. Roering.
The regularity of hill and valley landforms, he said, is reached after a long tug-of-war between erosion driven by runoff, which influences how rivers cut their paths in valley floors, and soil movement on hillsides caused by disturbances from such things as burrowing gophers, tree roots, digging ants and frost.
The National Science Foundation-funded project (EAR 1252177) is part of a growing effort in geomorphology — the study of the origin and evolution of many landscape features — to understand how soil processes at work on hillsides compete with water runoff in the formation of valley floors.
Put simply, runoff processes carve valleys while soil movement on hill slopes tends to fill them. The relative vigor of these competing forces determines the spacing of hills and valleys and the degree of drainage dissection. “Hill-slope processes help determine valley density and the way valleys and ridges form,” Roering said. “These networks are climate dependent.”
Over the course of five 20-hour experiments conducted in small sandboxes, UO doctoral student Kristin E. Sweeney, the study’s lead author, extruded crystalline silica to represent uplift due to tectonic forces. To induce erosion, she used mist from 42 nozzles to create precipitation-driven runoff and 625 blunt needles that fired periodic bursts of large water drops to mimic natural disturbances that occur on hill slopes. Each experiment showed how the processes, acting together, converted flat plains into ridges and valleys.
“In our experiments we were able to dictate the processes involved and observe the landscapes that arise,” Sweeney said. “We were able to directly control the various processes. Previous research has only attempted to replicate channel processes — what the rivers do. We essentially started from scratch, working to see the movement of sediment slopes in a realistic way.
“Ridges and valleys are part of a fundamental landscape pattern that people easily recognize,” she said. “From an airplane, you look down and you see watersheds, you see valleys, and they tend to have very regular spacing. Explaining this pattern is a fundamental question in geomorphology.”
The study’s three-member team also included Christopher Ellis, senior research associate at the University of Minnesota’s St. Anthony Falls Laboratory where the experiments were conducted. The team spent more than a year developing a workable methodology to study the sediment transfer processes.
The study confirms earlier work using mathematical computations and actual landscape measurements by Taylor Perron of the Massachusetts Institute of Technology and published in the journal Nature in July 2009. The UO study provides the first physical documentation of the processes involved.
“The contribution of hill slopes to drainage basin formation has not been widely appreciated,” Roering said. “The more water on landscapes, the more vegetation, the more varmints and more life that is out there doing hill slope work. If you make things drier you tend to decrease the vigor of hill-slope processes and drainage networks should reflect that.”
Reference:
K. E. Sweeney, J. J. Roering, C. Ellis. Experimental evidence for hillslope control of landscape scale. Science, 2015 DOI: 10.1126/science.aab0017
Note: The above post is reprinted from materials provided by University of Oregon. The original item was written by Jim Barlow.
ASU professor Christy Till strives to better understand the potential for future eruptions at Yellowstone volcano by studying those in the recent past. She and paper co-author Jorge Vazquez examine Yellowstone lavas in the field. Credit: Naomi Thompson
We’ve long known that beneath the scenic landscapes of Yellowstone National Park sleeps a supervolcano with a giant chamber of hot, partly molten rock below it.
Though it hasn’t risen from slumber in nearly 70,000 years, many wonder when Yellowstone volcano will awaken and erupt again. According to new research at Arizona State University, there may be a way to predict when that happens.
While geological processes don’t follow a schedule, petrologist Christy Till, a professor in ASU’s School of Earth and Space Exploration, has produced one way to estimate when Yellowstone might erupt again.
“We find that the last time Yellowstone erupted after sitting dormant for a long time, the eruption was triggered within 10 months of new magma moving into the base of the volcano, while other times it erupted closer to the 10 year mark,” says Till.
The new study, published Wednesday in the journal Geology, is based on examinations of the volcano’s distant past combined with advanced microanalytical techniques. Till and her colleagues were the first to use NanoSIMS ion probe measurements to document very sharp chemical concentration gradients in magma crystals, which allow a calculation of the timescale between reheating and eruption for the magma.
This does not mean that Yellowstone will erupt in 10 months, or even 10 years. The countdown clock starts ticking when there is evidence of magma moving into the crust. If that happens, there will be some notice as Yellowstone is monitored by numerous instruments that can detect precursors to eruptions such as earthquake swarms caused by magma moving beneath the surface.
And if history is a good predictor of the future, the next eruption won’t be cataclysmic.
Geologic evidence suggests that Yellowstone has produced three enormous eruptions within the past 2.1 million years, but these are not the only type of eruptions that can occur. Volcanologists say there have been more than 23 smaller eruptions at Yellowstone since the last major eruption approximately 640,000 years ago. The most recent small eruption occurred approximately 70,000 years ago.
If a magma doesn’t erupt, it will sit in the crust and slowly cool, forming crystals. The magma will sit in that state — mostly crystals with a tiny amount of liquid magma — for a very long time. Over thousands of years, the last little bit of this magma will crystallize unless it becomes reheated and reignites another eruption.
For Till and her colleagues, the question was, “How quickly can you reheat a cooled magma chamber and get it to erupt?”
Till collected samples from lava flows and analyzed the crystals in them with the NanoSIMS. The crystals from the magma chamber grow zones like tree rings, which allow a reconstruction of their history and changes in their environment through time.
“Our results suggest an eruption at the beginning of Yellowstone’s most recent volcanic cycle was triggered within 10 months after reheating of a mostly crystallized magma reservoir following a 220,000-year period of volcanic quiescence,” says Till. “A similarly energetic reheating of Yellowstone’s current sub-surface magma bodies could end approximately 70,000 years of volcanic repose and lead to a future eruption over similar timescales.”
Reference:
Christy B. Till, Jorge A. Vazquez, and Jeremy W. Boyce. Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming. Geology, July 1, 2015 DOI: 10.1130/G36862.1
Photographs (A-C) and line drawings (D-F) of the skulls of selected corytophanid species in left lateral view. (A) Corytophanes cristatus (AMNH R 16390), (B) Laemanctus serratus (photograph; AMNH R 44982), (C) Basiliscus vittatus (AMNH R 147832), (D) Laemanctus serratus (line drawing), (E) Geiseltaliellus maarius, and (F) Babibasiliscus alxi taxon nov. (UWBM 89090). Note that it is unclear whether Babibasiliscus alxi taxon nov. had a parietal crest. Reconstructed areas are represented as semi-opaque areas and/or dotted lines. Scale bars equal 10mm. Credit: Conrad JL.; PLoS ONE, 2015 DOI: 10.1371/journal.pone.0127900
A newly-discovered, 48-million-year-old fossil, known as a “Jesus lizard” for its ability to walk on water, may provide insight into how climate change may affect tropical species, according to a study published July 1 in the open-access journal PLOS ONE by Jack Conrad from American Museum of Natural History.
Modern relatives of the Jesus lizard live in an area stretching from central Mexico to northern Colombia, flourishing in the higher temperatures found at the equator. Members of various animal, plant, fungal, and other clades currently confined to the tropics or subtropical areas are often found in fossil records at mid-to-high latitudes from warm periods in Earth history.
The 48-million-year-old fossil, recovered from the Bridger Formation in Wyoming, is the first description of a new species, named Babibasiliscus alxi by the author, and may represent the earliest clear member of the Jesus lizard group, Corytophanidae. This group, which includes iguanas and chameleons, remains poorly understood, due to the small number of fossils available for study.
The author suggests Babibasilscus alxi was likely active during the day and spent a lot of time in trees. A ridge of bone on the skull gave it an angry look while providing shade for its eyes. Each small tooth had three points suitable for eating snakes, lizards, fish, insects and plants, but with a fairly large cheekbone, the lizard may have enjoyed larger prey items as well.
The author suggests that the two-foot long casquehead lizard Babibasiliscus alxi, may have skimmed the surfaces of lush, watery habitats in Wyoming, which at the time probably had a climate matching today’s tropics.
“Given our current period of global climate fluctuation, looking to the fossil record offers an important opportunity to observe what is possible,” said Jack Conrad, “and may give us an idea of what to expect from our dynamic Earth.”
Reference:
Conrad JL. A New Eocene Casquehead Lizard (Reptilia, Corytophanidae) from North America. PLoS ONE, 2015 DOI: 10.1371/journal.pone.0127900
Note: The above post is reprinted from materials provided by PLOS.
This July 6, 2011 photo, provided by the U.S. Geological Survey shows erosion along the northern Alaska coast in Barter Island, Alaska. Erosion is eating away at Alaska’s northern coast at some of the highest rates in the nation, threatening habitat and infrastructure, according to a new report published Wednesday, July 1, 2015. Credit: Ben Jones/U.S. Geological Survey via AP
Erosion is eating away at Alaska’s northern coast at some of the highest rates in the nation, threatening habitat and infrastructure, according to a new report published Wednesday.
The U.S. Geological Survey study looked at more than 50 years of data and found an average yearly shoreline change of 1.4 meters—or more than 4 1/2 feet—taking both beach erosion and expansion into account. Extreme cases showed an annual difference of more than 60 feet (18.3 meters).
“Probably the take-home message is that the north coast of Alaska is predominantly erosional—84 percent of the coast is eroding,” USGS geologist Ann Gibbs said Wednesday.
The report provides baseline information for an area studied far less than other parts of the country, Gibbs said. The new study looked at nearly 995 miles of the coast between Alaska’s icy Cape and the Canada border.
The study is part of an ongoing assessment of the nation’s shoreline. None of the studies address climate change.
Gibbs, the lead author in the study, said there is no national erosion average from the previous studies, but most places showed shoreline changes of less than 1 meter per year, and a bit higher in Gulf states like Mississippi and Louisiana. Extreme shoreline changes in Louisiana were as high as 22 feet (6.7 meters) per year, she said.
Still to be studied in the national project are Alaska’s western and southern coast, as well as the Great Lakes area on the mainland.
The erosion in northern Alaska tends to occur only in the few warmer months in the summers, Gibbs said.
Walt Audi has witnessed much of the shoreline changes himself as a 51-year resident of the far north village of Kaktovik, which lies within the Arctic National Wildlife Refuge about 640 miles (1,030 kilometers) north of Anchorage. As far as he’s concerned, climate change is to blame.
These days, Audi said, at the height of summer he can look out at the ocean and there’s no ice as far as he can see.
The 76-year-old owner of a local hotel, Audi remembers the old days when supply barges sometimes couldn’t come in to deliver goods because of thick summer shore ice. That served an important purpose in protecting the coastline, he said.
“That kept the waves from crashing in as bad as they are now,” he said.
An assortment of Early Cenozoic ichthyoliths. Credit: Elizabeth Sibert with Yale University
A pair of paleobiologists from Scripps Institution of Oceanography, UC San Diego have determined that the world’s most numerous and diverse vertebrates ¬- ray-finned fishes — began their ecological dominance of the oceans 66 million years ago, aided by the mass extinction event that killed off dinosaurs.
Scripps graduate student Elizabeth Sibert and Professor Richard Norris analyzed the microscopic teeth of fishes found in sediment cores around the world and found that the abundance of ray-finned fish teeth began to explode in the aftermath of the mass die-off of species, which was triggered by an asteroid strike in the Yucatan Peninsula. Scientists refer to this episode as the Cretaceous-Paleogene (K/Pg) extinction event.
Ninety-nine percent of all fish species in the world — from goldfish to tuna and salmon — are classified as ray-finned fishes. They are defined as species with bony skeletal structures and have teeth that are well preserved in deep ocean mud. Sharks, in contrast, have cartilaginous skeletons and are represented by both teeth and mineralized scales, also known as denticles, in marine sediments.
“We find that the extinction event marked an ecological turning point for the pelagic marine vertebrates,” write the authors in the study. “The K/Pg extinction appears to have been a major driver in the rise of ray-finned fishes and the reason that they are dominant in the open oceans today.”
The breakthrough for the researchers in reaching their conclusion came through their focus on fossilized teeth and shark scales. In cores from numerous ocean basins, they found that while the numbers of sharks remained steady before and after the extinction event, the ratio of ray-finned fish teeth to shark teeth and scales gradually rose, first doubling then becoming eight times more abundant 24 million years after the extinction event. Now there are 30,000 ray-finned fish species in the ocean, making this class the most numerically diverse and ecologically dominant among all vertebrates on land or in the ocean.
Scientists had known that the main diversification of ray-finned fishes had happened generally between 100 million and 50 million years ago.
“The diversification of fish had never been tied to any particular event. What we found is that the mass extinction is actually where fish really took off in abundance and variety,” said Sibert, who is the recipient of an NSF Graduate Research Fellowship. “What’s neat about what we found is that when the asteroid hit, it completely flipped how the oceans worked. The extinction changed who the major players were.”
Sibert and Norris believe that some key changes in the oceans might have helped ray-finned fishes along. Large marine reptiles disappeared during the mass extinction, as did the ammonites, an ancient cephalopod group similar to the chambered nautilus. Those species, the researchers believe, had been either predators of ray-finned fishes or competitors with them for resources.
“What’s amazing,” said Norris, “is how quickly fish double, then triple in relative abundance to sharks after the extinction, suggesting that fish were released from predation or competition by the extinction of other groups of marine life.”
Sibert noted that before the extinction event, ray-finned fishes existed in a state of relative ecological insignificance, just like mammals on land.
“Mammals evolved 250 million years ago but didn’t become really important until after the mass extinction. Ray-finned fishes have the same kind of story,” said Sibert. “The lineage has been around for hundreds of millions of years, but without the mass extinction event 66 million years ago, it is very likely that the oceans wouldn’t be dominated by the fish we see today.”
Reference:
Elizabeth C. Sibert, Richard D. Norris. New Age of Fishes initiated by the Cretaceous−Paleogene mass extinction. Proceedings of the National Academy of Sciences, 2015; 201504985 DOI: 10.1073/pnas.1504985112
Note: The above post is reprinted from materials provided by University of California – San Diego. The original item was written by Robert Monroe.
The meteor crater in Arizona, USA, with a diameter of 1.2 kilometers, is the most well-known impact crater. There must still be many undiscovered craters in this size category – but they are older and much less well preserved.
The geologists Prof. Dr. Stefan Hergarten and Prof. Dr. Thomas Kenkmann from the Institute of Earth and Environmental Sciences of the University of Freiburg have published the world’s first study on the question of how many meteorite craters there should be on the Earth’s surface. A total of 188 have been confirmed so far, and 340 are still awaiting discovery according to the results of a probability calculation presented by the two researchers in the journal Earth and Planetary Science Letters.
Meteorite impacts have shaped the development of the Earth and life repeatedly in the past. The extinction of the dinosaurs, for instance, is thought to have been brought on by a mega-collision at the end of the Cretaceous period. But how many traces of large and small impacts have survived the test of time? In comparison to the more than 300,000 impact craters on Mars, the mere 188 confirmed craters on Earth seem almost negligible. Moreover, 60 of them are buried under sediments. Advances in remote sensing have not led to the expected boom in crater discoveries: An average of only one to two meteorite craters are discovered per year, most of them already heavily eroded.
The probability of a meteorite impact on Earth is not fundamentally different than on Mars. However, the Earth’s surface changes much more quickly. As a result, the craters remain visible for a much shorter period of time, meaning that many less of them are detectible today. “The main challenge of the study was to estimate the long-term effect of erosion, which causes craters to disappear over time,” says Hergarten. The life span of a crater depends on the rate of erosion and its size. Large craters can achieve a life span of several 100 million years, depending on the region in which they are located. On the other hand, large impacts are much rarer than small impacts. The solution was to compare the amount of confirmed craters of different sizes, calculate the expected frequency of the impacts on the basis of the known probabilities, and combine this information to infer the rates of erosion.
“A surprising, initially sobering finding we made was that there are not many craters of above six kilometers in diameter left to discover on the Earth’s surface,” reports Hergarten. In the case of smaller craters, on the other hand, the scientists found the current list to be far from complete: Around 90 craters with a diameter of one to six kilometers and a further 250 with a diameter of 250 to 1000 meters are still awaiting discovery. While there are undoubtedly still a number undiscovered large craters buried deep under sediments, they are much more difficult to detect and confirm.
Reference:
S. Hergarten, T. Kenkmann. The number of impact craters on Earth: Any room for further discoveries? Earth and Planetary Science Letters, 2015; 425: 187 DOI: 10.1016/j.epsl.2015.06.009
