The fossilized hipbone of an ape called Sivapithecus is raising a host of new questions about whether the upright body plan of apes may have evolved multiple times. “What we do know is that the evolution of the orthograde body plan in apes is not a simple story,” noted Harvard’s Michèle Morgan, co-author of the paper. Jon Chase/Harvard Staff Photographer
For decades, scientists have recognized the upright posture exhibited by chimpanzees, gorillas, and humans as a key feature separating the “great apes” from other primates, but a host of questions about the evolution of that posture—particularly how and when it emerged—have long gone unanswered.
For more than a century, the belief was that the posture, known as the orthograde body plan, evolved only once, as part of a suite of features, including broad torsos and mobile forelimbs, in an early ancestor of modern apes.
But a fossilized hipbone of an ape called Sivapithecus is challenging that belief.
The bone, about 6 inches long, is described in a paper in the Proceedings of the National Academy of Sciences (PNAS) co-authored by Michèle Morgan, museum curator of osteology and paleoanthropology at Harvard’s Peabody Museum of Archaeology and Ethnology, and colleagues including Kristi Lewton, Erik Otárola-Castillo, John Barry, Jay Kelley, Lawrence Flynn, and David Pilbeam. The finding has raised a host of new questions about whether that upright body plan may have evolved multiple times.
“We always thought if we found this body part, that it would show some of the features we find in the living great apes,” Morgan said. “To find something like this was surprising.”
Where modern apes have large, broad chests, Sivapithecus is believed to have had a relatively narrow, monkey-like torso, but facial features that closely resemble modern orangutans. That mixture, showing some ape- and monkey-like features, has left researchers scratching their heads about the arrangement of the primate tree, and raises questions about how the stereotypically ape-like body plan evolved.
“Today, all the living great apes—gorillas, orangutans, chimps—have very broad torsos … and people had commonly thought that this torso shape was shared among all the great apes, meaning it must have evolved in a common ancestor,” Morgan said.
“We initially believed that Sivapithecus, with a narrow torso, was on the orangutan line, but if that is the case, then the great ape body shape would have had to evolve at least twice,” she added. “There are a lot of questions that this fossil raises, and we don’t have good answers for them yet. What we do know is that the evolution of the orthograde body plan in apes is not a simple story.”
What Sivapithecus may ultimately demonstrate, said Flynn, assistant director of the American School of Prehistoric Research at the Peabody Museum, is that evolution doesn’t occur in a straight line, but happens as a mosaic across many species.
“What this speaks to is a rich tree with a lot of branches,” Flynn said. “There are not just one or two branches that reach back into the Miocene (epoch). It’s a very rich and complex tree.
“I think we sometimes take the easy route of trying to understand these fossils based on creatures we find today,” Flynn said. “But what we’re finding out time and again is these 10- or 12- or 15-million-year-old creatures were their own entities. Today is not always a very good model for the past.”
To fully understand where Sivapithecus belongs in the evolutionary tree of apes, Flynn said, more fossils must be found, and additional research must be conducted.
“It’s a very easy thing for people to ask, why do we need to go find more fossils; don’t we already know everything? The answer is no,” he said. “We’re only just beginning to understand what we don’t know. And as we learn more, there are more interesting and exciting questions we can ask, and hopefully we can answer.”
Note : The above story is based on materials provided by Harvard University. The original article was written by Peter Reuell.
Acoustic-gravity waves—a special type of sound wave that can cut through the deep ocean at the speed of sound—can be generated by underwater earthquakes, explosions, and landslides, as well as by surface waves and meteorites. A single one of these waves can stretch tens or hundreds of kilometers, and travel at depths of hundreds or thousands of meters below the ocean surface, transferring energy from the upper surface to the seafloor, and across the oceans. Acoustic-gravity waves often precede a tsunami or rogue wave—either of which can be devastating.
Now a new study by an MIT researcher suggests that these immense deep-ocean waves can rapidly transport millions of cubic meters of water, carrying salts, carbons, and other nutrients around the globe in a matter of hours.
Usama Kadri, a postdoc in MIT’s Department of Mechanical Engineering, tracked the theoretical movement of fluid caught up in an acoustic-gravity wave at various depths in the ocean, ranging from hundreds to thousands of meters below the surface. Based on his calculations, Kadri found that acoustic-gravity waves can push parcels significant distances, depending on their depth.
“Deep-water transport is so vital—not only to local marine ecosystems, but to our global ecosystem and environment—that a cut in such transport will ultimately result in the death of marine life, create regions of extreme water temperatures, and dramatically affect our climate,” says Kadri, who has published his results in the Journal of Geophysical Research: Oceans. “To sustain a healthier global ecosystem and environment, there is a need to increase awareness of acoustic-gravity waves and deep-water transport.”
Kadri adds that such awareness may help scientists devise early-warning systems for seaside communities and offshore facilities vulnerable to tsunamis or rogue waves—monster waves that can come on suddenly, with potentially devastating effects.
“Since acoustic-gravity waves are so much faster than tsunamis or rogue waves, successful recordings of … acoustic-gravity waves would enhance current warning systems dramatically, and improve detection by minutes to hours depending on the source location,” Kadri says, “either of which is sufficient to [save] many lives.”
A gravity wave is generated in a fluid or at the interface between fluids, and is governed by gravity. A common example is an ocean surface wave.
Acoustic waves, by contrast, propagate through longitudinal compression. For example, sound travels by vibrating and pushing against a fluid medium. Unlike in gravity waves, compressibility dominates acoustic waves, while the effect of gravity is negligible.
For those reasons, Kadri says, scientists have generally studied either sound waves in the ocean from a purely acoustic perspective, or surface waves in an incompressible ocean.
Drifting with the wave
Kadri modeled the behavior of acoustic-gravity waves in the deep ocean by first considering the propagation of waves in an ideal, compressible ocean, where water volume changes slightly in response to pressure changes. In a two-dimensional model, he calculated the movement of fluid caused by a traveling acoustic-gravity wave at various depths in the ocean.
Kadri’s equations showed that acoustic-gravity waves may propagate throughout the ocean, up to thousands of meters deep, even traveling along the seafloor. He then looked into whether acoustic-gravity waves may cause water to drift long distances, or if they simply recirculate them back to their original location.
Kadri worked the equation out for acoustic-gravity waves at various depths in the deep ocean, and found that these waves can transport water at a velocity of a few centimeters per second. Such waves, Kadri estimates, can therefore transport millions of cubic meters of deep water per second.
According to these results, acoustic-gravity waves may be “major players,” Kadri says, in transporting water and producing currents in the deep ocean. Such waves may be instrumental in carrying plankton, algae, and bacteria across the oceans, as well as in delivering essential nutrients to sedentary marine organisms.
Knowing the properties of acoustic-gravity waves may also help researchers develop early-warning systems for potentially devastating ocean events, such as tsunamis and rogue waves. Toward that end, Kadri is continuing his work to develop predictive computations that can analyze acoustic signals for fast-traveling acoustic-gravity waves—a precursor to tsunamis.
Jerry Smith, a research oceanographer at the University of California at San Diego, says a striking contribution from Kadri’s research is the finding that surface waves have an effect on deep-ocean waves.
“The most significant finding in this particular paper is the contribution to deep-ocean transport,” says Smith, who was not involved in the research. “This has not been appreciated before. Since these acoustic-gravity waves can be generated by nonlinear interactions of ordinary wind-waves, the contribution to deep transport could be ubiquitous.”
Geographic map of main fossil localities that yield the Yanliao (Daohugou), Jehol and Fuxin biotas in northeast China. Credit: Science China Press
The most exciting findings covering Mesozoic mammals over the last two decades have come from the Jurassic and Cretaceous periods of China. Remarkably preserved fossils across nearly all major groups of Mesozoic mammals have provided a great amount of information about their morphology and biology. A researcher at the American Museum of Natural History reviews these discoveries and outlines potential future research efforts in the study of mammalian evolution.
It is generally accepted that the tree of life for mammals was rooted in the Mesozoic, but the specific time for the origin of mammals remains an issue of debate. This is partly because Mesozoic mammals are commonly known by fragmentary material, mostly dentitions, that restrained the search for the biology and evolution of our earliest ancestors.
During the last two decades, many Mesozoic mammals have been reported from all over the world. Notable among them are those from the southern continents, which have significantly enriched understanding of the morphology, diversity, geographic distribution and evolution of Mesozoic mammals. The most remarkable discoveries, however, have come from the Jurassic and Cretaceous periods of China; approximately 50 species, with most represented by superbly preserved skeletal specimens, have been reported. These discoveries have cast new light on some important issues in the study of Mesozoic mammals, such as the diversity and disparity, the mammalian affinity of “haramiyidans”, the divergence time of mammals and evolution of the mammalian middle ear.
Many issues regarding these findings are still being debated, and their resolution might depend on new discoveries and analyses. In a new study, Jin Meng, a scientist at the American Museum of Natural History in New York, reviews a spectrum of discoveries made surrounding the Mesozoic mammals of China. Meng, who is also based at the prestigious Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, outlines these findings in an article titled “Mesozoic mammals of China: implications for phylogeny and early evolution of mammals” published in the Beijing-based journal National Science Review.
The study reviews most known Mesozoic mammals from China, which can be divided into several assemblages according to their geographic and temporal distribution; it also covers different evolutionary stages that are largely consistent with the global pattern of mammalian evolution. Also reviewed are varying hypotheses on the divergent times and phylogenetic relationships of Mammalia and its subgroups (Fig. 1), which in turn significantly affect interpretation of character evolution in early mammals.
The divergence time of Mammalia is directly associated with how the phylogeny of mammals is reconstructed, particularly with the phylogenetic placement of ‘haramiyidans’, a long-time puzzle in paleo-mammalian taxonomy and phylogeny. In light of the discoveries of several species that formed the clade Euharamiyida, the mammalian affinity of ‘haramiyidans’ was strongly supported by dental, cranial and postcranial features from these euharamiyidans. In the preferred phylogeny (Fig. 1a), Allotheria (‘haramiyidans’ and multituberculates) are placed within Mammalia, which best incorporated available evidence of morphology, temporal distributions and most phylogenetic analyses of known Mesozoic mammals and kept character parallelisms at the minimum between ‘haramiyidans’ and multituberculates, as well as between allotherians and other mammals. This hypothesis suggests that mammals originated in an explosive fashion during the Late Triassic because members of allotherians were found in beds of the Late Triassic.
As an example of character evolution of mammals, the study outlines the evolution of the mammalian middle ear, a classic issue of gradual evolution in vertebrates. All extant mammals have three middle ear ossicles: the malleus, incus and stapes. In addition, there is the ectotympanic that holds the eardrum. It has been known from developmental studies that the malleus is a composite element equivalent to the articular and prearticular, the incus is equivalent to the quadrate and the ectotympanic is equivalent to the angular bone. It is also known from the fossil record that during the evolution of mammals, the postdentary bones in the lower jaw of non-mammalian cynodonts were gradually reduced in size and eventually migrated to the middle ear. Research on eutriconodontans and ‘symmetrodontans’ from the Jehol Biota has provided evidence on the transitional mammalian middle ear (TMME), an immediate form between the mandibular ear and the definitive mammalian middle ear (DMME). The mandibular middle ear is a complex in which the ear bones are small but still attached to the tooth-bearing dentary bone so that these small bones have a dual function: mastication and hearing, as seen in Morganucodon. In the DMME the ear ossicles were completely detached from the dentary bone and migrated to the basal cranial region where they function exclusively for hearing. The TMME demonstrates that during the transition from the mandibular middle ear to the DMME, the postdentary bones were detached from the dentary but were not yet securely supported by cranial structures; instead they were anteriorly in articulation with an ossified Meckel’s cartilage whose anterior portion was loosely lodged in a groove on the medial side of the dentary bone. The embryonic condition of the middle ear in living mammals displays a similar morphology to the TMME and probably recapitulates the evolutionary stage of the mammalian middle ear.
Jin Meng also proposes a hypothesis on the evolution of the allotherians tooth pattern to show the potential for future studies based on the Mesozoic mammals discovered in China. The basic allotherian tooth pattern consists of two rows of multiple cusps in the upper and lower molars and is capable of a posterior, not transverse, chewing motion. This tooth pattern differs from those of other mammals that evolved from a ‘triconodont’-like tooth pattern to a tribosphenic tooth pattern. How the allotherian tooth pattern evolved has remained an enigma in the study of mammalian evolution. It is puzzling because wherever allotherians are placed in the phylogeny, either within or outside Mammalia, it is equally difficult to derive the allotherian tooth pattern from any known mammals or their close kin. Given the preferred phylogeny (Fig. 1a), which suggests that allotherians were derived from a Haramiyavia-like ancestor, and the occlusal pattern revealed by the euharamiyidans, it is proposed that the primitive allotherian tooth pattern, as represented by Haramiyavia, could have evolved from a ‘triconodont’-like tooth pattern and then gave rise to those of euharamiyidans and multituberculates, respectively.
Reference:
Jin Meng. “Mesozoic mammals of China: implications for phylogeny and early evolution of mammals.” National Science Review, doi: 10.1093/nsr/nwu070
Note : The above story is based on materials provided by Science China Press.
The Lau Basin, in the South Pacific (top), is a V-shaped basin created by the subduction of the Pacific Plate at the Tonga Trench (the purple line in the central image). A seismic image (bottom) of part of the basin at a depth of 50 kilometers (31 miles) shows magma pooling to the north beneath areas that are unrifted (dark red) and provide no egress but little magma (pale yellow) along the southern end of the Eastern Lau Spreading Center, or ELSC, even though this area is intensely volcanic. Credit: Wei/Wiens
It was a bit like making a CT scan of a patient’s head and finding he had very little brain or making a PET scan of a dead fish and seeing hot spots of oxygen consumption. Scientists making seismic images of the mantle beneath a famous geological site saw the least magma where they expected to see the most.
What was going on? Was it an artifact of their technique or the revelation of something real but not yet understood?
In the online Feb. 2 issue of Nature, a team of scientists, led by S. Shawn Wei and Douglas Wiens of Washington University in St. Louis, published a three-dimensional seismic image of mantle beneath the Lau Basin in the South Pacific that had an intriguing anomaly.
The basin is an ideal location for studying the role of water in volcanic and tectonic processes. Because the basin is widening, it has many spreading centers, or deep cracks through which magma rises to the surface. And because it is shaped like a V, these centers lie at varying distances from the Tonga Trench, where water is copiously injected into Earth’s interior.
The scientists knew that the chemistry of the magma erupted through the spreading centers varies with their distance from the trench. Those to the north, toward the opening of the V, erupt a drier magma than those to the south, near the point of the V, where the magma has more water and chemical elements associated with water. Because water lowers the melting temperature of rock, spreading centers to the north also produce less magma than those to the south.
Before they constructed images from their seismic data, the scientists expected the pattern in the mantle to match that on the surface. In particular they expected to find molten rock pooled to the south, where the water content in the mantle is highest. Instead the seismic images indicated less melt in the south than in the north.
They were flummoxed. After considerable debate, they concluded they were seeing something real. Water, they suggest, increases melting but makes the melt less viscous, speeding its transport to the surface, rather like mixing water with honey makes it flow quicker. Because water-laden magma flushes out so quickly, there is less of it in the mantle at any given moment even though more is being produced over time.
The finding brings scientists one step closer to understanding how the Earth’s water cycle affects nearly everything on the planet — not just the clouds and rivers above the surface, but also processes that take place in silence and darkness in the plutonic depths.
The Lau Basin, which lies between the island archipelagos of Tonga and Fiji, was created by the collision of the giant slab of the Pacific Ocean’s floor colliding with the Australian plate. The older, thus colder and denser, Pacific plate nosed under the Australian plate and sank into the depths along the Tonga Trench, also called the Horizon Deep.
Water given off by the wet slab lowered the melting point of the rock above, causing magma to erupt and form a volcanic arc, called the Tonga-Kermadec ridge.
About 4 to 6 million years ago, the Pacific slab started to pull away from the Australian slab, dragging material from the mantle beneath it. The Australian plate’s margin stretched, splitting the ridge, creating the basin and, over time, rifiting the floor of the basin. Magma upwelling through these rifts created new spreading centers.
“Leave it long enough,” said Wei, a McDonnell Scholar and doctoral student in earth and planetary science in Arts & Sciences, “and the basin will probably form a new ocean.”
“The Tonga subduction zone is famous in seismology,” Wiens said, “because two-thirds of the world’s deep earthquakes happen there and subduction is faster there than anywhere else in the world. In the northern part of this area the slab is sinking at about 24 centimeters (9 inches) a year, or nearly a meter every four years. That’s four times faster than the San Andreas fault is moving.”
The magma that wasn’t there
The images of the mantle published in Nature are based on the rumblings of 200 earthquakes picked up by 50 ocean-bottom seismographs deployed in the Lau Basin in 2009 and 2010 and 17 seismographs installed on the islands of Tonga and Fiji.
The 2009-2010 campaign, led by Wiens, PhD, professor of earth and planetary sciences in Arts & Sciences, was one the largest long-term deployments of ocean-bottom seismographs ever undertaken.
When the scientists looked carefully at the southern part of the images created from their seismograph recordings, they were mystified by what they saw — or rather didn’t see. In their color-coded images, the area along the southern end of the spreading center in the tip of the basin, called the ELSC, should have been deep red.
Instead it registered pale yellow or green, as though it held little magma. “It was the reverse of our expectation,” Wei said.
To make these images, the scientists calculated the departure of the seismic velocities from reference values, Wei explained. “If the velocities are much lower than normal we attribute that to the presence of molten rock,” he said. “The lower the velocity, the more magma.”
Because water lowers melting temperatures, the scientists expected to see the lowest velocities and the most magma to the south, where the water content is highest.
Instead the velocities in the north were much lower than those in the south, signaling less magma in the south. This was all the more mystifying because the southern ELSC is intensely volcanic.
If the volcanoes were spewing magma, why wasn’t it showing up in the seismic images?
After considerable debate, the scientists concluded that water from the slab must make melt transport more efficient as well as lowering melting temperatures.
“Where there’s very little water, the system is not moving the magma through very efficiently,” Wiens said. “So where we see a lot of magma pooled in the north, that doesn’t necessarily mean there’s a lot of melting there, just that the movement of the magma is slow.”
“Conversely, where there’s water, the magma is quickly and efficiently transported to the surface. So where we see little magma in the south, there is just as much melting going on, but the magma is moving through so fast that at any one moment we see less of it in the rock,” Wiens said.
“The only way to explain the distribution of magma is to take account of the effect of water on the transport of magma,” Wei said. “We think water makes the magma significantly less viscous, and that’s why transport is more efficient.”
“This is the first study to highlight the effect of water on the efficiency of magma extraction and the speed of magma transport,” Wiens said.
Wei plans to continue following the water. “A recent paper in Nature described evidence that water is carried down to 410 kilometers (250 miles). I’d like to look deeper,” he said.
Video:
Reference:
S. Shawn Wei, Douglas A. Wiens, Yang Zha, Terry Plank, Spahr C. Webb, Donna K. Blackman, Robert A. Dunn, James A. Conder. Seismic evidence of effects of water on melt transport in the Lau back-arc mantle. Nature, 2015; DOI: 10.1038/nature14113
Color-shaded relief map with simplified tectonic units of eastern Asia. Since the Late Cretaceous, lithosphere extension was induced by the subduction of the western Pacific or Philippine plate. The Dabie and Sulu orogens contain the largest ultrahigh-pressure metamorphic belt in the world as a result of the convergence between the North and South China blocks during the Late Paleozoic–Triassic. Credit: Copyright Tian and Santosh, GSA Today Feb. 2015
Seismic investigations from the Qinling-Dabie-Sulu orogenic belt in eastern China suggest that this region was affected by extreme mantle perturbation and crust-mantle interaction during the Mesozoic era. The Qinling-Dabie-Sulu orogenic belt formed through the collision between the North and South China blocks, which produced large-scale destruction of the cratonic lithosphere, accompanied by widespread magmatism and metallogeny.
Global mantle convection significantly impacts processes at the surface of Earth and can be used to gain insights on plate driving forces, lithospheric deformation, and the thermal and compositional structure of the mantle. Upper-mantle seismic anisotropy is widely employed to study both present and past deformation processes at lithospheric and asthenospheric depths.
The majority of seismic data from stations located near Qinling-Dabie-Sulu orogenic belt show anisotropy with an E-W- or ENE-WSW-trending fast polarization direction, parallel to the southern edge of the North China block. This suggests compressional deformation in the lithosphere due to the collision between the North and South China blocks.
Although the deep root of the craton was largely destroyed by cratonic reactivation in the late Mesozoic, these results suggest that the “fossilized” anisotropic signature is still preserved in the remnant lithosphere beneath eastern China.
Reference:
Xiaobo Tian, M. Santosh. Fossilized lithospheric deformation revealed by teleseismic shear wave splitting in eastern China. GSA Today, 2015; 4 DOI: 10.1130/GSATG220A.1
While many areas of the ocean are rich in other nutrients, they often lack iron — a critical element for marine life. Dissolved iron in seawater can originate from three main sources: Dust from the atmosphere, sediment dissolution along continental margins, and fluids from hydrothermal vents. Credit: Jack Cook, Woods Hole Oceanographic Institution
A new study led by scientists at the Woods Hole Oceanographic Institution (WHOI) points to the deep ocean as a major source of dissolved iron in the central Pacific Ocean. This finding highlights the vital role ocean mixing plays in determining whether deep sources of iron reach the surface-dwelling life that need it to survive.
“Our study is a long-term view–over the past 76 million years–of where iron has been coming from in the central Pacific,” says Tristan Horner, a postdoctoral fellow in the Marine Chemistry and Geochemistry Department at WHOI and lead author of the paper to be published February 3, 2015, in Proceedings of the National Academy of Sciences.
While many areas of the ocean are rich in other nutrients, they often lack iron–a critical element for marine life. Iron is particularly important for the growth of phytoplankton, which are tiny plant-like organisms that form the base of the ocean food chain and play an important role in Earth’s climate.
In addition to producing about half of the planet’s oxygen, phytoplankton live at the ocean’s surface and act as sponges of carbon dioxide–a heat-trapping gas. Through photosynthesis, phytoplankton take carbon from the air into their bodies. When they die or are eaten, much of the carbon sinks to the deep ocean, where it cannot re-enter the atmosphere.
Using a mass spectromemter, the ferromanganese crust sample (Tristan Horner, Woods Hole Oceanographic Institution )
“In basic terms, iron is so important because it helps control climate,” says Sune Nielsen, a WHOI geologist and coauthor. “We need to understand where iron in the ocean is coming from in order to truly understand the role of iron in the marine carbon cycle.”
The scientific community has long thought that the vast majority of the ocean’s iron comes from atmospheric dust, with smaller inputs from dissolved sediment along continental margins, and fluids from hydrothermal vents, which are mineral-rich hot springs on the seafloor, miles below the surface.
Iron is readily soluble in low oxygen regions at hydrothermal vent sites and along continental margins, but it was believed the iron remained in these localized spots and didn’t contribute much to the overall iron content of the ocean. “According to conventional wisdom, as soon as these iron-rich fluids hit seawater with high oxygen concentrations, the iron would just dump out and never really go anywhere,” explains Nielsen.
However, Horner says, “That is not the case, at least in the central Pacific Ocean. We found that much of the dissolved iron in that region originated from hydrothermal vents and sediments thousands of meters below the sea surface. And we found that the iron from these deep sources can be transported long distances.”
To conduct their research, the researchers analyzed a marine sediment, called a ferromanganese crust, taken from a spot far from any hydrothermal vent sites in the central Pacific Ocean. The sample was collected from the flank of the Karin Ridge, a seamount located in the central Pacific, in the 1980s by coauthor Jim Hein of the U.S. Geological Survey (USGS) in Santa Cruz, from a dredge along the seafloor.
The team used a mass spectrometer to analyze the sample for long-term changes in seawater isotopic chemistry recorded in the growth layers of the ferromanganese crust, which forms very slowly. Drilling cross sections in the sample allowed scientists to look through “sections of time” to analyze variations in the composition of iron isotopes–stable natural isotopes iron-56 and iron-54–in order to track the origins of iron.
“The ratio of iron isotopes vary among the different iron sources–atmospheric dust, hydrothermal vents, and dissolved sediments– and are actually quite distinct, like fingerprints. We were able to measure those ratios in the growth layers of our sample, which tells us about where the iron came from and how the different iron sources have waxed and waned over time,” Horner says.
“This study is exciting in that it applies some of the recently developed metal isotope capabilities to parse the different sources of scarce iron in seawater going back through time, and builds on the emerging story about the importance of hydrothermal vents to the inventory of iron in the sea,” adds Mak Saito, a biogeochemist at WHOI and one of the coauthors of the study.
The researchers hope to use this technique to look at iron sources in other parts of the ocean. Future studies could help answer lingering questions about global iron budgets, the influence of iron on climate, and how hydrothermal vents affect the ocean as a whole. Reference:
Tristan J. Horner, Helen M. Williams, James R. Hein, Mak A. Saito, Kevin W. Burton, Alex N. Halliday, Sune G. Nielsen. Persistence of deeply sourced iron in the Pacific Ocean. Proceedings of the National Academy of Sciences, 2015; 201420188 DOI: 10.1073/pnas.1420188112
Deep-sea microorganisms are unchanged over more than 2 billion years. Credit : UCLA Center for the Study of Evolution and the Origin of Life
An international team of scientists has discovered the greatest absence of evolution ever reported — a type of deep-sea microorganism that appears not to have evolved over more than 2 billion years. But the researchers say that the organisms’ lack of evolution actually supports Charles Darwin’s theory of evolution.
The findings are published online today by the Proceedings of the National Academy of Sciences.
The scientists examined sulfur bacteria, microorganisms that are too small to see with the unaided eye, that are 1.8 billion years old and were preserved in rocks from Western Australia’s coastal waters. Using cutting-edge technology, they found that the bacteria look the same as bacteria of the same region from 2.3 billion years ago — and that both sets of ancient bacteria are indistinguishable from modern sulfur bacteria found in mud off of the coast of Chile.
“It seems astounding that life has not evolved for more than 2 billion years — nearly half the history of the Earth,” said J. William Schopf, a UCLA professor of earth, planetary and space sciences in the UCLA College who was the study’s lead author. “Given that evolution is a fact, this lack of evolution needs to be explained.”
Charles Darwin’s writings on evolution focused much more on species that had changed over time than on those that hadn’t. So how do scientists explain a species living for so long without evolving?
“The rule of biology is not to evolve unless the physical or biological environment changes, which is consistent with Darwin,” said Schopf, who also is director of UCLA’s Center for the Study of Evolution and the Origin of Life. The environment in which these microorganisms live has remained essentially unchanged for 3 billion years, he said.
A section of a 1.8 billion-year-old fossil-bearing rock. Credit : UCLA Center for the Study of Evolution and the Origin of Life
“These microorganisms are well-adapted to their simple, very stable physical and biological environment,” he said. “If they were in an environment that did not change but they nevertheless evolved, that would have shown that our understanding of Darwinian evolution was seriously flawed.”
Schopf said the findings therefore provide further scientific proof for Darwin’s work. “It fits perfectly with his ideas,” he said.
The fossils Schopf analyzed date back to a substantial rise in Earth’s oxygen levels known as the Great Oxidation Event, which scientists believe occurred between 2.2 billion and 2.4 billion years ago. The event also produced a dramatic increase in sulfate and nitrate — the only nutrients the microorganisms would have needed to survive in their seawater mud environment — which the scientists say enabled the bacteria to thrive and multiply.
Schopf used several techniques to analyze the fossils, including Raman spectroscopy — which enables scientists to look inside rocks to determine their composition and chemistry — and confocal laser scanning microscopy — which renders fossils in 3-D. He pioneered the use of both techniques for analyzing microscopic fossils preserved inside ancient rocks.
Co-authors of the PNAS research were Anatoliy Kudryavtsev, a senior scientist at UCLA’s Center for the Study of Evolution and the Origin of Life, and scientists from the University of Wisconsin, NASA’s Jet Propulsion Laboratory, Australia’s University of New South Wales and Chile’s Universidad de Concepción.
Schopf’s research is funded by the NASA Astrobiology Institute.
Reference :
Sulfur-cycling fossil bacteria from the 1.8-Ga Duck Creek Formation provide promising evidence of evolution’s null hypothesis
Author contributions: J.W.S., K.H.W., and J.W.V. designed research; J.W.S., A.B.K., M.R.W., M.J.V.K., K.H.W., R.K., V.A.G., C.E., and D.T.F. performed research; J.W.S., A.B.K., M.R.W., M.J.V.K., K.H.W., R.K., J.W.V., V.A.G., C.E., and D.T.F. analyzed data; and J.W.S., M.R.W., K.H.W., J.W.V., and V.A.G. wrote the paper. Doi: 10.1073/pnas.1419241112
The Nile River and Delta, viewed at night by the Expedition 25 crew on Oct. 28, 2010. Credit: NASA
Planet Earth boasts some very long rivers, all of which have long and honored histories. The Amazon, Mississippi, Euphrates, Yangtze, and Nile have all played huge roles in the rise and evolution of human societies. Rivers like the Danube, Seine, Volga and Thames are intrinsic to the character of some of our most major cities.
But when it comes to the title of which river is longest, the Nile takes top billing. At 6,583 km (4,258 miles) long, and draining in an area of 3,349,000 square kilometers, it is the longest river in the world, and even the longest river in the Solar System. It crosses international boundaries, its water is shared by 11 African nations, and it is responsible for the one of the greatest and longest-lasting civilizations in the world.
Officially, the Nile begins at Lake Victoria – Africa’s largest Great Lake that occupies the border region between Tanzania, Uganda and Kenya – and ends in a large delta and empties into the Mediterranean Sea. However, the great river also has many tributaries, the greatest of which are the Blue Nile and White Nile rivers.
Nile Delta from space by the MODIS sensor on the Terra satellite. Credit: Jacques Descloitres/NASA/GSFC
The White Nile is the source of the majority of the Nile’s water and fertile soil, and originates from Africa’s Great Lakes region of Central Africa (a group that includes Lake Victoria, Edward, Tanganyika, etc.). The Blue Nile starts at Lake Tana in Ethiopia, and flows north-west to where it meets the Nile near Khartoum, Sudan.
The northern section of the Nile flows entirely through the Sudanese Desert to Egypt. Historically speaking, most of the population and cities of these two countries were built along the river valley, a tradition which continues into the modern age. In addition to the capitol cities of Juba, Khartoum, and Cairo, nearly all the cultural and historical sites of Ancient Egypt are to be found along the riverbanks.
The Nile was a much longer river in ancient times. Prior to the Miocene era (ca. 23 to 5 million years ago), Lake Tangnayika drained northwards into the Albert Nile, making the Nile about 1,400 km. That portion of the river became blocked by the bulk of the formation of the Virunga Mountains through volcanic activity.
Between 8000 and 1000 B.C.E., there was also a third tributary called the Yellow Nile that connected the highlands of eastern Chad to the Nile River Valley. Its remains are known as the Wadi Howar, a riverbed that passes through the northern border of Chad and meets the Nile near the southern point of the Great Bend – the region that lies between Khartoum and Aswan in southern Egypt where the river protrudes east and west before traveling north again.
Lake Moeris and Faiyum Oasis, as seen from space, south-west of the Nile Delta and Cairo. Credit: Earth Snapshot
The Nile, as it exists today, is thought to be the fifth river that has flowed from the Ethiopian Highlands. Some form of the Nile is believed to have existed for 25 million years. Satellite images have been used to confirm this, identifying dry watercourses to the west of the Nile that are believed to have been the Eonile.
This “ancestral Nile” is believed to be what flowed in the region during the later Miocene, transporting sedimentary deposits to the Mediterranean Sea. During the late-Miocene Era, the Mediterranean Sea became a closed basin and evaporated to the point of being empty or nearly so. At this point, the Nile cut a new course down to a base level that was several hundred meters below sea level.
This created a very long and deep canyon which was filled with sediment, which at some point raised the riverbed sufficiently for the river to overflow westward into a depression to create Lake Moeris southwest of Cairo. A canyon, now filled by surface drift, represents an ancestral Nile called the Eonile that flowed during the Miocene.
Due to their inability to penetrate the wetlands of South Sudan, the headwaters of the Nile remained unknown to Greek and Roman explorers. Hence, it was not until 1858 when John Speke sighted Lake Victoria that the source of the Nile became known to European historians. He reached its southern shore while traveling with Richard Burton on an expedition to explore central Africa and locate the African Great Lakes.
Believing he had found the source of the Nile, he named the lake after Queen Victoria, the then-monarch of the United Kingdom. Upon learning of this, Burton was outraged that Speke claimed to have found the true source of the Nile and a scientific dispute ensued.
This in turn triggered new waves of exploration that sent David Livingstone into the area. However, he failed by pushing too far to the west where he encountered the Congo River. It was not until the Welsh-American explorer Henry Morton Stanley circumvented Lake Victoria during an expedition that ran from 1874 to 1877 that Speke’s claim to have found the source of the Nile was confirmed.
The Nile became a major transportation route during the European colonial period. Many steamers used the waterway to travel through Egypt and south to the Sudan during the 19th century. With the completion of the Suez Canal and the British takeover of Egypt in the 1870s, steamer navigation of the river became a regular occurrence and continued well into the 1960s and the independence of both nations.
Today, the Nile River remains a central feature to Egypt and the Sudan. Its waters are used by all nations that it passes through for irrigation and farming, and its important to the rise and endurance of civilization in the region cannot be underestimated. In fact, the sheer longevity of Egypt’s many ruling dynasties is often attributed by historians to the periodic flows of sediment and nutrients from Lake Victoria to the delta. Thanks to these flows, it is believed, communities along the Nile River never experienced collapse and disintegration as other cultures did.
The Nile is rivaled only by Amazon, which is also the world’s widest river.
Amber is fossilized tree resin (not sap), which has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry.
There are five classes of amber, defined on the basis of their chemical constituents. Because it originates as a soft, sticky tree resin, amber sometimes contains animal and plant material as inclusions. Amber occurring in coal seams is also called resinite, and the term ambrite is applied to that found specifically within New Zealand coal seams.
What is the History and names of Amber?
The English word amber derives from Arabic ʿanbar عنبر, Middle Latin ambar and Middle French ambre. The word was adopted in Middle English in the 14th century as referring to what is now known as ambergris (ambre gris or “grey amber”), solid waxy substance derived from the sperm whale. In the Romance languages, the sense of the word had come to be extended to Baltic amber (fossil resin) from as early as the late 13th century, at first called white or yellow amber (ambre jaune) for disambiguation, and this meaning was adopted in English by the early 15th century. As the use of ambergris waned, this became the main sense of the word.
The two substances (“yellow amber” and “grey amber”) conceivably became associated or confused because they both were found washed up on beaches. Ambergris is less dense than water and floats, whereas amber is less dense
The classical name for amber was electrum (ἤλεκτρον ēlektron), connected to a term for the “beaming Sun”, ἠλέκτωρ (ēlektōr). According to the myth, when Phaëton son of Helios (the Sun) was killed, his mourning sisters became poplars, and their tears became the origin of elektron, amber.
Amber is discussed by Theophrastus in the 4th century BC, and again by Pytheas (c. 330 BC) whose work “On the Ocean” is lost, but was referenced by Pliny the Elder, according to whose The Natural History (in what is also the earliest known mention of the name Germania):
Pytheas says that the Gutones, a people of Germany, inhabit the shores of an estuary of the Ocean called Mentonomon, their territory extending a distance of six thousand stadia; that, at one day’s sail from this territory, is the Isle of Abalus, upon the shores of which, amber is thrown up by the waves in spring, it being an excretion of the sea in a concrete form; as, also, that the inhabitants use this amber by way of fuel, and sell it to their neighbors, the Teutones.
Earlier Pliny says that a large island of three days’ sail from the Scythian coast called Balcia by Xenophon of Lampsacus, author of a fanciful travel book in Greek, is called Basilia by Pytheas. It is generally understood to be the same as Abalus. Based on the amber, the island could have been Heligoland, Zealand, the shores of Bay of Gdansk, the Sambia Peninsula or the Curonian Lagoon, which were historically the richest sources of amber in northern Europe. It is assumed that there were well-established trade routes for amber connecting the Baltic with the Mediterranean (known as the “Amber Road”). Pliny states explicitly that the Germans export amber to Pannonia, from where it was traded further abroad by the Veneti. The ancient Italic peoples of southern Italy were working amber, the most important examples are on display at the National Archaeological Museum of Siritide to Matera. Amber used in antiquity as at Mycenae and in the prehistory of the Mediterranean comes from deposits of Sicily.
Pliny also cites the opinion of Nicias, according to whom amber “is a liquid produced by the rays of the sun; and that these rays, at the moment of the sun’s setting, striking with the greatest force upon the surface of the soil, leave upon it an unctuous sweat, which is carried off by the tides of the Ocean, and thrown up upon the shores of Germany.” Besides the fanciful explanations according to which amber is “produced by the Sun”, Pliny cites opinions that are well aware of its origin in tree resin, citing the native Latin name of succinum (sūcinum, from sucus “juice”). “Amber is produced from a marrow discharged by trees belonging to the pine genus, like gum from the cherry, and resin from the ordinary pine. It is a liquid at first, which issues forth in considerable quantities, and is gradually hardened […] Our forefathers, too, were of opinion that it is the juice of a tree, and for this reason gave it the name of ‘succinum’ and one great proof that it is the produce of a tree of the pine genus, is the fact that it emits a pine-like smell when rubbed, and that it burns, when ignited, with the odour and appearance of torch-pine wood.”
He also states that amber is also found in Egypt and in India, and he even refers to the electrostatic properties of amber, by saying that “in Syria the women make the whorls of their spindles of this substance, and give it the name of harpax [from ἁρπάζω, “to drag”] from the circumstance that it attracts leaves towards it, chaff, and the light fringe of tissues.”
Pliny says that the German name of amber was glæsum, “for which reason the Romans, when Germanicus Cæsar commanded the fleet in those parts, gave to one of these islands the name of Glæsaria, which by the barbarians was known as Austeravia”. This is confirmed by the recorded Old High German glas and Old English glær for “amber” (c.f. glass). In Middle Low German, amber was known as berne-, barn-, börnstēn. The Low German term became dominant also in High German by the 18th century, thus modern German Bernstein besides Dutch Dutch barnsteen.
The Baltic Lithuanian term for amber is gintaras and Latvian dzintars. They, and the Slavic jantar or Hungarian gyanta (‘resin’), are thought to originate from Phoenician jainitar (“sea-resin”).
Early in the nineteenth century, the first reports of amber from North America came from discoveries in New Jersey along Crosswicks Creek near Trenton, at Camden, and near Woodbury.
What is the Composition and formation of Amber ?
Baltic amber inclusions 50 million years old Length 10 mm.
Amber is heterogeneous in composition, but consists of several resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. Amber is a macromolecule by free radical polymerization of several precursors in the labdane family, e.g. communic acid, cummunol, and biformene. These labdanes are diterpenes (C20H32) and trienes, equipping the organic skeleton with three alkene groups for polymerization. As amber matures over the years, more polymerization takes place as well as isomerization reactions, crosslinking and cyclization.
Heated above 200 °C (392 °F), amber suffers decomposition, yielding an “oil of amber”, and leaving a black residue which is known as “amber colophony”, or “amber pitch”; when dissolved in oil of turpentine or in linseed oil this forms “amber varnish” or “amber lac”.
Formation
Molecular polymerization, resulting from high pressures and temperatures produced by overlying sediment, transforms the resin first into copal. Sustained heat and pressure drives off terpenes and results in the formation of amber.
First, the starting resin must be resistant to decay. Many trees produce resin, but in the majority of cases this deposit is broken down by physical and biological process. Exposure to sunlight, rain, and temperate extremes tends to disintegrate resin, and the process is assisted by microorganisms such as bacteria and fungi. For resin to survive long enough to become amber, it must be resistant to such forces or be produced under conditions that exclude them.
Botanical origin
Fossil resins from Europe fall into two categories, the famous Baltic ambers and another that resembles the Agathis group. Fossil resins from the Americas and Africa are closely related to the modern genus Hymenaea, while Baltic ambers are thought to be fossil resins from Sciadopityaceae family plants that used to live in north Europe.
Inclusions
The abnormal development of resin has been called succinosis. Impurities are quite often present, especially when the resin dropped onto the ground, so that the material may be useless except for varnish-making, whence the impure amber is called firniss. Enclosures of pyrites may give a bluish color to amber. The so-called black amber is only a kind of jet. Bony amber owes its cloudy opacity to minute bubbles in the interior of the resin.
In darkly clouded and even opaque amber, inclusions can be imaged using high-energy, high-contrast, high-resolution X-rays.
Classification of Baltic amber by the IAA
Natural Baltic amber – gemstone which has undergone mechanical treatment only (for instance: grinding, cutting, turning or polishing) without any change to its natural properties
Modified Baltic amber – gemstone subjected only to thermal or high-pressure treatment, which changed its physical properties, including the degree of transparency and color, or shaped under similar conditions out of one nugget, previously cut to the required size.
Reconstructed (pressed) Baltic amber – gemstone made of Baltic amber pieces pressed in high temperature and under high pressure without additional components.
Bonded Baltic amber – gemstone consisting of two or more parts of natural, modified or reconstructed Baltic amber bonded together with the use of the smallest possible amount of a colorless binding agent necessary to join the pieces.
Geological record
The oldest amber recovered dates to the Upper Carboniferous period (320 million years ago). Its chemical composition makes it difficult to match the amber to its producers – it is most similar to the resins produced by flowering plants; however, there are no flowering plant fossils until the Cretaceous, and they were not common until the Upper Cretaceous. Amber becomes abundant long after the Carboniferous, in the Early Cretaceous, 150 million years ago, when it is found in association with insects. The oldest amber with arthropod inclusions comes from the Levant, from Lebanon and Jordan. This amber, roughly 125–135 million years old, is considered of high scientific value, providing evidence of some of the oldest sampled ecosystems.
In Lebanon more than 450 outcrops of Lower Cretaceous amber were discovered by Dany Azar a Lebanese paleontologist and entomologist. Among these outcrops 20 have yielded biological inclusions comprising the oldest representatives of several recent families of terrestrial arthropods. Even older, Jurassic amber has been found recently in Lebanon as well. Many remarkable insects and spiders were recently discovered in the amber of Jordan including the oldest zorapterans, clerid beetles, umenocoleid roaches, and achiliid planthoppers.
Baltic amber or succinite (historically documented as Prussian amber) is found as irregular nodules in marine glauconitic sand, known as blue earth, occurring in the Lower Oligocene strata of Sambia in Prussia (in historical sources also referred to as Glaesaria). After 1945 this territory around Königsberg was turned into Kaliningrad Oblast, Russia, where amber is now systematically mined.
It appears, however, to have been partly derived from older Eocene deposits and it occurs also as a derivative phase in later formations, such as glacial drift. Relics of an abundant flora occur as inclusions trapped within the amber while the resin was yet fresh, suggesting relations with the flora of Eastern Asia and the southern part of North America. Heinrich Göppert named the common amber-yielding pine of the Baltic forests Pinites succiniter, but as the wood does not seem to differ from that of the existing genus it has been also called Pinus succinifera. It is improbable, however, that the production of amber was limited to a single species; and indeed a large number of conifers belonging to different genera are represented in the amber-flora.
Paleontological significance
Amber is a unique preservational mode, preserving otherwise unfossilizable parts of organisms; as such it is helpful in the reconstruction of ecosystems as well as organisms; the chemical composition of the resin, however, is of limited utility in reconstructing the phylogenetic affinity of the resin producer.
Amber sometimes contains animals or plant matter that became caught in the resin as it was secreted. Insects, spiders and even their webs, annelids, frogs, crustaceans, bacteria and amoebae, marine microfossils, wood, flowers and fruit, hair, feathers and other small organisms have been recovered in ambers dating to 130 million years ago.
In August 2012, two mites preserved in amber were determined to be the oldest animals ever to have been found in the substance; the mites are 230 million years old and were discovered in north-eastern Italy.
Note : The above story is based on materials provided by Wikipedia 1 & 2.
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This figure shows the number of genes that gained or lost expression in the uterus during the evolution of pregnancy at three major points in mammalian evolution. Credit: Vincent Lynch, Cell Reports
An international team of scientists has identified large-scale genetic changes that marked the evolution of pregnancy in mammals.
They found thousands of genes that evolved to be expressed in the uterus in early mammals, including many that are important for maternal-fetal communication and suppression of the immune system. Surprisingly, these genes appear to have been recruited and repurposed from other tissue types by transposons — ancient mobile genetic elements sometimes thought of as genomic parasites.
The study, published online in Cell Reports on Jan. 29, sheds light on how organisms evolve new morphological structures and functions.
“For the first time, we have a good understanding of how something completely novel evolves in nature, of how this new way of reproducing came to be,” said study author Vincent Lynch, PhD, assistant professor of human genetics at the University of Chicago. “Most remarkably, we found the genetic changes that likely underlie the evolution of pregnancy are linked to domesticated transposable elements that invaded the genome in early mammals. So I guess we owe the evolution of pregnancy to what are effectively genomic parasites.”
To study genetic changes during the evolution of pregnancy in mammals, Lynch and his colleagues used high-throughput sequencing to catalog genes expressed in the uterus of several types of living animals — placental mammals (a human, monkey, mouse, dog, cow, pig, horse and armadillo), a marsupial (opossum), an egg-laying mammal (platypus), a bird, a reptile and a frog. Then they used computational and evolutionary methods to reconstruct which genes were expressed in ancestral mammals.
The researchers found that as the first mammals evolved — and resources for fetal development began to come more from the mother and less from a yolk — hundreds of genes that are important for cellular signaling, metabolism and uterine development started to be expressed in the uterus. As the eggshell was lost and live-birth evolved in the common ancestor to marsupials and placental mammals, more than 1,000 genes were turned on, many of which were strongly linked to the establishment of maternal-fetal communication. As prolonged pregnancy evolved in placental mammals, hundreds of genes began to be expressed that greatly strengthened and elaborated maternal-fetal communication, as well as locally suppressing the maternal immune system in the uterus — thus protecting the developing fetus.
The team also identified hundreds of genes that were turned off as these lineages evolved, many of which had been involved in egg shell formation.
“We found lots of genes important for maintaining hormone signaling and mediating maternal-fetal communication, which are essential for pregnancy, evolved to be expressed in the uterus in early mammals,” Lynch said. “But immune suppression genes stand out. The fetus is genetically distinct from the mother. If these immune genes weren’t expressed in the uterus, the fetus would be recognized by the mother’s immune system as foreign and attacked like any other parasite.”
In addition to function, Lynch and his colleagues investigated the origin of these genes. They found most already had roles in other organ and tissue systems such as the brain, digestive and circulatory systems. But during the evolution of pregnancy, these genes were recruited to be expressed in the uterus for new purposes. They evolved regulatory elements that allowed them to be activated by progesterone, a hormone critical in reproduction.
The team found that this process was driven by ancient transposons — stretches of non-protein coding DNA that can change their position within the genome. Sometimes called “jumping genes,” transposons are generally thought to be genomic parasites that serve only to replicate themselves. Many of the ancient mammalian transposons possessed progesterone binding sites that regulate this process. By randomly inserting themselves into other places in the genome, transposons appear to have passed on this activation mechanism to nearby genes.
“Genes need some way of knowing when and where to be expressed,” Lynch said. “Transposable elements appear to have brought this information, allowing old genes to be expressed in a new location, the uterus, during pregnancy. Mammals very likely have a progesterone-responsive uterus because of these transposons.”
Lynch and his colleagues note their findings represent a novel explanation for how entirely new biological structures and functions arise. Rather than genes gradually evolving uterine expression one at a time, transposable elements coordinated large-scale, genome-wide changes that allowed numerous genes to be activated by the same signal — in this case, progesterone, which helped drive the evolution of pregnancy.
“It’s easy to imagine how evolution can modify an existing thing, but how new things like pregnancy evolve has been much harder to understand,” Lynch said. “We now have a new mechanistic explanation of this process that we’ve never had before.”
Reference:
Vincent J. Lynch, Mauris C. Nnamani, Aurélie Kapusta, Kathryn Brayer, Silvia L. Plaza, Erik C. Mazur, Deena Emera, Shehzad Z. Sheikh, Frank Grützner, Stefan Bauersachs, Alexander Graf, Steven L. Young, Jason D. Lieb, Francesco J. DeMayo, Cédric Feschotte, Günter P. Wagner. Ancient Transposable Elements Transformed the Uterine Regulatory Landscape and Transcriptome during the Evolution of Mammalian Pregnancy. Cell Reports, 2015; DOI: 10.1016/j.celrep.2014.12.052
This global positioning satellite receiver is part of Iceland’s network of 62 such receivers that geoscientists are using to detect movements of the Icelandic crust that are as small as one millimeter per year. Langjökull glacier can be seen in the background. Credit: Richard A. Bennett/ University of Arizona
Earth’s crust under Iceland is rebounding as global warming melts the island’s great ice caps, a University of Arizona-led team reports in an upcoming issue of Geophysical Research Letters.
The paper is the first to show the current fast uplift of the Icelandic crust is a result of accelerated melting of the island’s glaciers and coincides with the onset of warming that began about 30 years ago, the scientists said.
Some sites in south-central Iceland are moving upward as much as 1.4 inches (35 mm) per year — a speed that surprised the researchers.
“Our research makes the connection between recent accelerated uplift and the accelerated melting of the Icelandic ice caps,” said first author Kathleen Compton, a UA geosciences doctoral candidate.
Geologists have long known that as glaciers melt and become lighter, Earth rebounds as the weight of the ice decreases.
Whether the current rebound geologists detect is related to past deglaciation or modern ice loss has been an open question until now, said co-author Richard Bennett, a UA associate professor of geosciences.
“Iceland is the first place we can say accelerated uplift means accelerated ice mass loss,” Bennett said.
To figure out how fast the crust was moving upward, the team used a network of 62 global positioning satellite receivers fastened to rocks throughout Iceland. By tracking the position of the GPS receivers year after year, the scientists “watch” the rocks move and can calculate how far they have traveled — a technique called geodesy.
The new work shows that, at least for Iceland, the land’s current accelerating uplift is directly related to the thinning of glaciers and to global warming.
“What we’re observing is a climatically induced change in Earth’s surface,” Bennett said.
He added there is geological evidence that during the past deglaciation roughly 12,000 years ago, volcanic activity in some regions of Iceland increased thirtyfold.
Others have estimated the Icelandic crust’s rebound from warming-induced ice loss could increase the frequency of volcanic eruptions such as the 2010 eruption of Eyjafjallajökull, which had negative economic consequences worldwide.
The article “Climate driven vertical acceleration of Icelandic crust measured by CGPS geodesy” by Compton, Bennett and their co-author Sigrun Hreinsdóttir of GNS Science in Avalon, New Zealand, was accepted for publication Jan. 14, 2015, and is soon to be published online. The National Science Foundation and the Icelandic Center for Research funded the research.
Some of Iceland’s GPS receivers have been in place since 1995. Bennett, Hreinsdóttir and colleagues had installed 20 GPS receivers in Iceland in 2006 and 2009, thus boosting the coverage of the nation’s geodesy network. In central and southern Iceland, where five of the largest ice caps are located, the receivers are 18 miles (30 km) or less apart on average.
The team primarily used the geodesy network to track geological activity such as earthquakes and volcanic eruptions.
In 2013, Bennett noticed one of long-running stations in the center of the country was showing that site was rebounding at an accelerated rate. He wondered about it, so he and his colleagues checked the nearby stations to see if they had recorded the same changes.
“The striking answer was, yes, they all do,” he said. “We wondered what in the world could be causing this?”
The team began systematically analyzing years of signals from the entire network and found the fastest uplift was the region between several large ice caps. The rate of uplift slowed the farther the receiver was from the ice cap region.
Other researchers had been measuring ice loss and observed a notable uptick in the rate of melting since 1995. Temperature records for Iceland, some of which go back to the 1800s, show temperatures increasing since 1980.
To determine whether the same rate of ice loss year after year could cause such an acceleration in uplift, Compton tested that idea using mathematical models. The answer was no: The glaciers had to be melting faster and faster every year to be causing more and more uplift.
Compton found the onset of rising temperatures and the loss of ice corresponded tightly with her estimates of when uplift began.
“I was surprised how well everything lined up,” she said.
Bennett said, “There’s no way to explain that accelerated uplift unless the glacier is disappearing at an accelerated rate.”
Estimating ice loss is laborious and difficult, he said. “Our hope is we can use current GPS measurements of uplift to more easily quantify ice loss.”
The team’s next step is to analyze the uplift data to reveal the seasonal variation as the ice caps grow during the winter snow season and melt during the summer.
Reference:
Kathleen Compton, Richard A. Bennett, Sigrun Hreinsdóttir. Climate driven vertical acceleration of Icelandic crust measured by CGPS geodesy. Geophysical Research Letters, 2015; DOI: 10.1002/2014GL062446
Note : The above story is based on materials provided by University of Arizona. The original article was written by Mari N. Jensen.
New FSU study says some is sitting on the Gulf floor
After 200 million gallons of crude oil spilled into the Gulf of Mexico in April 2010, the government and BP cleanup crews mysteriously had trouble locating all of it.
Now, a new study led by Florida State University Professor of Oceanography Jeff Chanton finds that some 6 million to 10 million gallons are buried in the sediment on the Gulf floor, about 62 miles southeast of the Mississippi Delta.
“This is going to affect the Gulf for years to come,” Chanton said. “Fish will likely ingest contaminants because worms ingest the sediment, and fish eat the worms. It’s a conduit for contamination into the food web.”
The article, published in the latest edition of the journal Environmental Science & Technology, details how oil caused particles in the Gulf to clump together and sink to the ocean floor.
The researchers used carbon 14, a radioactive isotope as an inverse tracer to determine where oil might have settled on the floor. Oil does not have carbon 14, so sediment that contained oil would immediately stand out.
Chanton then collaborated with Tingting Zhao, associate professor of geography at Florida State, to use geographic information system mapping to create a map of the oiled sediment distribution on the sea floor.
Chanton said in the short term, the oil sinking to the sea floor might have seemed like a good thing because the water was clarified, and the oil was removed from the water. But, in the long term, it’s a problem, he said.
Less oxygen exists on the sea floor relative to the water column, so the oiled particles are more likely to become hypoxic, meaning they experience less oxygen. Once that happens, it becomes much more difficult for bacteria to attack the oil and cause it to decompose, Chanton said.
Chanton’s research is supported by the Florida State University-headquartered Deep-C Consortium as well as the Ecogig consortium, centered at the University of Mississippi. The work was funded by the Gulf of Mexico Research Institute created to allocate the money made available to support scientific research by BP.
His previous research examined how methane-derived carbon from the oil spill entered the food web.
In addition to Chanton and Zhao, the other authors are Samantha Bosman of Florida State, Brad E. Rosenheim and David Hollander from University of South Florida and Samantha Joye from University of Georgia. Charlotte Brunner, Kevin Yeager and Arne Diercks of University of Southern Mississippi also contributed.
This illustration shows what the newly discovered long-necked dinosaur may have looked like. Credit: Xing Lida
University of Alberta paleontologists including PhD student Tetsuto Miyashita, former MSc student Lida Xing and professor Philip Currie have discovered a new species of a long-necked dinosaur from a skeleton found in China. The findings have been published in a new paper in the Journal of Vertebrate Paleontology.
Qijianglong (pronounced “CHI-jyang-lon”) is about 15 metres in length and lived about 160 million years ago in the Late Jurassic. The name means “dragon of Qijiang,” for its discovery near Qijiang City, close to Chongqing. The fossil site was found by construction workers in 2006, and the digging eventually hit a series of large neck vertebrae stretched out in the ground. Incredibly, the head of the dinosaur was still attached. “It is rare to find a head and neck of a long-necked dinosaur together because the head is so small and easily detached after the animal dies,” explains Miyashita.
The new species belongs to a group of dinosaurs called mamenchisaurids, known for their extremely long necks sometimes measuring up to half the length of their bodies. Most sauropods, or long-necked dinosaurs, have necks only about one third the length of their bodies.
Unique among mamenchisaurids, Qijianglong had neck vertebrae that were filled with air, making their necks relatively lightweight despite their enormous size. Interlocking joints between the vertebrae also indicate a surprisingly stiff neck that was much more mobile bending vertically than sideways, similar to a construction crane.
“Qijianglong is a cool animal. If you imagine a big animal that is half-neck, you can see that evolution can do quite extraordinary things.” says Miyashita.
Mamenchisaurids are only found in Asia, but the discovery of Qijianglong reveals that there could be as many differences among mamenchisaurids as there are between long-necked dinosaurs from different continents.
“Qijianglong shows that long-necked dinosaurs diversified in unique ways in Asia during Jurassic times–something very special was going on in that continent,” says Miyashita. “Nowhere else we can find dinosaurs with longer necks than those in China. The new dinosaur tells us that these extreme species thrived in isolation from the rest of the world.”
Miyashita believes that mamenchisaurids evolved into many different forms when other long-necked dinosaurs went extinct in Asia. “It is still a mystery why mamenchisaurids did not migrate to other continents,” he says. It is possible that the dinosaurs were once isolated as a result of a large barrier such as a sea, and lost in competition with invading species when the land connection was restored later.
The Qijianglong skeleton is now housed in a local museum in Qijiang. “China is home to the ancient myths of dragons,” says Miyashita, “I wonder if the ancient Chinese stumbled upon a skeleton of a long-necked dinosaur like Qijianglong and pictured that mythical creature.”
Reference:
Lida Xing, Tetsuto Miyashita, Jianping Zhang, Daqing Li, Yong Ye, Toru Sekiya, Fengping Wang, Philip J. Currie. A new sauropod dinosaur from the Late Jurassic of China and the diversity, distribution, and relationships of mamenchisaurids. Journal of Vertebrate Paleontology, 2015; e889701 DOI: 10.1080/02724634.2014.889701 Note : The above story is based on materials provided by University of Alberta. The original article was written by Kristy Condon.
A new technique for passively probing the seafloor using weak seismic waves generated by ocean waves was tested at the Ekofisk oil field in the North Sea. Credit: Wikipedia /Creative Commons
A technology developed by Stanford scientists for passively probing the seafloor using weak seismic waves generated by the ocean could revolutionize offshore oil and natural gas extraction by providing real-time monitoring of the subsurface while lessening the impact on marine life.
“We’ve shown that we can generate images of the subsurface nearly every day instead of taking snapshots just two or three times a year,” said Biondo Biondi, professor of geophysics at Stanford’s School of Earth Sciences.
Currently, many energy companies use a technique called time-lapse reflection seismology to monitor offshore oil and gas deposits to optimize production and look for hazards such as hidden gas pockets. Reflection seismology involves ships towing arrays of “air guns” that explode every 10 to 15 seconds to produce loud sound pulses. The pulses bounce off the seafloor and geological formations beneath, then journey back to the surface, where they are recorded by hydrophones. The data are then deciphered to reveal details about subsurface structures.
Each survey can cost tens of millions of dollars, and as a result they are only conducted two to three times a year. Environmental groups and marine biologists have expressed concerns about the use of air guns for contributing to noise pollution in the ocean that can disturb or even injure marine animals, including humpback whales and giant squid.
The new technique developed by Biondi and Sjoerd de Ridder, a student of Biondi’s who is now a postdoctoral scientist at the University of Edinburgh, is different. It exploits naturally occurring seismic waves generated by Earth’s oceans that are several orders of magnitude weaker than those produced by earthquakes.
As ocean waves collide with one another, they create pressures on the sea floor, where they generate seismic waves that then propagate in every direction. Scientists have known about this “ambient seismic field” for nearly a century, but it was only recently that they understood ways to harness it.
“We knew the ambient seismic energy was there, but we didn’t know what we could do with it,” De Ridder said. “That understanding has only been developed in recent years. Our technique provides the first large-scale application to harness it for oil and gas production.”
The technique that Biondi and De Ridder developed, called ambient seismic field noise-correlation tomography, or ASNT, uses sensors embedded in the seafloor. The sensors, which are typically installed by robotic submersibles, are connected to one another by cables and arranged into parallel rows that can span several kilometers of the seafloor. Another cable connects the sensor array to a platform in order to collect data in real time.
The sensors record ambient seismic waves traveling through Earth’s crust. The waves are ubiquitous, continuously generated and traveling in every direction, but using careful signal-processing schemes they developed, Biondi and De Ridder can digitally isolate only those waves that are passing through one sensor and then another one downstream. When this is done repeatedly, and for multiple sensors in the network, what emerges is a “virtual” seismic wave pattern that is remarkably similar to the kind generated by air guns.
Less disruptive
Because the ASNT technique is entirely passive, meaning it does not require a controlled explosion or a loud air gun blast to create a seismic wave signature, it can be performed for a fraction of the cost of an active-reflection-seismology survey and should be far less disruptive to marine life, the scientists say.
Since 2007, Biondi and De Ridder have been testing and refining their technique in a real-world laboratory in Europe. The scientists worked with the energy companies BP and ConocoPhillips to study recordings from existing sensor arrays in the Valhall and Ekofisk oil fields in the North Sea that are capable of recording ambient seismic waves.
The proof-of-concept experiment has been successful, and the scientists have demonstrated that they can image the subsurface at Valhall down to a depth of nearly 1,000 feet. “We’ve now shown that our technique can very reliably and repeatedly retrieve an image of the near-surface,” De Ridder said. “Our hope is that they can also reveal changes in the rocks that could signal an impending problem.”
The Stanford scientists outlined their technique and detailed some of their results from Valhall, as well as from Ekofisk, in a series of technical papers, the latest of which was recently published in the journal Geophysical Research Letters.
This is a conception of Earth’s core overlaid by the electronic structure of iron; the width (fuzziness) of the lines results from the electron-electron scattering. Image courtesy of Ronald Cohen. Credit: Ronald Cohen
Earth’s magnetic field is crucial for our existence, as it shields the life on our planet’s surface from deadly cosmic rays. It is generated by turbulent motions of liquid iron in Earth’s core. Iron is a metal, which means it can easily conduct a flow of electrons that makes up an electric current. New findings from a team including Carnegie’s Ronald Cohen and Peng Zhang shows that a missing piece of the traditional theory explaining why metals become less conductive when they are heated was needed to complete the puzzle that explains this field-generating process. Their work is published in Nature.
The center of the Earth is very hot, and the flow of heat from the planet’s center towards the surface is thought to drive most of the dynamics of the Earth, ranging from volcanoes to plate tectonics. It has long been thought that heat flow drives what is called thermal convection — the hottest liquid becomes less dense and rises, as the cooler, more-dense liquid sinks — in Earth’s liquid iron core and generates Earth’s magnetic field. But recent calculations called this theory into question, launching new quests for its explanation.
In their work, Cohen and Zhang, along with Kristjan Haule of Rutgers University, used a new computational physics method and found that the original thermal convection theory was right all along. Their conclusion hinges on discovering that the classic theory of metals developed in the 1930’s was incomplete.
The electrons in metals, such as the iron in Earth’s core, carry current and heat. A material’s resistivity impedes this flow. The classic theory of metals explains that resistivity increases with temperature, due to atoms vibrating more as the heat rises. The theory says that at high temperatures resistivity happens when electrons in the current bounce off of vibrating atoms. These bounced electrons scatter and resist the current flow. As temperature increases, the atoms vibrate more, and increasing the scattering of bounced electrons. The electrons not only carry charge, but also carry energy, so that thermal conductivity is proportional to the electrical conductivity.
The work that had purportedly thrown the decades-old prevailing theory on the generation of Earth’s magnetic field out the window claimed that thermal convection could not drive magnetic-field generation. The calculations in those studies said that the resistivity of the molten metal in Earth’s core, which is generated by this electron scattering process, would be too low, and thus the thermal conductivity too high, to allow thermal convection to generate the magnetic field.
Cohen, Zhang, and Haule’s new work shows that the cause of about half of the resistivity generated was long neglected: it arises from electrons scattering off of each other, rather than off of atomic vibrations.
“We uncovered an effect that had been hiding in plain sight for 80 years,” Cohen said. “And now the original dynamo theory works after all!”
Reference:
Peng Zhang, R. E. Cohen, K. Haule. Effects of electron correlations on transport properties of iron at Earth’s core conditions. Nature, 2015; 517 (7536): 605 DOI: 10.1038/nature14090
This map of the California Current shows the extent of the low-oxygen seafloor. Yellow indicates intermediate hypoxia, while red zones are areas of severe oxygen loss. Credit: UC Davis
Seafloor sediment cores reveal abrupt, extensive loss of oxygen in the ocean when ice sheets melted roughly 10,000-17,000 years ago, according to a study from the University of California, Davis. The findings provide insight into similar changes observed in the ocean today.
In the study, published in the journal PLOS ONE, researchers analyzed marine sediment cores from different world regions to document the extent to which low oxygen zones in the ocean have expanded in the past, due to climate change.
From the subarctic Pacific to the Chilean margins, they found evidence of extreme oxygen loss stretching from the upper ocean to about 3,000 meters deep. In some oceanic regions, such loss took place over a time period of 100 years or less.
“This is a global story that knits these regions together and shows that when you warm the planet rapidly, whole ocean basins can lose oxygen very abruptly and very extensively,” said lead author Sarah Moffitt, a postdoctoral scholar with the UC Davis Bodega Marine Laboratory and formerly a Ph.D. student with the Graduate Group in Ecology.
Marine organisms, from salmon and sardines to crab and oysters, depend on oxygen to exist. Adapting to an ocean environment with rapidly dropping oxygen levels would require a major reorganization of living things and their habitats, much as today polar species on land are retreating to higher, cooler latitudes.
The researchers chose the deglaciation period because it was a time of rising global temperatures, atmospheric carbon dioxide and sea levels — many of the global climate change signs the Earth is experiencing now.
“Our modern ocean is moving into a state that has no precedent in human history,” Moffitt said. “The potential for our oceans to look very, very different in 100-150 years is real. How do you use the best available science to care for these critical resources in the future? Resource managers and conservationists can use science like this to guide a thoughtful, precautionary approach to environmental management.”
The study’s co-authors include: Russell Moffitt with the Marine Conservation Institute; Tessa Hill, professor in the UC Davis Department of Earth and Planetary Sciences and at the Bodega Marine Laboratory; Wilson Sauthoff and Catherine Davis of the Department of Earth and Planetary Sciences; and Kathryn Hewett, UC Davis Department of Civil and Environmental Engineering.
The study arose from a graduate level course that was taught at UC Davis in winter 2013 by Hill. The research was supported by the National Science Foundation.
Reference:
Sarah E. Moffitt, Russell A. Moffitt, Wilson Sauthoff, Catherine V. Davis, Kathryn Hewett, Tessa M. Hill. Paleoceanographic Insights on Recent Oxygen Minimum Zone Expansion: Lessons for Modern Oceanography. PLOS ONE, 2015; 10 (1): e0115246 DOI: 10.1371/journal.pone.0115246
Pieces of sediment from the Cretaceous period encased in lava floated to the surface with the underwater eruption of El Hierro in 2011, bringing scientists valuable data on the islands’ ocean floor. The analysis of the materials matches the origin of the Canary Islands archipelago to the model of how Hawaii was formed and confirms that the oldest islands are found to the east and the youngest to the west.
In July 2011, the island of El Hierro experienced the first signs of a possible volcanic eruption with low intensity but unusually numerous earthquakes. The seismicity became ever more intense, culminating in the underwater eruption two kilometres south of the village of La Restinga on 10 October 2011.
As part of research published in Scientific Reports, from the group Nature, scientists from centres in Sweden, Spain and Portugal have studied the volcanic material which floated to the surface of the sea after the eruption. The nannofossils that they contain confirm that the islands were formed from east to west. This data sheds light on the origin and life cycle of oceanic islands, which has been debated since the beginnings of geology.
“Our study confirms, for the first time, that the underwater activity which starts off the construction of the islands follows the pattern of the known age progression of subaerial volcanic activity (the emerging part of the islands) with older ages to the east of the archipelago, Fuerteventura and Lanzarote, and the youngest to the west, El Hierro and La Palma,” as Vicente Soler, researcher at the Volcanological Station of the Canary Islands (CSIC) tells SINC.
The new finding brings the origin of the Canaries closer to the Hawaiian model, given that the Canary Islands archipelago is not located in an area where plates meet, but in the middle of the African plate. This also occurs with Hawaii; its islands are in the middle of the Pacific plate and are located in an almost straight line.
“With the Canary Islands, a string of islands was formed as the oceanic plate shifted over a deep set magmatic source, contrary to the theory which attributes the origin of the archipelago to regional tectonics, which are responsible, amongst other things, for the formation of the neighbouring Atlas mountains in northern Morocco,” the scientist points out.
The origin of the volcanic materials
Soler explains that these floating volcanic materials are better known as ‘restingolites’, while in scientific literature they have been given the confusing name of ‘xeno pumice’.
“There is much scientific controversy regarding what restingolites are and where they come from. The materials of interest for this study were collected floating on the sea during the first days of eruption and a week later after their arrival ashore,” he adds.
Due to the small fossils they contain, they are attributed to the Cretaceous period, in full formation of the Atlantic ocean with America, on separating from what are today Europe and Africa.
According to the researchers who participated in this study, including Valentín R. Troll, from Uppsala University and Juan Carlos Carracedo from the University of Las Palmas de Gran Canaria, these fragments must be pieces of pre-island sediments ‘reworked’ by the column of magma where the eruption occurred while en-route to the surface.
“Also, due to the silica content, they would seem to be rhyolites, rocks related to a potentially dangerous type of volcanic activity. Yet the existence of nannofossils inside the restingolites is a compelling argument in favour of the first hypothesis,” concludes Soler.
Reference:
Kirsten Zacze, Valentin R. Troll, Mario Cachao, Jorge Ferreira, Frances M. Deegan, Juan Carlos Carracedo, Vicente Soler, Fiona C. Meade y Steffi Burchardt. “Nannofossils in 2011 El Hierro eruptive products reinstate plume model for Canary Islands” Scientific Report 5: 7945 | DOI: 10.1038/srep07945 . January 2014.
Mars has two differently shaped hemispheres: the lowlands of the northern hemisphere and the volcanic highlands (yellow to red regions) of the southern hemisphere. A “giant impact” on the southern pole is suspected to be the reason for this. Credit: MOLA Science Team
The two hemispheres of Mars are more different from any other planet in our solar system. Non-volcanic, flat lowlands characterise the northern hemisphere, while highlands punctuated by countless volcanoes extend across the southern hemisphere. Although theories and assumptions about the origin of this so-called and often-discussed Mars dichotomy abound, there are very few definitive answers. ETH Zurich geophysicists under Giovanni Leone are now providing a new explanation. Leone is the lead author of a paper recently published in the journal Geophysical Research Letters.
Using a computer model, the scientists have concluded that a large celestial object must have smashed into the Martian south pole in the early history of the Solar System. Their simulation shows that this impact generated so much energy that it created a magma ocean, which would have extended across what is today’s southern hemisphere. The celestial body that struck Mars must have been at least one-tenth the mass of Mars to be able to unleash enough energy to create this magma ocean. The molten rock eventually solidified into the mountainous highlands that today comprise the southern hemisphere of Mars.
In their simulation, the researchers assumed that the celestial body consisted to a large degree of iron, had a radius of at least 1,600 kilometres, and crashed into Mars at a speed of five kilometres per second. The event is estimated to have occurred around 4 to 15 million years after the Red Planet was formed. Mars’ crust must have been very thin at that time, like the hard, caramelised surface of a crème brûlée. And, just like the popular dessert, hiding beneath the surface was a liquid interior.
When the celestial object impacted, it added more mass to Mars, particularly iron. But the simulation also found that it triggered strong volcanic activity lasting three billion years. Around the equator in particular, numerous mantle plumes were generated as a consequence of the impact, which migrated to the south pole where they ended. Mantle plumes are magma columns that transport liquid material from the mantle to the surface.
In the model, the researchers found that activity on Mars died down after around three billion years, after which time the Red Planet experienced neither volcanic activity nor a magnetic field — this is consistent with observations and measurements.
Volcanic activity and topography modelled under realistic conditions
Earlier theories posited the opposite, namely that there must have been a gigantic impact or many smaller strikes against the northern hemisphere. The most important theory about the origin of the Mars dichotomy was formulated by two American researchers in 1984 in an article in the journal Nature. They postulated that a large celestial object struck the Martian north pole. In 2008 a different team revived this idea and published it once again in Nature.
This theory did not convince Leone: “Our scenarios more closely reflect a range of observations about Mars than the theory of a northern hemisphere impact,” states Leone. The volcanoes on Mars are very unevenly distributed: they are common and widespread on the southern hemisphere, but are rare and limited to only a few small regions in the northern hemisphere. “Our model is an almost identical depiction of the actual distribution of volcanic identity,” asserts Leone. According to the researcher, no other model has been able to portray or explain this distribution before.
Their simulation was also able to reproduce the different topographies of the two hemispheres in an extremely realistic manner, says Leone. And he goes on to explain that the model — depending on the composition of the impact body chosen — is a virtually perfect representation of the size and shape of the hemispheres. One condition, however, is that the celestial body impacting Mars consist of 80 per cent iron; when the researchers simulated the impact with a celestial body made of pure silicate rock, the resulting image did not correspond to the reality of the dichotomy.
Magnetic field tipped the balance
Lastly, the model developed by the ETH researchers confirmed the date on which the magnetic field on Mars ceased to exist. The date calculated by the model corresponds to around 4.1 billion years ago, a figure previously proven by other scientists. The model also demonstrates why it ceased: a sharp decrease in heat flow from the core into the mantle and the crust in the first 400 million years after the impact. After a billion years, the heat flow was only one-tenth its initial value, which was too low to maintain even the volcanism. The model’s calculations closely match previous calculations and mineralogical explorations.
The volcanic activity is related to the heat flow, explains Leone, though the degree of volcanic activity could be varied in the simulation and influenced by the strength of the impact. This, he states, is in turn linked to the size and composition of the celestial object. In other words, the larger it is, the stronger the volcanic activity is. Nevertheless, after one billion years the volcanic vents were extinguished — regardless of the size of the impact.
It has become increasingly clear to Giovanni Leone that Mars has always been an extremely hostile planet, and he considers it almost impossible that it ever had water. “Since the beginning of time, this planet was characterised by intense heat and volcanic activity, which would have evaporated any possible water and made the emergence of life highly unlikely,” asserts the planet researcher.
Reference:
Giovanni Leone, Paul J. Tackley, Taras V. Gerya, Dave A. May, Guizhi Zhu. Three-dimensional simulations of the southern polar giant impact hypothesis for the origin of the Martian dichotomy. Geophysical Research Letters, 2014; 41 (24): 8736 DOI: 10.1002/2014GL062261
Note : The above story is based on materials provided by ETH Zurich.
Artist’s conception of three of the four newly identified ancient snakes: (top left) Portugalophis lignites (Upper Jurassic) in a gingko tree, from coal swamp deposits at Guimarota, Portugal; (top right) Diablophis gilmorei (Upper Jurassic), hiding in a ceratosaur skull, from the Morrison Formation in Fruita, Colorado; (bottom) Parviraptor estesi (Upper Jurassic/Lower Cretaceous) swimming in freshwater lake with snails and algae, from the Purbeck Limestone in Swanage, England. Credit: Julius Csotonyi
Fossilized remains of four ancient snakes between 140 and 167 million years old are changing the way we think about the origin of snakes, and how and when it happened.
The discovery by an international team of researchers, including University of Alberta professor Michael Caldwell, rolls back the clock on snake evolution by nearly 70 million years.
“The study explores the idea that evolution within the group called ‘snakes’ is much more complex than previously thought,” says Caldwell, professor in the Faculty of Science and lead author of the study published today in Nature Communications. “Importantly, there is now a significant knowledge gap to be bridged by future research, as no fossils snakes are known from between 140 to 100 million years ago.”
The oldest known snake, from an area near Kirtlington in Southern England, Eophis underwoodi, is known only from very fragmentary remains and was a small individual, though it is hard to say how old it was at the time it died. The largest snake, Portugalophis lignites, from coal deposits near Guimarota in Portugal, was a much bigger individual at about a metre long. Several of these ancient snakes (Eophis, Portugalophis and Parviraptor) were living in swampy coastal areas on large island chains in western parts of ancient Europe. The North American species, Diablophis gilmorei, was found in river deposits from some distance inland in western Colorado.
This new study makes it clear that the sudden appearance of snakes some 100 million years ago reflects a gap in the fossil record, not an explosive radiation of early snakes. From 167 to 100 million years ago, snakes were radiating and evolving toward the elongated, limb-reduced body shape characterizing the now well known, ~100-90 million year old, marine snakes from the West Bank, Lebanon and Argentina, that still possess small but well-developed rear limbs.
Caldwell notes that the identification of definitive snake skull features reveals that the fossils — previously associated with other non-snake lizard remains — represent a much earlier time frame for the first appearance of snakes.
“Based on the new evidence and through comparison to living legless lizards that are not snakes, the paper explores the novel idea that the evolution of the characteristic snake skull and its parts appeared long before snakes lost their legs,” he explains.
He adds that the distribution of these newly identified oldest snakes, and the anatomy of the skull and skeletal elements, makes it clear that even older snake fossils are waiting to be found.
Video:
Reference:
Michael W. Caldwell, Randall L. Nydam, Alessandro Palci, Sebastián Apesteguía. The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution. Nature Communications, 2015; 6: 5996 DOI: 10.1038/ncomms6996
Note : The above story is based on materials provided by University of Alberta. The original article was written by Julie Naylor.
