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Rust under pressure could explain deep Earth anomalies

Rust under pressure could-GeologyPage
An artwork depicting the decomposition of FeOOH in lower mantle conditions. The cycle starts from α-FeOOH (blue dot on the top) to its high-pressure form (brown dot), to FeO2 (center crystal) and hydrogen (cyan bubbles), and finally produce other minerals (bubbles on the left side). Credit: Ms. Xiaoya.

Using laboratory techniques to mimic the conditions found deep inside the Earth, a team of Carnegie scientists led by Ho-Kwang “Dave” Mao has identified a form of iron oxide that they believe could explain seismic and geothermal signatures in the deep mantle. Their work is published in Nature.

Iron and oxygen are two of the most geochemically important elements on Earth. The core is rich in iron and the atmosphere is rich in oxygen, and between them is the entire range of pressures and temperatures on the planet.

“Interactions between oxygen and iron dictate Earth’s formation, differentiation—or the separation of the core and mantle—and the evolution of our atmosphere, so naturally we were curious to probe how such reactions would change under the high-pressure conditions of the deep Earth,” said Mao.

The research team—Qingyang Hu, Duck Young Kim, Wenge Yang, Liuxiang Yang, Yue Meng, Li Zhang, & Ho-Kwang Mao—put ordinary rust, or FeOOH, under about 900,000 times normal atmospheric pressure and at about 3200 degrees Fahrenheit and were able to synthesize a form of iron oxide, FeO2, that structurally resembles pyrite, also known as fool’s gold. The reaction gave off hydrogen in the form of H2.

FeOOH is found in iron ore deposits that exist in bogs, so it could easily move into the deep Earth at plate tectonic boundaries, as could samples of ferric oxide, Fe2O3, which along with water will also form the pyrite-like iron oxide under deep lower mantle conditions.

Why does this interest the researchers? For one thing, this type of reaction could have started in Earth’s infancy, and understanding it could inform theories of our own planet’s evolution, as well as its current geochemistry.

Furthermore, the H2 released in this reaction would work its way upward, possibly reacting with other materials on its way. Meanwhile, the iron oxide would settle planet’s depths and form reservoirs of oxygen there, particularly if one of these patches of iron oxide moved upward along the pressure gradient to the middle part of the mantle and separated into iron and O2.

“Pools of free oxygen under these conditions could create many reactions and chemical phases, which might be responsible for seismic and geochemical signatures of the deep Earth,” Mao explained.

“Our experiments mimicking mantle conditions demonstrate that more research is needed on this pyrite-like phase of iron oxide.” Hu added.

The research team believes their findings could even offer an alternate explanation for the Great Oxygenation Event that changed Earth’s atmosphere between 2 and 2.5 billion years ago. The rise of bacteria performing photosynthesis, which releases oxygen as a byproduct, is often considered the source of the rapid increase in atmospheric oxygen, which had previously been scarce. But releases of oxygen from upwelling of deep mantle FeO2 patches could provide an abiotic explanation for the phenomenon, they say.

Reference:
FeO2 and FeOOH under deep lower-mantle conditions and Earth’s oxygen–hydrogen cycles, Nature, DOI:10.1038/nature18018

Note: The above post is reprinted from materials provided by Carnegie Institution for Science.

New research counters claim that the ‘Hobbit’ had Down syndrome

New research counters claim that-GeologyPage
Profiles of the midline of the skull as seen in an x-ray or CT scan for people with and without Down syndrome as well as LB1, the type specimen of Homo floresiensis. The differences between the two groups of humans are minor compared to the very distinct shape of LB1. Credit: Figure courtesy of the authors

Analysis of a wealth of new data contradicts an earlier claim that LB1, an ~80,000 year old fossil skeleton from the Indonesian island of Flores, had Down syndrome, and further confirms its status as a fossil human species, Homo floresiensis.

From the start, fossils of a tiny population of human-like creatures from Flores (the so-called “Hobbits” of Southeast Asia) have been controversial. Are these remains evidence of a new species of fossil human, Homo floresiensis? Or are these remains simply a population of small-bodied humans (Homo sapiens), like ourselves, but with one or more individuals suffering from a developmental disorder? Researchers recently diagnosed LB1, the most complete individual recovered, with Down syndrome.

New analysis of features from across the skeleton by an international team of researchers led by Karen Baab, Ph.D., Assistant Professor of Anatomy at Midwestern University in Glendale, AZ, convincingly demonstrates that LB1 did not have Down syndrome. In addition to measuring individual bones, the scientists used CT scanning to reconstruct the brain and view internal structures of the skull, as well as assessing the 3-dimensional (3D) shape of the skull.

The study, titled “A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis,” is published in the June 8, 2016 edition of PLOS ONE.

Down Syndrome

The diagnosis of Down syndrome is the most recent in a long line of diseases attributed to this particular skeleton. Down syndrome is a chromosomal disorder characterized by cognitive delays and often certain physical features, including reduced stature and brain size. The original diagnosis also emphasized the wide and short (front-to-back) shape of the skull, shape of the chin, and short femur (thigh bone) in LB1 as evidence of Down syndrome. Diagnosing Down syndrome in fossils is complicated by the fact that many common features are found in the soft tissues of the body, which do not fossilize. Nevertheless, this study provides new information about the size and shape of the brain and skull in the Down syndrome population.

Down Syndrome Diagnosis a Bust

For the current study, the team compared physical traits preserved in the skeleton of LB1 to those found in Down syndrome. While people with Down syndrome are not identical to one another, it was nevertheless clear that LB1 was very distinct from all humans, including those with Down syndrome.

The study found that LB1’s brain was much smaller than that seen in Down syndrome individuals. Likewise, the shape of the skull vault, which surrounds the brain, and chin anatomy were both outside the range seen in humans, with or without Down syndrome. Moreover, the diminutive LB1 individual, estimated to be just over a meter (1.09 m) in height (or 3′ 7″), was well below the height range of comparable individuals with Down syndrome. In fact, females with Down syndrome from Turkey reach a comparable height as the adult LB1 by 6.5 years of age and are considerably taller as adults (1.45 m or 4′ 9″ on average). The femur is disproportionately short in LB1 relative to the feet and arms compared to all humans, regardless of whether they have Down syndrome.

LB1 Remains Type Specimen of Homo Floresiensis

Importantly, this study indicated that LB1 not only differed from individuals with Down syndrome, but was more clearly aligned with more archaic human species. Its small brain, low cranial vault shape, absence of a chin, smaller body size and limb proportions all point to a pre-Homo sapiens ancestry. The authors conclude: “The skeletal evidence overwhelmingly contradicts a diagnosis of Down syndrome. Rather, our study is yet further evidence that Homo floresiensis was a distinct species with a fascinating, if somewhat nebulous, evolutionary history.”

Reference:
Karen L. Baab, Peter Brown, Dean Falk, Joan T. Richtsmeier, Charles F. Hildebolt, Kirk Smith, William Jungers. A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis. PLOS ONE, 2016; 11 (6): e0155731 DOI: 10.1371/journal.pone.0155731

Note: The above post is reprinted from materials provided by Midwestern University.

Likely ancestor of mystery ‘hobbit’ found

Likely ancestor of mystery-GeologyPage
Reconstruction of Homo floresiensis by Atelier Elisabeth Daynes. Credit: Kinez Riza

Half-sized humans who lived 700,000 years ago were almost certainly the ancestors of enigmatic “hobbits” whose fossils were found on the same Indonesian isle in 2013, scientists stunned by their own discovery reported Wednesday.

Two studies, published in Nature, fill a huge gap in our understanding of these diminutive people, whose tortuous evolutionary saga hit a dead-end some 50,000 years ago.

A modest haul of teeth and bones from an adult and two children has bolstered the theory that the hobbits, known to scientists as Homo floresiensis, arrived on Flores island as a different, larger species of hominin, or early man, probably about a million years ago.

And then, something very strange happened.

These upright, tool-wielding humans shrank, generation after generation, until they were barely half their original weight and height.

The process, called “island dwarfism,” was well known in animals, with some species shrinking as much as six fold in adapting to an environment with fewer resources.

Indeed, Flores was also home to a miniature race of elephant-like creatures—possibly hunted to extinction by the mini-men—called Stegodons.

This is the first hard evidence of humans becoming smaller after being marooned on a spit of land transformed into an island by rising seas.

“The hobbit was real,” said Adam Brumm, an archaeologist at the Research Centre of Human Evolution at Griffith University in Queensland, Australia, and lead author of one of the studies.

“It was an ancient human species that is separate to ours and that no longer exists on the planet today.”

The new fossils were unearthed in central Flores in 2014, about 100 kilometres (70 miles) from the 2003 discovery of the hobbit remains.

The find provided partial answers to key questions: from which species did H. floresiensis evolve, and how long did it take to shrink?

Two plausible evolutionary scenarios remain regarding their origins, said Brumm.

“The first is that the ‘hobbits’ represent a kind of dwarfed Homo erectus from Java,” he told AFP.

Homo erectus, up to 1.8 metres (six feet) tall and weighing up to 70 kilogrammes (154 pounds), is thought to have been the first human species to venture out of Africa.

A ‘huge surprise’

A specimen dated to about 1.2 million years ago—when much of the Indonesian archipelago was a single land mass—was found on the island of Java in the late 19th century.

Similarities in the teeth point to this as the most likely parent of the Flores humans, Brumm said.

“The alternative theory is that these creatures descend from an earlier radiation of more archaic, small-boned hominins from Africa.”

One theory that can now be set aside, the researchers said, is that Flores’ hobbits were actually modern humans diminished by disease or genetic disorders.

“This find quashes once and for all any doubters that believe Homo floresiensis was merely a sick Homo sapiens,” said Gert van der Bergh, leader of the excavation and a professor at the University of Wollongong’s Centre for Archaeological Science.

Most surprising was that the recently exhumed specimens were no larger than those still living on the island more than 600,000 years later.

“I was stunned when I first saw these new fossils,” said co-author Yousuke Kaifu, a scientist at the National Museum of Nature and Science in Tokyo.

Anything that old, he said, had been expected to resemble the bigger Homo erectus, or some other more primitive species.

“What we found was a huge surprise,” added Brumm.

“This suggests that H. floresiensis is an extremely ancient species that evolved its small size on Flores at a very early period, possibly soon after it arrived on the island about a million years ago.”

Reference:

  1. Homo floresiensis-like fossils from the early Middle Pleistocene of Flores, DOI:10.1038/nature17999
  2. Age and context of the oldest known hominin fossils from Flores, DOI:10.1038/nature17663

Note: The above post is reprinted from materials provided by AFP.

Constraining the composition of Earth’s interior with mineral elasticity

Constraining the composition-GeologyPage
The schematic plot of VP and VS anomaly caused by thermal anomaly under spin transition of iron in ferropericalse. Credit: Science China Press

The composition and temperature of the Earth’s interior are fundamental for understanding the Earth’s interior and dynamics. Because it’s impossible to directly access most areas of the Earth’s interior, the combination of the elasticity of minerals at high pressure and temperature (PT) and seismic results is one of most practical ways to constrain the temperature and chemical composition of Earth’s interior. This is done by determining what kinds of mineral aggregates have the same sound velocities and densities as Earth’s interior.

Therefore, the elasticity of minerals at high PT is crucial for translating the seismic sound velocity into composition and temperature. However, obtaining elasticity of minerals at high PT is highly challenging for experimental measurements and extremely expensive using the first-principles calculations. Wu and Wentzcovitch (2011) developed a new method, which reduces the computational loads to one-tenth of the traditional method.

The method has been successfully applied to many minerals whose elastic data are ideal in constraining the composition and temperature and understanding the velocity structure of the lower mantle. Zhongqing Wu and Wenzhong Wang, two scientists at University of Science and Technology of China, recently reviewed this technique.

The traditional method requires vibration density of state (DOS) of ~ 100 configurations with various kinds of strains and volumes. By analyzing the relations between volume dependence and strain dependence of lattice vibration, Wu found how to obtain the strain dependence of lattice vibration needed to calculate the elasticity from the volume dependence of vibration, which avoids the vibration DOS for the configurations under strain.

Therefore, the number of the vibrational DOS that need to be calculated is reduced to ~10 from ~100 in the traditional method. It is clear that the computational and manual loads of the new method are less than one tenth those of the traditional method. The elastic data show that the new method has precision comparable to the traditional method.

The effect of iron spin transition on the properties of ferropericalse has been conducted extensively in the last decade. Taking advantage of the new method, the researchers for the first time obtained the elastic data of ferropericlase and found that the spin transition can produce some visible features in seismic tomography and some reported seismic tomography results show features consistent with the spin crossover. This opens the possibility to take direct advantage of the spin crossover to advance our understanding of the lower mantle.

In general, the bulk modulus of the materials decreases slowly with increasing temperature. The spin transition leads to an unusual effect: The bulk modulus of ferropericlase increases quickly with increasing temperature in a certain temperature range. The effect is so significant that the bulk modulus of the lower mantle can increase with increasing temperature at some depths—even the lower mantle has only ~15 wt% Fp.

Therefore, the temperature effect of the bulk modulus and of the shear modulus of the lower mantle cancel out and the VP of the lower mantle becomes insensitive to the temperature at a certain range of depths (~1750 km). VP anomaly caused by thermal anomaly should be much smaller at a depth of ~1750 km than those at the adjoined depths. The structure of VP appears to have a disruption (Figure 1). Geodynamic simulation shows that spin transition plays a critical role for structure feature of the large low shear velocity provinces in the lower mantle due to the anomalous effect of spin transition on the thermodynamic properties of ferropericalse. Therefore, the spin transition of iron in ferropericalse in the lower mantle has been suggested by three main branches of geophysics: mineral physics, seismology and geodynamics.

Using the obtained elastic data, Wu constrained the composition of the lower mantle and showed that (1) the content of Fp locates between the pyrolite and chondritic model, two main composition models of the mantle and (2) any composition well constrained by the seismic model has a sufficient amount of ferropericalse to show the positive temperature dependence of the bulk sound velocity but is not sufficient to exhibit the positive temperature dependence of the compressional wave velocity at the middle lower mantle. Anticorrelation between the bulk sound velocity and the shear velocity without involving any composition variation is a robust feature at the middle lower mantle.

Reference:
ZhongQing Wu et al, First-principles calculations of elasticity of minerals at high temperature and pressure, Science China Earth Sciences (2016). DOI: 10.1007/s11430-016-5296-6

Note: The above post is reprinted from materials provided by Science China Press.

Mammals began their takeover long before the death of the dinosaurs

Mammals began their takeover-GeologyPage
An example of an early therian mammal, Purgatorius unio. Credit: © Nobu Tamura

It’s a familiar story—the mighty dinosaurs dominated their prehistoric environment, while tiny mammals took a backseat, until the dinosaurs (besides birds) went extinct 66 million years ago, allowing mammals to shine. Just one problem—it’s not true. A new article in the Proceedings of the Royal Society B reports that mammals actually began their massive diversification ten to twenty million years before the extinction that ended the age of the dinosaurs.

“The traditional view is that mammals were suppressed by the dinosaurs’ success, and that they didn’t really take off until after the dinosaurs went extinct. This study shows that therian mammals, the ancestors of most modern mammals, were already diversifying before the dinosaurs died out,” says lead author David Grossnickle, a Field Museum Fellow and PhD candidate at the University of Chicago.

The old hypothesis hinged upon the fact that many of the early mammal fossils that had been found were from small, insect-eating animals—there didn’t seem to be much in the way of diversity. But over the years, more and more early mammals have been found, including some hoofed animal predecessors the size of dogs. The animals’ teeth were varied, too. Grossnickle, along with his co-author Elis Newham at the University of Southampton, analyzed the molars of hundreds of early mammal specimens in museum fossil collections. They found that the mammals that lived during the years leading up to the dinosaurs’ demise had widely varied tooth shapes, meaning that they had widely varied diets. These different diets proved key to an unexpected finding regarding mammal species going extinct along with the dinosaurs.

Not only did mammals begin diversifying earlier than previously expected, but the mass extinction wasn’t the perfect opportunity for mammal evolution that it’s traditionally been painted as. Early mammals were hit by a selective extinction at the same time the dinosaurs died out—generalists that could live off of a wide variety of foods seemed more apt to survive, but many mammals with specialized diets went extinct.

The scientists involved with the study were surprised to see that mammals were initially negatively impacted by the mass extinction event. “I fully expected to see more diverse mammals immediately after the extinction,” said Grossnickle. “I wasn’t expecting to see any sort of drop. It didn’t match the traditional view that after the extinction, mammals hit the ground running. It’s part of the reason why I went back to study it further—it seemed wrong.”

The reason behind the mammals’ pre-extinction diversification remains a mystery. Grossnickle notes a possible link between the rise of mammals and the rise of flowering plants, which diversified around the same time. “We can’t know for sure, but flowering plants might have offered new seeds and fruits for the mammals. And, if the plants co-evolved with new insects to pollinate them, the insects could have also been a food source for early mammals,” he says.

The article comes at a time when paleontologists are debating whether dinosaurs were already declining before the mass extinction, notes Grossnickle. “If you believe that dinosaurs were already on the downswing before the asteroid hit, this is an interesting counterpoint, that mammals were already on the upswing.”

Grossnickle notes that the study is particularly relevant in light of the mass extinction the earth is currently undergoing—”The types of survivors that made it across the mass extinction 66 million years ago, mostly generalists, might be indicative of what will survive in the next hundred years, the next thousand.”

Reference:
Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the K-Pg boundary, Proceedings of the Royal Society B: Biological Sciences, DOI: 10.1098/rspb.2016.0256

Note: The above post is reprinted from materials provided by University of Southampton.

Big bird sex life revealed

Big bird sex life-GeologyPage
Representative Image: Dromornis stirtoni, a flightless bird from the Late Miocene of Australia, pencil drawing Credit: Nobu Tamura

The sex life of the biggest bird to have ever roamed the planet has been revealed – and it’s more akin to a goose than an emu.

The mighty mihirung Dromornis stirtoni, an extraordinary kind of fowl, was most likely a family oriented bird that mated for life, the females brooded the eggs, and both sexes aggressively defended nests and shared parental care.

Unlike most of the large flightless birds that survive today, which are ratites and include the emu, the male mihirungs were larger than the females.

“It was probably the largest bird ever to have lived. With an average weight of 480kg, it was more than ten times the weight of an emu,” Mr Handley says.

An international team of scientists, led by researchers at Flinders University, have unlocked the sex secrets of the mihirungs from bone fragments.

Published in the highly regarded Journal of Vertebrate Paleontology, the discovery of evidence in the bones of egg-laying was the key to distinguishing the gender and breeding characteristics that establish the mihirung as a breed apart from most other fowl.

Flinders University researcher Warren Handley says the largest of these Australian flightless giants, Stirton’s mihirung, stood some three metres tall and could weigh more than half a tonne.

Mr Handley says the mihirung had little to fear.

“With their formidable height and huge size, especially of males that may have exceeded 600kg, they were capable of protecting the growing chicks from predators, such as the dog-sized ancestral thylacines and marsupial lions that were around at the time.”

The largest of all mihirungs roamed Australia about eight million years ago. The bones in the study were those of individuals which died in their dozens around a shrinking waterhole in the Northern Territory along with many marsupials, including sheep-to-cow sized herbivores and their predators, distant relatives of the marsupial lion.

The remnant bones, although fractured and fragmented by the ravages of time, remain awe-inspiring, according to the researchers.

Initially, two size groups among the bones led the researchers to consider whether they were looking at two species, but the discovery of medullary bone, a specialist type of tissue found only in the hollow bones of female birds before they lay eggs, enabled them to identify the smaller bones as female.

Sections of the bones were then sent to South Africa for preparation by histologist Professor Chinsamy-Turan, and microscopy revealed the tell-tale medullary bone. She said “It was quite a surprise to find that four of the birds in our sample had medullary bone. This discovery was a real scoop since we now could say with certainty that these were egg-laying female mihirungs.”

Scientists have long wondered about the sexual behaviour in extinct groups of birds, and the new evidence provided by the bones shows that mihirungs were sexually dimorphic, with females being smaller than males.

The bones, which are held at the Museum of Central Australia in Alice Springs, were originally collected from Alcoota in the Northern Territory. The NT Government recently announced $4 million of funding for further development of the extraordinarily rich fossil site.

“This study provides a spectacular example of how the integration of multidisciplinary techniques and collaboration can reveal details of the biology of long extinct animals from their fragmented osseous remains,” says Dr Trevor Worthy, palaeontologist and Postdoctoral Fellow in the School of Biological Science at Flinders University.

Reference:
Warren D. Handley et al, Sexual dimorphism in the late Miocene mihirung(Aves: Dromornithidae) from the Alcoota Local Fauna of central Australia, Journal of Vertebrate Paleontology (2016). DOI: 10.1080/02724634.2016.1180298

Note: The above post is reprinted from materials provided by Flinders University.

‘Zombie volcano’ slowly grows beneath New Zealand

Zombie volcano slowly-GeologyPage
Champagne Pool is a lake in Rotorua, one of New Zealand’s most active volcanic regions. Credit: Colin Monteath/Minden/NGC

Geologists in New Zealand have discovered a magma chamber being born in a surprising place — not under the country’s most active volcanoes, but off to one side.

The finding suggests that molten rock can accumulate underground in complex and unexpected patterns, but does not indicate that an eruption is imminent.

“There’s no need to panic, but chances are there are lots of bodies of magma dotted throughout the crust,” says Ian Hamling, a geophysicist at GNS Science in Lower Hutt, New Zealand. He and his colleagues describe the discovery on 3 June in Science Advances.

The team used radar data from satellites, such as the European Space Agency’s now-defunct Envisat, to study ground motions in the Taupo Volcanic Zone. This region, which runs down the centre of New Zealand’s North Island, has seen 25 enormous eruptions in the past 1.6 million years. Today, it is home to some of the country’s most spectacular volcanic features, from the bubbling hot pots of Rotorua to frequent eruptions at Whakaari, or White Island, in the Bay of Plenty off of the North Island. The most recent eruption at Whakaari was in April.

Mysterious growth

A 2015 study found that much of the main Taupo Volcanic Zone was subsiding, or sinking, as is expected after magma erupts and drains from an underground chamber. But one area, to the north and west along the Bay of Plenty coast, seemed to be rising. “I just discounted it at the time, because we were so focused on looking at the more volcanic part,” says Hamling.

Later, the team took a closer look, taking in data from global-positioning stations as well as geodetic surveys dating back to the 1950s. They found that the ground had risen by 5 millimetres per year in the 1950s, but that rate had more than doubled to about 12 millimetres a year starting in the mid-2000s. It has since dropped back to the lower rate.

Calculations suggest that about 9 million cubic metres of magma — 3,600 Olympic swimming pools’ worth — pushed into the crust each year during peak growth. The molten rock would have gathered in a chamber about 10 kilometres below the surface. “When you compare it to other places, like Yellowstone, we’re smaller than that,” Hamling says. “But it’s still pretty significant.”

Danger zone?

The city of Tauranga, with more than 100,000 residents, lies about 50 kilometres west of the uplift. Elaine Smid, a volcanologist at the University of Auckland, notes that people in the area are already at risk from volcanic hazards, especially ashfall from the Taupo volcanoes.

It’s unclear whether the oddball magma chamber will pose an extra risk. There has been no increase in volcanic activity in the northern Taupo region. And the uplift may not necessarily be related to magma at all, says Nico Fournier, a volcanologist with GNS Science, based out of the town of Taupo. Some other geologic process may be at work.

The study is not the first to suggest that magma is pushing into Earth’s crust somewhere other than under an active volcano. Examples have also been found in the central Andes, says Matthew Pritchard, a geophysicist at Cornell University in Ithaca, New York. He calls them “zombie volcanoes” — because they show signs of life when they should be dead.

“Not to be too glib, but we are not undergoing a zombie-volcano invasion,” he says. Rather, the magma chambers are being found now because the sharp vision of radar satellites has improved scientists’ view of ground movements.

Hamling’s team wants to do a more detailed study of the Bay of Plenty area, using a range of techniques to probe the size and shape of the magma chamber.

Note: The above post is reprinted from materials provided by nature.

Lucy had neighbors: A review of African fossils

A review of African fossils-GeologyPage
The left half of the lower jaw of Australopithecus deyiremeda (BRT-VP-3/14), a 3.5 to 3.3 million-year-old human ancestor species discovered by the Woranso-Mille project. Credit: Yohannes Haile-Selassie

If “Lucy” wasn’t alone, who else was in her neighborhood? Key fossil discoveries over the last few decades in Africa indicate that multiple early human ancestor species lived at the same time more than 3 million years ago. A new review of fossil evidence from the last few decades examines four identified hominin species that co-existed between 3.8 and 3.3 million years ago during the middle Pliocene. A team of scientists compiled an overview that outlines a diverse evolutionary past and raises new questions about how ancient species shared the landscape.

The perspective paper, “The Pliocene hominin diversity conundrum: Do more fossils mean less clarity?” will be published June 6, 2016 as part of a Human Origins Special Feature in the Early Edition of the Proceedings of the National Academy of Sciences.

Authors Dr. Yohannes Haile-Selassie and Dr. Denise Su of The Cleveland Museum of Natural History and Dr. Stephanie Melillo of the Max Planck Institute for Evolutionary Anthropology in Germany provide an up-to-date review of middle Pliocene hominin fossils found in Ethiopia, Kenya and Chad. The researchers trace the fossil record, which illustrates a timeline placing multiple species overlapping in time and geographic space. Their insights spur further questions about how these early human ancestors were related and shared resources.

“It is now obvious that more than one species of early hominin co-existed during Lucy’s time,” said lead author Dr. Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History. “The question now is not whether Australopithecus afarensis, the species to which the famous Lucy belongs, was the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia during the middle Pliocene, but how these species are related to each other and exploited available resources.”

The 1974 discovery of Australopithecus afarensis, which lived from 3.8 to 2.9 million years ago, was a major milestone in paleoanthropology that pushed the record of hominins earlier than 3 million years ago and demonstrated the antiquity of human-like walking. Scientists have long argued that there was only one pre-human species at any given time before 3 million years ago that gave rise to another new species through time in a linear manner. This was what the fossil record appeared to indicate until the end of the 20th century. The discovery of Australopithecus bahrelghazali from Chad in 1995 and Kenyanthropus platyops from Kenya in 2001 challenged this idea. However, these two species were not widely accepted, rather considered as geographic variants of Lucy’s species, Australopithecus afarensis. The discovery of the 3.4 million-year-old Burtele partial foot from the Woranso-Mille announced by Haile-Selassie in 2012 was the first conclusive evidence that another early human ancestor species lived alongside Australopithecus afarensis. In 2015, fossils recovered from Haile-Selassie’s ongoing research site at the Woranso-Mille area of the Afar region of Ethiopia were assigned to the new species Australopithecus deyiremeda. However, the Burtele partial foot was not included in this species.

“The Woranso-Mille paleontological study area in Ethiopia’s Afar region reveals that there were at least two, if not three, early human species living at the same time and in close geographic proximity,” said Haile-Selassie. “This key research site has yielded new and unexpected evidence indicating that there were multiple species with different locomotor and dietary adaptations. For nearly four decades, Australopithecus afarensis was the only known species — but recent discoveries are opening a new window into our evolutionary past.”

Co-author Dr. Denise Su, curator of paleobotany and paleoecology at The Cleveland Museum of Natural History, reconstructs ancient ecosystems. “These new fossil discoveries from Woranso-Mille are bringing forth avenues of research that we have not considered before,” said Su. “How did multiple closely related species manage to co-exist in a relatively small area? How did they partition the available resources? These new discoveries keep expanding our knowledge and, at the same time, raise more questions about human origins.”

Paleoanthropologists face the challenges and debates that arise from small sample sizes, poorly preserved prehistoric specimens and lack of evidence for ecological diversity. Questions remain about the relationships of middle Pliocene hominins and what adaptive strategies might have allowed for the coexistence of multiple, closely related species.

“We continue to search for more fossils,” said Dr. Stephanie Melillo of the Max Planck Institute for Evolutionary Anthropology in Germany. “We know a lot about the skeleton of A. afarensis, but for the other middle Pliocene species, most of the anatomy remains unknown. Ultimately, larger sample sizes will be the key to sorting out which species are present and how they are related. This makes every fossil discovery all the more exciting.”

Reference:
Yohannes Haile-Selassie, Stephanie M. Melillo, and Denise F. Su. The Pliocene hominin diversity conundrum: Do more fossils mean less clarity? PNAS, June 6, 2016 DOI: 10.1073/pnas.1521266113

Note: The above post is reprinted from materials provided by Cleveland Museum of Natural History.

Devonian Fish Provides Unique Insights into Early Evolution of Modern Lobe-finned Fishes

Devonian Fish Provides Unique Insights-GeologyPage
Life Reconstrution of Qingmenodus yui. Credit: Brian Choo

Crown or modern sarcopterygians comprise three major groups: coelacanths, lungfishes and tetrapods. With the exception of the tetrapods, sarcopterygians have a long evolutionary history of diversity decline and are nowhere near as diverse today as they were at the beginning of their history. They differ substantially from stem or primitive sarcopterygians such as Guiyu and Psarolepis, and a lack of transitional fossil taxa limits our understanding of the origin of the modern group.

Onychodonts are an exclusively Devonian group of mostly marine predatory sarcopterygians. Until recently, they were represented by only six named genera and seem to have characteristics of both primitive and modern sarcopterygians, but are difficult to place because of insufficient anatomical information, particularly in braincase components.

In a study published June 3 in the journal Science Advances, Drs. LU Jing and ZHU Min, of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, and their collaborators described newly discovered skull material of Qingmenodus, an onychodont from South China about 409 million years ago, using high-resolution computed tomography to image internal structures of the braincase. This study provides the first detailed interpretation of internal neurocranial anatomy in onychodonts, and helps us to understand the sequence of character acquisition in the early evolution of sarcopterygians, illuminating the early evolution and diversification of modern sarcopterygians.

The new specimens of Qingmenodus, including a completely ossified anterior cranial portion (IVPP V16003.5) and a posterior cranial portion (IVPP V16003.6), were collected from the type site of Qingmenodus yui during field trips from 2009 to 2012. The anterior cranial portion is referred to as Qingmenodus yui based on the shared ornamentation and comparable size with the holotype of Qingmenodus yui (IVPP V16003.1). The new posterior cranial portion has not preserved the ventral part of the otic capsules; however, its preserved part matches well with the holotype, such as vermiculate impressions on the dermal surface, and the elongate otic shelf.

Qingmenodus, one of the oldest known onychodonts from the Early Devonian of South China, shows a virtually complete set of neurocranial structures of an onychodont. It exhibits a mosaic of features present in both primitive sarcopterygians and coelacanths.

“In addition to its remarkable similarities with primitive sarcopterygians in the ethmosphenoid portion, Qingmenodus exhibits coelacanth-like neurocranial features in the otic region,” said lead author Dr. LU Jing. “It thus further bridges the morphological gap between primitive sarcopterygians, such as Guiyu, Psarolepis and Achoania, and modern sarcopterygians, and provides unique insights into the sequence of neurocranial character acquisition involved in the origin and early diversification of the latter.”

“Our completely reconstructed virtual cranial endocast of Qingmenodus allows extensive comparisons with other sarcopterygians, in particular those that have been studied by serial grinding or computerized tomography (CT) scanning,” said Dr. ZHU Min, project designer and study co-author. “It provides the first detailed interpretation of internal neurocranial anatomy in onychodonts, and helps us to understand the sequence of character acquisition in the early evolution of sarcopterygians.”

“Our phylogenetic analysis based on a revised data set unambiguously assigns onychodonts to crown sarcopterygians as stem coelacanths. Qingmenodus thus bridges the morphological gap between stem sarcopterygians and coelacanths, and helps to illuminate the early evolution and diversification of crown sarcopterygians,” said co-author Dr. Per Erik Ahlberg, of Sweden’s Uppsala University.

This work was supported by the Major Basic Research Projects of China, the National Natural Science Foundation of China, the National Major Scientific Instrument and Equipment Development Project of China, the Swedish Research Council, and a Wallenberg Scholarship from the Knut and Alice Wallenberg Foundation.

Reference:
Jing Lu1, Min Zhu1, Per Erik Ahlberg, Tuo Qiao, You’an Zhu, Wenjin Zhao1 and Liantao Jia. A Devonian predatory fish provides insights into the early evolution of modern sarcopterygians. DOI: 10.1126/sciadv.1600154

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

Human Evolution: A 24-million-year record of African plants plumbs deep past

Human Evolution A 24-million-GeologyPage
At Nairobi’s Kenya National Museum, two Homo sapiens visit the skeleton of Turkana Boy, member of a precursor species known as Homo erectus. By his time, some 1.6 million years ago, the east African landscape was largely dominated by grasses. Credit: Kevin Krajick/Lamont-Doherty Earth Observatory

Buried deep in seabed sediments off east Africa, scientists have uncovered a 24-million-year record of vegetation trends in the region where humans evolved. The authors say the record lends weight to the idea that we developed key traits—flexible diets, large brains, complex social structures and the ability to walk and run on two legs—while adapting to the spread of open grasslands. The study appears today in a special human-evolution issue of the journal Proceedings of the National Academy of Sciences.

Based on genetic evidence, the earliest hominins, or human ancestors, are thought to have split off from chimpanzees some 6 million to 7 million years ago. Many scientists have argued that they were set on the path to become modern humans as east Africa’s vegetation gradually shifted from dense forest to savanna—open grasslands punctuated by woodland patches and rivers. This would have forced our ancestors to descend from the trees, move rapidly over open ground, and develop social skills needed for survival. In recent years, the long-held notion that humans evolved in grasslands alone has given way to a more nuanced view, that it was the increasing diversity of such landscapes including the grasses that led to the success of the hominins who were smartest and most flexible at adapting to a changing world.

The new study supplies by far the longest and most complete record of ancient plant life in much of what is now Ethiopia and Kenya, the assumed birthplace of humanity. It strongly suggests that between 24 million and 10 million years ago—long before any direct human ancestors appeared—there were few grasses, and woodlands thus presumably dominated. Then, with an apparent shift in climate, grasses began to appear. The study shows that the trend continued through all known human evolution, leading to a dominance of grasses by a few million years ago.

“The entire evolution of our lineage has involved us living and working in or near grasslands,” said lead author Kevin Uno, a postdoctoral research scientist at Columbia University’s Lamont-Doherty Earth Observatory. “This now gives us a timeline for the development of those grasses, and tells us they were part of our evolution from the very beginning.” Uno says the grasslands were probably small and patchy at first, and thus were not the only factor. Rather, he, said, it “probably led to a more diverse set of niches we could occupy and compete in successfully.” For instance, he said, one could imagine that in a more open landscape, hominins “would learn how to team up. Some could hunt or scavenge prey. Some could throw stones at the hyenas to keep them away, while someone else would run in and grab the meat.”

Scientists have previously collected plant pollen, chemical isotopes and other evidence from land-based sediments suggesting that grasslands became dominant around the time humans evolved. But these records come only from scattered finds in highly eroded outcrops, and most go back only about 4 million years.

In the new study, the researchers examined a series of sediment cores drilled by a research ship in the Red Sea and the western Indian Ocean, off northeast Africa. The cores contain chemicals created by vegetation on land that were later washed or blown out to sea and laid down in layers for tens of millions of years. “The deep ocean might seem like a funny place to look for signs of vegetation, but it’s one of the best, because everything is buried and preserved. It’s like a bank vault,” said Uno. Using a fairly new technique, Uno and his colleagues analyzed carbon-based chemicals called alkanes, which make up the waxy outer parts of leaves, and contain the fingerprints of different plant types.

Sediments older than 10 million years had alkanes signaling a form of photosynthesis used mainly by woody plants, the so-called C3 pathway. But starting 10 million years ago, a different form linked mainly to grasses—the C4 pathway—began showing up. The area covered by grass seemed to grow 7 or 8 percent every million years, until it apparently dominated by 2 million or 3 million years ago. This kind of vegetation is still the main plant life in east Africa today. Other scientists have shown that grasslands spread also in south Asia, the Americas and southern Africa somewhat later.

Uno says the study data matches chemical analyses of tooth enamel from ancient elephants and other large herbivores showing that some east African animals began switching to more grass-based diets around 10 million years ago. The earliest known hominins appeared several million years later. By 3.8 million years ago, tooth enamel shows they developed a flexible diet, including foods based on grasses—if not the grass itself, presumably meat of creatures that ate grass. A study last year coauthored by Lamont scientist Christopher Lepre showed that hominins were making stone tools in northwest Kenya by 3.3 million years ago. Pronounced elongation of the legs, larger brains and other traits followed, until the emergence of recognizable Homo sapiens—our own species—by about 200,000 years ago.

“Lots of people have conjectured that grasslands had a central role in human evolution,” said study coauthor Peter deMenocal, a climate scientist at Lamont-Doherty. “But everyone has been waffling about when those grasslands emerged and how widespread they were. This really helps answer the question.”

Thure Cerling, a geologist at the University of Utah who has assembled some of the most important land-based African vegetation records, said the study gives an unprecedented “long-term view of the regional vegetation,” and thus the environments in which humans evolved. But, he said, “it will always be hard to associate a cause with an effect.”

Smithsonian Institution anthropologist Richard Potts, another authority in the field, said that the paper “is the very best examination and most compelling demonstration” of long-term grassland expansion.” But he said, “the broad-brush time scale of the analysis appears to miss the details of environmental dynamics on time scales that influence gene pools.” Potts says there is ample evidence from finer-scale studies that even as grasses spread, east Africa’s climate swung from wet to dry over much shorter time periods. These swings became most intense over the last few million years, and he argues that this is the perhaps the real key. Potts says that grasses spread because they were flexible enough to adapt to such swings—as were humans. “Bipedality emerged as a way of combining walking on the ground and climbing trees; toolmaking expanded the adjustments to a much wider range of foods; brains are the quintessential organ of flexibility,” he said. “Geographic expansion requires adaptability to change.”

The other authors of the study are Pratigya Polissar, also of Lamont-Doherty; and Kevin Jackson of Lafayette College.

Reference:
Neogene biomarker record of vegetation change in eastern Africa, PNAS, DOI: 10.1073/pnas.1521267113

Note: The above post is reprinted from materials provided by Columbia University.

Ice age bison fossils shed light on early human migrations in North America

Ice age bison fossils shed light-GeologyPage
The steppe bison had much larger horns than modern bison. Radiocarbon dating and DNA analysis of bison fossils enabled researchers to track the migration of Pleistocene steppe bison into an ice-free corridor that opened along the Rocky Mountains about 13,000 years ago. Credit: Government of Yukon

Scientists using evidence from bison fossils have determined when an ice-free corridor opened up along the Rocky Mountains during the late Pleistocene. The corridor has been considered a potential route for human and animal migrations between the far north (Alaska and Yukon) and the rest of North America, but when and how it was used has long been uncertain.

The researchers combined radiocarbon dating and DNA analysis to track the movements of bison into the corridor, showing that it was fully open by about 13,000 years ago. Their findings, published June 6 in Proceedings of the National Academy of Sciences, indicate that the corridor could not account for the initial dispersal of humans south of the ice sheets, but could have been used for later movements of people and animals, both northward and southward.

In the 1970s, geological studies suggested that the corridor might have been the pathway for the first movement of humans southward from Alaska to colonize the rest of the Americas. More recent evidence, however, indicated that the Cordilleran and Laurentide ice sheets coalesced at the height of the last ice age, around 21,000 years ago, closing the corridor much earlier than any evidence of humans south of the ice sheets. The initial southward movement of people into the Americas more than 15,000 years ago now seems likely to have been via a Pacific coastal route, but the Rocky Mountains corridor has remained of interest as a potential route for later migrations.

“The opening of the corridor provided new opportunities for migration and the exchange of ideas between people living north and south of the ice sheets,” said first author Peter Heintzman, a postdoctoral researcher at UC Santa Cruz who led the DNA analysis.

Previous work by coauthor Beth Shapiro, professor of ecology and evolutionary biology at UC Santa Cruz, had shown that the bison populations north and south of the ice sheets were genetically distinct by the time the corridor opened. By analyzing bison fossils from within the corridor region, the researchers were able track the movement of northern bison southward into the corridor and southern bison northward.

“The radiocarbon dates told us how old the fossils were, but the key thing was the genetic analysis, because that told us when bison from the northern and southern populations were able to meet within the corridor,” Heintzman said.

The results showed that the southern part of the corridor opened first, allowing southern bison to start moving northward as early as 13,400 years ago, before the corridor fully opened. Later, there was some movement of northern bison southward, with the two populations overlapping in the corridor by 13,000 years ago.

“Bison fossils are the most widespread Quaternary mammal in western North America and of interest because they survived the extinctions at the end of the Pleistocene, unlike most other North American large mammals,” said coauthor Duane Froese of the University of Alberta. “We were able to sample bison fossils, largely from museum collections, including critical ones from central Alberta that dated to the initial opening of the corridor.”

According to Shapiro, archeological evidence suggests that human migration within the corridor was mostly from south to north. Sites associated with the Clovis hunting culture and its distinctive fluted point technology were widespread south of the corridor around 13,000 years ago and decline in abundance from south to north within the corridor region. A Clovis site in Alaska has been dated to no earlier than 12,400 years ago.

“When the corridor opened, people were already living south of there. And because those people were bison hunters, we can assume they would have followed the bison as they moved north into the corridor,” Shapiro said.

The steppe bison of the Pleistocene (Bison priscus) were much bigger than modern bison (Bison bison), she said. Before the corridor closed, prior to the last glacial maximum, they moved freely up and down between the ice-free regions in the north and grasslands south of the ice sheets. After the ice sheets coalesced, the population that was cut off to the south contracted, leaving one genetically distinct southern lineage.

The DNA analysis used in this study focused on mitochondrial DNA, which is easier to recover from fossils than the DNA in chromosomes, because each cell has thousands of copies of the relatively short mitochondrial DNA sequence. While Shapiro’s lab led the DNA analyses, Froese’s lab led the radiocarbon dating work.

Many of the fossils they analyzed came from collections at the Royal Alberta Museum in Edmonton and other institutions. “Thousands of steppe bison fossils are recovered in northern Canada every year,” said coauthor Grant Zazula of the Government of Yukon Palaeontology Program in Whitehorse. “Most of these fossils are uncovered by mining or gravel pit operators and later made available to scientists for study. These results speak to the importance of collecting and preserving fossils in order to better understand our history.”

Reference:
Bison phylogeography constrains dispersal and viability of the Ice Free Corridor in western Canada, PNAS, DOI: 10.1073/pnas.1601077113

Note: The above post is reprinted from materials provided by University of California – Santa Cruz.

Dean’s Blue Hole

Dean's Blue Hole-GeologyPage

Dean’s Blue Hole is said to be the deepest blue hole in the world, and  the second largest underwater chamber. Experts at Reeldivers and  Vertical Blue, who have done dives at the site, report that: “It is enclosed on three sides by a natural rock amphitheatre, and on the fourth side by a turquoise lagoon and powder white beach. There is never any swell or waves inside the Hole, and visibility is usually between 50 – 100 feet (15 – 30m).”

The Blue Hole dips some 663 feet (203 meters) into the ocean floor right off shore. At the surface it is 80 x 120 feet (25 x 35m), but opens out after 60 feet (20m) into a cavern with a diameter of at least 330 feet (100m).

It is located west of Clarence Town on Long Island, Bahamas., and is also the site where the Freediving World Record was set in April 2007.

Formation

Blue hole is a term for water-filled sinkholes with the entrance below the water level. They can be formed in different karst processes, for example, by the rainwater soaking through fractures of limestone bedrock onto the watertable. Sea level here has changed: for example, during the glacial age during the Pleistocene epoch (ice age), some 15,000 years ago, sea level was considerably lower. The maximum depth of most other known blue holes and sinkholes is 110 metres (360 ft), which makes the 203 metres (666 ft) depth of Dean’s Blue Hole quite exceptional.

Dean’s Blue Hole is roughly circular at the surface, with a diameter ranging from 25 to 35 metres (82–115 ft). After descending 20 metres (66 ft), the hole widens considerably into a cavern with a diameter of 100 metres (330 ft).

There are several freshwater water-filled sinkholes on land that are deeper than Dean’s Blue Hole. These include the 270 m (890 ft) Boesmansgat in South Africa, Mexico’s Zacatón at 335 metres (1,099 ft) and the 392 metres (1,286 ft) Pozzo del Merro in Italy.

Fauna

There is a great variety of sea animals to be found inside Dean’s blue hole. Snorkelers and divers alike will be able to spot snapper fish, tarpons, turtles seahorses, rays and many colourful tropical fish.

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Reference:
Wikipedia: Dean’s Blue Hole
The Islands Of The Bahamas:  Dean’s Blue Hole

Antarctica’s “Upside-Down Rivers”

Antarctica's Upside-GeologyPage

“Upside-down rivers” of warm ocean water threaten the stability of floating ice shelves in Antarctica, according to a new study led by researchers at the University of Colorado Boulder’s National Snow and Ice Data Center. The study highlights how parts of Antarctica’s ice sheet may be weakening due to contact with warm ocean water.

“We found that warm ocean water is carving these ‘upside-down rivers,’ or basal channels, into the undersides of ice shelves all around the Antarctic continent. In at least some cases these channels weaken the ice shelves, making them more vulnerable to disintegration,” said Karen Alley, a Ph.D. student in CU-Boulder’s Department of Geological Sciences and lead author of an analysis published today in Nature Geoscience.

Ice shelves are thick floating plates of ice that have flowed off the Antarctic continent and spread out onto the ocean. As ice shelves flow out to sea, they push against islands, peninsulas, and bedrock bumps known as “pinning points.” Contact with these features slows the flow of grounded ice off the continent. While ice shelves take thousands of years to grow, previous work has shown that they can disintegrate in a matter of weeks. If more ice shelves disintegrate in the future, loss of contact with pinning points will allow ice to flow more rapidly into the ocean, increasing the rate of sea level rise.

“Ice shelves are really vulnerable parts of the ice sheet, because climate change hits them from above and below,” said NSIDC scientist and study co-author Ted Scambos. “They are really important in braking the ice flow to the ocean.”

The features form as buoyant plumes of warm and fresh water rise and flow along the underside of an ice shelf, carving channels much like upside-down rivers. The channels can be tens of miles long, and up to 800 feet “deep.”

When a channel is carved into the base of an ice shelf, the top of the ice shelf sags, leaving a visible depression, or “wrinkle,” in the relatively smooth ice surface. Alley and her colleagues mapped the locations of these wrinkles all around the Antarctic continent using satellite imagery, as well as radar data that images the channels through the ice, mapping the shape of the ice-ocean boundary.

The team also used satellite laser altimetry, which measures the height of an ice shelf surface with high accuracy, to document how quickly some of the channels were growing. The data show that growing channels on the rapidly melting Getz Ice Shelf in West Antarctica can bore into the ice shelf base at rates of approximately 10 meters (33 feet) each year.

The mapping shows that basal channels have a tendency to form along the edges of islands and peninsulas, which are already weak areas on ice shelves. The team observed two locations where ice shelves are fracturing along basal channels, clear evidence that basal channel presence can weaken ice shelves to the point of breaking in vulnerable areas.

While no ice shelves have completely disintegrated due to carving by basal channels, the study points to the need for more observation and study of the features, said co-author Helen Amanda Fricker of Scripps Institution of Oceanography at UC San Diego. “It’s feasible that increasing ocean temperatures around Antarctica could continue to erode ice shelves from below.”

Note: The above post is reprinted from materials provided by CIRES.

Pluto’s Heart: Like a Cosmic ‘Lava Lamp’

Pluto’s Heart Like a Cosmic-GeologyPage
Scientists from NASA’s New Horizons mission used state-of-the-art computer simulations to show that the surface of Pluto’s informally named Sputnik Planum is covered with churning ice “cells” that are geologically young and turning over due to a process called convection. The scene above, which is about 250 miles (400 kilometers) across, uses data from the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC), gathered July 14, 2015. Credits: NASA/JHUAPL/SwRI

Combining computer models with topographic and compositional data gathered by NASA’s New Horizons spacecraft last summer, New Horizons team members have determined the depth of this layer of solid nitrogen ice within Pluto’s distinctive “heart” feature – a large plain informally known as Sputnik Planum – and how fast that ice is flowing. The study is published in the June 2 issue of the journal Nature.

Mission scientists used state-of-the-art computer simulations to show that the surface of Sputnik Planum is covered with icy, churning, convective “cells” 10 to 30 miles (16 to 48 kilometers) across, and less than one million years old. The findings offer additional insight into the unusual and highly active geology on Pluto and, perhaps, other bodies like it on the outskirts of the solar system.

“For the first time, we can determine what these strange welts on the icy surface of Pluto really are,” said William B. McKinnon, from Washington University in St. Louis, who led the study and is a co-investigator on the New Horizons science team. “We found evidence that even on a distant cold planet billions of miles from Earth, there is sufficient energy for vigorous geological activity, as long as you have ‘the right stuff,’ meaning something as soft and pliable as solid nitrogen.”

McKinnon and colleagues believe the pattern of these cells stems from the slow thermal convection of the nitrogen-dominated ices that fill Sputnik Planum. A reservoir that’s likely several miles deep in some places, the solid nitrogen is warmed by Pluto’s modest internal heat, becomes buoyant and rises up in great blobs – like a lava lamp – before cooling off and sinking again to renew the cycle.

The computer models show that ice need only be a few miles deep for this process to occur, and that the convection cells are very broad. The models also show that these blobs of overturning solid nitrogen can slowly evolve and merge over millions of years. Ridges that mark where cooled nitrogen ice sinks back down can be pinched off and abandoned, resulting in Y- or X-shaped features in junctions where three or four convection cells once met.

“Sputnik Planum is one of the most amazing geological discoveries in 50-plus years of planetary exploration, and the finding by McKinnon and others on our science team that this vast area—bigger than Texas and Oklahoma combined – is created by current day ice convection is among the most spectacular of the New Horizons mission,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado.

These convective surface motions average only a few centimeters a year – about as fast as your fingernails grow – which means cells recycle their surfaces every 500,000 years or so. While slow on human clocks, it’s a fast clip on geological timescales.

“This activity probably helps support Pluto’s atmosphere by continually refreshing the surface of ‘the heart,’” McKinnon said. “It wouldn’t surprise us to see this process on other dwarf planets in the Kuiper Belt. Hopefully, we’ll get a chance to find out someday with future exploration missions there.”

New Horizons could also potentially take a close-up look at a smaller, more ancient object much farther out in the Kuiper Belt – the disk-shaped region beyond the orbit of Neptune believed to contain comets, asteroids and other small, icy bodies. New Horizons flew through the Pluto system on July 14, 2015, making the first close observations of Pluto and its family of five moons. The spacecraft is on course for an ultra-close flyby of another Kuiper Belt object, 2014 MU69, on Jan. 1, 2019, pending NASA approval of funding for an extended mission.

Note: The above post is reprinted from materials provided by NASA.

Great Blue Hole

Great Blue Hole, Coast of Belize - a phenomenon of Karst topography. Credit: U.S. Geological Survey (USGS)
Great Blue Hole, Coast of Belize – a phenomenon of Karst topography.
Credit: U.S. Geological Survey (USGS)

The Great Blue Hole is a giant submarine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll 70 km (43 mi) from the mainland and Belize City. The hole is circular in shape, over 300 m (984 ft) across and 124 m (407 ft) deep. It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).

Exploration and name

This site was made famous by Jacques Cousteau, who declared it one of the top ten scuba diving sites in the world. In 1971 he brought his ship, the Calypso, to the hole to chart its depths. Investigations by this expedition confirmed the hole’s origin as typical karst limestone formations, formed before rises in sea level in at least four stages, leaving ledges at depths of 21 m (69 ft), 49 m (161 ft), and 91 m (299 ft). Stalactites were retrieved from submerged caves, confirming their previous formation above sea level. Some of these stalactites were also off-vertical by 5˚ in a consistent orientation, indicating that there had also been some past geological shift and tilting of the underlying plateau, followed by a long period in the current plane.

Initial measured depth of Great Blue Hole was 125 m (410 ft) which is the most often cited depth up to this day. An expedition by the Cambrian Foundation in 1997 measured the hole’s depth as 124 m (407 ft) at its deepest point. This difference in measurement can be explained by ongoing sedimentation or by imprecision in measurements. The expedition’s goal was to collect core samples from the Blue Hole’s floor and document the cave system. To accomplish these tasks, all of the divers had to be certified in cave diving and mixed gases.

The name “The Great Blue Hole” was coined by British diver and author Ned Middleton in the book “Ten Years Underwater” (Immel Publishing 1988, ISBN 0907151434)

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Note: The above post is reprinted from materials provided by Wikipedia.

Durdle Door, England

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Durdle Door is a natural limestone arch on the Jurassic Coast near Lulworth in Dorset, England. It is privately owned by the Welds, a family who owns 12,000 acres (50 km2) in Dorset in the name of the Lulworth Estate. It is open to the public. The name Durdle is derived from the Old English ‘thirl’ meaning bore or drill.

Geology

The form of the coastline around Durdle Door is controlled by its geology—both by the contrasting hardnesses of the rocks, and by the local patterns of faults and folds. The arch has formed on a concordant coastline where bands of rock run parallel to the shoreline. The rock strata are almost vertical, and the bands of rock are quite narrow. Originally a band of resistant Portland limestone ran along the shore, the same band that appears one mile along the coast forming the narrow entrance to Lulworth Cove. Behind this is a 120-metre (390 ft) band of weaker, easily eroded rocks, and behind this is a stronger and much thicker band of chalk, which forms the Purbeck Hills. These steeply dipping rocks are part of the geological structure known as the Lulworth crumple, itself part of a broader monocline (a kinked type of geological fold) produced by the building of the Alps during the mid-Cenozoic.

The limestone and chalk are in closer proximity at Durdle Door than at Swanage, 10 miles (16 km) to the east, where the distance is over 2 miles (3 km). Around this part of the coast nearly all of the limestone has been removed by sea erosion, whilst the remainder forms the small headland which includes the arch. Erosion at the western end of the limestone band has resulted in the arch formation. UNESCO teams monitor the condition of both the arch and adjacent beach.

The 120-metre (390 ft) isthmus which joins the limestone to the chalk is made of a 50-metre (160 ft) band of Portland limestone, a narrow and compressed band of Cretaceous Wealden clays and sands, and then narrow bands of greensand and sandstone.

In Man O’ War Bay, the small bay immediately east of Durdle Door, the band of Portland and Purbeck limestone has not been entirely eroded away, and is visible above the waves as Man O’War Rocks. Similarly, offshore to the west, the eroded limestone outcrop forms a line of small rocky islets called (from east to west) The Bull, The Blind Cow, The Cow, and The Calf.

As the coastline in this area is generally an eroding landscape, the cliffs are subject to occasional rockfalls and landslides; a particularly large slide occurred just to the east of Durdle Door in April 2013, resulting in destruction of part of the South West Coast Path.

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Note: The above post is reprinted from materials provided by Wikipedia.

Scientists discover magma buildup under New Zealand town

Scientists discover magma-GeologyPage
A drawing looking south along the Taupo Volcanic Zone showing the subduction of the Pacific Plate under the North Island of New Zealand. Uplift of the surface measured by satellite radar and GPS suggests the presence of a magmatic body beneath the Bay of Plenty coast at a depth of 9.5 km. Credit: Ian Hamling

Scientists say they’ve discovered a magma buildup near a New Zealand town that explains a spate of recent earthquakes and could signal the beginnings of a new volcano—although they’re not expecting an eruption anytime soon.

Geophysicist Ian Hamling said that since 1950, enough magma to fill 80,000 Olympic-size swimming pools has squeezed up beneath the surface near the coastal town of Matata, about 200 kilometers (120 miles) southeast of Auckland.

A paper published Saturday in the online journal Science Advances outlines the findings. Hamling, the paper’s lead author, said that while other parts of New Zealand have active volcanoes, there have been none near Matata for at least 400,000 years.

“It was quite a big surprise,” he said in an interview with The Associated Press.

Using GPS data and satellite images, the scientists say they discovered an area of land about 400 square kilometers (154 square miles) has risen by 40 centimeters (16 inches) since 1950.

Hamling said a period of quick uplift between 2004 and 2011 likely triggered thousands of small earthquakes. Scientists had previously thought tectonic shifts caused the quakes.

Hamling said the magma remained about 10 kilometers (6 miles) below the surface, deep enough that he didn’t expect a volcano to develop within his lifetime. He said a volcano could develop over hundreds or thousands of years, or the magma could eventually cool and harden.

Matata is home to about 650 people. Hamling said he hoped further study would allow scientists to develop a warning system for earthquakes in the area. He said the quakes are likely triggered by magma stressing and breaking rock.

Hamling said it was unusual worldwide to discover magma buildup in an area with no volcanoes. He said modern equipment allowed them to accurately measure tiny horizontal and vertical changes in the coastal land.

Just over half of the area studied is offshore, however, and Hamling said the scientists needed to rely on inferences from what happened on the land to gauge the changes underwater.

Victoria Miller, a volcanologist with Geoscience Australia who was not involved in the research, said the location was of interest because it was outside of an active volcanic area.

“The scientific analysis seems robust and notes the limitations of modelling an offshore source,” Miller wrote in an email.

Reference:
I. J. Hamling et al. Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand, Science Advances (2016). DOI: 10.1126/sciadv.1600288

Note: The above post is reprinted from materials provided by The Associated Press.

Scientists discover oldest plant root stem cells

Scientists discover oldest-GeologyPage
The oldest fossilized remains of an actively growing plant root. Credit: Sandy Hetherington/Oxford University Herbaria

Scientists at Oxford University have discovered the oldest known population of plant root stem cells in a 320-million-year-old fossil.

The cells, which gave rise to the roots of an ancient plant, were found in a fossilized root tip held in the Oxford University Herbaria.

As well as revealing the oldest plant root stem cells identified to date, the research also marks the first time an actively growing fossilised root has been discovered — in effect, an ancient plant frozen in time.

The study is published in the journal Current Biology.

Oxford Plant Sciences PhD student Alexander (Sandy) Hetherington, who made the discovery during the course of his research, said: ‘I was examining one of the fossilised soil slides held at the University Herbaria as part of my research into the rooting systems of ancient trees when I noticed a structure that looked like the living root tips we see in plants today.

‘I began to realise that I was looking at a population of 320 million-year-old plant stem cells preserved as they were growing — and that it was the first time anything like this had ever been found.

‘It gives us a unique window into how roots developed hundreds of millions of years ago.’

Stem cells — self-renewing cells responsible for the formation of multicellular organisms — are located in plants at the tips of shoots and roots in groups called meristems. The 320 million-year-old stem cells discovered in Oxford are different to all those living today, with a unique pattern of cell division that remained unknown until now. That tells us that some of the mechanisms controlling root formation in plants and trees have now become extinct and may have been more diverse than thought.

These roots were important because they comprised the rooting structures of the plants growing in Earth’s first global tropical wetland forests with tall trees over 50m in height and were in part responsible for one of the most dramatic climate change events in history. The evolution of deep rooting systems increased the rate of chemical weathering of silicate minerals in rocks — a chemical reaction that pulled CO2 out of the atmosphere, leading to the cooling of Earth and thus one of the planet’s great ice ages.

The fossils studied during this research are the remains of the soil from the first giant tropical rainforests on Earth. The rock in which the soil is preserved formed in the Carboniferous swamps that gave rise to the coal sources spanning what is now Appalachia to central Europe, including the coal fields in Wales, northern England and Scotland.

Sandy has named the stem-cell fossil Radix carbonica (Latin for ‘coal root’).

Professor Liam Dolan, Head of the Department of Plant Sciences at Oxford University and senior author of the paper, said: ‘These fossils demonstrate how the roots of these ancient plants grew for the first time. It is startling that something so small could have had such a dramatic effect on Earth’s climate.

‘This discovery also shows the importance of collections such as the Oxford University Herbaria — they are so valuable, and we need to maintain them for future generations.’

Reference:
Alexander J. Hetherington, Joseph G. Dubrovsky, Liam Dolan. Unique Cellular Organization in the Oldest Root Meristem. Current Biology, 2016; DOI: 10.1016/j.cub.2016.04.

Note: The above post is reprinted from materials provided by University of Oxford.

Geosciences team to place GPS sensors around Tanzanian volcano in effort to predict eruptions

Geosciences team to place GPS sensors-GeologyPage
While a doctoral student at Purdue University, D. Sarah Stamps was in Tanzania to see the Ol Doinyo Lengai volcano erupt. This is among the many photos she took during her trip in 2008. She has been back several times since, and is returning this month as part of a research expedition. Credit: Virginia Tech

Tanzania’s Ol Doinyo Lengai is unique for two reasons: It’s the only active volcano that erupts natroncarbonatite lava, and it’s within a region where the Earth’s surface is just beginning to rift apart.

This month, Assistant Professor D. Sarah Stamps of the Virginia Tech Department of Geosciences is launching an observatory there to track activity of both the volcano and the continental rift.

The journey, taking place from June 2 to June 30, brings Stamps and graduate student Josh Jones to a remote village in the Arusha Region, Tanzania. There, Stamps, who has been to the area several times, and Jones—this trip will be his first to Africa—along with researchers from the region and Korea, will place five high-precision GPS sensors around the volcano. The sensors will have the capability to send data in near-real-time from the volcano to Stamps upon her return to Blacksburg.

The volcano is known as the “Mountain of God” in the local Maasai language. Stamps has been to the volcano many times, first traveling to the region in 2006 as an undergraduate in earth sciences while at the University of Memphis, Tennessee, and again as a doctoral student at Purdue University. In 2008, she witnessed the volcano erupt.

Stamps is a leading expert on the tectonics of the East African Rift System, in which Ol Doinyo Lengai volcano resides. The June trip with Jones will further Stamps’ knowledge of the area, and provide other experts and locals with a better warning system of volcanic activity and tectonic movement along a nearby fault. The relationship between the two— does volcanic activity lead to plate movement or the opposite, or neither—is a key component of Stamps’ work.

Additional trips to Tanzania will follow in this multiyear project.

“Our goal is to advance scientific knowledge in the field of plate tectonics,” said Stamps. “We will understand, for the first time, the link between present-day volcanism and the long-term tectonic development of continental rifts. To do so, we are employing state-of-the-art sensors and cybertools that allow us to monitor deformation of the volcano and fault movement along the Natron fault in real-time.”

Among the tools in Stamps’ employ is CHORDS – that’s short for Cloud Hosting for Real-time Data in the geoSciences – developed through EarthCube, the National Science Foundation (NSF) cyberinfrastructure program. The NSF has funded many of Stamps’ trips to Tanzania, including a portion of this trek.

When Stamps and Jones place high-precision GPS sensors around the perimeter of the volcano they also will install an internet satellite system nearby—roughly 5 miles away—  to serve as a local base. Their work will provide locals with the open access to the internet for the first time.

Language barriers have abounded in previous research efforts, with English-speaking researchers working with Swahili translators, who then translate requests, questions, and the like into the local Maasai language, and back again.

“Many petrologists and geochemists have studied the volcano, but no one has developed a volcano observatory at Ol Doinyo Lengai,” added Stamps. “The lack of a volcano observatory is due to the remoteness and challenges of working in a developing region.

There is no electricity in the area and all access to the region is limited to unpaved roads. We are bringing open access to the area for the first time. There is closed-access internet restricted to tourists and employees of the Tanzania Tourism Board.”

Stamps’ previous research trips to Tanzania also involved sensors and GPS markers, but real-time data collection was not an option. “Real-time data transmission and visualization of GPS data is truly at the cutting-edge of technology,” said Stamps. “The capacity to do this has only been developed in the last year—really just in the past few months.” Her goal is to make monitoring data from Ol Doinyo Lengai as effective as tracking information from the Yellowstone Volcano observatory in Wyoming.

The research project at Ol Doinyo Lengai is truly international, with Stamps working with Tanzania’s Ardhi University and the Korea Institute for Geosciences and Mineral Resources.

Jones, of Yorktown, Virginia, who earned his bachelor’s degree in geosciences from Virginia Tech in 2015, called the research trip a dream of a lifetime. “I am very excited about exploring and studying the only active carbonatite volcano in the world,” he said. “I have always been drawn to the beauty and awe of volcanoes throughout my time as an undergraduate at Virginia Tech. The chance to climb and study an active volcano is a dream come true. Hopefully, I will be able to explore more of the volcano than just what our research requires and, if at all possible, reach the summit.”

The natroncarbonatite lava rock that is produced by Ol Doinyo Lengai may be familiar to Virginia Tech. It is the compositional equivalent of Hokie Stone. While not an exact match to limestone, its coloring is near identical when cooled. Older carbonatite volcanoes, such as Homa Mountain are nearby, but extinct.

The nearby fault is young for Earth, roughly 5 million to 10 million years old, whereas other rifts in Africa date back 25 million years and older. “This volcano is the best place on Earth to study how volcanism influences continental rifting in its early phases of development,” said Stamps of her work.

Research efforts for Stamps and Jones reach out far beyond tectonics. With high-precision global navigation satellite systems and sensors that can detect earth movement with millimeter precision, both researchers will be using computational modeling and big-data mathematics to study seismic activities.

Note: The above post is reprinted from materials provided by Virginia Tech.

Hydraulic fracturing chemical spills on agricultural land need scrutiny

Hydraulic fracturing chemical-GeologyPage
Colorado State University researchers set out to discover whether degradation of hydraulic fracturing chemicals in agricultural soil are affected by co-contamination. Credit: Borch Lab/Colorado State University

Hydraulic fracturing, a widely used method for extracting oil and gas from otherwise impenetrable shale and rock formations, involves not only underground injections composed mostly of water, but also a mixture of chemical additives. These chemicals range from toxic biocides and surfactants, to corrosion inhibitors and slicking agents, and many are also used by other industries.

A Colorado State University research team desired a deeper understanding of the fate of these chemicals when they are spilled accidentally during either transportation or production in oil and gas operations. These spills, especially in Colorado, often take place on or near agricultural lands.

The researchers set out to discover whether the degradation of these chemicals in agricultural soil are affected by co-contamination. The team consisted of Thomas Borch, a professor in the Department of Soil and Crop Sciences in the College of Agricultural Sciences, with joint appointments in civil and environmental engineering and chemistry; Jens Blotevogel, a research assistant professor in civil and environmental engineering; and their graduate student Molly McLaughlin.

Their results are online in the journal Environmental Science and Technology, published by the American Chemical Society (ACS).

In the paper, Borch, Blotevogel and McLaughlin cite 838 total hydraulic fracturing fluid spills in Colorado, reported to the Colorado Oil and Gas Conservation Commission in 2014. These spills only include those larger than five barrels of fluid when they happen within a well pad, and larger than one barrel when outside a well pad.

Simulating spill reactions in the lab

For their proof-of-concept experiments, the researchers used reactors to simulate chemical reactions and biodegradation of hydraulic fracturing additives spilled on agricultural soil. Later, they plan to test their conclusions at actual spill sites.

They tested three well-known organic chemicals: polyethylene glycol (PEG), a commonly used surfactant; glutaraldehyde, a biocide that prevents pipe corrosion from microbial activity; and polyacrylamide, a slicking agent that allows hydraulic fracturing fluid to better penetrate shale. They looked at how these chemicals interact both with each other, and with naturally occurring salts underground.

They found that the PEG (surfactant) by itself completely biodegrades within about 70 days, but that in combination with glutaraldehyde (biocide), the PEG stayed in the soil much longer. That biodegradation was fully inhibited by salt concentrations typical for oil and gas extraction activities.

“Our motivation for doing this is because the chemicals often come up as mixtures,” Borch said. “While you may see biodegradation of a surfactant under normal circumstances, if you spill that together with a biocide that kills bacteria, maybe you don’t break that surfactant down as quickly. And that’s exactly what we see. If chemicals don’t degrade as quickly, it gives them more time to be transported to groundwater or sensitive surface water.”

They also looked at the degradation cycle of glutaraldehyde (biocide), which occurred within about two months. While polyacrylamide stuck around in the soil for six months, it covalently bonded with the glutaraldehyde, effectively lowering the toxicity of the biocide.

Follow-up studies needed

The bottom line is that more science is needed around how spilled chemicals interact with each other and the underground chemical environment – and this applies not just to oil and gas extraction, but to many industrial processes, the researchers say. Such follow-up studies could lead to better understanding of the potential uptake of pollutants in crops, or contamination of groundwater and surface water, with the ultimate goal of helping improve human health risk assessment of spills.

“We cannot say our findings are valid for all the different chemicals used worldwide in hydraulic fracturing,” Blotevogel said. “There are probably 1,000 different chemicals used globally, and they all behave very differently with respect to how they are broken down.”

Borch and Blotevogel previously published a comprehensive review of the biocide toxicity in hydraulic fracturing fluids and have worked together for almost nine years. The ES&T study was supported primarily by CSU’s School of Global and Environmental Sustainability (SoGES), a grant from the CSU Water Center, and by the Borch-Hoppess Fund for Environmental Contaminant Research.

Reference:
Molly C. McLaughlin, Thomas Borch, and Jens Blotevogel. Spills of Hydraulic Fracturing Chemicals on Agricultural Topsoil: Biodegradation, Sorption, and Co-contaminant Interactions. DOI: 10.1021/acs.est.6b00240

Note: The above post is reprinted from materials provided by Colorado State University.

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