zooks777

When did the Greenland ice cap last melt?

Published on December 12, 2016 by zooks777Leave a comment

The record preserved in cores through the thickest part of the Greenland ice cap goes back only to a little more than 120 thousand years ago, unlike in Antarctica where data are available for 800 ka and potentially further back still. One possible reason for this difference is that a great deal more snow falls on Greenland so the ice builds up more quickly than in Antarctica. Because ice flows under pressure this might imply that older ice on Greenland long flowed to the margins and either melted or calved off as icebergs. So, although it is certain that the Antarctic ice cap has not melted away, at least in the last million years or so, we cannot tell if Greenlandic glaciers did so over the same period of time. Knowing whether or not Greenland might have shed its carapace of ice is important, because if ever does in future the meltwater will add about 7 metres to global sea level: a nightmare scenario for coastal cities, low-lying islands and insurance companies.

Margin of the Greenland ice sheet (view from p... — Edge of the Greenland ice sheet with a large glacier flowing into a fjiord at the East Greenland coas (Photo credit: Wikipedia)

One means of judging when Greenland was last free of ice, or at least substantially so, is based on more than a ice few metres thick being opaque to cosmic ‘rays’. Minerals, such as quartz, in rocks bared at the surface to ultra-high energy, cosmogenic neutrons accumulate short-lived isotopes of beryllium and aluminium – ¹⁰Be and ²⁶Al with half-lives of 1.4 and 0.7 Ma. Once rocks are buried beneath ice or sediment, the two isotopes decay away and it is possible to estimate the duration of burial from the proportions of the remaining isotopes. After about 5 Ma the cosmogenic isotopes will have decreased to amounts that cannot be measured. Conversely, if the ice had melted away at any time in the past 5 Ma and then returned it should be possible to estimate the timing and duration of exposure of the surface to cosmic ‘rays’. Two groups of researchers have applied cosmogenic-isotope analysis to Greenland. One group (Schaefer, J.G. et al. 2016. Greenland was nearly ice-free for extended periods during the Pleistocene. Nature, v. 540, p. 252-255) focused on bedrock, currently buried beneath 3 km of ice, that drilling for the ice core finally penetrated. The other systematically analysed the cosmogenic isotope content of mineral grains at different depths in North Atlantic seafloor sediment cores, largely supplied from East Greenland since 7.5 Ma ago (Bierman, P.R. et al. 2016. A persistent and dynamic East Greenland Ice Sheet over the past 7.5 million years Nature, v. 540, p. 256-260). As their titles suggest, the two studies had conflicting results.

The glacigenic sediment grains contained no more than 1 atom of ¹⁰Be per gram compared with the 5000 to 6000 in grains deposited and exposed to cosmic rays along the shores of Greenland since the end of the last ice age. These results challenge the possibility of any significant deglaciation and exposure of bedrock in the source of seafloor sediment since the Pliocene. The bedrock from the base of Greenland’s existing ice cap, however, contains up to 25 times more cosmogenic isotopes. The conclusion in that case is that there must have been a protracted, >280 ka, exposure of the rock surface in what is now the deepest ice cover at 1.1 Ma ago at most. Allowing for the likelihood of some persistent glacial cover in what would have been mountainous areas in an otherwise substantially deglaciated Greenland, the results are consistent with about 90% melting suggested by glaciological modelling.

Clearly, some head scratching is going to be needed to reconcile the two approaches. Ironically, the ocean-floor cores were cut directly offshore of the most likely places where patches of residual ice cap may have remained. Glaciers there would have transported rock debris that had remained masked from cosmic rays until shortly before calved icebergs or the glacial fronts melted and supplied sediment to the North Atlantic floor. If indeed the bulk of Greenland became ice free around a million years ago, under purely natural climatic fluctuations, the 2° C estimate for global warming by 2100 could well result in a 75% glacial melt and about 5-6 m rise in global sea level.

Read more about glaciation here and here.

Tree-climbing australopithecines

Published on December 9, 2016 by zooks7771 Comment

We know that Lucy, the famous Australopithecus afarensis, could climb trees because her many bone fractures show that she fell out of a tree to her death. But that does not mean her species was an habitual tree-climber: plenty of modern humans fall to their deaths from trees, cliffs and the like. But the issue seems to have been resolved by using X-ray tomography of Lucy’s limb bones (Ruff, C.B. et al. 2016. Limb bone structural proportions and locomotor behaviour in A.L. 288-1 (“Lucy”). PLOS ONE v. 11, e0166095. doi:10.1371/journal.pone.0166095) during the skeleton’s triumphal series of exhibits in the US.



Embed from Getty Images

The authors, including two of those who showed that Lucy died after a fall using similar data, compared the digital 3-D models of her surviving arm- and leg bones with those of other hominins and living primates, estimating their relative strengths at different positions. Lucy was probably stronger in the arm than in the leg, but not to the same degree as chimpanzees. This is a feature that would significantlyassist climbing , but her bipedal locomotion on the ground would have been only slightly different from that of later Homo species. If anything, her strength relative to size would have been greater than ours, perhaps reflecting less reliance on tools for getting food and defending herself. But almost certainly Australopithecus afarensis habitually spend more time in trees, perhaps foraging and as a defence against predation, especially at night.

The new data for Lucy allows palaeoanthropologists to better judge the capabilities of other hominins. Interestingly Homo habilis, the earliest of our genus, may have had similar habits. But later species, beginning with H. erectus/ergaster, were as Earth-bound as we are. This suggests a shift in hominin ecology from an early and probably long history of semi-arboreal behavior until humans became masters of their terrain about 1.9 Ma ago, probably through their invention of better tools and the controlled use of fire.

Read more about human evolution here and here

A challenge to the concept of species

Published on November 25, 2016 by zooks777Leave a comment

Comparison of DNA from ancient hominin fossils with that obtained from a broad spectrum of living people showed that on the road out of Africa in the last 130 thousand years some anatomically modern humans successfully interbred with Neanderthals and Denisovans to produce fertile offspring. All non-African people contain a trace of those liaisons and include fertile hybrids in their ancestry, whereas Africans do not. Using quick, low-cost and sensitive genomic analyses these discoveries made similar searches for hybridisation among other supposedly distinct species a popular and fruitful line of research (Pennisi, E. 2016. Shaking up the tree of life. Science, v. 354, p. 817-820; doi: 10.1126/science.354.6314.817). They also challenge the long-held view that individual species are incapable of fertile interbreeding with others. Yet fertile hybrids have long been known among plants and butterflies without recourse to genomics. Now that it is a basic tool, it has been shown that up to 10% of known plant species have arisen from hybrids and examples are quickly being found among birds, insects, fish and mammals, including the famous Galapagos finches. Hybridisation introduces genetic variation more quickly than does mutation, potentially a major advantage in adaptive radiation.

Page from Darwin's notebooks around July 1837 ... — Page from Darwin’s notebooks around July 1837 showing his first sketch of an evolutionary tree. (credit: Wikipedia)

Of course, the concept of ‘species’ is arbitrarily based on biological ‘form and function’, and in the same fashion as discoveries about epigenetics have shown genetic determinism to have an air of dogma, so hybridisation suggests that a ‘web’ is more apt as shorthand for the progress of evolution than is Darwin’s ‘tree’ or even a tangled ‘bush’. Another welcome outcome spurred by the pioneers of hominin comparative genetics is a powerful challenge to the dominant philosophies of reductionism and dualism among scientists; legacies of René Descartes bound up with the ‘scientific method’ – especially among physical scientists – and ideas such as ‘nature versus nurture’. A major revolution is in progress, from which the seekers for a Theory of Everything, from quantum mechanists through particle physicists to cosmologists need to draw some sharp and perhaps embarrassing lessons.

It is appropriate that the driving agency lies within anthropology, and thrilling too, for everyone can quickly learn a new way of approaching the world by contemplating their own origins. They would be hard-pressed to do that by pondering on the early nanoseconds of the cosmos …

DNA From Mystery Human Species Detected in Pacific Islanders

K-T (K-Pg) boundary impact probed

Published on November 24, 2016 by zooks777Leave a comment

One of the most eagerly followed ocean-floor drilling projects has just released some results. Its target is 46 km radially away from the centre of the geophysical anomaly associated with the Chixculub impact structure just to the north of Mexico’s Yucatan Peninsula. In the case of large lunar impact craters the centre is often surrounded by a ring of peaks. Modelling suggests such features are produced by the deep penetration of immense seismic shock waves. In the first minute these excavate and fling out debris to leave a cavity penetrating deep into the crust. Within three minutes the cavity walls collapse inwards creating a rebound superficially similar to the drop flung upwards after an object is dropped in liquid. This, in turn, collapses outwards to emplace smashed and partially melted deep crustal material on top of what were once surface materials, creating a crustal inversion beneath a mountainous ring of Himalayan dimensions that surrounds a by-now shallow crater. That is the story modelled from what is known about well-studied, big craters on the Moon and Mercury. Chixculub is different because the impact was into the sea and involved debris-charged tsunamis that finally plastered the actual impact scar with sediments. The drilling was funded for several reasons, some palaeontological others relating to the testing of theories of impact processes and their products. Chixculub is probably the only intact impact crater on Earth, and the first reports of findings are in the second category (Morgan, J.V. and 37 others 2016. The formation of peak rings in large impact craters. Science, v. 354, p. 878-882; doi: 10.1126/science.aah6561).

The drill core, reaching down to about 1.3 km below the sea floor penetrates post-impact Cenozoic sediments into a 100 m thick zone of breccias containing fragments of impact melt rock, probably the infill of the central crater immediately following the first few minutes of impact. Beneath that are coarse grained granites representing the middle continental crust from original depths around 10 km. The granite is intensely fractured and riven by dykes and pods of impact melt, and contains intensely shocked grains that typify impacts that produce a transient pressure of ~60 GPa – around six hundred thousand times atmospheric pressure. From seismic reflection surveys this crustal material overlies as yet un-drilled Mesozoic sedimentary rocks. Its density is significantly less than that of unshocked granite – averaging 2.4 compared with 2.6 g cm³. So it is probably filled with microfractures and sufficiently permeable for water to have penetrated once the impact site had cooled. This poses the question, yet to be addressed in print, of whether or not this near-surface layer became colonised by microorganisms in the aftermath (Barton, P. 2016. Revealing the dynamics of a large impact. Science, v. 354, p. 836-837). That is, was the surrounding ocean sterilised at the time of the K-T (K-Pg) mass extinction?; an issue whose resolution is awaited with bated breath by the palaeobiology audience. OK; so theory about the physical process of cratering has been validated to some extent, but will later results be more interesting, outside the planetary sciences community?

Read more about impacts here and mass extinctions here .

Lunar gravity and the Orientale Basin

Published on November 6, 2016 by zooks777Leave a comment

Mapping the Earth’s gravitational field once involved painstaking use of highly sensitive gravimeters at points on the surface, then interpolating values in the spaces between. How revealing maps produced in this way are depends on the spacing of the field sites, and that is still highly variable because of accessibility and how much money is available to carry out such a task in different areas. Space-borne methods have been around for decades. One uses radar measurement of sea-surface height, which depends on the underlying gravitational field. The other deploys two satellites in tandem orbits (the US-German Aerospace Centre Gravity Recovery and Climate Experiment – GRACE), the distance between them – measureable using radar – varying along each orbit according to variations in the Earth’s gravity. Respectively, these methods have produced gravity maps of the ocean floor and estimates melting rates of ice caps and the amount of groundwater extraction from sedimentary basins. The problem with GRACE is that satellites need to avoid the Earth’s atmosphere by using orbits hundreds of kilometres above the surface, otherwise drag soon brings them down. So the resolution of the gravity maps that it produces is too coarse (about 270 km) for most useful applications. If a world has no atmosphere, however, there is no such limit on orbital altitude, other than surface topography. A similar tandem-system to GRACE has been orbiting the Moon at 55 km since 2011. The Gravity Recovery and Interior Laboratory (GRAIL) mission has produced full coverage of lunar gravity at a resolution of 20 km. In a later phase of operation, GRAIL has been skimming the tops of the highest mountains on the Moon at an average altitude of 6 km; close enough to give a resolution of between 3 and 5 km.

This capacity has given a completely new take on lunar near-surface structure, about as good as that provided by conventional gravity mapping for parts of the Earth. The first pay-off has been for the best preserved major impact feature on the lunar surface: the Orientale basin that formed at the end of the Late Heavy Bombardment of the Solar System, around 3.8 billion years ago. The ~400 km diameter Orientale basin is at the western border of the moon’s disk visible from Earth, and looks like a gigantic bullseye. Its central crater, floored by dark-coloured basalt melted from the mantle by the power of the impact, is surrounded by three concentric rings extending to 900 km across; a feature seen partially preserved around even larger lunar maria. The structure of such giant ringed basins – also seen on other bodies in the Solar System – has been something of a puzzle since their first recognition on the Moon. A popular view has been that they are akin to the rippling produced dropping a pebble in water, albeit preserved in now solid rock.

The Orientale basin superimposed by the strength of the moon's gravity field. Areas shaded in red have higher gravity, while areas in blue have the least gravity. (Credit: Ernest Wright, NASA/GSFC Scientific Visualization Studio) — The Orientale basin superimposed by the strength of the moon’s gravity field. Areas shaded in red have higher gravity, while areas in blue have the least gravity. (Credit: Ernest Wright, NASA/GSFC Scientific Visualization Studio)

GRAIL has allowed planetary scientists to model a detailed cross section through the lunar crust (Zuber, M.T. and 27 others, 2016. Gravity field of the Orientale basin from the Gravity Recovery and Interior Laboratory Mission. Science, v. 354, p. 438-441). The 40 km thick anorthositic (feldspar-rich) lunar crust has vanished from beneath the central crater, which is above a great upwards bulge of the lunar mantle mantled by about 2 km of mare basalts. The shape of the crust-mantle boundary beneath the rings shows that it has been thickened by anorthositic debris flung out by the impact. But the rings seem to be controlled by huge faults that penetrate to the mantle: signs of 2-stage gravitational collapse of the edifice produced initially by the impact.

Palaeontologists with beards: some shocking news

Published on October 21, 2016 by zooks777Leave a comment

Mary Anning, now something of a feminist icon, combed the foreshores and undercliffs of the Jurassic Coast of southern England for fossils, including those of marine reptiles. Self-taught, she unearthed, prepared and described the first ichthyosaurs and plesiosaurs known to science. Being a working class woman – and she did work in the early 19^th century – she was not allowed to publish. Instead, she provided fossils to notables like Owen, Buckland and Cuvier who published and got the credit, only rarely acknowledging her as the collector. In 1964, during my induction as a fresher in the Lapworth Library of the Geology Department at Birmingham University, the ‘Prof’ Fred Shotton declared to the 14 young men sitting meekly before him, ‘There will be no women students in this department while I am its Head’. By my final year, Fred had relented and the first ever female undergraduate enrolled. When I left with a PhD in 1970, there were more and now my guess is the proportion is around 40%.. But professional geoscience is still largely a man’s world. In the US, where geoscience is still a major science – it has declined in Britain as a result of ‘rationalisation’ of UK Earth science departments that followed the 1987 Oxburgh Report – a mere 16% of faculty are women; female PhDs are paid 12% less than males; fellowship of learned societies is below 20%, and there is a host of other issues in which women are ‘less favoured’. It’s much the same, although perhaps a little less blatant, in most sciences. Being in a discipline that is still largely focussed on field work by individuals, female ‘lone workers’ in often remote places sometimes face worse problems.

Three of the presenters in the Bearded Lady project pose on the foreshore at Lyme Regis - note Golden Cap in the background. (Credit: Kelsey Vance) — Three of the presenters in The Bearded Lady Project pose on the foreshore at Lyme Regis – note the weathered Cretaceous Upper Greensand forming Golden Cap in the background. (Credit: Kelsey Vance)

Asking themselves a few rhetorical questions, such as, ‘What comes to mind when you hear the word “palaeontologist”?’ or ‘List as many female scientists as you can’, three women professionals – a palaeontologist, a performance art director and a photographer – decided to challenge a few stereotypes. Their project is a feature length, live-action documentary plus a series of photographic exhibitions to inspire young women to become geoscientists. It centres on what most ‘geos’ really enjoy; field work conducted exclusively by women. It is as realistic as the common perception of field geology might suggest, yet at some point each of the presenters has a beard or moustache. Hence, The Bearded Lady Project! Part of the film is to include footage shot at Lyme Regis, as a tribute to Mary Anning, the whole project covering many different aspects of practical geoscience.

For British readers: The Bearded Lady Project’s portrait exhibition is planned to be in Exeter.

See also: Witze, A. 2016. Q&A: Lexi Jamieson Marsh and Ellen Currano: Face to face. Nature v. 538, p. 316.

Impact linked to the Palaeocene-Eocene boundary event

Published on October 20, 2016 by zooks777Leave a comment

The Palaeocene–Eocene (P-E) boundary at 55.8 Ma marks the most dramatic biological changes since the mass extinction at the Cretaceous-Palaeogene boundary 10 million years earlier. They included the rapid expansions of mammals and land plants and major extinction of deep-water foraminifera. It was a time of sudden global warming (5-10°C in 10-20 ka) superimposed on the general Cenozoic cooling from the ‘hothouse’ of the Cretaceous Period. It coincided with a decrease in the proportion of ¹³C in marine carbonates. Because photosynthesis, the source of organic carbon, favours light ¹²C, such a negative δ¹³C “spike” is generally ascribed to an unusually high release of organic carbon to the atmosphere. The end-Palaeocene warming may have resulted from a massive release of methane from gas-hydrate buried in shallow seafloor sediments. But another process may yield such a signature; massive burning of organic material at the land surface. Since its discovery, the P-E thermal maximum has been likened to the situation that we may face should CO₂ emissions from fossil-fuel burning continue to rise without control. Unsurprisingly, funds are more easily available for research on this topic than, say, ‘Snowball Earth’ events.

Climate change during the last 65 million year... — Climate change during the last 65 million years. The Paleocene–Eocene Thermal Maximum is labelled PETM. (Photo credit: Wikipedia)

Three seafloor sediment cores off the east coast of the US that include the P-E boundary have been found to contain evidence for an impact that occurred at the time of the δ¹³C “spike” (Schaller, M.F. et al. 2016. Impact ejecta at the Paleocene-Eocene boundary. Science, v. 354, p. 225-229). The evidence is dominated by tiny spherules and tear-shaped blobs of glass, some of which contain tiny crystals of shocked and high-temperature forms of silica (SiO₂). These form part of the suite of features that have been used to prove the influence of asteroid impacts. Two other onshore sites have yielded iridium anomalies at the boundary, so it does look like there was an impact at the time. The question is, was it large enough either to cause vast amounts of methane to blurt out from shall-water gas hydrates or set the biosphere in fire? Two craters whose age approximates that of the P-E boundary are known, one in Texas the other in Jordan, with diameters of 12 and 5 km respectively; far too small to have had any global effect. So either a suitably substantial crater of the right age is hidden somewhere by younger sediments or the association is coincidental – the impact that created the Texan crater could conceivably have flung glassy ejecta to the area of the three seafloor drilling sites.

Almost coinciding with the spherule-based paper’s publication another stole its potential thunder. Researchers at Southampton University used a mathematical model to investigate how a methane release event might have unfolded (Minshull, T.A. et al. 2016. Mechanistic insights into a hydrate contribution to the Paleocene-Eocene carbon cycle perturbation from coupled thermohydraulic simulations. Geophysical Research Letters, v. 43, p. 8637-8644, DOI: 10.1002/2016GL069676). Their findings challenge the hypothesized role of methane hydrates in causing the sudden warming at the P-E boundary. But that leaves out the biosphere burning, which probably would have neded a truly spectacular impact.

More on mechanisms for ancient climate change

Can melting of frozen methane explain rapid climate change 56 million years ago?

Scablands: megaflood hypothesis tempered

Published on October 14, 2016 by zooks7771 Comment

The eastern side of Washington State in the US includes a vast, barren area that has been scoured virtually free of superficial sediment, including soils. Its landscape is among the most odd in North America, consisting of a network of unusually wide canyons or couleés that incise a regional plateau formed by the Columbia River flood basalts. The now largely dry canyon floors contain immense potholes, megaripples and erratic boulders, together with strangely streamlined hillocks made of residual, windblown loess deposits, which collectively resemble features of normal river beds but at a gargantuan scale. The canyon network emerges from the Rocky Mountains near the city of Spokane, then criss-crosses what had previously been a wide basalt plain to merge with the Columbia River in southern Washington. The couleés are up to 100 km long and reach 100 m in depth.

Dry Falls, WA Français : Les Dry Falls dans l'... — Dry Falls in Grand Colee, Washington state, US, showing typical features of the Channelle Scablands. (credit: Wikipedia)

In the 1920s J. Harlen Bretz suggested that the Channelled Scablands had been formed by a massive flood, a view that met disbelief until his colleague Joseph Pardee discovered that a huge lake of glacial meltwater (Lake Missouala) had formed in the intricate valleys of the Montana Rockies when their outflow into Washington had been blocked by a southward-surging finger of the Cordilleran ice sheet. Lake Missouala is estimated to have been about half the size of modern Lake Michigan (~7700 km²) and up to 610 m deep, reaching a maximum volume of 2100 km³ between 15 to 13 ka ago. Bretz’s idea was vindicated; melting of the ice dam was widely thought to have produced a single vast outburst flood and the removal of approximately 320 km³ of basalt and loess. The later discovery of strandlines, similar to those on a smaller scale in Glen Roy, western Scotland, on the flanks of former lake modified the theory to a series of individual, but still huge outburst flood events. Their magnitudes, estimated by assuming that each filled the coulees to their brim, were thought to be up to 60 km³per hour, i.e. 100 times greater than the largest recorded historically, that of the Amazon. A recent study tempers the awe long-associated with the Scablands.

Isaac Larsen and Michael Lamb of the University of Massachusetts and the California Institute of Technology examined Moses Couleé, one of the largest, in detail (Larsen, I.J. & Lamb, M.P. 2016. Progressive incision of the Channelled Scablands by outburst floods. Nature, v. 538, p. 229-232; doi;10.1038/nature19817). Terraces in Moses Couleé allow successive topographic profiles of the canyon to be reconstructed, and the flow features on its floor allow water depth during some of the flows to be estimated. Far from being brim-full at any time, except during the first incision, individual discharges of meltwater were probably 5 to 10 times less than those previously suggested. Moreover, the pattern of the Scablands reflects major fracture zones n the Columbia River flood basalts, which suggests that floods followed lines of least resistance and greatest ease of erosion by removal of joint-bound blocks of basalt. Yet the floods still reached a magnitude never recorded for modern ones, and Larsen and Lambs modelling may well apply to the even vaster outburst canyons on Mars, such as Valles Marineris.

See also: Perron, J.T. & Venditti, J.G. 2016, Megafloods downsized. Nature, v. 538, p. 174-175; nature.com/newsandviews

Neanderthal culture confirmed

Published on October 2, 2016 by zooks7771 Comment

The Châtelperronian material culture represents the earliest sign of the Upper Palaeolithic in Europe and its products span a period from about 45 to 40 ka. It includes stone tools, such as points and long, thin blades with a single cutting edge and a blunt back, reminiscent of a modern knife, and others with notched, or denticulate edges that resemble saw blades. A great many of the tools, including ivory and bone ones, are probably designed for working and stitching skins. But the most revealing worked objects are animal teeth, shells and fossils that are either bored or grooved to be strung together. The best have been found in the Grotte du Renne in eastern France. The most controversial aspect of the Châtelperronian is that its artefacts are sometimes found with the fossil remains of Neanderthals who had previously produced less sophisticated, Mousterian tools since around 160 ka. The controversy centres on whether or not Neanderthals created the Châtelperronian culture, and if so, did they develop them independently or through cultural exchange with or copying from the newly arrived anatomically modern humans (AMH).

Science Magazine — Châtelperronian ornaments from the Grotte du Renne eastern France, probably parts of a necklace. (Credit: ©Marian Vanhaeren, CNRS, University of Bordeaux)

The Grotte du Renne material is especially rich in ornaments, but insufficient fossil material is present to tell from anatomical characteristics whether or not they were made by AMH or Neanderthals. It has now become possible using traces of bone proteins to detect hominin bone fragments and DNA to assess which group is implicated (Welker, F. and 127 others, 2016. Palaeoproteomic evidence identifies archaic hominins associated with the Châtelperronian at the Grotte du Renne. Proceedings of the National Academy of Science, www.pnas.org/cgi/doi/10.1073/pnas.1605834113). Analyses of mtDNA and radiometric dating of the bones that yielded it show that the Grotte du Renne tools and ornaments link with Neanderthals who lived there about 37 ka ago. Interestingly, the stratigraphic horizon beneath the definite Neanderthal occupation level contains their earlier, Mousterian artefacts. So it seems that they developed new manufacturing techniques and material culture. Yet, the findings do not resolve the issue of independent invention or copying AMH methodology.

Importantly, Grotte du Renne shows that Neanderthals, even if they copied AMH techniques, were capable of appreciating, producing and using personal ornamentation: they could learn and transmit ideas. In that respect, here is support for the notion that, apart from significant anatomical differences from AMH they were not that different intellectually.

More on Neanderthals, Denisovans and anatomically modern humans

Wade, L. 2016. Neandertals made jewelry, proteins confirm. Science, v. 353, p. 1350.

Humans and Neanderthals had sex. But was it for love?

Free course on remote sensing for water exploration

Published on September 26, 2016 by zooks7771 Comment

250 million people who live in the drylands of Africa and Asia face a shortage of water for their entire lives. Hundreds of millions more in less drought-prone regions of the ‘Third World’ have to cope repeatedly with reduced supplies. A rapid and effective assessment of how to alleviate the shortfall of safe water is therefore vital. In arid and semi-arid areas surface water storage is subject to a greater rate of evaporation than precipitation, so groundwater, hidden beneath the land surface, provides a better alternative. Rainwater is also lost by flowing away far more quickly than in areas with substantial vegetation. Harvesting that otherwise lost resource and diverting it to storage secure from evaporation – ideally by using it to recharge groundwater – is an equally important but less-used strategy. Securing a sustainable water supply for all peoples is the most important objective that geoscientists can address.

In practice, to assure good quality water supplies to a community in the form of productive wells, surface water harvesting schemes or planning the recharge of exploited aquifers requires skill, a great deal of work and considerable financial resources. Yet in many parts of sub-Saharan Africa and arid areas of Asia knowing where to focus effort and increase the chances of it being fruitful is one the biggest hurdles to overcome. Such reconnaissance – highlighting the most probable localities on geological and hydrological grounds, and screening out those least likely to yield water for drinking and hygiene – depends on details of the geology and topography of the terrain in which needy communities are situated. For most of the Afro-Asian dryland belt adequate geological and topographic maps are in as short supply as potable water itself. Remote sensing combined with an understanding of groundwater storage and surface-water harvesting is a powerful tool for bridging that knowledge gap, and is routinely used successfully in areas blessed with abundances of experienced geoscientists, money and engineering infrastructure. Again, most of the Afro-Asian dryland belt is poorly endowed in these respects.

Having long ago written a textbook on general remote sensing for geoscientists, now out of print (Image Interpretation in Geology (3^rd edition): 2001. Nelson Thorne/Blackwell Science), I decided to re-issue revised parts of it framed in the specific context of water exploration in arid and semi-arid terrains, and to add practical case studies and exercises based on a free version of professional image processing and desktop mapping software. Some of the most geologically revealing remotely sensed image data – those from the Landsat series of satellites and the joint US-Japan ASTER system carried by Terra, one of NASA’a Earth Observing System satellites – are now easily and freely available for the whole of the Earth’s land surface. Given basic familiarity with theory and practicalities, a computer and appropriate software together with a moderately fast internet connection there is nothing to stop any geoscientist, university geology student or engineer working in the water, sanitation and hygiene (WASH) sector from becoming a proficient, self-contained practitioner in water reconnaissance. Water Exploration: Remote Sensing Approaches has that aim. Online access to the theoretical parts is free, and a DVD that combines theory, software, exemplary data and several exercises that teach the use of image processing/desktop mapping software is available at cost of reproduction and postage.

If you visit the website, find what you see potentially useful and wish to know more, contact me through the Comments form at the H2Oexplore homepage.

Related articles

Share this:

Related articles

Share this:

Related articles

Share this:

Related articles

Share this:

Related articles

Share this:

Share this:

Related articles

Share this:

Share this:

Related articles

Share this:

Share this: