Month: December 2004

Another year passed

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Because of the horrific events at the end of 2004, this is not a time to celebrate geoscientific achievements during the year that has passed.

The horror of Boxing Day

Unlike the collapse of Manhattan’s Twin Towers on 11 September 2001 the world’s cameras were unable to focus on the minutiae of terrible events around the rim of the northern Indian Ocean.  They did not catch the sudden dawning of fear, but the tsunamis of 26 December 2004 were witnessed by millions of coast dwellers in Indonesia, SW Thailand, Sri Lanka, eastern India and as far away as Somalia, Tanzania and Kenya.  At the time of writing the death toll had reached 150 thousand, but it will rise inexorably, and countless people’s lives will be blighted for years to come.  The world did change on Boxing Day 2004 in a way that dwarfs the events of “9/11”.  The majority of those swept in minutes into a debris-loaded sea were among the poorest of their communities, and the dead are dominated by children and old people who simply did not have the strength to save themselves.  News came first from popular tourist resorts dotted on palm-fringed beaches, through cell phones and from hastily shot videos of what must at first have seemed a curiosity.  Before great waves appeared, the sea drew back to leave fish flapping on beaches, which local children rushed to gather as an unexpected benefice.  Ocean waves driven by great seismic events have immense wavelengths, so previously unseen sea floor lingered for 10 to 20 minutes before devastating surges suddenly rose above the horizon..

Off the western coast of Sumatra, a subduction-zone thrust displaced the sea floor by several metres, into which an unimaginable tonnage of ocean rushed.  Its rebound set in motion the most devastating natural phenomena, yet on the open ocean their passage would have been imperceptible because of their broad wavelength.  Unlike wind-waves, tsunamis travel extremely fast, around 400 km per hour; they are seismic disturbances affecting the entire water body.  The further they travel the greater the volume they affect, so they dissipate with distance.  Two days after the initial shock, sea-level rose perceptibly in California, half a world away.  When tsunamis meet shallows, the frictional effect causes the wave to slow, rise and steepen.  The wave breaks far offshore in shallow water, resulting in a surge that rises inexorably on land.  It rips up sea-floor materials, including boulders where they are present.  Damage and deaths result mainly from the backwash that can rip debris and victims several kilometres out to sea, until the next tsunami arrives, and in this case there were at least three.  We have all seen the aftermath, like nuclear devastation but not sterile.  Debris, rotting flesh and sewage breed disease, and as many may die from cholera, insect-borne disease and exposure as perished on Boxing Day morning.

The magnitude of the Sumatran sea-quake was 9.0 on the Richter Scale.  That is a logarithmic measure of the ground displacement, so that for every increase of 1.0 in magnitude ground motion increases by 10 times.  However, it is the energy released that damages and the corresponding increase is 32 times.  The Sumatran sea-quake was the largest recorded since that off Alaska in 1964 (magnitude 9.2) and the fourth largest in a century.  Tsunamis generated off Alaska reached a height of over 60 metres close to the epicentre, but they travelled parallel to the coast of the Americas and caused only 130 deaths.  Those of 26 December 2004 hit land head on, and there are large, densely populated coastal tracts around the Indian Ocean that are below 10 m above mean sea level.  Buildings, particularly for poor people, are fragile and lightweight, so the devastation was almost total, unlike the effects of on-land earthquakes.  In their case, single-storey dwellings that are little more than wood and grass structures cause less deaths than in areas with multi-storey dwellings made of stone or concrete, and the effects are localised.

The US National Oceanographic and Atmospheric Administration (NOAA) is responsible for tsunamis warnings for the eastern Pacific (http://wcatwc.gov/), which are issued in the same way as extreme weather warnings.  Other organisations maintain a permanent watch and warning service for the entire Pacific basin, which is surrounded by the majority of the world’s large earthquake zones, mainly connected to subduction, and is the most prone to tsunamis.  Using bathymetry and landmasses, it is possible to model in detail the wavefronts of tsunamis and their travel times for any circum-Pacific earthquake.  So adequate warning is possible for most coastal areas following a major earthquake.  The Indian Ocean has only one major, tectonically dangerous plate margin, where the Indian Plate drives beneath Eurasia to form the Sunda Trench off the Indonesian archipelago.  Although discussed as recently as mid-2004, no tsunami-warning service is in place for the Indian Ocean.  One reason given for this lack of foresight is that the north-western part of the Sunda Arc has had little major seismicity for more than 150 years.  Therein lay the danger; subduction was locked and a major earthquake grew more likely the longer the quiescence lasted.   All the world’s seismic observatories recorded the massive disturbance and the exact location of the Sumatran event within minutes of its occurrence, but no warnings were issued.  The tsunamis arrived in Sri Lanka and India over 4 hours later, though within less than half an hour in Thailand and Sumatra, which were most devastated.  For the millions whose lives have ended or are in ruins, the greatest advance in the geosciences, plate tectonics, utterly failed them.

What is to be done?

Many geoscientists take pride (and a fair amount of public funding) in focusing their research on dangerous natural phenomena, supposedly aimed at giving warnings or mitigating their effects.   Take any natural calamity, whether it be earthquake or tsunami, volcanic eruption, mudslide, flood or even something so simple as helping provide clean water for the victims of drought or displacement by conflict.  Now list the lives saved by the direct efforts of geoscientists against the torrent of their publications and attendances at conferences.  Is there any cause for pride in the instrumentation, the theory and the field experience?  Or should we reflect on the hubris of scientific endeavour in the aftermath of such awful events?  Two days after the disaster struck I put together detailed topographic elevation data (from the Shuttle Radar Topography Mission – SRTM) for the coastlines that surround the Indian Ocean.  I had had them for 6 months, but did nothing except make some pretty maps for a conference presentation.  I had known what potential they have for predicting areas of flooding, and more important where refuges from inundation might be, but I found “better” things to do.  All coastal areas below 15 m elevation are at risk, and a great many correlate with the tsunamis’ worst effects.  What we could have done and what we did do generally emerge only in retrospect, and indulging in mea culpa serves no purpose.  Individuals have their own agendas, and they are rarely useful in any wider sphere.  The organisations that draw scientists together are not in themselves altruistic, but serve largely academic ends.  However, human tragedies surely remind us of a wider set of responsibilities, even if only momentarily.

A collective organisation of both knowledge and real needs, which sets aside career and the “advancement of science”, is probably the only means of putting the geosciences to work for fully human benefit.  For 40 years such a collective existed in the small form of the Association of Geoscientists for International Development (AGID), which aimed at knowledge transfer from its members to less fortunate areas.  For the latter half of its existence, AGID was subsidised by the Canadian International Development Agency.  A handful of members met at the 32nd International Geological Congress in Florence during late August 2004, the agenda being wholly about its survival or winding up following CIDA’s withdrawal of financial support.  The vote went for continuation.  But, despite helping some young geoscientists of the “Third World” make progress, AGID’s small size and limited aims and funding have proved unable to make it a force that matches real needs or the geosciences’ potential for assisting development.  Data and theory now present the opportunity to resolve two great challenges: giving every man, woman and child on the planet access to safe drinking water; and predicting and mitigating all natural hazards.  Every senior politician in the developed world pays lip service to both, each UN agency convenes to discuss them on a regular basis, and the International Union of Geological Sciences (IUGS) has proposed the International Year of Planet Earth (2005-2007) with those themes at the top of its agenda.  IGC-32, the largest ever gathering of geoscientists was dominated by humanitarian themes and the launch of the IUGS initiative. The International Year of Planet Earth was supposed to have been proposed by the Peoples’ Republic of China at the September 2004 UN General Assembly 59.  It does not appear on the UN web site, and the supporting web site www.esfs.org gives no news of its adoption. But there have been many “Years of…” and even several “Decades of…” from which we have yet to see any tangible outcomes, and little of the “awareness” that they are supposed to generate, certainly not in those areas of the world towards which they were directed.

One collective of professionals that has had a powerful impact on emergencies since 1971 is Médicins sans Frontières (www.msf.org), founded and administered independently of the world’s “great and good”.  Would a geosciences equivalent be feasible and supported?  Yet there are measures that even individuals can take.  At a UN Office for Outer Space Affairs meeting on the use of satellite data for mitigating disasters (Munich, 18-21 October 2004) www.zki.caf.dlr.de/events/2004/unoosa_workshop/unoosa_programme_en.html – Margaret Andrews Deller of the UK Open University presented her ideas (see link at the above web site) on a simple and low-cost way to reduce the impact of natural disasters.  Briefly, she based her suggestions on indigenous people’s deep knowledge of their surroundings.  Recognising that, it should be possible to provide communities with graphic images that highlight potential threats, in forms that are low-cost and easily understood by anyone, such as the use of images that incorporate perspective and show features in near-natural colours.  Her most important point is that such information would not be just a warning, but a means of showing people their homeland in a way that they can learn from and value. That would bring together those affected with those who come to their aid, should catastrophe strike, and would empower local people to take charge of their lives instead of being victims.

Easily understood information and advice is vital for potential victims of catastrophes, and a quick search of the internet reveals lots on all manner of hazards and how to avoid them.  NOAA’s tsunamis website http://wcatwc.gov/ is an excellent example.  Such information needs to be recast into forms that people outside the “information society” can easily understand, and to be distributed – not such a massive task.  What drew children to south Asian beaches on Boxing Day, the massive withdrawal of the sea, is the first sign of a tsunami.  On Pacific islands everyone knows what threat such a weird occurrence signifies, but nobody on the rim of the Indian Ocean did.  But isn’t it also essential for geoscientists to donate some of their publicly and industrially funded time to share their expertise directly with those so much less fortunate than ourselves?  Without that, our claim to be resolving humanity’s problems is a transparent sham.

Another large igneous province implicated in mass extinction

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At the end of the Triassic Period, around 200 Ma ago, life underwent a major crisis that so far has not been believably connected to either extraterrestrial or geological causes.  Previous studies have shown that the mass extinction was accompanied by an decrease in 13C in sediments that suggests a short-lived global warming of  between 2-4 °C at the Tr-J boundary.  That CO2 levels rose is suggested by a decrease in the density of pores (stomata) on fossil leaves.  It has been suspected for some time that the largest known continental igneous event, which accompanied early rifting of the modern Atlantic Ocean basin may have been responsible, but so far the dating of this Central Atlantic magmatic province (CAMP) has not been tied to the boundary conclusively.  A large consortium of Italian, French, US, Moroccan and Swiss has addressed the sedimentary and igneous record around Tr-J times in the High Atlas of Morocco (Marzoli, A and 14 others 2004.  Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis.  Geology, v. 32, p. 973-976).  There, one of the few uneroded continental flood basalt sequences of CAMP (most preserved CAMP magmas are in the form of sills and dykes in offshore basins) occurs among Triassic and Jurassic sediments.  Their base deforms the underlying sediments, suggesting that eruption was onto unlithified sediments, shortly after their deposition.  Fossils from the sediments are of little help in tying down the age of eruption, however, Ar-Ar ages of the lavas are all within error of 200 Ma, and tally with magnetic stratigraphy from the Tr-J boundary elsewhere.  Both age and geochemistry of the flows are remarkably similar to those of flood basalts from the other side of the Atlantic.  Magmatic duration, like that in other large igneous provinces was of short duration, no more than a couple of million years.  So it now seems that three of the “big five” mass extinctions (the others are end-Permian, connected with the Siberian Traps, and the K-T boundary and associated Deccan Traps) have at least a partial cause from CO2 release by massive volcanism.

Iron isotopes enter the Archaean life debate

Some years ago geochemists obtained carbon-isotope data from 3.8 Ga rocks in Greenland that seemed at the time to be persuasive evidence for the emergence of life during or shortly after Earth’s most traumatic period.  Up to 3.8 Ga the Moon was bombarded by huge projectiles, and its companion Earth would have received at least 13 times the flux of destruction.  The carbon was within sturdy apatite grains from supposed iron-rich metasediments, and may have been preserved from later high-grade metamorphism.  Doubt has been cast on that hypothesis, either because of the unlikelihood of any carbon remaining unfractionated by heating, or because some aspects of the rocks’ geochemistry suggested that they we of igneous origin rather than sediments.  Readers will have seen in previous years’ EPN that a controversy rages over even tangible signs that suggest cellular material from rocks half a billion years younger.  Geochemists from France and the US have taken a different tack with the ancient Greenlandic rocks that ought to at least resolve the igneous versus sedimentary origin of the banded iron-rich rocks (Dauphas, N. et al. 2004.  Clues from Fe isotope variations on the origin of Early Archean BIFs from Greenland.  Science, v. 306, p. 2077-2080).  They found that the heavy iron isotope 57Fe is more enriched in the ironstones than in any igneous rocks, with little chance that the difference was induced by thermal fractionation.  They are metasediments.  But therein lies a surprise.  The heavy-iron signatures are greater than in less aged banded ironstones.  One way in which that could have arisen is from biogenic precipitation of soluble reduced Fe-2, perhaps involving anoxygenic photosynthesisers – because of the strong capacity of photosynthesis for setting electrons in motion, all such organic reactions create local oxidising conditions, whether or not oxygen itself is produced.

Torrid times in the Cretaceous Arctic

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Despite its latitude (above the Arctic Circle) the sedimentary depocentre of northern Alaska is becoming famous for its Cretaceous terrestrial flora and fauna.  Plant remains indicate luxuriant vegetation cover, and high excitement greeted the discovery of 8 species of dinosaurs (4 herbivores and 4 theropod predators (Fiorillo, A.R. 2004.  The dinosaurs of Arctic Alaska.  Scientific American, v. 291(6), p. 60-67).  How dinosaurs were able to survive the darkness of the Arctic winter is a bit of a mystery, unless the migrated as do modern caribou – Fiorillo cites evidence for small juveniles that would have been unlikely to have migrated far, because compared with adults they were much smaller than young caribou.  There would have been sufficient winter biomass for survival during the Cretaceous, but seeing and being active as cold-blooded reptiles pose problems.  At least one of the species had unusually large eyes, so one of the conditions for dinosaur’s remaining year-round seems established.  New data regarding climatic conditions in the far north have turned up after an most unusual and intrepid programme of drilling through a drifting island of pack ice over the Arctic Ocean’s Alpha Ridge, not far short of the geographic North Pole.  An extraordinary feature of the programme is that it took place between 1963-74, the core having only been examined in detail in the last year (Jenkyns, H.C. et al. 2004.  High temperatures in the Late Cretaceous Arctic Ocean.  Nature, v. 432, p. 888-892).  The Late Cretaceous part of the cores is black mud rich in terrestrial vegetation remains and marine diatoms, and totally lacking in evidence for dropstones and other debris from floating ice shelves.  Unfortunately, the Arctic sediments lack carbonate-shelled plankton remains,  so the now standard method of sea-surface temperature measurement is not possible.  However, Jenkyns et al. were able to use a method based on the fatty acids that survive in plankton membranes, results from which match oxygen-isotope palaeo-temperature measurements in Cretaceous cores from lower latitudes.  Astonishingly, even at polar latitudes, the Cretaceous Arctic Ocean seems to have been as warm as 15°C.  Climate modelling based on lower latitude data and estimates of CO2 concentration in the Late Cretaceous atmosphere falls around 10° short of these levels.  The conventional modelling requires 3 to 6 times more “greenhouse” warming than generally accepted, to account for Arctic sea temperatures in which we could swim in moderate comfort.  Possibly the modelling is awry.  One of the most important features of Late Cretaceous palaeogeography was a major seaway across North America that connected the Arctic with tropical latitudes.  It existed because global sea level was far higher than now, probably due to the oceans’ volume having been substantially reduced by huge magmatic outpourings on the floor of the West Pacific basin (the Ontong-Java Plateau), earlier in Cretaceous times, together with higher rates of sea-floor spreading.  The seaway would have been shallow, and thereby easily warmed.  Had poleward currents been possible in it, their flow would have acted very like the modern Gulf Stream to warm high latitudes.  Despite palaeoclimatologists reliance on models of heat circulation, it needs to be remembered that they are based on grossly simplified geographic features.  If they get it very wrong indeed for the well-studied Cretaceous, that casts doubts on climate modelling’s predictive powers for the course of current climate evolution.

See also: Poulsen, C.J. 2004.  A balmy Arctic.  Nature, v. 432, p. 814-815

An electronic antidote to eclecticism

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It is a plain to me as to any reader that EPN  is eclectic, and in some cases pretty impressionist; how else to write a monthly weblog about the broad spectrum of geoscientific developments?  So it is good to see websites with a much narrower focus, yet that manage to inform entertainingly and provocatively.  Such a site is www.mantleplumes.org, organised by Gillian Foulger of Durham University, currently a visiting scientist with the Volcano Hazards Team at USGS, Menlo Park, USA.  It covers the whole of “plumeology”; the tectonics, the magmatism, ages and wider features, even ideas about the presence or absence of plume-related features on other planets.  It has some powerful contributing essayists, such as Don Anderson and Warren Hamilton, who are not averse to scepticism and critiques, and represent work in progress on a book, Plates, Plumes & Paradigms just submitted to the Geological Society of America – a rare event to see preprints of book chapters.  It serves an educational role as well, with well-illustrated and up-to-date reviews of the mechanisms involved in large-igneous provinces., and thumbnails on a continent-by continent basis. Jason Morgan came up with the “hot-spot” idea about 33 years ago and launched a revolutionising force in plate tectonics.  It is good to see that there is still a vibrancy about the topic.

Ancient art

The hallmark of modern human’s abilities is the art left behind by our ancestors since about 30-40 thousand years ago.  Among the most enigmatic are those by Australian native people, that might date back as far as 50 ka.  The first were discovered by Joseph Bradshaw and his brother in the Kimberly Ranges of northern Western Australia in 1891.  The Geneva-based Bradshaw Foundation (http://www.bradshawfoundation.com/) is developing a comprehensive archive of rock-art images from across the globe, which will uplift anyone who visits it.

Bacterial reduction of arsenic contamination

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Following the tragic discovery ten years ago that tens of millions of Bangladeshis drink groundwater that is naturally contaminated by arsenic, the lessons learnt there have been applied on a global scale.  That has resulted in further cases with similar causes coming to light.  Remediation is chemically quite simple, and since the US reduced the maximum permissible arsenic level in public water supplies from 50 to 10 parts per billion in 2001 research into methods of removal have increased rapidly.  There are a number of methods that are based on adsorption of arsenic by iron and aluminium hydroxides and are low-cost.  But it seems that biological activity in aquifers can be equally effective (Kirk, M.F. et al. 2004.  Bacterial sulphate reduction limits natural arsenic contamination in groundwater.  Geology, v. 32, p. 953-956).  In the anaerobic conditions that favour the dissolution of iron hydroxide, which is often the most important source of arsenic in sediments, the conditions are also suitable for chemotrophic bacteria.  Among these are species that obtain metabolic energy from the reduction of sulphate ions to sulphide.  Where metal ions are also present, they combine with the sulphur to precipitate sulphide minerals.  In turn, sulphides readily accept arsenic from solution, thereby helping decontaminate potentially dangerous groundwater.  Arsenic-bearing groundwater is also found to have high methane levels, which suggests that methanogenic bacteria dominate its micro-ecosystem when sulphate ions are at low concentrations.  Perhaps it will prove possible to encourage sulphate-reducers to thrive in such waters, by the addition of some sulphate by injection.  That would a cheap remedy to what seems to be a growing risk in areas that extract groundwater from aquifers that are full of organic matter that creates the oxygen-free conditions that release arsenic into solution.

Bacteria in groundwater seem to have another benefit.  Where landfill contaminates subsurface waters with a cocktail of pollutants, the nutrients encourage bacterial colonisation, often in the form of biofilms in pore spaces.  It seems that their metabolism generates electrical currents (Gosline, A. 2004.  Bug “batteries” send out pollution alert.  New Scientist !8 December 2004, p. 17).  These create electrical potentials of several hundred millivolts that are easily detected by passive electrical monitoring.  The voltage highs occur at the margins of pollutant plumes in the groundwater, and can therefore be used to monitor spread of contamination and to indicate safe supplies.

Jared Diamond on the Flores “hobbits”

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Jared Diamond is a behavioural scientist who specialises in birds of east Asia and the Pacific, but he has made a major contribution to the popularisation of anthropology through his books The Third Chimpanzee and Guns, Germs and Steel.  His vast knowledge of the west Pacific makes him an able commentator on the amazing find of tiny people on the island of Flores (see: The little people of Flores, Indonesia in November 2004 issue of EPN).  He writes of the sheer diversity of opportunities for colonisation of the archipelagos that separate New Guinea from mainland Asia by Homo erectus, who populated the Far East for around 1.8 Ma (Diamond, J.  2004.  The astonishing micropygmies.  Science, v. 306, p. 2047-2048).  There has been speculation that Homo floresiensis became so small in response to a limited biological productivity on Flores, but Diamond is not at all sure – the Indonesian island chain has luxuriant flora and fauna compared with the Asian mainland.  But islands have limits to any population. Homo floresiensis probably arrived as a tiny group that flourished because of negligible competition.  Soon reaching the limits of support by the island ecosystem, full-sized colonisers with a limited gene pool would either die out or quickly generate smaller offspring, larger numbers of which could be sustained and reproduce.  Another of Diamond’s insights concerns the matter of similar populations on the many equally attractive islands in the chain.  If there were, that would imply easy island hopping, and therefore no reason for miniaturisation through evolution.  Modern humans have done just that, on the scale of the entire Pacific basin over the last 45 thousand years with no sign of evolving as dwarfed island populations – they had boats. Homo floresiensis’ ancestors almost certainly did not.  They could have swum the short distances between the islands at times of low sea-level, indeed they could have seen one island in the chain from the next.  In the case of New Guinea, had they reached the nearest island to it in modern Indonesia, they could never have seen it in the distance.  Diamond’s greatest surprise is how the micropygmies survived later fully human colonisation from 50 to 18 thousand years, when large people would have colonised the entire chain with ease, before proceeding to Australasia and Oceania.  Perhaps they coexisted through having a complementary food economy, as do modern African and Philippino pygmies, by some form of trade.  They may even have been too dangerous to hunt or attack.  Intellectually attractive as Homo floresiensis might be to us, steeped in Tolkienesque lore, Diamond cuts out the fantasy – they were so unhuman as to make the possibility of their disappearance through interbreeding highly unlikely.  Like chimpanzees, they would not only have been unappealing but possibly too unpredictable and strong for cross-species sex to have crossed the minds of fully human colonisers.

Mars in Science and Nature

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A year on from the landings of US Mars Rovers, Science devotes much of its early December 2004 issue to findings from the more revealing of the two missions, Opportunity (multi-authored 2004. Opportunity runneth over.  Science, v. 306, p. 1697-1756).  The articles are highly detailed accounts of the main finding from the various instruments aboard Opportunity, including the evidence for the activity of acid waters on the ancient Martian surface.  Equally interesting and considerably more graphic are important findings about volcanic and glacial activity in much more recent times, that come from the European Space Agency’s Mars Express Orbiter and the High Resolution Stereo Camera carried by it (Neukum, G and 42 others 2004.  Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera.  Nature, v. 432, p. 971-979). Recently, excitement about evidence for living organisms on Mars rose with the discovery of significant amounts of methane in the Martian atmosphere.  Methane is likely to have a short life span (around 300 years) in the atmospheres of rocky planets.  There are two possible sources: methane-generating bacteria or release from volcanoes.  The High Resolution Stereo Camera shows conclusively that volcanoes were active on Mars until at least 5 Ma, when previously the planet was thought to be magmatically dead.  If fumarole activity continues, that could explain the traces of methane.