Growth rings in tree trunks are among the best records of local climate variation that there are: they provide an annual “stratigraphy”. So intricate are the records that it has proved possible to match ring sequences in ancient but still growing trees to those found in logs of even greater antiquity, thereby building up a “dendrochronology” that extends back into history. Tree rings help historians link human affairs to a background of changing conditions for life. Henri Grissino-Mayer of the University of Tennessee has brought together a wealth of dendrochronological information in his Ultimate Tree Ring Pages at web.utk.edu/%7Egrissino/default.html.
There are so many places one might wish to visit for their scenery and physical geography, yet only limited resources and, of course, time. The availability of high-resolution satellite images, together with free data that show variations in topographic elevation newly released from the Shuttle Radar Topography Mission, enables realistic simulations of just about anywhere. William Bowen of the California State University has exploited this opportunity to give all-comers a view of most parts of the land surface, as if they were looking obliquely downwards from a high-altitude aircraft – geogdata.csun.edu/world_atlas/index.html
Although there are many glossy books about museum quality mineral specimens, as well as being expensive they often only cover a selection of those minerals known to science. One of the beauties of the web is that a site can cram in as many pictures and ancillary data as its server permits, and anyone can browse what is on offer. One such site has been set up by consulting geologist David Barthelmy, which not only illustrates more than 2000 different minerals (half the site’s content of 4300) but allows users to examine their molecular structure interactively – webmineral.com
Most of us have grown used to thinking that earthquakes have an epicentre at some fixed point beneath the surface. That is not at all true, as the event that set the Boxing Day 2004 tsunamis in motion as been shown to have been a lengthy rip that propagated from Sumatra NNE to the Nicobar Islands, over a period of about an hour. Even quite small earthquakes are distributed and often migrate along a fault line. Christine arson of the University of Colorado has captured what is effectively a movie of a magnitude 8.3 event off the island of Hokkaido, Japan, which can be viewed at spot.colorado.edu/~kristine/tokachi_rupture.gif. The data that she used comes from a network of a thousand highly sensitive GPS receivers set up throughout Japan. Instead of acceleration, measured by conventional seismometers, GPS records actual position in x, y, z coordinates. That enable the actual motions to be imaged as in the movie.
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.
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.
Three web sites that have been suggested are well worth browsing. Bernie Gunn has assembled a monumental database of the geochemistry of volcanic rocks at http://www.geokem.com . That, in itself, is a magnificent resource for anyone working on the topic, but the site also has a comprehensive guide to good laboratory practice that will be invaluable to anyone beginning to work in the field., plus a host of good reference material and links. Its quality is hardly surprising since Bernie has been engaged in geochemical research for more than 3 decades at the University of Montreal. Another dimension to geological web resources is revealed by that compiled by Fettes College in Edinburgh at http://www.fettes.com/shetland . It is an encyclopaedic source of environmental information on one of Britain’s many microcosms of Earth science. It ranges from the Shetland Isles’ long geological evolution to its present geomorphology. Fettes is a private school, with a glittering roll of alumni. Equally encyclopaedic is http://paleodb.org , which is as near to a global database of palaeontology as you can get at present. One of the highlights is being able to plot occurrences at the genus and species level on interactive maps, as well as browse and analyse the contents statistically. Users do need to know how to spell taxonomic names! Once you have compiled a map (the only trilobite whose name I can spell is Dalmanites!), you can zoom in. If you click on an occurrence up comes a summary of the locality, with links to other parts of the database, including other fossils at the locality. Wisely, location detail is crude enough to deter collectors from ravaging sites. The database is compiled by 140 contributors in 11 countries. This a site for specialists, but a beginner can learn a great deal from it.
Information on mineralogy is often hard to find on the web, so the University of Wurzburg Institute of Mineralogy in Germany has created a comprehensive set of links that cover a wealth of topics. They include teaching materials at different levels, information on experimental and analytical techniques, thermobarometry, mineral descriptions and crystallography, economic mineralogy, gemmology and much more besides. Go to http://www.uni-wuerzburg.de/mineralogie/links.html
This seems to be a blog well worth examining and mining – www.talkorigins.org/faqs/homs . The blogger, Jim Foley, maintains an excellent sense of humour as well as what appears to be considerable energy and knowledge. There is a link to a masterful April Fool’s Day joke at the expense of the Institute for Creation Research, which gulled their radio show, Science, Scripture and Salvation in 2000 into accepting at face value a spoof article in the April 1997 issue of Discover magazine. This was penned by the German palaeoanthropologist Oscar Todkopf (Deadheads are fans of the Grateful Dead) of Hindenburg University (Led Zeppelin and a well-known, flaming bag of gas), which documented a find of assorted musical instruments, (a 6 foot length of mammoth tusk turned into a tuba, a bagpipe-like instrument made from the bladder of a large animal, a triangle of thin bones, a collection of hollowed out bones of different lengths, which Todkopf suggested might be part of a xylophone (he called it a ‘xylobone’), the first known Neanderthal cave painting, showing marching musicians alongside some suspected musical notation, and a Neanderthal skull) in the famous Neander Valley, Germany. Even the fact that the eponymous author claimed that Neanderthal musicians played the bagpipes with their remarkably huge noses, did not deter the ICR’s Marvin Lubenow, author of the leading creationist book on human origins, Bones of Contention, from commenting, “There’s overwhelming evidence that Neanderthals were musically inclined.”, along with a further stream of howlers. For that alone, you must visit this site. However, it is probably the best source of human-origins information, illustrations and news that there is on the Web, and puts the EPN anthropology and geoarchaeology section to shame! There is a balance, for the site includes a great many items on creationist ideas, but this has to be tongue in cheek, despite the accuracy of the accounts there. I wonder who Jim Foley is….
Algorithms that model the physical effects of extraterrestrial impacts from the Lunar and Planetary Laboratory of the University of Arizona, headed by Jay Melosh, have been assembled into a handy on-line calculator, with notes on the processes involved. If you want to find out if you will be fried, buried or blown to smithereens (probably all three if our luck is really out), and the chances of being harmed by alien lumps of rock or ice, you can find the calculator at http://www.lpl.arizona.edu/impacteffects/ . It is not recommended for estate agents, because, unlike many other disastrous events, impacts can be anticipated anywhere.
The US Geological Survey has made publicly available a large repository of geochemical data (63 of the 91 naturally occurring elements) that it has acquired through a continuing nation-wide survey of stream sediments (available at http://tin.er.usgs.gov/geochem/doc/home.htm). The data coverage is incomplete and involves several generations of previous surveys. The most revealing stream sediment surveys involve collection of panned sediment samples in every small stream that has no upstream tributary, but that is a daunting task for such a vast area as the USA. That method allows the analyses to be treated as accurate representations of stream sediment composition in upstream catchments around 1 x 1 km in size. The USGS data are a mixed bunch, some dating from the National Uranium Resource Evaluation (NURE) of the 1970s when there was a scramble to find new uranium ore bodies. The NURE survey involved a sample density based on a 17 x 17 km grid, and made no distinction between stream order. The latest USGS survey is based on sample collection that uses 10 x 10 km grids drawn in the UTM co-ordinate system. Each 10 x 10 km cell is divided into four quadrants, and one is selected at random for sampling. In that one small stream selected at random is chosen for analysis. The data set is too coarse and too varied to create meaningful gridded interpolations that can be displayed as continuous tone images, unlike comparable geochemical atlases based on systematic, small-stream sampling, such as that developed for commercial leasing by the British Geological Survey. The NGS data will be a useful resource for scanning broad geochemical features of the country, such as for high levels of potentially toxic elements in water, bearing in mind that the analyses are of solid minerals not the water itself.
The last issue of EPN showed that the debate over mantle plumes, their sources, and even their existence is hotting up (see Geoscience consensus challenged in EPN January 2004). However that pans out, vast areas of continental and submarine flood basalts compel geoscientists to ponder over them, the more so because they represent events never witnessed by humans and are therefore unimaginable. Now they have their own website (http://www.mantleplumes.org/) that has been compiled by Gillian Foulger of Durham University. It is an impressive and highly useful resource, the outstanding feature being pages on most aspects of large igneous provinces written by experts who are also excellent communicators. There is even a linked site at the Geological Society that hosts discussion on the Great Plume Debate, as well as a letters page, links and up to date news. For information, without unnecessary frills, this is the place to go, especially if you have to write an essay!
If you like that frisson of fear that comes from contemplating the demise of the world as we know it, then the Near Earth Objects Dynamic Site (NEODyS) will give you hours of it (newton.dm.unipi.it/neodys). The more than 2500 NEOs that orbit within 45 million km of the Earth’s are fully catalogued there, along with impact risk assessment. The site also links to the on-line newletter Tumbling Stone, that has news on asteroidal matters, especially near misses…..and impending doom…..