Eastern Himalayan alpine plant ecology,Tibetan ethnobotany,and climate change

Tibetan culture and livelihoods depend on native plants for medicine, food, grazing, wood, as well as cash from market sales. The Medicine Mountains (part of the Hengduan Mountains) of the eastern Himalayas, with tremendous plant diversity derived from steep gradients of both elevation and precipitation, have traditionally been an important source of Tibetan medicinal plants. We examine climate change in this area and vegetation patterns influenced by biogeography, precipitation and elevation (NMS and CCA ordinations of GLORIA plots). The Alpine environment has the highest plant diversity and most useful plants and is the most susceptible to climate change with impacts on traditional Tibetan culture and livelihoods—particularly Tibetan medicine and herding.     

Hydrostatic pressure tests for the permeability - formation factor relation on crystalline rocks from the KTB drilling project

Transport properties (permeability and electrical conductivity) have been measured at different hydrostatic pressure runs on 7 crystalline rocks (gneisses and amphibolites) sampled from the KTB drilling project. The decrease of permeability by pressure are compared with the pressure-dependent data of the electrical conductivity (formation factor) resulting from complex impedance measurements. According to the equivalent-channel model (ECM), there exists a linear relationship between these parameters by representing both properties on logarithmic scales. The results show that it is possible to extrapolate high-pressure permeability from low-pressure (< 60 MPa) permeability data by using the pressure-dependent electrical conductivity (up to 300 MPa).     

Mechanism of the water and carbon dioxide solubility in oxides and silicates and the role of O−

The dissolution of water does not stop at the OH^– stage but may proceed further towards H₂ plus O^– formation. The discovery of atomic carbon dissolved in minerals suggests that, if CO₂ enters oxides and silicates at high pressures and temperatures, not only [CO₃]^2– ions but also [CO ₄ ^. ]^4– complexes are formed via a charge transfer which produces O^– and essentially zero-valent, atomic carbon. Under P —T-conditions of the mantle, where the solubility for water and CO₂ is high, the silicate phases formed may therefore consist to a large volume fraction of O^– ions which are much smaller than O^2–ions and strongly cova-lently bonding. The implications for the crystal chemistry of high pressure phases, for the petrology of mantle rocks are outlined.     

Carbon in solid solution in forsterite—a key to the untractable nature of reduced carbon in terrestrial and cosmogenic rocks

Carbon is an incompatible element in oxide and silicate lattices. Until now it has been believed to exist only in the form of CO^2?₃ ions, molecularily dissolved CO₂ or graphitic inclusions. Recently it has been shown that carbon can dissolve in refractory oxides, like MgO and CaO, in the form of carbon atoms.The experimental results obtained with carbonaceous MgO are reviewed and new results are presented which demonstrate that synthetic forsterite and natural olivines can also take up atomic carbon in solid solution. The incorporation of the carbon atoms is treated thermodynamically. Near the melting point they probably occupy cation vacancies, but with decreasing temperature they are progressively transferred on interstitial sites. On these sites they are very mobile and tend to segregate into the elastically relaxed subsurface zone, but exsolution to graphite is prevented by the strain fields surrounding each carbon atom.Upon heating, however, the atomic carbon may react with lattice oxygen to give CO₂ and with co-dissolved hydrogen to give a wide variety of hydrocarbons. The underlying reaction mechanisms, involving the formation and decay of O^? ions, are discussed in view of the so-called ‘carbonatic carbon’ and ‘reduced carbon’ in magmatic minerals and meteorites, in view of the diamond genesis and also in view of the reversible CO₂ solubility in silicate magmas at high pressures and temperatures.     

Tsunami imprints on the Leeward Netherlands Antilles (Aruba, Curaçao, Bonaire) and their relation to other coastal problems

Tsunami are one of the major natural hazards in the Caribbean. The historical record lists 88 tsunami, from local events to teletsunami, in the time period from 1489 to 1998. This study focuses on the spatial distribution and geomorphologic evidence related to coarse littoral sediment and boulder deposition by tsunami events of Holocene age in the Southern Caribbean. At a worldwide scale, these debris deposits represent the most extensive and impressive records of Holocene paleo-tsunami so far studied. Hitherto, the Leeward Lesser Antilles, consisting of the islands of Aruba, Curaçao and Bonaire, were not known to have had tsunami affecting their coastlines. The possible contribution of tsunami to configuring coastlines (e.g. the questions of embayment development, the coastal environment changes, and the absence of Holocene fringing reefs along the windward coasts) is discussed.     

A Comparison of the Sequential Gaussian and Markov-Bayes Simulation Methods for Small Samples

We compared the performance of sequential Gaussian simulation (sGs) and Markov-Bayes simulation (MBs) using relatively small samples taken from synthetic datasets. A moderate correlation (approximately r = 0.70) existed between a continuous primary variable and a continuous secondary variable. Given the small sample sizes, our objective was to determine whether MBs, with its ability to incorporate the secondary information, would prove superior to SgS. A split-split-plot computer experiment was conducted to compare the two simulation methods over a variety of primary and secondary sample sizes as well as spatial correlations. Using average mean square prediction error as a measure of local performance, sGs and MBs were roughly equivalent for random fields with short ranges (2 m). As range increased (15 m) the average mean square prediction error for sGs was less than or equal to that for MBs, even when number of noncollocated secondary observations was twice the number of collocated observations. Median variance within nonoverlapping subregions was used as a measure of the local heterogeneity or surface texture of the image. In most situations sGs images more faithfully reflected the true local heterogeneity, while MBs was more erratic, sometimes oversmoothing and sometimes undersmoothing.     

Charge generation and propagation in igneous rocks

Various electrical phenomena have been reported prior to or concurrent with earthquakes such as resistivity changes, ground potentials, electromagnetic (EM), and luminous signals. Doubts have been raised as to whether some of these phenomena are real and indeed precursory. One of the reasons for uncertainty is that, despite decades of intense work, there is still no physically coherent model. Using low- to medium-velocity impacts to measure electrical signals with microsecond time resolution, it has now been observed that when dry gabbro and diorite cores are impacted at relatively low velocities, 100 m/s, highly mobile charge carriers are generated in a small volume near the impact point. They spread through the rocks, causing electric potentials exceeding +400 mV, EM, and light emission. As the charge cloud spreads, the rock becomes momentarily conductive. When a dry granite block is impacted at higher velocity, 1.5 km/s, the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. After the sound waves have passed, the surface of the granite block becomes positively charged, suggesting the same charge carriers as observed during the low-velocity impact experiments, expanding from within the bulk. During the next 2–3 ms the surface potential oscillates, indicating pulses of electrons injected from ground and contact electrodes. The observations are consistent with positive holes, e.g. defect electrons in the O²⁻ sublattice, traveling via the O 2p-dominated valence band of the silicate minerals. Before activation, the positive holes lay dormant in the form of electrically inactive positive hole pairs (PHP), chemically equivalent to peroxy links, O₃X/^OO\XO₃, with X=Si⁴⁺, Al³⁺, etc. PHPs are introduced into the minerals by way of hydroxyl, O₃X–OH, which all nominally anhydrous minerals incorporate when crystallizing in H₂O-laden environments. The fact that positive holes can be activated by low-energy impacts, and their attendant sound waves, suggests that they can also be activated by microfracturing. Depending on where in the stressed rock volume the charge carriers are activated, they will form rapidly moving or fluctuating charge clouds that may account for earthquake-related electrical signals and EM emission. Wherever such charge clouds intersect the surface, high fields are expected, causing electric discharges and earthquake lights.     

The drainage pattern of Hansbreen and Werenskioldbreen, two polythermal glaciers in Svalbard

To improve our understanding of Svalbard-type polythermal glacier drainage, hydraulic geometry models of the subglacial hydrology of two contrasting glaciers in Svalbard have been constructed. The models are tested against a uniquely long and rich set of field observations spanning 45 years. Digital elevation models (DEMs) were constructed from bedrock data measured with ground penetrating radar and surface data of two medium-sized polythermal glaciers, Hansbreen and Werenskioldbreen, in south-west Spitsbergen. Hansbreen has a low angle bed with over-deepenings and a calving front, while Werenskioldbreen has steeper bed and terminates on land. Together they are representative of many Svalbard glaciers. The DEMs were used to derive maps of hydraulic potential and subglacial drainage networks. Validation of the models was done using field observations including location mapping and speleological exploration of active moulins, positions of main river outflows, dyetracing and water chemistry studies, and observations of water pressure inside moulins. Results suggest that the water pressure is generally close to ice overburden pressure but varies greatly depending on local conditions such as bed location, the thickness of cold ice layer, the thickness of the glacier and seasonal changes in meltwater input.     

Holocene paleoenvironmental change inferred from two sediment cores collected in the Tibetan lake Taro Co

Journal of Paleolimnology - The Tibetan Plateau, also known as the “Water Tower of Asia” because of its function as a water storage and supply region, responds dramatically to modern...     

Earthquake chemical precursors in groundwater: a review

We review changes in groundwater chemistry as precursory signs for earthquakes. In particular, we discuss pH, total dissolved solids (TDS), electrical conductivity, and dissolved gases in relation to their significance for earthquake prediction or forecasting. These parameters are widely believed to vary in response to seismic and pre-seismic activity. However, the same parameters also vary in response to non-seismic processes. The inability to reliably distinguish between changes caused by seismic or pre-seismic activities from changes caused by non-seismic activities has impeded progress in earthquake science. Short-term earthquake prediction is unlikely to be achieved, however, by pH, TDS, electrical conductivity, and dissolved gas measurements alone. On the other hand, the production of free hydroxyl radicals (?OH), subsequent reactions such as formation of H₂O₂ and oxidation of As(III) to As(V) in groundwater, have distinctive precursory characteristics. This study deviates from the prevailing mechanical mantra. It addresses earthquake-related non-seismic mechanisms, but focused on the stress-induced electrification of rocks, the generation of positive hole charge carriers and their long-distance propagation through the rock column, plus on electrochemical processes at the rock-water interface.