weathering model for the quantification of atmospheric oxygen evolution during the paleoproterozoic abstract a weathering model has been developed to quantify atmospheric oxygen evolution during the paleoproterozoic the weathering model calculates the concentrations of fe2 dissolved from fe2 bearing primary minerals and oxidized fe3 out of the dissolved fe2 at a given partial pressure of atmospheric oxygen p o 2 during weathering and establishes the relationships between p o 2 and where is the ratio of oxidized and then precipitated fe3 out of the fe2 dissolved from primary minerals to the dissolved fe2 in a whole weathering profile the weathering model considers controlling factors of the redistribution of fe during weathering that is the dissolution rate of fe2 bearing primary minerals the oxidation rate of fe2 and the groundwater flow rate the validity of the model was confirmed by applying the model to the experimental data of olivine dissolution carried out under low o2 conditions the sensitivity analysis of the model has revealed that the formation time of weathering the mineral dissolution rate and the diffusion of o2 into a weathering profile have no or slight influence on resulting in 0 0 and 0 3 changes in log p o 2 caused by four orders of magnitude change of the formation time more than 10 orders change of the mineral dissolution rate and assumed change of the o2 diffusion respectively on the other hand the temperature the ph and the groundwater flow rate have moderate to large effects on 0 6 1 4 and 1 5 changes in log p o 2 for changes of 5 c in temperature 0 5 in ph and one order of magnitude in groundwater flow rate respectively using possible surface temperature ph and groundwater flow rate estimated from the literature we calculated the p o 2 relationships which were then applied to the values of paleosols fossil weathering profiles formed between 2 5 and 1 8 ga taking account of the constraints given by the records of mass independent fractionation in sulfur isotopes and other geological proxies i e 10 6 atm at 2 32 ga and 10 3 atm at 2 0 ga our model implies that the p o 2 levels were 10 9 atm at 2 46 ga 10 4 5 10 2 atm at 2 25 2 0 ga and 10 2 atm at 1 85 ga the present weathering model can constrain p o 2 levels during the possible paleoproterozoic hot periods but not those during the glacial periods when temperature was

seismic activity accompanying the outbreak of the 1991 1993 eruption of mt etna italy abstract the character and location of seismic activity accompanying the onset of the 1991 1993 eruption at mt etna are compatible with the surface evidence of the volcanic pile rupture both the epicentral distribution and the focal mechanisms of a swarm that occurred on december 14 1991 agree with magma ascent occurring along the main nnw sse trending structure of the volcano and the consequent opening of a system of effusive fissures with the same trend a typical mainshock aftershock sequence recorded the day after and indicating transcurrent displacement occurring along the second principal structure of etna ne sw depicts the tectonic response of the volcanic pile and the underlying basement to major stresses applied by the magma push

constancy of silicate mineral weathering rate ratios between natural and experimental weathering implications for hydrologic control of differences in absolute rates abstract inverse models which apportion watershed effluxes geochemical mass balance over estimated mineral surface area give weathering rates for individual silicate minerals e g feldspar 1 3 orders of magnitude slower than laboratory rates comparisons of rates calculated from several recent watershed geochemical mass balance studies with experimentally determined rates reveal that the ratio of mineral weathering rates for a given silicate mineral pair determined in an internally consistent field study equals the ratio of rates for the same minerals in any internally consistent set of laboratory experimental data thus the coefficient which corrects the weathering rate for any mineral from a laboratory data set to a field setting is identical to the corresponding coefficient for any other mineral in the same data sets the correction factor linking experimental and natural rates must be independent of composition physical e g hydrologic controls rather than compositional or chemical controls cause the difference between weathering rates in nature and the laboratory because flow in natural weathering profiles is spatially heterogeneous not all of the potentially available surface in natural systems actually participates in reactions with pore fluids

seismicity of the caldera making eruption of mount katmai alaska in 1912 the seismic activity associated with the century s largest eruption and caldera collapse at mount katmai alaska during june 1912 was poorly understood and is studied here in detail the epicenter of the large shock of 10 june was long thought to be 140 km northeast of mount katmai but it is relocated to be 12 km west of mount katmai near the novarupta dome origin times surface wave magnitudes ms and broadband body wave magnitudes mb are assigned to 50 new shocks from instrumentally observed data of more than 60 worldwide milne s and other seismological stations of 50 shocks detected 14 have ms 6 0 and greater and the largest is 7 0 both the frequency magnitude relation and the mb ms relation apparently exhibit normal appearance for the alaskan region the strong earthquakes were concentrated in the nights of 6 and 7 june it is inferred that the substantial collapse of mount katmai took place in these two nights the total energy released in seismic waves is 7 1 1015 j corresponding to the energy of a single shock with ms 7 4 the total seismic moment is estimated to be 1 4 1020 nm from ms values this total moment can be interpreted in terms of failures caused by the total volume change of 5 km3 this volume agrees well with the estimated volume of the caldera collapse which presumably took place in response to transfer of supporting magma from beneath mount katmai toward novarupta

basalt and olivine dissolution under cold salty and acidic conditions what can we learn about recent aqueous weathering on mars 1 to test which variables may be important for weathering on mars the effects of temperature 22 c 6 c and 19 c high ionic strength and oxygen concentrations were investigated in batch dissolution experiments containing forsterite fayalite and basalt glass cacl2 nacl h2o brine can remain liquid to temperatures of 55 c and thus may be liquid in the cold dry climate that currently characterizes mars to understand weathering under such conditions dissolution rates were measured in experiments in distilled water with and without cacl2 and nacl as observed by others dissolution rates increased with temperature and only fayalite dissolution was significantly affected by the presence or absence of oxygen enhanced fayalite dissolution under anoxic conditions suggests that fe rich olivine would dissolve more rapidly than mg rich olivine on mars dissolution in the two most dilute experimental solutions deionized water and cacl2 nacl h2o solution of ionic strength 0 7 m were the same within uncertainty but apparent dissolution rate constants in cacl2 nacl h2o brines were significantly slower steady silica concentrations are decreased in the brines consistent with other work and precipitation rates of silica decrease with decreasing temperatures these results suggest that enhanced silica precipitation could be an indicator of high ionic strength solutions on mars consistent with these observations weathering of basalt has been observed to sometimes be accompanied by precipitated layers of silica in cold dry environments on earth if dissolution on mars occurs or occurred under conditions similar to our experiments cation leaching would be expected to be accompanied by silica precipitates on weathering surfaces

role of hydraulic diffusivity in the decrease of weathering rates over time summary springs emerging within massifs of crystalline rocks were monitored for discharge rate q and the q values combined with geomorphic and hydrographic parameters in a hydrologic model to calculate hydraulic conductivity k and effective porosity n e of the spring watersheds the spring waters several borehole waters and rain water were analyzed for major dissolved compounds strontium and isotopes 18 o 2 h 13 c and 87 sr 86 sr with a shift to less negative values 18 o and 2 h were fitted by a line approximately parallel to the gmwl but no significant dependence on altitude was found the 18 o and 2h values correlate better with those of precipitation amount the 87 sr 86 sr ratios in drilled well waters correlate positively with the depth of water circulation reported in the borehole logs the corresponding regression equations were used to extrapolate the depth of hydraulic circuits within the spring watersheds the previous data together with groundwater travel times calculated by a water balance model and with reactions of granite metassediment plagioclase and biotite precipitating halloysite gibbsite and vermiculite were assembled in a mass balance model to calculate solute flux weathering rates of plagioclase w pl the w pl s were described as a function of d k n e where d is the hydraulic diffusivity the discrepancies between the w pl values and solid state rates based on the differences between elemental isotopic and mineral compositions measured in present day regoliths and in the assumed protolith were assigned to a decrease in d over time from values in the protolith to values in the weathered aquifer

the diavik waste rock project particle size distribution and sulfur characteristics of low sulfide waste rock three large scale instrumented waste rock piles were constructed at the diavik diamond mine in the northwest territories canada these experimental waste rock piles test piles are 15 m high and are part of an integrated field and laboratory research program to characterize and compare low sulfide waste rock and drainage at various scales during test pile construction samples of the 0 08 wt s for the higher s waste rock type the third test pile has a low permeability till layer and a low sulfide waste rock thermal layer covering a core of waste rock with average 0 082 wt s in the 0 08 wt s for the higher s waste rock particle size distributions for the lower and higher s waste rock are similar but the higher s waste rock has a higher proportion of fine grained particles sulfur determinations for discrete particle sizes of the 10 m scale from composite blast hole cuttings are lower than those calculated for the 0 05 wt s is of uncertain acid generating potential and effluent data indicate this waste rock generates acidic effluent whereas lower s waste rock does not produce acidic effluent consistent with the acid base accounting predictions

rupture history of the january 1 1996 ms 6 6 volcanic earthquake preceding the simultaneous eruption of karymsky and akademia nauk volcanoes in kamchatka russia the intensive foreshock mainshock aftershock sequence of earthquakes preceded and accompanied the january 2 1996 simultaneous eruption of the active karymsky and the dormant akademia nauk volcanoes in kamchatka russia the finite fault broad band teleseismic p waveform inversion was applied to the ms 6 6 mainshock of this sequence which occurred on january 1 1996 about 14 hours before the beginning of eruption it was one of the strongest volcano tectonic earthquakes in this century after the 1912 1914 great ms 7 0 volcanic earthquakes related to the katmai alaska and sakurajima japan volcanic eruptions the main feature of the rupture process inferred from the inversion was the breaking of a sequence of four asperities with displacement greater than 200 cm which were situated at depths from 0 to 35 km just beneath the akademia nauk volcano there were no broken asperities beneath the karymsky volcano the majority of small earthquake foci were located out of maximum asperities and filled a space between two zones of asperities at depths from 12 to 20 km the position of broken asperities allows us to suggest that during the large earthquake rupturing an ancient magmatic column beneath the volcano was destroyed small earthquakes which were recorded mainly from 5 to 20 km depth were able only to destroy the intermediate depth part of this column between 12 and 20 km the main work for opening a way to move magma to the surface was made by a large shock which had broken the upper and deep parts of the ancient magma column

a modeling study of oceanic nitrous oxide during the younger dryas cold period 1 the marine production cycling and air sea gas exchange of nitrous oxide n2o are simulated in a coupled climate biogeochemical model of reduced complexity the model gives a good representation of the large scale features of the observed oceanic n2o distribution and emissions to the atmosphere the transient behavior of the model is tested for the younger dryas y d cold period 12 700 11 550 bp which is simulated by releasing a freshwater pulse into the north atlantic causing a temporary collapse of the model s atlantic thermohaline circulation thc a temporary drop in atmospheric n2o of about 10 ppb results while ice core measurements show a total drop of 25 to 30 ppb this suggests that terrestrial changes have also contributed to the observed variations the main cause of the modeled reduction in atmospheric n2o is increased oceanic storage in the short term and a reduction of new production in the long term due to increased stratification

biogeochemical weathering in sedimentary chronosequences of the rhone and oberaar glaciers swiss alps rates and mechanisms of biotite weathering abstract we analysed the composition of phyllosilicate minerals in sediments deposited by the rhone and oberaar glaciers swiss alps in order to identify processes and rates of biogeochemical weathering in relation to glacial erosion the investigated sediments are part of chronosequences consisting of a suspended fresh sediment in melt water b terminal moraines from the little ice age lia approximately 1560 1850 and c tills of the younger dryas interval yd approximately 11 500y bp secondary weathering products associated with the suspended sediment have not been observed we therefore exclude intermittent subglacial storage and weathering of this material and assume that the suspended sediment is directly derived from mechanically abraded bedrock this implies that biogeochemical weathering processes started once the glacially derived sediment was deposited in the proglacial area the combination of a developing vegetation cover the generally high permeability allowing the percolation of precipitation and the chemical reactivity related to the dominance of fine grained material biotite weathering rates are calculated using the difference in the biotite content between unweathered and weathered glacial sediments within the investigated profiles the reactive mineral surface area is estimated geometrically both with regards to the total relative surface wr t as well as to the relative edge surface wr e wr t biotite weathering rates are estimated as 10 13 10 15 mol biotite m 2 biotite s 1 wr e biotite weathering rates are on the order of 10 13 10 14 mol biotite m 2 biotite s 1 biotite weathering rates obtained by this study are in the order of one magnitude higher in comparison to other published field based weathering rates using biotite as an indicator we therefore suggest that glacially derived material in the area of the oberaar and rhone glaciers is generally subjected to enhanced biogeochemical weathering starting immediately after deposition in the proglacial zone and subsequently continuing for thousands of years after glacier retreat

villarrica volcano chile characteristics of the volcanic tremor and forecasting of small explosions by means of a material failure method villarrica volcano chile 39 42 s 71 93 w is one of the most active volcanoes in the andes it shows persistent strombolian activity in a small lava lake situated at the bottom of the summit crater from september to december 2000 the volcano exhibited anomalous behaviour after a regional tectonic seismic event on 22 september the eruption of a small volume of lava apparently plugged the conduit this situation then lasted for ten days on 5 and 8 october a series of explosions reopened the system this eruption behaviour has allowed us to study the evolution of the characteristic tremor in the open and closed states of the conduit a shift in the peak frequency from 1 hz open to 2 hz closed the explosions related to the opening of the conduit were forecasted by means of a material failure method

volcanic earthquakes of kamchatka classification nature of source and spatio temporal distribution abstract volcanic earthquakes on kamchatka can be divided into two large groups earthquakes with depths of 0 40 km generated by stresses which arise during magma migration in the earth s crust under volcanos the first group and the earthquakes directly connected with the eruptions volcanic tremor explosive earthquakes etc the second group this paper presents a review of some energetic spectral and spatio temporal characteristics of the kamchatkan volcanic earthquakes of the first group and their relationship with volcanic phenomena seismicity related to volcanic activity has the following specific features a local and predominantly swarm like pattern of earthquake origination iteration of earthquake swarms in the same seismically active zones many shallow and relatively small events a small magnitude limit up to 5 5 6 the existence of longer period variations of volcanic earthquake foci as compared to the tectonic one and a comparatively high value of the slope of the earthquake recurrence plot at the same time similarity in behaviour of some parameters of the seismic regime during the preparation and development of eruptions and prior to large earthquakes as well as the destruction of samples are noted

the october 9 1995 colima jalisco mexico earthquake mw8 an aftershock study and a comparison of this earthquake with those of 1932 data from portable seismographs and a permanent local network called resco are used to locate the aftershocks of the october 9 1995 colima jalisco earthquake mw 8 0 the maximum dimension of the aftershock area which is rectangular in shape is 170 km 70 km our study shows that the mainshock nucleated 24 km south of manzanillo near the foreshock of october 6 1995 mw 5 8 and propagated 130 km to the nw and 40 km to se the aftershock area lies offshore and is oriented parallel to the coast the observed subsidence of the coast is a consequence of this offshore rupture area the aftershocks reach unusually close to the trench within 20 km this may be due to lack of sediments with high pore pressure at shallow depth there are some similarities between this earthquake and the two great earthquakes of 1932 3 june ms 8 1 18 june ms 7 8 which occurred in this region in both cases the aftershocks were located offshore and the coastline subsided the sum of seismic moments and the rupture lengths of the 1932 events 1 8 1021 n m and 280 km respectively however were greater than the 1995 earthquake also a comparison of seismograms of 1932 and 1995 earthquakes show great differences it seems that the 1995 event is not a repeat of either june 3 or june 18 1932 earthquakes

modelling the impact of a hypothetical sub plinian eruption at la soufriere of guadeloupe lesser antilles abstract this paper describes the development and application of an impact model for a future hypothetical sub plinian eruption of la soufriere of guadeloupe the model was designed to assess the impact from either a single or multiple eruption scenarios each defined in terms of a map of the intensity of three volcanic hazards volcanogenic earthquake tephra fallout and pyroclastic density currents the impact from the three hazards can be assessed independently or alternatively the joint impact of the three hazards can be assessed the outputs that are produced from the model are the number of buildings with collapsed roofs and the number of fatal and non fatal casualties two versions of the impact model were developed one that uses a spreadsheet and another that is implemented using a geographical information system gis both versions use the same types of hazard inputs and vulnerability functions to derive the number of building collapses and casualties but have different spatial resolution of the final outputs the spreadsheet version aggregates the results at a zone level defined specifically for this project whereas the gis was designed to produce results using 250 m grid squares the outputs from the two versions when using the same eruption scenario produced somewhat different results highlighting the importance of defining the appropriate spatial resolution the vulnerability functions were developed using data on the building stock that was collected by a local survey in which data on the form of construction condition location and types of openings and the variation of these parameters across the affected area were collected the vulnerability functions incorporated new assessments of fire risks induced by pyroclastic density currents the model was applied to la soufriere using a range of input hazard scenarios based on reconstruction of the most recent sub plinian magmatic eruption which occurred in 1530 ad a sensitivity analysis of the model was carried out choosing the inputs from a range of defined input values the effect on losses and casualties of a range of possible mitigation measures was assessed by running the original model and the modified model using the same input eruption scenario a separate casualty treatment model was also developed and tested

chemical weathering in two adirondack watersheds past and present day rates rates of chemical weathering in two forested adirondack watersheds were determined from mineral and elemental depletion trends in soil profiles and from input output budgets based on precipitation and surface water chemistry long term rates of weathering have averaged about 500 to 600 eq ha yr for both watersheds since the glaciers retreated from the region about 14 000 yr ago present day denudation rates average 1679 eq ha yr in the panther lake watershed and only 198 eq ha yr in the woods lake watershed mineral weathering reactions in both watersheds involve primarily the dissolution of plagioclase potassium feldspar and hornblende mass balance calculations however indicate that hornblende weathers in disproportionately large amounts in the panther lake watershed relative to its abundance in soils and till cation exchange in the glacial till mantling the panther lake watershed may also play an important role in controlling surface water chemistry in the basin in the panther lake watershed the current rate of weathering which is about a factor of 3 greater than the long term average may reflect a recent adjustment for higher hydrogen ion fluxes brought about by acid deposition the capacity of the thick till deposits in the panther lake watershed to neutralize acidity is ultimately reflected by the circum neutrality of panther lake in the woods lake watershed the soils and thin till deposits cannot effectively neutralize current acid loadings and therefore woods lake is acidic with a ph below 5

the 1968 andesitic lateral blast eruption at arenal volcano costa rica the magmatic andesitic eruption of arenal volcano on july 29 31 1968 after centuries of dormancy produced three new fissural craters a b and c on its western flank and a multilayered pyroclastic deposit emplaced by complex transport mechanisms the explosions were initially triggered by a volatile oversaturated 4 7 wt h2o magma several lines of evidences suggest a small blast surge where a wood rich pyroclastic deposit was emplaced as a ground layer followed by several units of coarse grained md between 0 65 and 5 40 tephra deposits lu lapilli units dau double ash units lu 1 2 3 dau 1 and 2 consist of unconsolidated and well to poorly sorted vesiculated bombs and lapilli of andesite some blocks ash and shredded wood the individual units are possibly correlated with the major explosions of july 29 the thickness of the deposits decreases with the distance from the volcano from 5 6 m to a few centimeters on average 90 of the components are juvenile 10 dense andesite and 90 vesicular these coarse grained beds were deposited in rapid succession by a complex transport process involving normal fallout strong ballistic trajectories with a lateral hot 400 c blast surge lu equivalent to a1 ballistic and coarse tephra sprayed in a narrow 85 area within about 5 5 km from the lowest crater and a high ca 10 km eruption column dispersed airfall fine lapilli ash 100 km from the volcano ashcloud forming explosions producing thin pyroclastic surge and muddy phreatomagmatic fallout deposits flau equivalent to a2 and a3 closed the blast surge sequence the successive explosions on july 30 31 mainly produced block and ash flows and widely dispersed ash fall the total volume of pyroclastic material is calculated as 25 8 5 5 10 6 m 3 9 4 2 0 10 6 m 3 dre a model is proposed to explain the peculiarities of the formation transportation and emplacement of the blast deposits the intrusion of the presumed andesitic cryptodome possibly happened through an active thrust fault favoring not only the formation of the lowest crater a but also the low angle explosive events prior to the eruption several minerals were settling to the bottom of the magma chamber as is suggested by the increase of incompatible elements towards the bottom of the stratigraphic section the major elements indicate that some crystal redistribution occurred and the maximum concentration of al2o3 and eu and sr support plagioclase enrichment in early phases of the eruption top of lu 1 and dau 1 from the about 20 recognized prehistoric and historic blast deposits in the world approximately half were produced by sector collapse of the volcano and the other half by sudden decompression of cryptodomes or lava dome collapses the recent blasts 1888 1990s elsewhere have an apparent recurrence of one event decade compared to just a

from gullies to mountain belts a review of sediment budgets at various scales this paper reviews the state of the art in the concept as well as in the application of sediment budgets in sedimentary research sediments are a product of mass dispersal at the earth surface and take part in global cycles sediment budgets aim at quantifying this mass transfer based on the principle of mass conservation and are the key to determine ancient fluxes of solid matter at the earth surface this involves fundamental questions about the interplay of uplift climate and denudation in mountain belts and transfer of sediments from the continents to the oceans as well as applied issues such as soil and gully erosion reservoir siltation and coastal protection first after introducing basic concepts relevant scales and methodologies the different components of quaternary routing systems from erosion in headwaters river systems glacial and paraglacial systems lakes deltas estuaries coasts shelves epicontinental seas and deep sea fans are discussed in terms of their sediment budget most suitable are sedimentologically closed or semi closed depositional environments e g alluvial fans lakes deltas and deep sea fans in a second step the dynamics of passive active and collisional tectonic settings and sediment budgets in related sedimentary basins are explored and new concepts of sediment portioning at large geodynamic scales are introduced ancient routing systems are more or less incomplete and may be intensively fragmented or destroyed in active tectonic settings in terms of sedimentary basin types rifts intracontinental and epicontinental settings are preferred objects of sediment budgets because of their persistence and relatively simple overall sedimentary architecture however closing basins such as foreland forearc retroarc piggy back and wedge top basins may provide excellent snapshots of orogenic sediment fluxes in a third step the large long lived routing systems of the amazon the ganges brahmaputra and the rhine are reviewed for each system estimates of either sediment volumes mass or sediment fluxes of continental and marine subsystems have been compiled in order to receive a complete routing in terms of mass conservation for specific time periods since the late glacial maximum as well as the cenozoic following lessons can be taken from these case studies i depositional centers and fluxes show strong shifts in space and time and call for caution when simply looking at subsystems ii the response times of these large systems are within the milankovich time interval thus lower than predicted from diffusion models iii cyclic routing of sediments in continental basins is much more dominated by climate human control than by eustacy and iv at long time scales ultimate sinks win over intermittent storage it is concluded from this review that the quantitative understanding of global sediment cycling over historic and geologic time and its response to allogenic forcing is still in its infancy and further research is needed towards a holistic view of sediment routing systems at various temporal and spatial scales and their coupling with global biogeochemical cycles this includes i to better determine response times of large routing systems by linking quaternary with cenozoic sediment budgets and continental with marine sub systems ii to combine advanced provenance techniques with sediment budgets in order to reconstruct ancient systems iii to study sediment partitioning at the basin scale iv to reconcile continental supply dominated sequence stratigraphy with the eustatic dominated marine concept and iv to account for non actualism of ancient systems with respect to their erosion and transport mode in particular during glaciations and pronounced arid intervals glacial and eolian sediment routing may cross over hydrologic boundaries of drainage basins thus challenging the principle of mass conservation

enigmatic earthquake generated large scale clastic dyke in the biberach area sw germany abstract we discovered and describe a large scale exposed dimensions 17 m in lateral and 15 m in vertical extension and up to 10 cm in width clastic dyke in the middle miocene between 17 1 and 14 5 ma sandy deposits fluviatile untere serie of the north alpine foreland basin close to biberach an der ris in sw germany the dyke appears to be of sedimentary tectonic origin it formed by liquefaction and injection of clastic material that occurred simultaneously with fracture opening and propagation in sandy deposits presumably as a result of strong seismic shaking triggered by an intense earthquake we therefore interpret the dyke as a seismite and a useful palaeoseismic indicator the clastic dyke cuts through a layer of distal ries ejecta brockhorizont and thus postdates the ries impact the age of the ries event in combination with other stratigraphic constraints defines a relatively narrow time frame of 14 8 to 14 5 ma for the formation of the clastic dyke the source of the strong earthquake responsible for dyke formation might be seismicity related to the alpine orogeny and tectonism seismic activity in one of the volcanic fields of the paleogene to quaternary european volcanic province or seismicity induced by a miocene impact event in southern germany we suggest the relatively strong earthquake in question may have been triggered by a large phreatomagmatic explosion in the urach kirchheim volcanic field or perhaps more likely the steinheim impact event on the eastern swabian alb plateau

field measurement of high temperature bulk reaction rates ii interpretation of results from a field site near simplon pass switzerland bulk metamorphic reaction rates have been measured using sr isotopes as tracers of reactive transport processes at a field site near simplon pass switzerland employing the technique described in part i of this study baxter and depaolo 2002a the reaction rate r inferred similar to the value first reported in baxter and depaolo 2000 is 1 4 1 1 0 4 x 10 7 yr 1 or r 7 0 5 5 2 0 x 10 9 g cm 2 yr normalized to the geometric surface area of plagioclase which is several orders of magnitude slower than extrapolations of laboratory data this rate suggests that attainment of local equilibrium may require 10 s of millions of years and consequently equilibrium may not be closely approached in dynamic metamorphic systems if significant changes in p t x occur over shorter timescales these data suggest that there is a problem in current extrapolations or applicability of laboratory kinetic data to natural high temperature systems possible reasons for this discrepancy include differences in reactive surface area reactant supply limited by slow diffusion of major elements or an armoring effect by which access to grain interiors is limited on the basis of microchemical patterns in plagioclase we identify grain boundary migration gbm as the rate limiting process for accessing grain interiors and thus for bulk reaction calculation of reaction quotients for six balanced mineral reactions suggests local disequilibrium for garnet with respect to its ca content the characteristic equilibrium lengthscales le for sr and ca are both about 1 meter equilibrium based geochemical tools such as isochron geochronology or geothermobarometry are compromised within a distance le of the lithologic contact bulk sr diffusivity measured at the field site changes from 10 9 to 10 7 m yr suggesting that the characteristics of the intergranular transporting medium itm changed significantly during the early retrograde history of the field site

preferential flow in a sandy vadose zone 1 field observation abstract field experiments of water movement in the lower portion of an unsaturated zone i e vadose zone are far more difficult to conduct than those in the root zone thus our concept of the transport mechanism in the vadose zone is still primitive and mainly an extrapolation of our understanding of transport in the root zone recent results from field experiments conducted at the hancock agricultural research station indicated that water and solute applied uniformly to soil surfaces did not flow through the entire vadose zone by using dye tracing and profile excavation field experiments were conducted during the 1987 growing season to examine water flow patterns in the unsaturated zone of the central sand area of wisconsin csaw the results confirmed that preferential flow paths constitute the dominant flow pattern at this location water flowing through the root zone was funneled into concentrated flow paths that occupied only a small portion of the soil matrix in the vadose zone yet accounted for most of the transport the observed phenomena of preferential flow in a sandy vadose zone are discussed in this paper the mechanism and implications of preferential flow are presented in a companion paper

estimating building exposure and impact to volcanic hazards in icod de los vinos tenerife canary islands abstract principal and subsidiary building structure characteristics and their distribution have been inventoried in icod tenerife canary islands and used to evaluate the vulnerability of individual buildings to three volcanic hazards tephra fallout volcanogenic earthquakes and pyroclastic flows the procedures described in this paper represent a methodological framework for a comprehensive survey of all the buildings at risk in the area around the teide volcano in tenerife such a methodology would need to be implemented for the completion of a comprehensive risk assessment for the populations under threat of explosive eruptions in this area the information presented in the paper is a sample of the necessary data required for the impact estimation and risk assessment exercises that would need to be carried out by emergency managers local authorities and those responsible for recovery and repair in the event of a volcanic eruption the data shows there are micro variations in building stock characteristics that would influence the likely impact of an eruption in the area as an example of the use of this methodology for vulnerability assessment we have applied a deterministic simulation model of a volcanic eruption from teide volcano and its associated ash fallout which when combined with the vulnerability data collected allows us to obtain the vulnerability map of the studied area this map is obtained by performing spatial analysis with a geographical information system gis this vulnerability analysis is included in the framework of an automatic information system specifically developed for hazard assessment and risk management on tenerife but which can be also applied to other volcanic areas the work presented is part of the eu funded exploris project explosive eruption risk and decision support for eu populations threatened by volcanoes evr1 2001 00047

formation and evolution of soils from an acidified watershed plastic lake ontario canada abstract the plastic lake watershed contains podzols developed on glacial tills deposited 12 000 years ago present day cationic fluxes from the soils are greater by a factor of 2 than long term fluxes averaged over the age of the tills the high rates of present day chemical weathering may be a result of increased input of anthropogenic acids into the plastic lake watershed time averaged proportions of cations leached from the soils are strikingly different from the proportions of cations now being leached indicating that the character of chemical weathering has changed over time weathering was and is dominated by mineral dissolution but cation exchange has become increasingly important as the soils have matured the large amount of ca now released to the soil solutions probably is derived from exchange substrates promoted by preferential uptake of al onto the substrates aluminum is derived primarily through dissolution of feldspars bulk compositional analyses of soil profiles demonstrate that feldspars of the ae horizon release base cations na k ca and al to solution in near stoichiometric proportions just as is observed experimentally for feldspar dissolution in acidic solutions furthermore surface area normalized dissolution rates of plagioclase k feldspar quartz and micas of plastic lake soils are similar to rates obtained experimentally the favourable comparison between natural and experimental dissolution rates and near stoichiometric release of base cations and al from feldspars to acidic solutions in both natural and experimental settings suggests that recent laboratory release rates can be applied to dissolution of feldspars within the ae horizon of the plastic lake podzols surface area normalized time averaged dissolution rates of primary minerals of plastic lake soils are significantly greater than present day rates measured for mature soil profiles rapid release from plastic lake soils probably results from reaction of acidic soil solutions with highly reactive biotite and ultrafine grains of feldspars produced by comminution during glaciation exhaustion of these reactive phases may well explain the low leach rates observed for mature profiles after just 12 000 years of weathering biotite has been effectively exhausted in the plastic lake soils and much of the fine grained feldspar probably has been dissolved time averaged concentrations of elements removed from the soil recast into essential mineralogy indicate that vermiculite weathers most rapidly followed closely by plagioclase k feldspar weathers less rapidly than plagioclase but more rapidly than quartz or hornblende al silicate possibly imogolite and goethite are added to the soils during weathering plagioclase dissolution consumes more acid than all other reactions accounting for 60 of the total acid consumed combined with k feldspar they account for more than 80 of the total acid neutralized the dissolution rate of quartz is one half that of plagioclase furthermore the rate is consistent with the experimentally determined rates the combination of high abundance and dissolution rate results in large amounts of quartz being dissolved from the soils of plastic lake it may also contribute significantly to total elemental fluxes from other catchments

broad accommodation of rift related extension recorded by dyke intrusion in saudi arabia volcanic fields at the eastern margin of the red sea rift were regarded as seismically quiet until a swarm of 30 000 earthquakes struck in 2009 geological analyses reveal the intrusion of a volcanic dyke and indicate that rift related extension is spread over a broad region far from the rift axis

geochemical mass balances and weathering rates in forested watersheds of the southern blue ridge ii effects of botanical uptake terms abstract geochemical mass balance methods are commonly used in small watershed studies to estimate rates of primary mineral weathering and soil formation and the contribution of these processes to cation budgets nutrient cycling and landscape susceptibility to acid deposition many researchers employ the balance sheet approach a system of simultaneous linear equations with constant coefficients which represent the steady state behavior of the modelled system most workers also assume that the steady state assumption for the entire system means that botanical factors can be ignored in other words that there is no net elemental transfer between biomass and inorganic compartments of the system however the widely invoked assumption that biomass is at steady state is mathematically a second explicit assumption not a built in mathematical consequence of the assumption of overall steady state the common assumption that the biomass is necessarily at steady state in a steady state system ignores the possibility of uptake of elements into the forest biomass to quantify the implications of the separate mathematical assumptions weathering rates for seven forested watersheds in the southern blue ridge mountains are calculated twice once allowing for net element exchange with biomass and once assuming no net exchange with biomass our calculations show that misunderstanding the mathematical constraints which are built into the most widely used geochemical mass balance equations commonly causes errors underestimates of up to a factor of 4 in the calculated rates of mineral weathering and soil formation this problem is most pronounced for minerals which contain major nutrient elements and for rates calculated from mass balances of those nutrient elements

process of the 1977 nyiragongo eruption inferred from the analysis of long period earthquakes and volcanic tremors abstract the lava lake present in the summit crater of nyiragongo from 1928 to 1977 completely disappeared after the short lived eruption of january 10th 1977 the sequence of events during this eruption was elucidated by analysis of seven long period earthquakes lp events and volcanic tremors recorded at stations lwi nai and bul the seven lp events observed were composed mainly of rayleigh waves with large amplitudes and were classified into two groups one containing three and the other containing four events based on waveform similarities it was determined that the former events were excited by the vertical downward single forces and the latter events by the vertical upward ones the short period seismograms recorded at lwi and nai showed that continuous volcanic tremors began roughly 6 min before the occurrence of the first lp event after the appearance of seven burst type tremor activities tremor amplitudes suddenly increased and then gradually decreased taking the analytical results of seismic events and observed surface activities into consideration we inferred the process of the 1977 nyiragongo eruption to be as follows 1 1 quick draining of the liquid lava through the fissures and disappearance of the long lived lava lake less than 6 min 2 2 large terraces collapsing onto the bottom of crater causing the first three lp events during the next 8 min 3 3 intermittent vesiculation of lava at the top of magma chamber exciting the last four lp events during the next 8 min 4 4 magma flowing in deeper parts of the conduit generating the intense tremors measurable at nai and lasting for roughly 30 min

preferential flow and the generation of runoff 1 boundary layer flow theory approaches to soil water flow which are based on the theory of potential flow often overestimate either the volume of flow or the response time at the hillslope scale when their results are compared with observations macropore flow is frequently thought to be the reason for the discrepancy between observations and model performance the expression macropore flow is considered to be too restricting it confines the rapid flow and transport processes to the easily observed channels concealing the more general question as to what degree potential flow theory adequately describes flow in porous media the application of potential flow theory to infiltration leads to the richards equations only when hydrodynamic dispersion of soil water and capillary potential are perfectly correlated in this paper a boundary layer infiltration model is presented which is based on kinematic theory it is also expanded to lateral flow in a sloping soil

seismological aspects of the 1988 1989 lonquimay chile volcanic eruption abstract more than 1600 earthquakes were recorded in a four month period on portable seismographic stations installed in the lonquimay area immediately after the initiation of the volcanic eruption of december 25 1988 hypocentral parameters were calculated on a subset of 150 events showing clear p and s arrivals seismic activity was restricted to a north south elongated region that included the main crater of the lonquimay volcano the new navidad crater lies along the eastern margin of the area of seismicity most of the hypocenters are located at depths shallower than 6 km and none have depths exceeding 10 km the largest earthquakes of the sequence took place on dec 28 m 4 7 jan 12 13 m 4 8 and 5 0 and feb 24 m 5 3 the number of events per day varied it peaked on dec 27 with more than 260 events and more than 200 events were recorded on jan 13 both of which corresponded to the days of large earthquakes the relation of large to small events given by the b value of the magnitude frequency distribution log n a bm is typical of volcanic sequences b 1 7 and much larger than the equivalent for tectonic environments the rate of decay of the number of aftershocks of each large earthquake is proportional to t p with p increasing from 0 63 to 1 08 as the eruption progressed in time initial low values of p indicate a slow stress release in the region larger absolute values of p are comparable with tectonic environments and might be indicators of the last stages of the eruption process the total seismic energy release is 9 6 10 19 ergs about five orders of magnitude less than the estimated thermal energy the spatial distribution of earthquakes suggests that the sources of stress change associated with the eruption are located under and possibly to the south of the main crater of the lonquimay volcano and that the evacuation channels of magma occupied a zone of weakness in the region of the new crater

granite hydrothermal interaction a simultaneous estimation of the mineral dissolution rate based on the isotopic doping technique we propose an experimental evaluation of the simultaneous dissolution rate of k feldspar biotite and plagioclase during the interaction between a granite and a fluid artificially enriched in the less abundant strontium and potassium isotopes experiments were carried out at 453 k and 10 bars for a time of 6 months putting powered granite in contact with fluids spiked in 39k and 84sr and saturated with respect to kaolinite low temperature albite prehnite calcite adularia and quartz the evolution of the rb 39k sol vs 41k 39k sol and 87sr 86sr sol vs 84sr 86sr sol ratios allows us to identify a single rock end member from the first month of interaction this indicates that the dissolving mineral assemblage remains constant during the remaining 5 months of interaction associating the mass conservation law to the isotopic mixing equations for both sr and k we evaluate that the mass of dissolved plagioclase is 3 4 times higher the mass of dissolved biotite and 10 20 times higher the mass of dissolved sanidine the rate of potassium dissolution is estimated assuming that the 41k 39k sol ratio is continuously in equilibrium with the ratio in neogenic phases coupling the proportion of dissolved minerals to the overall rate of potassium dissolution and normalising to the mineral surface area we finally estimate that in our experimental conditions plagioclase and biotite dissolve with a rate of respectively 3 1 10 12 and 6 2 10 13 mol m 2 s 1 while the k feldspar dissolution rate is 4 2 10 13 mol m 2 s 1

seismological study of the kliuchevskoi flank eruption of 1983 kamchatka abstract a flank eruption called the predskazanny eruption occurred at an altitude of 2875 m on the east flank of the kliuchevskoi volcano from march 8 to june 27 1983 the eruption was largely effusive with a constant chemical composition of the lavas calc alkaline aluminium basalts their volume is estimated at 0 11 km 3 the seismic precursors of the predskazanny eruption was concentrated beneath the new eruption center first at depths of between 10 and 15 km earthquake of february 28 k s 8 3 m 3 5 and then at depths between 5 km b s l and 3 km a s l earthquake swarm of march 1 7 volcanic tremor during the earthquake swarm of march 1 7 was absent with the approach of an eruption the depth of earthquake foci in the swarm decreased an analysis of the seismicity implies that the magma was apparently ascending in the newly formed channel from a depth of at least 5 km the feeding area of the predskazanny eruption was apparently connected with the major magma channel of kliuchevskoi at depths between 5 and 10 km but not deeper than 15 km

seismicity and crustal deformation preceding the january 1996 eruptions at karymsky volcanic center kamchatka two explosive eruptions occurred on 2 january 1996 at karymsky volcanic center kvc in kamchatka russia the first dacitic from the central vent of karymsky volcano and the second several hours later from karymskoye lake in the caldera of akademia nauk volcano the main significance of the 1996 volcanic events in kvc was the phreatomagmatic eruption in karymskoye lake which was the first eruption in this lake in historical time and was a basaltic eruption at the acidic volcanic center the volcanic events were associated with the 1 january ms 6 7 mw 7 1 earthquake that occurred at a distance of about 9 17 km southeast from the volcanoes just before the eruptions we study the long term 1972 1995 and short term 1 2 january 1996 characteristics of crustal deformations and seismicity before the double eruptive event in kvc the 1972 1995 crustal deformation was homogeneous and characterized by a gradual extension with a steady velocity the seismic activity in 1972 1995 developed at the depth interval from 0 to 20 km below the akademia nauk volcano and spread to the southeast along a regional fault the seismic activity in january 1996 began with a short sequence of very shallow microearthquakes m 0 beneath karymsky volcano then seismic events sharply increased in magnitude up to mb 4 9 and moved along the regional fault to the southeast culminating in the ms 6 7 earthquake its aftershocks were located to the southeast and northwest from the main shock filling the space between the two active volcanoes and the ancient basaltic volcano of zhupanovsky vostryaki the eruption in karymskoye lake began during the aftershock sequence we consider that the ms 6 7 earthquake opened the passageway for basic magma located below zhupanovsky vostryaki volcano that fed the eruption in karymskoye lake

throughflow and solute transport in an isolated sloping soil block in a forested catchment a 3m wide by 9m long by 1m deep soil block on a forested hillslope near orono me was isolated by excavation of encircling trenches a sprinkler system for application of water and potassium bromide tracer was constructed over the plot outflow was collected at six locations with troughs experiments were conducted at application rates of 2 5 5 and 10 cm h 1 pulses of tracer were applied subsequent to attainment of steady flow and breakthrough curves were measured at all outflow points recession limbs of outflow hydrographs exhibited distinct breaks when plotted on semilogarithmic axes indicating drainage from at least two distinguishable pore size classes or flow pathways solute breakthrough curves were dominated by a single peak travel times of solute were inversely related to the application rate a secondary peak in the outflow curve which is inconsistent with transport theories for a homogeneous soil was observed in all cases this second peak is unexplained but is conceptually consistent with the notion of transport in at least two pore size classes an undisturbed soil core diameter of 30 cm and length of 40 cm was sprinkled at the same rates as was the soil block using methylene blue as tracer in the last run drainage hydrographs and visual examination of dye stains in the block indicated also at this smaller scale that flow and transport are controlled by preferred paths in the soil paths that cannot be morphologically distinguished from the surrounding soil matrix theoretical explanations of processes on such hillslopes need to account for this fact

aqueous corrosion of olivine in the mars meteorite miller range mil 03346 during antarctic weathering implications for water on mars abstract several nakhlites clinopyroxenite meteorites from mars contain olivine phenocrysts with corrosion features identical in size shape and distribution to the smaller etch pits of well characterized weathered terrestrial olivine miller range mil 03346 is an antarctic nakhlite find recovered after long exposure to antarctic conditions the distribution of discrete olivine etch pits almost exclusively within a few hundred microns of allocation mil 03346 171 s documentably exposed surface suggests that they formed by terrestrial weathering in antarctica the small size of olivine etch pits in mil 03346 171 relative to commonly much larger etch pits in even incipiently weathered terrestrial examples suggests that the duration of its exposure to weathering conditions was short or the weathering conditions to which it was exposed did not favor olivine corrosion in the form of etch pit formation or both time scales for the formation of etch pits estimated from experimentally determined dissolution rates of olivine over a range of phs are comparable to the measured terrestrial age of the meteorite and short relative to the time available for possible similar corrosion on mars etch pits of the observed size on mil 03346 olivine phenocrysts would be relatively easy to form supraglacially under brief episodic acidic antarctic conditions but the terrestrial age of mil 03346 is long enough that its olivine might have been weathered to the observed state by englacial films of alkaline antarctic water the paucity of similar etch pits in olivine from the interior of mil 03346 suggests that olivine in this mars meteorite was exposed to even less aqueous alteration after iddingsitization during its 1 3 billion years on mars than its exterior was subjected to during its pleistocene holocene exposure to antarctic weathering conditions

climatic thresholds for pedogenic iron oxides under aerobic conditions processes and their significance in paleoclimate reconstruction abstract iron oxides are widely distributed across the surface of the earth as a result of the aerobic weathering of primary fe bearing minerals pedogenic iron oxides which consist mainly of hematite hm goethite gt maghemite mgh are often concentrated synchronously in aerobic soils under low to moderate rainfall regimes magnetic susceptibility and redness which respectively reflect the content of mgh and hm in soils are considered reasonable pedogenic and climatic indicators in soil taxonomy and paleorainfall reconstruction however under high rainfall regimes the grain growth of mgh and transformation to hm combined with the prior formation of gt under conditions of high relative humidity rh can result in magnetic reduction and dramatic yellowing of soils and sediments which explains the existence of rainfall thresholds for mgh and hm at a large scale even before the pedogenic environment turns anaerobic in order to capture the rainfall thresholds for mgh and hm occurring under aerobic conditions we explored a tropical transect across a granitic region where the soil color turned from red to yellow under a wide rainfall range of 900 2200 mm yr and a corresponding mean annual rh range of 77 85 we observed a lower rainfall threshold of 1500 mm yr and a corresponding rh 80 for mgh and hm along this transect as well as a higher rainfall threshold of 1700 mm yr and a corresponding rh of 81 for gt and total pedogenic iron oxides citrate bicarbonate dithionite extractable fe fe d cross referencing with comparable studies in temperate and subtropical regions we noted that the rainfall or rh thresholds for fe d and hm or mgh likewise increase with temperature moreover the different thresholds for total and individual iron oxide phase indicates that a negative correlation between chemical weathering intensity and redness or in sediment sequences can occur under the prevalent climate regime just between their thresholds finally we developed an integrated model to interpret the sequential formation of rainfall thresholds for different pedogenic iron oxides in soils and sediments with conditions from aerobic to anaerobic

volcano tectonic earthquakes a new tool for estimating intrusive volumes and forecasting eruptions abstract we present data on 136 high frequency earthquakes and swarms termed volcano tectonic vt seismicity which preceded 111 eruptions at 83 volcanoes plus data on vt swarms that preceded intrusions at 21 other volcanoes we find that vt seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from vei 0 to ultraplinian vei 6 at such previously long dormant volcanoes because large eruptions occur most commonly during resumption of activity at long dormant volcanoes vt seismicity is an important precursor for the earth s most dangerous eruptions vt seismicity precedes all explosive eruptions of vei 5 and most if not all vei 4 eruptions in our data set surprisingly we find that the vt seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption and rarely if ever starts beneath the eruption site itself the distal vt swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance beyond which hypocenter depths level out we summarize several important characteristics of this distal vt seismicity including swarm like nature onset days to years prior to the beginning of magmatic eruptions peaking of activity at the time of the initial eruption whether phreatic or magmatic and large non double couple component to focal mechanisms most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the vt seismicity from log10 v 0 77 log moment 5 32 with volume v in cubic meters and seismic moment in newton meters because the cumulative seismic moment can be approximated from the size of just the few largest events and is quite insensitive to precise locations the intruded magma volume can be quickly and easily estimated with few short period seismic stations notable cases in which distal vt events preceded eruptions at long dormant volcanoes include nevado del ruiz 1984 1985 pinatubo 1991 unzen 1989 1995 soufriere hills 1995 shishaldin 1989 1999 tacana 1985 1986 pacaya 1980 1984 rabaul 1994 and cotopaxi 2001 additional cases are recognized at frequently active volcanoes including popocateptl 2001 2003 and mauna loa 1984 we present four case studies pinatubo soufriere hills unzen and tacana in which we demonstrate the above mentioned vt characteristics prior to eruptions using regional data recorded by neic we recognized in near real time that a huge distal vt swarm was occurring deduced that a proportionately huge magmatic intrusion was taking place beneath the long dormant sulu range new britain island papua new guinea that it was likely to lead to eruptive activity and warned rabaul volcano observatory days before a phreatic eruption occurred this confirms the value of this technique for eruption forecasting we also present a counter example where we deduced that a vt swarm at volcan cosiguina nicaragua indicated a small intrusion insufficient to reach the surface and erupt finally we discuss limitations of the method and propose a mechanism by which this distal vt seismicity is triggered by magmatic intrusion

bridging the gap between laboratory measurements and field estimations of silicate weathering using simple calculations weathering rates of silicate minerals observed in the laboratory are in general up to five orders of magnitude higher than those inferred from field studies simple calculations show that even if the field conditions were fully simulated in standard laboratory experiments it would be impossible to measure the slow rates of mineral dissolution that are observed in the field as it is not possible to measure the dissolution rates under typical field conditions one should extrapolate the available data to the field conditions to do this a rate law for the dissolution of plagioclase in the field was formulated by combining the far from equilibrium dissolution rate of weathered natural oligoclase at 25 c with the effect of deviation from equilibrium on dissolution rate of fresh albite at 80 c in contrast to the common view that laboratory experiments predict dissolution rates that are faster than those in the field the simulation based on this rate law indicates that laboratory dissolution experiments actually predict slower rates than those observed in the field this discrepancy is explained by the effect of precipitation of secondary minerals on the degree of saturation of the primary minerals and therefore on their dissolution rate indeed adding kaolinite precipitation to the simulation significantly enhances the dissolution rate of the plagioclase moreover a strong coupling between oligoclase dissolution and kaolinite precipitation was observed in the simulation we suggest that such a coupling must exist in the field as well therefore any attempt to predict the dissolution rate in the field requires knowledge of the rate of the secondary mineral precipitation

using the chemical composition of carbonate rocks on mars as a record of secondary interaction with liquid water in the search for habitable environments on mars sites that have been altered by liquid water represent an important target quickly dissolving and precipitating carbonates found in multiple locations on mars represent a key potential mineral indicator of locations with a history of aqueous alteration and therefore possible habitability recent liquid surface water on mars may differ significantly from the fluids either sedimentary hydrothermal or pedogenic that formed carbonate minerals on mars interactions of carbonate rocks with such recent surface water may therefore cause changes in chemistry and mineralogy with depth that form weathering profiles recording the conditions of alteration to test the prediction that martian carbonates may record a signature of aqueous alteration on mars we performed reactive transport modeling of putative carbonate outcrops on mars using the reactive transport code crunchflow model inputs included two parent rocks chosen based on the carbonate rich rock at gusev crater comanche one consisting of 60 magnesite 20 siderite and 20 porosity and one consisting of 50 magnesite 20 siderite 9 calcite 1 6 rhodochrosite and 20 porosity reacting solutions consisted of four scenarios acidic sulfate containing solutions perhaps resulting from an acid vapor scenario dilute solutions resulting from martian analog basalt dissolution concentrated solutions resulting from modeled evaporation of the dilute solutions and solutions based on the results of the phoenix lander modeling was performed under low oxidation and high oxidation conditions based on the modeling results a carbonate rock would become enriched in siderite upon interaction with acidic water under low oxidation conditions the same rock would become enriched in calcite after interaction with ca enriched solutions a carbonate rock reacting under more oxidizing conditions would preferentially dissolve siderite leaving a surface enriched in magnesite and ferric oxide therefore the mg rich carbonates on mars are consistent with possible interaction with liquid water under oxidizing conditions similar to those measured at the phoenix landing site future detailed chemical and mineralogical profiles through weathered rock into the unaltered interior of carbonate rocks may therefore allow the quantitative interpretation of the aqueous history and possible habitability of locations on mars

seismic hazard of volcanic activity abstract seismic activity is a common feature of volcanic eruptions the majority of volcanic earthquakes are small their magnitudes do not exceed 2 or 3 at the same time significant moderate size and large volcanic earthquakes may also occur the study of 28 significant m w 4 5 earthquakes associated with volcanic eruptions of 20th century allowed us to formulate the following results about seismic hazard of volcanic activity 1 during the 20th century only three large m w 7 0 earthquakes directly associated with volcanic eruptions in the world were recorded 2 the maximum magnitude m w was estimated to be 5 4 for earthquakes related to central eruptions 7 0 for caldera collapse 5 9 for central eruptions accompanied by flank and or fissure eruptions 7 1 for flank and or fissure eruptions without central eruptions and 5 9 for submarine eruptions for seismicity just before the eruption the maximum magnitude of earthquakes was estimated to be m w 7 1 for seismicity at the initial stage of eruption m w 7 0 for paroxysmal stage of eruption m w 5 6 and for final stage of eruption m w 6 1 3 it was shown that the recurrence time of eruptions of the same type of volcano associated with significant m w 4 5 earthquakes was more than 100 years for 86 of events studied

biotite dissolution processes and mechanisms in the laboratory and in nature early stage weathering environment and vermiculitization biotite dissolution in the laboratory and in nature was examined and compared to elucidate certain aspects of the weathering processes batch dissolution experiments of fresh biotite k 0 9 1 na 0 0 1 mg 0 4 0 fe 2 0 7 mn 0 0 5 al 0 1 4 ti 0 1 9 si 2 8 2 al 1 1 8 o 1 0 oh 2 in granite were carried out at 150 c for 1 to 56 days examination by scanning electron microscope sem equipped with an energy dispersive x ray spectrometer eds revealed that in the early stage dissolution proceeds from the edges of crystals inward and secondary minerals such as fe oxide are precipitated mostly at the edges with only a few secondary minerals found on the basal surfaces a dissolution experiment using a mixture of biotite and muscovite done at 150 c for 7 days indicated that hematite crystals formed mostly at the edges of biotite but not on muscovite this observation suggests that released fe is precipitated before it diffuses into the bulk solution because a dissolution rate at the edge is larger by two orders of magnitude than at the basal surface turpault and trotignon 1994 precipitation before diffusion of dissolved elements to bulk solution well explains the preferential secondary mineralization at the edges in the laboratory experiments sem eds of fresh to slightly weathered biotites revealed that early stage weathering proceeds in the same way as in the laboratory with the edges being preferentially weathered and secondary minerals being precipitated mostly at the edges because of the similarity between the occurrence of secondary minerals in the laboratory experiments and in nature the laboratory results elucidate the early stage weathering conditions namely that 1 supersaturation with respect to secondary minerals in a solution occurs around biotite i e the solution is poorly connected to a main flow pathway of water and 2 once supersaturation is achieved secondary minerals are precipitated mainly at the edge before some released elements diffuse into the solution the immobility of water immediately adjacent to primary minerals partly explains the large difference in dissolution rate between the laboratory and natural samples a phlogopite dissolution experiment was done at 150 c for 5 5 days to examine the effect of biotite composition on vermiculitization high resolution transmission electron microscopy revealed that vermiculite layers are formed by layer by layer transformation within phlogopite after 5 5 day dissolution but not within biotite after 56 day dissolution or within slightly weathered biotite a comparison of our data with results of other studies indicates that the formation of vermiculite layers between biotite layers occurs even in the early stage when biotite is not fe rich more than 0 8 mg per o 1 0 oh 2 when biotite is fe rich less than 0 4 mg per o 1 0 oh 2 like the present one released fe is precipitated as for example fe hydroxide and vermiculite is rarely formed because of limited availability of mg thus a higher mg content in biotite facilitates the formation of vermiculite at least in the early stage because vermiculite dissolves at a much slower rate than biotite mg rich biotite dissolves at a slower rate than fe rich biotite in the late stage biotite dissolution still continues from the edge and within biotite which results in a fine comb like texture for weathered biotite vermiculite occurs as a domain within chemically and structurally altered biotite as well as at the edge even during weathering of mg poor biotite

variation in soil surface area in a chronosequence of soils from glen feshie scotland and its implications for mineral weathering rate calculations abstract the inorganic component of soil horizons from a chronosequence of six soils developed in glen feshie scotland shows an increase in surface area with soil age and a decrease in surface area with increasing depth in the soil profiles surface area increases due to the development of discontinuous porous coatings on mineral grains the preferential dissolution of specific areas of individual minerals resulting in complex highly irregular grain shapes and a general reduction in grain size due to dissolution the discontinuous coatings consist predominantly of oxalate extractable al si oxyhydroxides and account for between 61 and 94 of the total inorganic surface area failure to take into account the increase of mineral surface area with time can lead to predictions of decreasing mineral dissolution rate with soil age in contrast to laboratory studies which assume that mineral dissolution can reach a steady state the difference between total and reactive mineral surface area may help to explain the frequently reported result that laboratory measured mineral dissolution rates are up to several orders of magnitude greater than those measured in the field

deformation and seismicity near sabancaya volcano southern peru from 2002 to 2015 we use interferometric synthetic aperture radar insar and local seismic data to investigate the cause of earthquake sequences near sabancaya volcano in southern peru from 2002 to 2014 with a particular focus on events leading up to the august 2014 phreatic eruption insar observed deformation associated with earthquake swarms in late 2002 february 2013 and july 2013 is modeled by fault slip with no need for magmatic sources to explain the deformation the majority of the seismicity is an expression of the regional tectonic system which is characterized by e w trending normal faults but a link to the magmatic system is possible the mw 5 9 earthquake on 17 july 2013 occurred on a previously unmapped normal fault that continued to deform in the months following the earthquake an increase in long period and hybrid seismicity and changes in fumarolic emissions in 2013 2014 culminating in the august 2014 eruption indicates the involvement of both tectonic and magmatic systems

seismicity and volcanism of jan mayen island the small arctic jan mayen island site of the world s northernmost active volcano beerenberg is part of the mid atlantic ridge system and located along the jan mayen fracture zone jmfz recent data from the local seismic network and fault plane solutions from the global network indicate that the island is located at a ridge crest intersection which might explain the origin of the island and the associated volcanism moreover the new data suggest a series of offset segments of the mohn s ridge overlapping in an en echelon pattern in january 1985 a flank eruption was for the first time observed with the local seismic network volcanic tremors and low frequency events were observed on 5 january at 2230 h and 10 hours later the first large earthquake occurred no visual confirmation of the eruption was made until 6 january at 1630 h the seismic observations rule out the possibility that the large earthquake caused the eruption it seems more likely that the changes in local stress conditions triggered the earthquake and that the eruption started before the first large earthquake recent observations show that the local network provides an efficient tool for monitoring and warning of volcanic activity however since there was no change in the local seismicity in the days or months before the 1985 eruption it seems to be difficult to make long term predictions of beerenberg flank eruptions without using other techniques such as observations of tilt

basalt weathering across scales abstract weathering of silicate minerals impacts many geological and ecological processes for example the weathering of basalt contributes significantly to consumption of atmospheric carbon dioxide co2 and must be included in global calculations of such consumption over geological timeframes here we compare weathering advance rates for basalt wd where d and indicate the scale at which the rate is determined and surface area measured respectively from the laboratory to the watershed scales data collected at the laboratory weathering rind soil profile and watershed scales show that weathering advance rate of basalt is a fractal property that can be described by a fractal dimension dr 2 3 by combining the fractal description of rates with an arrhenius relationship for basalt weathering we derive the following equation to predict weathering advance rates at any spatial scale from weathering advance rates measured at the bet scale w d k 0 a d r 2 e e a r t here k0 is the pre exponential factor 1 29 107 mm3 mm 2 yr 1 ea is the activation energy 70 kj mol 1 and a is a spatial constant related to the scale of measurement of bet surface area 10 7 mm the term a d r 2 is the roughness the roughness fractal dimension can be conceptualized as a factor related to both the thickness of the reaction front and the specific surface area within the reaction front however the above equation can also be written in terms of a surface fractal dimension and the hypothetical average grain radius these fractal dimensions provide insight into reaction front geometry and should vary with lithology once the surface area discrepancy has been accounted for using this method we find a one to two order of magnitude range in weathering advance rates measured at any scale or temperature that can be attributed to factors such as changes in erosional regime parent lithology mechanism climate composition of reacting fluid and biological activity our scaled equation when used to predict global basalt co2 consumption based upon global lithologic maps yields an uptake flux 1 75 1013 mol co2 yr 1 within the predicted error of fluxes estimated based upon riverine measurements

discriminations between volcanic earthquakes associated with central and lateral eruptions abstract differences in source radiation are considered for volcanic earthquakes associated with central and lateral flank eruptions p wave spectra are used to estimate seismic moment energy class and other source parameters for 16 small alaid volcano kurile islands earthquakes associated with the 1972 flank and 1981 central eruptions source parameters were studied for both earthquake swarms higher m o values are noted for earthquakes associated with the central eruption of the volcano providing the energy class is equal for earthquakes of both groups simultaneously a relatively higher level of radiation of longitudinal waves is also characteristic seismic moment was estimated for 14 relatively large volcanic earthquakes associated with the eruptions of the volcanoes of the world seismic moment surface wave magnitude relations were studied higher m o values for earthquakes associated with central eruptions are found the noted discrepancies in source radiation of the two types of earthquake swarms are accounted for by the different nature of eruptive fractures through which the magma rises during the central and flank eruptions eruptive fractures of flank eruptions are characterized by the presence of a number of asperities barriers which may cause a higher amount of short period waves whereas the eruptive fractures of central eruptions are essentially smoother

chemical weathering in a tropical watershed luquillo mountains puerto rico i long term versus short term weathering fluxes abstract the pristine rio icacos watershed in the luquillo mountains in eastern puerto rico has the fastest documented weathering rate of silicate rocks on the earth s surface a regolith propagation rate of 58 m ma 1 calculated from iso volumetric saprolite formation from quartz diorite is comparable to the estimated denudation rate 25 50 ma 1 but is an order of magnitude faster than the global average weathering rate 6 ma 1 weathering occurs in two distinct environments plagioclase and hornblende react at the saprock interface and biotite and quartz weather in the overlying thick saprolitic regolith these environments produce distinctly different water chemistries with k mg and si increasing linearly with depth in saprolite porewaters and with stream waters dominated by ca na and si such differences are atypical of less intense weathering in temperate watersheds porewater chemistry in the shallow regolith is controlled by closed system recycling of inorganic nutrients such as k long term elemental fluxes through the regolith e g si 1 7 10 8 moles m 2 s 1 are calculated from mass losses based on changes in porosity and chemistry between the regolith and bedrock and from the age of the regolith surface 200 ma mass losses attributed to solute fluxes are determined using a step wise infiltration model which calculates mineral inputs to the shallow and deep saprolite porewaters and to stream water pressure heads decrease with depth in the shallow regolith 2 03 m h2o m 1 indicating that both increasing capillary tension and graviometric potential control porewater infiltration interpolation of experimental hydraulic conductivities produces an infiltration rate of 1 m yr 1 at average field moisture saturation which is comparable with libr tracer tests and with base discharge from the watershed short term weathering fluxes calculated from solute chemistries and infiltration rates e g si 1 4 10 8 moles m 2 s 1 are compared to watershed flux rates e g si 2 7 10 8 moles m 2 s 1 consistency between three independently determined sets of weathering fluxes imply that possible changes in precipitation temperature and vegetation over the last several hundred thousand years have not significantly impacted weathering rates in the luquillo mountains of puerto rico this has important ramifications for tropical environments and global climate change

lacustrine turbidites as a tool for quantitative earthquake reconstruction new evidence for a variable rupture mode in south central chile understanding the long term earthquake recurrence pattern at subduction zones requires continuous paleoseismic records with excellent temporal and spatial resolution and stable threshold conditions south central chilean lakes are typically characterized by laminated sediments providing a quasi annual resolution our sedimentary data show that lacustrine turbidite sequences accurately reflect the historical record of large interplate earthquakes among others the 2010 and 1960 events furthermore we found that a turbidite s spatial extent and thickness are a function of the local seismic intensity and can be used for reconstructing paleo intensities consequently our multilake turbidite record aids in pinpointing magnitudes rupture locations and extent of past subduction earthquakes in south central chile comparison of the lacustrine turbidite records with historical reports a paleotsunami subsidence record and a marine megaturbidite record demonstrates that the valdivia segment is characterized by a variable rupture mode over the last 900 years including i full ruptures mw 9 5 1960 1575 1319 9 1127 44 ii ruptures covering half of the valdivia segment mw 9 1837 and iii partial ruptures of much smaller coseismic slip and extent mw 7 5 8 1737 1466 4 also distant or smaller local earthquakes can leave a specific sedimentary imprint which may resolve subtle differences in seismic intensity values for instance the 2010 event at the maule segment produced higher seismic intensities toward southeastern localities compared to previous megathrust ruptures of similar size and extent near concepci n

influence of reaction kinetics and mesh refinement on the numerical modelling of concrete clay interactions large quantities of cements and concretes need to be incorporated in geological disposal facilities for long lived radwaste an alkaline plume diffusing from an aged concrete ph 12 5 through argillite type rocks has been modelled considering feedback of porosity value variations on transport properties using the reactive transport code toughreact the mineralogical composition of the argillite is modified at the interface with the concrete diffusion of cementitious elements leads to rapid and strong porosity occlusion in the argillite numerical results show that both reaction rates and spatial refinement affect mineralogical transformation pathways the variations in porosity and the extension of the zone affected by the alkaline perturbation are compared at different times the major effects of mineral precipitation under kinetic constraints rather than local equilibrium are a delay in the porosity clogging and an increase in the extension of the alkaline perturbation in the clay formation the same time delay rise for the porosity occlusion also appears for the roughest spatial resolutions a simulation as representative as possible of temporal and spatial scales of cementation processes must then be supported by more comparative data such as long term experimental investigations or natural analogues

replacement of olivine by serpentine in the carbonaceous chondrite nogoya cm2 abstract coarse chondrule and isolated olivine in some cm chondrites is replaced by serpentine in both centripetal and meshwork replacement textures locally preserved textures formed by partial replacement of coarse olivine by serpentine in the carbonaceous chondrite nogoya cm2 establish unique associations between each individual mass of serpentine and the specific olivine from which that serpentine formed electron probe microanalyses show that the composition of serpentine replacing coarse olivine is uniform throughout all analyzed volumes of nogoya and is independent of the composition of the olivine being replaced if as previously proposed late stage alteration fluids were mg rich because fe source minerals were depleted in earlier stages then the uniform mg rich composition of the serpentine replacing large silicate grains during advanced stages of alteration may indicate diffusional homogenization of the aqueous solutions over progressively larger spatial scales enabled by long timescales and previously proposed stagnant or slow moving fluids the range of olivine compositions replaced in nogoya is even larger than previously reported from alh 81002 cm2 this militates against hypotheses of strong primary mineral control on the compositions of alteration products at least at advanced stages of alteration the serpentine formed by olivine replacement in nogoya is more magnesian than the counterpart serpentine replacing all anhydrous primary silicates in alh 81002 this intermeteorite heterogeneity of replacement serpentine composition between alh 81002 and nogoya indicates that the aqueous solutions in which the olivine serpentine replacement reactions occurred were of different compositions in the two different cm parent body volumes sampled by alh 81002 and nogoya the more magnesian character of serpentines in nogoya than in alh 81002 indicates that the nogoya aqueous alteration environment was even more highly evolved toward mg rich solutions than the environment indicated by the composition of the serpentine in alh 81002 persistence of primary silicate remnants within centripetal and meshwork serpentine indicates that either the aqueous alteration episodes in the parent body volumes represented by individual meteorites were too short to allow complete replacement of olivine by serpentine or one or more reactants most likely water were completely consumed before the coarse primary silicate was completely replaced seemingly incompatible arguments for and against primary mineral control of serpentine composition during cm chondrite alteration may be reconciled by considering the different grain sizes and reaction timescales that likely existed in different textural settings

probabilistic seismic hazard at mt etna italy the contribution of local fault activity in mid term assessment abstract in this work we tackle the problem of seismic hazard at etna deriving from the recurrent seismogenic activity of local faults by adopting two independent methods based on probabilistic approaches we assess the hazard in terms of macroseismic intensity and represent the occurrence probability calculated for different exposure times both on maps and at fault scale seismic hazard maps obtained by applying the site approach through the sasha code and a new probabilistic attenuation model indicate the eastern flank of the volcano as the most hazardous with expected intensity i exp in 50 years i e the standard exposure time adopted in the seismic regulations ranging from degrees ix to x ems in shorter exposure periods 20 10 5 years values of i exp up to ix are also reached in the same area but they are clearly determined by the earthquakes generated by the timpe fault system in order to quantify the contribution of local seismogenic sources to the hazard of the region we reconstruct the seismic history of each fault and calculate with sasha the probability that earthquakes of a given intensity may be generated in different exposure times results confirm the high level of hazard due to the s tecla moscarello and fiandaca faults especially for earthquakes of moderate intensity i e vi i 0 vii with probabilities respectively exceeding 50 and 20 in 10 years and 30 and 10 in 5 years occurrence probability of major events i 0 viii at the fault scale has also been investigated by statistics on intertimes under stationary assumptions we obtain a probability of 6 8 in 5 years for each structure by introducing the time dependency time elapsed since the last event occurred on each fault through a bpt model we identify the moscarello and s tecla faults as the most probable sources to be activated in the next 5 years 2013 2017 this result may represent a useful indication to establish priority criteria for actions aimed at reducing seismic risk at a local scale

time dependent feldspar dissolution rates resulting from surface passivation experimental evidence and geochemical implications abstract to which extent does the apparent negative correlation reported between silicate weathering rates and time result from the spontaneous physicochemical evolution of the fluid mineral interface to address this question labradorite powders inserted in nylon bags and buried into two different topsoil horizons for four years were subjected to nanoscale characterization of their near surface regions using transmission electron microscopy these characterizations revealed the occurrence of a 30 to 70 nm thick discontinuous amorphous silica rich surface layer assl with a sharp crystalline amorphous interfacial boundary between labradorite and the layer dissolution experiments conducted in mixed flow reactors at ambient temperature and acidic ph demonstrated that the reactivity of fresh and naturally weathered labradorite powders decreased with time with the dissolution rate of fresh powders remaining systematically greater than that of naturally weathered powders all over the duration of the experiments 3 weeks in addition the dissolution rate of all labradorite batches was noticeably lower in solutions containing elevated concentrations of sio2 aq which we attributed to the passivating effect of the assls this suggestion was confirmed with a simple passivation model which enabled to capture i the greater reactivity of fresh powders ii the dependence of the dissolution rate on sio2 aq iii the gradual decline of powder dissolution rate with time and iv the discontinuous occurrence of assls the model further supports that surface passivation could be one of the non exclusive mechanisms that could account for the so called kinetic field lab discrepancy the geochemical implications of the recognition of the passivation mechanism are broad ranging from the need to revisit the kinetic rate laws implemented in geochemical codes to the questioning of the formalism used for determining weathering rates from the study of u series nuclides in soils and weathering profiles

using a mineral lifetime diagram to evaluate the persistence of olivine on mars we present a diagram that shows the effect of ph temperature grain size composition hydrodynamics and the laboratory field discrepancy on the lifetime of olivine grains in weathering environments because the persistence of olivine grains on mars can be used to constrain the duration of liquid water we can use this diagram to predict a range of possible maximum contact times for olivine grains with liquid water before they dissolve away completely depending upon the physicochemical conditions this contact time could range between a few thousand and several million years

biomineralization and global biogeochemical cycles biological activity is a dominant force shaping the chemical structure and evolution of the earth surface environment the presence of an oxygenated atmosphere hydrosphere surrounding an otherwise highly reducing solid earth is the most striking consequence of the rise of life on earth biological evolution and the functioning of ecosystems in turn are to a large degree conditioned by geophysical and geological processes understanding the interactions between organisms and their abiotic environment and the resulting coupled evolution of the biosphere and geosphere is a central theme of research in biogeology biogeochemists contribute to this understanding by studying the transformations and transport of chemical substrates and products of biological activity in the environment biogeochemical cycles provide a general framework in which geochemists organize their knowledge and interpret their data the cycle of a given element or substance maps out the rates of transformation in and transport fluxes between adjoining environmental reservoirs the temporal and spatial scales of interest dictate the selection of reservoirs and processes included in the cycle typically the need for a detailed representation of biological process rates and ecosystem structure decreases as the spatial and temporal time scales considered increase much progress has been made in the development of global scale models of biogeochemical cycles although these models are based on fairly simple representations of the biosphere and hydrosphere they account for the large scale changes in the composition redox state and biological productivity of the earth surface environment that have occurred over geological time since the cambrian explosion mineralized body parts have been secreted in large quantities by biota because calcium carbonate silica and calcium phosphate are the main mineral phases constituting these hard parts biomineralization plays an important role in the global biogeochemical cycles of carbon calcium silicon and phosphorus the chapter starts with introducing the basic concepts of

volcanic risk assessment quantifying physical vulnerability in the built environment abstract this paper presents structured and cost effective methods for assessing the physical vulnerability of at risk communities to the range of volcanic hazards developed as part of the mia vita project 2009 2012 an initial assessment of building and infrastructure vulnerability has been carried out for a set of broadly defined building types and infrastructure categories with the likelihood of damage considered separately for projectile impact ash fall loading pyroclastic density current dynamic pressure and earthquake ground shaking intensities in refining these estimates for two case study areas kanlaon volcano in the philippines and fogo volcano in cape verde we have developed guidelines and methodologies for carrying out physical vulnerability assessments in the field these include identifying primary building characteristics such as construction material and method as well as subsidiary characteristics for example the size and prevalence of openings that may be important in assessing eruption impacts at risk buildings around kanlaon were found to be dominated by timber frame buildings that exhibit a high vulnerability to pyroclastic density currents but a low vulnerability to failure from seismic shaking around fogo the predominance of unreinforced masonry buildings with reinforced concrete slab roofs suggests a high vulnerability to volcanic earthquake but a low vulnerability to ash fall loading given the importance of agriculture for local livelihoods around kanlaon and fogo we discuss the potential impact of infrastructure vulnerability for local agricultural economies with implications for volcanic areas worldwide these methodologies and tools go some way towards offering a standardised approach to carrying out future vulnerability assessments for populated volcanic areas

seismic moment frequency relation for shallow earthquakes regional comparison we determine the parameter values for the seismic moment frequency relation using flinn engdahl s regionalization of global seismicity and the harvard centroid moment tensor data the earthquake size distribution is approximated by the gamma law a version of the gutenberg richter distribution with an exponential taper at the maximum moment there is no statistically significant variation of the fj value the analog of the b value for all seismic regions except for the midocean ridge systems for the latter regions fj 0 93 whereas for all other zones fj 0 63 the maximum moment mxg can be statistically evaluated only for subduction zones treated as a whole mxg 10 21 2 x 10 22 newton m which corresponds to the worldwide mxg value for other regions as well as for single subduction zones mxg is determined by comparing the number of events in each zone with the seismic moment rate calculated on the basis of the nuvel 1 model of plate motion for subduction zones we obtain the estimate of mxg which agrees with the statistical value giving evidence that most tectonic deformation is released by earthquakes we test the hypothesis that no statistically significant variation in mxg occurs in subduction and continent collision zones the hypothesis cannot be rejected with available data for the midocean ridges the mxg estimate cannot be unambiguously determined it is quite possible that the estimate is significantly biased because only a small part of tectonic deformation at the ridges is released by earthquakes these results have importance in evaluating seismic risk and may also lead to developing a physical theory for earthquake generation

chemical weathering studies in relation to geomorphological research in southeastern canada abstract although chemical weathering provides fundamental information relevant to geomorphology the subject has been overlooked during the 20th century in canada this paper provides an overview of the current state of canadian research on chemical weathering in southeastern canada and takes into account three spatial and temporal contexts 1 the formation of bedrock morphology by chemical weathering 2 occurrences characteristics and age of saprolites and 3 contemporary chemical denudation rates long term geomorphological evolution of southeastern canadian landscapes shows that chemical weathering has played an important role an example is taken from the laurentide region of the canadian shield north of montreal quebec the present topography resulted from the stripping of the former weathering mantle and from the probable subsequent modification of the weathering front first by the action of hillslope processes and rivers and then by glaciers before and during plio pleistocene times the present landscape reflects the timing of the formation of erosion surfaces and of the stripping of the paleozoic cover rocks and exposure of the shield since the late seventies several isolated occurrences of saprolite soil profiles have been discovered in eastern canada and prompted a renewal of the study of these materials about the cenozoic evolution of these regions one of the problems in this field of research is the dating of saprolites and their inclusion in a chronostratigraphic framework along with the other cenozoic surficial deposits and landforms because of the multiple factors involved in the development of secondary minerals in saprolites during the course of weathering it is preferable to distinguish the dating of saprolites from the study of their mineralogical and geochemical evolution fortunately several new techniques are becoming available for the absolute dating of surficial deposits and saprolites including the use of cosmogenic radionuclides saprolites provide a strong potential field of research for our understanding of the geological evolution of eastern canada during the cenozoic contemporary weathering and erosion rates are fields of research that have gained increasing interest recently since modeling landscape geochemical response can be applied to various environmental stress situations such as acidification by rain and forest harvesting rock type may be the main factor explaining the large differences between watersheds in fact variability of cation removal in the temperate zone is probably most closely related to flow paths of water investigations at different scales from entire watersheds to slopes to individual pedons highlight the problem in the catamaran brook watershed new brunswick water chemistry is explained by a mix of groundwater and soil solution from the horizons at the base of the floodplain soils geochemical mass balances based on net outputs give little information on the weathering reactions of primary minerals the weathering products or on the nature of the weathering processes that provide the dissolved load of streams mineralogic and petrographic analysis of selected soil pedons are necessary to determine weathering reactions and their role as sources or sinks for bases silica aluminum and iron in the various compartments through which water percolates before it reaches the stream

apparent stress of earthquakes within the shallow subduction zone near kamchatka peninsula apparent stresses of 105 moderate sized magnitude mb from 4 5 to 6 0 shallow earthquakes from the subduction zone near kamchatka peninsula nw pacific were analyzed our results allowed us to formulate the following properties of the earthquake apparent stress for the seismic moment range 1015 to 1018 n m and the focal depth range from 0 to 60 km 1 apparent stresses depend on the fault nature of earthquakes they are greater for thrusts and smaller for normal faults a difference of a factor of 3 2 average apparent stresses were greater in the coastal zone near kamchatka where subducting oceanic and overriding continental plates interact 2 5 mpa and just under the trench axis 2 9 mpa but lower in near trench zones on the western slope of the trench 0 4 mpa this difference is a factor of 6

kaolinisation of granite in an urban environment under natural acid and wet conditions one of the main weathering processes affecting granitic rocks is the kaolinisation of na ca and k feldspar minerals by h2o co2 attack we here report the occurrence of authigenic kaolinite on the surface of an eighteenth century granitic monument covered with sulphate rich weathering patinas we suggest that in humid mesothermic climates anthropogenically derived gaseous so2 from air pollution is responsible for accelerated kaolinisation of feldspars in an urban environment so2 from air pollution thus plays a dual role in the weathering of silicate rocks being responsible for the well known sulphation of ca bearing materials leading to the formation of sulphate salts such as gypsum as well as the weathering of feldspar minerals to kaolinite the kaolinisation reaction weakens the granite microfabric leading to enhanced decay of the building stone

precursory earthquakes of the 1943 eruption of paricutin volcano michoacan mexico abstract paricutin volcano is a monogenetic volcano whose birth and growth were observed by modern volcanological techniques at the time of its birth in 1943 the seismic activity in central mexico was mainly recorded by the wiechert seismographs at the tacubaya seismic station in mexico city about 320 km east of the volcano area in this paper we aim to find any characteristics of precursory earthquakes of the monogenetic eruption though there are limits in the available information such as imprecise location of hypocenters and lack of earthquake data with magnitudes under 3 0 the available data show that the first precursory earthquake occurred on january 7 1943 with a magnitude of 4 4 subsequently 21 earthquakes ranging from 3 2 to 4 5 in magnitude occurred before the outbreak of the eruption on february 20 the s p durations of the precursory earthquakes do not show any systematic changes within the observational errors the hypocenters were rather shallow and did not migrate the precursory earthquakes had a characteristic tectonic signature which was retained through the whole period of activity however the spectra of the p waves of the paricutin earthquakes show minor differences from those of tectonic earthquakes this fact helped in the identification of paricutin earthquakes except for the first shock the maximum earthquake magnitudes show an increasing tendency with time towards the outbreak the total seismic energy released by the precursory earthquakes amounted to 2 10 19 ergs considering that statistically there is a threshold of cumulative seismic energy release 10 17 18 ergs by precursory earthquakes in polygenetic volcanoes erupting after long quiescence the above cumulative energy is exceptionally large this suggests that a monogenetic volcano may need much more energy to clear the way of magma passage to the earth surface than a polygenetic one the magma ascent before the outbreak of paricutin volcano is interpretable by a model of magma filled crack formation proposed by weertman based on seismic data and other field observations

volcanic and seismic hazards at a proposed nuclear power site in central java abstract a nuclear power plant site has been proposed near the base of mount muria a long dormant volcano in indonesia over a period of eight years the volcanic and seismic hazards were investigated first by the contractor and later by a joint team of indonesian geologists and consultants to the international atomic energy agency in order to assess the risk posed by a large volcano for which there is no record of historical eruptions it was necessary to determine the age of the last activity by geological and geochronological means and to deduce from this whether the volcano posed a credible risk similarly because there was no adequate record of seismic activity the seismic hazards were investigated mainly by geological geomorphological and geophysical methods that identified and characterized potential seismogenic sources related to the volcano or tectonic movements i e active capable faults muria volcano has not erupted since about two thousand years ago but the last activity was sufficiently recent to rule out any assumption that the volcano is extinct detailed studies indicated that the proposed site may be vulnerable to the effects of air borne tephra pyroclastic flows and surges debris flows lahars and opening of new vents a more serious factor however was the poor geotechnical properties of the foundation material that required a careful analysis of the seismic hazards although the project was suspended the study proved useful because it provided an opportunity to develop procedures and techniques that could be applied in similar studies elsewhere

the dissolution kinetics of a granite and its minerals implications for comparison between laboratory and field dissolution rates the present study compares the dissolution rates of plagioclase microcline and biotite chlorite from a bulk granite to the dissolution rates of the same minerals in mineral rich fractions that were separated from the granite sample the dissolution rate of plagioclase is enhanced with time as a result of exposure of its surface sites due to the removal of an iron oxide coating removal of the iron coating was slower in the experiment with the bulk granite than in the mineral rich fractions due to a higher fe concentration from biotite dissolution as a result the increase in plagioclase dissolution rate was initially slower in the experiment with the bulk granite the measured steady state dissolution rates of both plagioclase 6 2 1 2 10 11 mol g 1 s 1 and microcline 1 6 0 3 10 11 mol g 1 s 1 were the same in experiments conducted with the plagioclase rich fraction the alkali feldspar rich fraction and the bulk granite based on the observed release rates of the major elements we suggest that the biotite chlorite rich fraction dissolved non congruently under near equilibrium conditions in contrast the biotite and chlorite within the bulk granite sample dissolved congruently under far from equilibrium conditions these differences result from variations in the degree of saturation of the solutions with respect to both the dissolving biotite chlorite and to nontronite which probably was precipitating during dissolution of the biotite and chlorite rich fraction following drying of the bulk granite the dissolution rate of biotite was significantly enhanced whereas the dissolution rate of plagioclase decreased the presence of coatings wetting and drying cycles and near equilibrium conditions all significantly affect mineral dissolution rates in the field in comparison to the dissolution rate of fully wetted clean minerals under far from equilibrium laboratory conditions to bridge the gap between the field and the laboratory mineral dissolution rates these effects on dissolution rate should be further studied