processes spatio temporal factors and measurements of current erosion in the french southern alps a review present erosion in mountainous areas of western europe causes land management problems particularly for areas located downstream of erosion zones except for transalpine roads and ski resorts economic activities no longer require as much space as they did in the past therefore natural reforestation has provided signi cant protection for alpine hillslopes during the 20th century however extreme oods continue to cause severe damage in intra alpine valleys as well as in piedmont and surrounding plains making the study of present water erosion phenomena very important many studies have investigated the processes and factors of water erosion on slopes at both the catchment and plot scales they have focused on rock fragmentation and transportation in different elds the spatial and temporal explanatory variables the consequences downstream ooding sedimentation river bed evolution and the impact of oods in the french alps present erosion has been studied in a variety of outcrops with several recent studies conducted in elds such as marls clayey deposits molasses and moraines these kinds of outcrops are found throughout the alpine massif including an area of special interest on the great jurassic black marl outcrop where badlands are frequently observable geomorphologists and hydrologists have been particularly interested in the strong erosion processes in marls seeking to determine the main patterns and the impact of spatial and temporal factors on soil loss quantities the main climatic factors of rock disaggregation were found to be the freeze thaw and wet dry cycles which destroy rock cohesion and the splash effect of rain the principal site variables are vegetation cover exposure and dip slope angle erosion rates are two or three orders of magnitude higher on bare soils than on pastures northern aspect slopes suffer two to four times as much soil loss as southern aspect slopes finally the angle formed by the slope and the dip also determines different behaviours erosion rates are higher when slope and dip are perpendicular than when they are parallel the transportation agents are mostly debris ows and runoff caused by intense precipitation annual erosion depth in the marls is generally assumed to be substantial up to 10 mm the high value can be explained by the severity of the climatic conditions and the brittleness of the lithology which results in numerous fractures copyright 2003 john wiley sons ltd

detailed chemical analyses of groundwater as a tool for monitoring urban archaeological deposits results from bryggen in bergen abstract urban deposits are amongst the most complex and information rich archaeological sites and may contain artefacts and ecofacts in an excellent state of preservation especially in waterlogged deposits they are however also under severe pressure from building activity and there is a strong need for research on the effects of this activity monitoring is necessary to obtain a better insight into the nature of the deposits and to characterise their preservation conditions and not at least their response to changes the heterogeneity of the deposits can be a major challenge when designing a monitoring program do the deposits consist of innumerable small completely different micro environments or are there some general trends that allow us to look at larger units in the former case a representative monitoring is literally impossible while in the latter case monitoring is more realistic at bryggen in bergen monitoring has been ongoing since 2002 focusing on an area of two hectares that comprises ca 100 000 m3 of archaeological deposits mainly waterlogged the monitoring includes studies of the archaeology modern materials analogous to archaeological artefacts site hydrology and environmental parameters but this article focuses solely on the information obtained from groundwater samples groundwater from 14 dipwells has been analysed using an extended groundwater analysis package covering 17 different chemical species the detailed analyses reveal some interesting correlations between the different species that are discussed in the text for instance strong correlations are found between ammonium potassium alkalinity and the filter depth of the dipwell the correlations show that even if the deposits are heterogeneous the groundwater chemistry is not completely random across the site the results allow us to set up a relatively simple model for the groundwater chemistry at bryggen using three different types of water seawater rainwater and old stagnant groundwater and characterise areas with very good preservation conditions and areas with more questionable conditions comparison is made to a few other monitoring programs from urban archaeological sites that include groundwater or soil pore water chemistry comparison is also made to groundwater studies from modern landfill sites where there is a longer tradition for monitoring and more knowledge about the biogeochemistry of the deposits

archaeological deposits and tunnel constructions simulations of groundwater head at the old wharf of bergen norway abstract the purpose of this study was to examine the impact of tunnel constructions on the steady state groundwater head in the archaeological deposits at the old wharf bryggen of bergen water infiltration permeabilities and boundary conditions were deduced from available data and supplemented by leakage measurements into the existing railway tunnel located upstream of the bryggen area the pore water in the deposits at bryggen has different origins viz precipitation leakage from drainage systems infiltration of seawater infiltration via the bedrock and based on these observations a 2d horizontal and a 2d vertical numerical model were constructed where the seawater was the boundary at one side of the model and the groundwater divide at the other side given estimates of bedrock permeability and steady state infiltration rate it was possible to calculate groundwater heads in the sediments at bryggen that were consistent with observations assuming that all the water percolating into the sediments flow through fractures in the bedrock by this extreme assumption a maximum sensitivity of the relation between groundwater flux in the bedrock and the groundwater level in the archaeological deposits was achieved after simulation of the natural groundwater level i e without any artificial extraction of water in the catchment the impact of the water leakage into the existing tunnels was calculated given the relatively rough estimates of water leakage into the existing tunnels 4 l day meter of tunnel the calculated decline of the groundwater head in the archaeological deposits was less than 1 of the natural groundwater level

gully morphology hillslope erosion and precipitation characteristics in the appalachian valley and ridge province southeastern usa this study investigates gully erosion on an east tennessee hillslope in a humid subtropical climate the study area is deeply gullied in ultisols acrisol according to the world reference base for soil with thirty years of undisturbed erosional history with no efforts to correct or halt the erosion the objectives are 1 to examine how different gully morphologies channel sidewall and interfluve behave in response to precipitation driven erosion and 2 to identify an appropriate temporal scale at which precipitation driven erosion can be measured to improve soil loss prediction precipitation parameters total accumulation duration average intensity maximum intensity extracted from data collected at an on site weather station were statistically correlated with erosion data erosion data were collected from erosion pins installed in four gully systems at 78 locations spanning three different morphological settings interfluves channels and sidewalls kruskal wallis non parametric tests and mann whitney u tests indicated that different morphological settings within the gully system responded differently to precipitation p 0 00 for channels and sidewalls regression models relating erosion and precipitation parameters retained antecedent precipitation and precipitation accumulation or duration r2 0 50 p 0 00 for channels r2 0 28 p 0 00 for sidewalls but precipitation intensity variables were not retained in the models for interfluves less than 20 of variability in erosion data could be explained by precipitation parameters precipitation duration and accumulation including antecedent precipitation accumulation were more important than precipitation intensity in initiating and propagating erosion in this geomorphic and climatic setting but other factors including mass wasting and eolian erosion are likely contributors to erosion high correlation coefficients between aggregate precipitation parameters and erosion indicate that a suitable temporal scale to relate precipitation to soil erosion is the synoptic time scale this scale captures natural precipitation cycles and corresponding measurable soil erosion

imaging of volcanic activity on jupiter s moon io by galileo during the galileo europa mission and the galileo millennium mission the solid state imaging ssi instrument provided the first high and medium resolution views of io as the galileo spacecraft closed in on the volcanic body in late 1999 and early 2000 while each volcanic center has many unique features the majority can be placed into one of two broad categories the promethean eruptions typified by the volcanic center prometheus are characterized by long lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years of decades in contrast pillanian eruptions are characterized by large pyroclastic deposits and short lived but high effusion rate eruptions from fissures feeding open channel or open sheet flows both types of eruptions commonly have 100 km tall bright so2 rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas

3d modelling of geological and anthropogenic deposits at the world heritage site of bryggen in bergen norway the landscape of many historic cities and the character of their shallow subsurface environments are defined by a legacy of interaction between anthropogenic and geological processes anthropogenic deposits and excavations result from processes ranging from archaeological activities to modern urban development hence in heritage cities any geological investigation should acknowledge the role of past and ongoing human activities while any archaeological investigation should be conducted with geological processes in mind in this paper it is shown that 3d geological and anthropogenic models at different scales can provide a holistic system for the management of the subsurface it provides a framework for the integration of other spatial and process models to help assess the preservation potential for buried heritage such an integrated framework model is thus contributing to a decision support system for sustainable urban re development and regeneration in cities while preserving cultural heritage a collaborative approach is proposed to enhance research and implementation of combined geological and archaeological modelling for sustainable land use planning and heritage preservation using york and bryggen as prime examples this paper presents the status of 3d framework modelling at bryggen in norway as an example

the influence of geometry on the ascent of magma in open fissures during steady eruption the flow conditions emitted mass flux exit velocity and exit pressure depend on the geometry of the conduit in which the eruption occurs this dependence is examined for the onedimensional isothermal ascent of a homogeneous basaltic magma with an aqueous volatile phase and newtonian rheology by fixing the geometry of the feeding fissure the mass flux flowing in steady conditions can be determined at any depth as well the magma pressure and vertical velocity flow behaviour is analysed for three fissure shapes constant width slowly upward narrowing and lenticular in all the cases examined the magma arrives at the earth s surface with a pressure greater than atmospheric the results are compared with those obtained when a lithostatic pressure gradient is assumed for the magma column some speculations are made moreover about the change in eruption style if conduit geometry varies during a non steady phase

hydrogeomorphic processes in a steep debris flow initiation zone 1 many debris flows initiate in steep channels 20 degrees yet studies have focused on lower gradient streams where failure is controlled by water height above channel deposits multiple debris flows in a steep channel in ohya landslide central japan were linked to infilling processes i e freeze thaw and dry ravel and partial saturation of accumulated sediment because of very active geomorphic processes in this catchment 39 debris flows were observed in the past 6 yr pre and post event imagery indicates selective transport of finer materials during most debris flows that comprise saturated and unsaturated flows however fluvial sediment processes important in relation to debris flow initiation in gentler channels were minimal critical conditions for the movement of such unsaturated materials are derived by equating shear stress with solid friction of the channel bed

seasonal patterns of runoff and erosion responses to simulated rainfall in a badland area in mediterranean mountain conditions vallcebre southeastern pyrenees regolith surface characteristics and response were examined over a three year period in a badland area in a mediterranean middle mountain zone near vallcebre eastern pyrenees preliminary work carried out in this area indicated clear seasonal patterns of regolith properties driven by frost heaving in winter and crusting and erosion in the rest of the year rainfall simulations were performed with a small portable nozzle simulator in order to study seasonal changes in runoff generation erosion rates and raindrop effect on bulk density changes the results showed large seasonal variations in runoff and erosion responses in ltration rates after runoff start were correlated with precipitation depth before runoff start runoff generation was therefore related to regolith saturation only to a very limited extent erosion rates were more controlled by runoff rates than by the weakness of regolith against raindrop splash and sediment grain size increased with concentration the combined role of antecedent regolith moisture and bulk density explained most of the seasonal variability in in ltration bulk density changes during rainfall and erosion rates but some seasonal differences in sediment detachability were not explained by these variables and may be attributed to changes in roughness overall runoff and erosion responses were relatively stable during spring and autumn whereas wide variations in in ltration rates and sediment detachment occurred in winter and summer respectively experiments conducted in a single season would have produced poorly representative if not erroneous results copyright 2004 john wiley sons ltd

temporal and spatial variation of infilling processes in a landslide scar in a steep mountainous region japan the duration of the soil depth recovery needed for reoccurrence of shallow colluvial landslides at a given site in humid regions is much longer than the return period of rainfall needed to generate sufficient pore water pressure to initiate a landslide knowledge of the rate of change in soil depth in landslide scars is therefore necessary to evaluate return intervals of landslides spatial variation in sediment transport at the kumanodaira landslide scar in central japan was investigated by field observations spatial distribution of the rate of change in soil depth was estimated using sediment transport data and geographic information system gis analysis observations revealed that the timing of sediment transport differed for shallow and deep soil layers near surface sediment transport mostly dry ravel and some shallow soil creep at depths 0 05 m measured in sediment traps was active in winter and early spring and was affected by freezing thawing soil creep of subsoil i e 0 05 m monitored by strain probes was active in summer and autumn when precipitation was abundant near surface sediment flux was estimated by a power law function of slope gradient deeper soil creep was more affected by relative location to the landslide scar which influences soil depth than by slope gradient our study indicated that the rate of soil depth recovery is high just below the head scarp of the landslide abrupt changes in the longitudinal slope topography immediately above within and just below the head scarp became smoother with time due to degradation proximate to the landslide head scarp and flanks as well as aggradation just below the head scarp copyright 2014 john wiley sons ltd

near vertical supersonic and shock free gas magma flow at ionian volcanoes application to pillan in 1997 the pillan volcano on io was home to a fierce volcanic eruption that emplaced extensive lava flows and a circular plume deposit the gas magma flow issuing from the unresolved vent region appeared to form an almost vertical jet we consider steady eruptions of gas and magma and take the vent to be either a fissure or a point source in the fissure scenario the upper conduit flow must reach mach 1 in the 25 75 m depth range to produce the vent velocities of 550 600 m s that are required to explain the observed plume heights conduit wall deflections in the range 20 30 degrees from vertical values referring to the upper meter of the conduit and similar to 26 30 by mass of incorporated crustal so2 are also needed in the point source scenario sonic flow conditions and similar velocities are achieved in the depth range 350 500 m for similar conduit wall deflections and gas mass proportions in the erupting mixture probably the source of the 140 km high plume imaged in 1997 was either a similar to 6 11 m wide fissure active for similar to 14 40 km along strike or a circular vent similar to 125 216 m in diameter the former scenario being preferred finally a shock free conduit flow is more likely to sustain a tall lava fountain in a near vacuum

the fate of pyroclasts produced in explosive eruptions on the asteroid 4 vesta we evaluate the consequences of explosive activity having taken place during volcanic eruptions on the differentiated asteroid 4 vesta which is the likely parent body of the howardite eucrite diogenite hed meteorites for a wide range of magma volatile contents we calculate the eruption speeds and subsequent trajectories of the pyroclastic magma droplets produced by considering the size distribution and eruption speeds of the droplets and the mass fluxes at which they are ejected we show that under all realistic circumstances the droplets will have formed lava fountains that were extremely optically dense as a result virtually all of the droplets will have reached the surface having suffered a negligible amount of radiative cooling and will have coalesced into lava ponds feeding lava flows typically 1 of the pyroclasts will have undergone enough cooling to allow them to accumulate into a recognizable fall deposit consisting of unwelded or partly welded volcanic glass beads this result is consistent with the apparent absence of identifiable pyroclastic material in the hed and other types of differentiated meteorites

seasonal changes in the sediment flux on steep hillslopes in a humid diurnal frost environment mountain hillslopes are generally shaped by a combination of various types of sediment transport processes e g surface erosion soil creep and dry ravel which can occur simultaneously in the same area since sediment transport is generally affected by multiple microclimatic factors such as heavy rainfall and changes in ground temperature the types of predominant sediment transport processes vary by season we conducted field observations in the southern japanese alps in the period from 2009 to 2013 using sediment traps and time lapse cameras to investigate the seasonal changes in the type and flux of hillslope sediment transport on steep mountains in which both rainfall and diurnal freeze thaw triggered sediment transport in winter and early spring sediment transport via diurnal freeze thaw soil creep and dry ravel was highly active whereas rainfall induced soil creep and selective transport by overland flow were active in summer and autumn when precipitation is abundant average sediment flux of 0 033 and 0 074 kg m 1 day 1 respectively sediment flux was spatially variable and was affected by the form of the slope sediment flux on the concave slope was higher than on the ridge shaped slope during both freeze thaw and rainfall periods sediment flux on an old landslide exceeded that in second growth forest regardless of the slope shape temporal changes in the sediment flux were not completely synchronized among monitoring plots and were affected by slope shape grain size and episodic sediment supply events such as release of sediment from woody debris copyright 2016 john wiley sons ltd

a model for large scale volcanic plumes on io implications for eruption rates and interactions between magmas and near surface volatiles 1 volcanic plumes deposit magmatic pyroclasts and so2 frost on the surface of io we model the plume activity detected by galileo at the pillan and pele sites from 1996 to 1997 assuming that magmatic eruptions incorporate liquid so2 from near surface aquifers intersecting the conduit system and that the so2 eventually forms a solid condensate on the ground the temperature and pressure at which deposition of solid so2 commences in the ionian environment and the radial distance from the volcanic vent at which this process appears to occur on the surface are used together with observed vertical heights of plumes to constrain eruption conditions the temperature pressure and density of the gas magma mixtures are related to distance from the vent using continuity and conservation of energy similar eruption mass fluxes of order 5 107 kg s 1 are found for both the pillan and the pele plumes the pele plume requires a larger amount of incorporated so2 29 34 mass than the pillan plume up to 6 mass implied vent diameters range from 90 m at pillan to 500 m at pele the radial extents of the optically dense isothermal incandescent parts of the eruption plumes immediately above the vents are 100 m at pillan and 1300 m at pele gas pressures in the vents are 20 kpa at pillan and 2 kpa at pele and the eruption conditions appear to be supersonic in both cases though only just so at pele

io heat flow from small volcanic features abstract we identify nine new faint thermal sources on io via color ratio images constructed from relatively high spatial resolution galileo nims data acquired late in the mission all of these identifications are associated with small dark paterae we utilize nims data to quantify their volcanic thermal emission as 0 53 1012 w or 0 5 of io s total heat flow in addition we refine our previous estimates of the thermal emission from 47 hot spots and highlight several hot spots within the amirani flow field small dark paterae still out number faint close to the limit of detection hot spots identified in high spatial resolution multi wavelength nims data in particular we point out 24 small dark paterae that were scanned by nims at resolutions down to 17 km pixel but had no detectable volcanic thermal emission all dark paterae are expected to have some volcanic thermal emission but the small size and finite number of detectable faint sources limit their contribution to the total heat flow on io compared to small paterae small dark flows are more numerous but must have significantly lower surface temperatures finally we update and summarize our results for the global heat flow on io due to 242 recently active volcanic features including other dark paterae as well as large dark flows the volcanic thermal emission from known hot spots undetected scanned dark patera and outbursts can account for only 56 2 1012 w or 54 of io s total heat flow approximately 49 1012 w or 46 of io s heat flow remains an enigma

monsoonal hillslope processes determine grain size specific suspended sediment fluxes in a trans himalayan river sediments in rivers record the dynamics of erosion processes while bulk sediment fluxes are easily and routinely obtained sediment caliber remains underexplored when inferring erosion mechanisms yet sediment grain size distributions may be the key to discriminating their origin we have studied grain size specific suspended sediment fluxes in the kali gandaki a major trans himalayan river two strategically located gauging stations enable tracing of sediment caliber on either side of the himalayan orographic barrier the data show that fine sediment input into the northern headwaters is persistent while coarse sediment comes from the high himalayas during the summer monsoon a temporally matching landslide inventory similarly indicates the prominence of monsoon driven hillslope mass wasting thus mechanisms of sediment supply can leave strong traces in the fluvial caliber which could project well beyond the mountain front and add to the variability of the sedimentary record of orogen erosion

linking variable explosion style and magma textures during 2002 at stromboli volcano italy microtextural characteristics of fresh ejecta from stromboli volcano were examined from three periods of differing eruption style and intensity in 2002 activity shifted from relatively weak and infrequent ash charged explosions during january through may into two broad cycles of waxing activity in june through late september and late september through december followed by the onset on 28 december of the 2002 2003 effusive eruption analyzed sets of lapilli from may september october and 28 december show contrasts in the physical properties of magma resident in the shallow conduit during this range of activity three distinct textures are observed among the analyzed pyroclasts low density ld with an abundance of subspherical bubbles the presence of large irregularly shaped bubbles and a light to transparent glass matrix transitional texture tt with an intermediate number of subspherical bubbles a high frequency of large irregularly shaped bubbles and a honey colored glass matrix and high density hd with sparse relatively small bubbles conspicuous large irregular bubbles and a dark glass matrix observational and quantitative data density vesicle size indicate that these textures are linked through variable residence time in stromboli s shallow conduit with an ongoing evolution from ld to hd magma calculations suggest that residual ld magma will evolve to hd texture in a period of hours to days contrasting amounts of the ld tt and hd magmas are present in each sample with the most tt in may the most ld in september october and the most hd in december this implies that the shallow magma had a different rheology at each collection period the viscosity of ld and hd magmas are calculated to be in the range of 2 000 to 2 600 and 3 000 to 5 000 pa s respectively which with their changing proportions must have implications for rates of bubble slug ascent and processes of fragmentation this study suggests that an increasing maturity of magma in stromboli s shallow conduit with resultant increase in viscosity feeds back to reduce the intensity of explosions whereas a steady flux of ld magma favors more powerful explosions

active volcanism on io as seen by galileo ssi abstract active volcanism on io has been monitored during the nominal galileo satellite tour from mid 1996 through late 1997 the solid state imaging ssi experiment was able to observe many manifestations of this active volcanism including 1 changes in the color and albedo of the surface 2 active airborne plumes and 3 glowing vents seen in eclipse about 30 large scale tens of kilometers surface changes are obvious from comparison of the ssi images to those acquired by voyager in 1979 these include new pyroclastic deposits of several colors bright and dark flows and caldera floor materials there have also been significant surface changes on io during the galileo mission itself such as a new 400 km diameter dark pyroclastic deposit around pillan patera while these surface changes are impressive the number of large scale changes observed in the four months between the voyager 1 and voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive there are two reasons why this was not actually the case first it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years second it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of io s surface the plume monitoring has revealed 10 active plumes comparable to the 9 plumes observed by voyager one of these plumes was visible only in the first orbit and three became active in the later orbits only the prometheus plume has been consistently active and easy to detect observations of the pele plume have been particularly intriguing since it was detected only once by ssi despite repeated attempts but has been detected several times by the hubble space telescope at 255 nm pele s plume is much taller 460 km than during voyager 1 300 km and much fainter at visible wavelengths prometheus type plumes 50 150 km high long lived associated with high temperature hot spots may result from silicate lava flows or shallow intrusions interacting with near surface so2 a major and surprising result is that 30 of io s volcanic vents glow in the dark at the short wavelengths of ssi these are probably due to thermal emission from surfaces hotter than 700 k with most hotter than 1000 k well above the temperature of pure sulfur volcanism active silicate volcanism appears ubiquitous there are also widespread diffuse glows seen in eclipse related to the interaction of energetic particles with the atmosphere these diffuse glows are closely associated with the most active volcanic vents supporting suggestions that io s atmopshere is dominated by volcanic outgassing globally volcanic centers are rather evenly distributed however 14 of the 15 active plumes seen by voyager and or galileo are within 30 of the equator and there are concentrations of glows seen in eclipse at both the sub and antijovian points these patterns might be related to asthenospheric tidal heating or tidal stresses io will continue to be observed during the galileo europa mission which will climax with two close flybys of io in late 1999

the geothermal gradient of io consequences for lithosphere structure and volcanic eruptive activity we solve numerically the equations describing the transfer of heat through the lithosphere of io by a mixture of conduction and volcanic advection as proposed by o reilly and davies o reilly t c davies g f 1981 geophys res lett 8 313 316 removing the requirement that average material properties must be used as expected the dominance of advective heat transfer by volcanic eruptions means that io s geothermal gradient well away from volcanic centres is very small of order 1 k km 1 this result is independent of any reasonable assumptions about the radiogenic heating rate in the lithosphere the lithosphere temperature does not increase greatly above the surface temperature until the base of the lithosphere is approached except in limited areas around shallow magma bodies as a consequence solid volatile sulphur compounds mobilized by volcanic processes and re deposited on the surface of io commonly remain solid until they reach great depths as they are progressively buried by ongoing activity for current estimates of the volcanic heat transfer rate melting of so2 does not begin until a depth of 20 km and sulphur remains solid to a depth of 26 km in a 30 km thick lithosphere rising magmas can incorporate fluids from these deep sulphur compound aquifers and we quantify the major influence that this can have on the bulk density of the magma and hence the resulting possible intrusion and eruption styles

lava fountains from the 1999 tvashtar catena fissure eruption on io implications for dike emplacement mechanisms eruption rates and crustal structure the first direct evidence that patterns of basaltic eruptive activity may be very similar on io and earth was seen on november 26 1999 when the solid state imaging system on board the galileo spacecraft obtained high resolution images of a fissure eruption taking place in one of the calderas of the tvashtar catena complex we analyzed the dynamics of the fissure eruption from the morphology of the lava fountains and pyroclastic deposits and derived an estimate of the eruption rate our best estimate of the volume eruption rate per unit length of fissure lies in the range 0 7 to 7 m3 s 1 m 1 and multiplying this rate by the fissure length of 25 km yields a total volume eruption rate of magma of 2 104 to 2 105 m3 s 1 the upper end of the inferred eruption rate is very close to the upper end of the range of eruption rates observed or inferred for fissure eruptions on earth theoretical models of the possible dike systems feeding the fissure show that for eruptions of positively buoyant magma the elastic properties of rocks are such that a magma flux of 6 to 7 m3 s 1 m 1 is the largest value that can ever be realized in such eruptions this limiting value being independent of planetary gravity and thus the same on all silicate bodies the eruption rate inferred for tvashtar can also be achieved by a negatively buoyant magma but in that case the source depth cannot be much greater than a few tens of kilometers we find that some eruptive events are consistent with the effusion of magmas which are buoyant relative to the crust whereas others appear to involve magmas which are not this implies that the distribution of crustal volatiles is laterally very inhomogeneous our analyses suggest that the depths from which magmas make their final ascent to the surface of io are generally of order tens rather than hundreds of kilometers

the influence of freeze thaw cycles and soil moisture on aggregate stability of three soils in norway abstract winter conditions with seasonally frozen soils may have profound effects on soil structure and erodibility and consequently for runoff and erosion such effects on aggregate stability are poorly documented for nordic winter conditions the purpose of this study was to quantify the effect of variable freeze thaw cycles and soil moisture conditions on aggregate stability of three soils silt structured clay loam clay a and levelled silty clay loam clay b which are representative of two erosion prone areas in southeastern norway a second purpose was to compare aggregate stabilities measured by the norwegian standard procedure rainfall simulator and the more widely used wet sieving procedure surface soil was sampled in autumn field moist soil was sieved into the fraction 1 4 mm and packed into cylinders the water content of the soil was adjusted corresponding to matric potentials of 0 75 2 and 10 kpa the soil cores were insulated and covered and subjected to 0 1 3 or 6 freeze thaw cycles freezing at 15 c for 24 h and thawing at 9 c for 48 h aggregate stability was measured in a rainfall simulator all soils and a wet sieving apparatus silt and clay b the rainfall stability of silt was found to be significantly lower than of clay a and clay b clay a and clay b had similar rainfall stabilities even though it was expected that the artificially levelled clay b would have lower stability freezing and thawing decreased the rainfall stability of all soils but the effect was more severe on the silt soil there was no evident effect of water content on the stability probably due to experimental limitations the same effects were observed for wet sieved soil but the wet sieving resulted in less aggregate breakdown than the rainfall simulator rainfall impact seemed to be more detrimental than wet sieving on more unstable soil that is on silt soil and soil subjected to many freeze thaw cycles such conditions are expected to occur frequently during field conditions in unstable winters

keck observations of eruptions on io in 2003 2005 abstract we report observations of four energetic volcanic eruptions on io at tupan patera on ut 8 march 2003 tung yo patera on ut 28 may 2004 sui jen patera on ut 30 may 2004 and south of babbar patera on ut 31 may 2005 the tung yo sui jen and south of babbar paterae eruptions are in locations where no activity had been seen before our observations were obtained at near infrared wavelengths 1 2 4 7 m with the 10 m keck telescope equipped with adaptive optics we report single and two temperature blackbody fits as well as single component and dual component io flow model ifm fits davies 1996 icarus 124 45 61 to all four eruptions where applicable we use 2 m and 5 m radiant fluxes the 2 5 m radiant flux ratio and radiant flux density of each thermal source to constrain the likely style of volcanic eruption all eruptions are characterized by a high temperature ifm component ranging from 1475 to 900 k from a relatively small area

the maritime subantarctic a distinct periglacial environment recent research on slope processes and weathering on marion island has highlighted distinctive attributes of the maritime subantarctic periglacial environment compared to other periglacial environments this is reflected morphologically by sorted stripe characteristics and stratified solifluction forms but the wind factor and low diurnal temperature range also results in differences with other diurnal frost environments its hyper maritime setting at low mean annual temperatures results in very high frost cycle frequencies with associated effectiveness in surface sediment transport and patterned ground development in addition a high frequency of wetting and drying cycles is observed in rocks small seasonal temperature ranges and steep temperature profiles indicate a high sensitivity to climate change in the subantarctic as reflected in a rich relict periglacial record on most islands this sensitivity appears absent in high tropical environments of low annual temperature range

soil moisture and texture controls of selected parameters of needle ice growth needle ice was grown in the laboratory to determine the limits of soil moisture and texture on the growth of needle ice as the percentage of fines in the soil increases the lower limit of soil moisture required for growth decreases and may be defined by a linear boundary the efficiency of conversion of soil water to needle ice in soil samples used peaked at about 16 per cent soil fines contrary to expectations the finer textured soils produced significantly thicker ice crystals quantity of soil lifted by needle ice was related to ice height the ice mass to atmospheric void ratio soil texture and moisture and soil surface roughness however no definite quantitative relationships could be determined a test to determine if needle ice is selective in the grain sizes of particles lifted suggested no selectivity

runoff and erosion processes after a forest fire in mount carmel a mediterranean area in the mediterranean forest area of israel fires increase runoff and sediment yield rates relative to undisturbed forested land the september 1989 fire covered an area of 4 km2 in the main recreation area of mount carmel a typical mediterranean forest area the lithology is chalk and limestone and about 40 of the burnt area has steep slopes exceeding 30 three study plots were established in burnt and unburnt areas plots were located on 100 300 m2 areas with different slope exposures runoff and sediments were collected after each storm by a collector system a hydrometric station was established draining an area of 1 km2 in the burnt zone rainfall was measured by two recorders and several rain gauges at the experimental sites in the first rainfall season after the fire runoff and sediment yield were 500 and 100 000 times higher respectively in the burnt areas rainfall intensity is a dominant factor in runoff and sediment yield rates in the measured basin total runoff in the first year was 1 6 revegetation recovery of the area was rapid as shown by the results from the second season runoff decreased by one order of magnitude from an average of 10 mm to 1 5 mm sediment yield decreased by two orders of magnitude from 1200 g m 2 to 10 g m 2 the third season 1991 1992 was an exceptionally rainy year and therefore runoff and sediment yield increased but to less than in the first year runoff and sediment yield are related to vegetation cover rainfall intensity soil properties slope steepness and exposure and fire intensity logging activities after fire increase sediment yields through its effects on vegetation cover and soil fire severity increases the potential for erosion

thermal signature eruption style and eruption evolution at pele and pillan on io the galileo spacecraft has been periodically monitoring volcanic activity on io since june 1996 making it possible to chart the evolution of individual eruptions we present results of coanalysis of near infrared mapping spectrometer nims and solid state imaging ssi data of eruptions at pele and pillan especially from a particularly illuminating data set consisting of mutually constraining near simultaneous nims and ssi observations obtained during orbit c9 in june 1997 the observed thermal signature from each hot spot and the way in which the thermal signature changes with time tightly constrains the possible styles of eruption pele and pillan have very different eruption styles from september 1996 through may 1999 pele demonstrates an almost constant total thermal output with thermal emission spectra indicative of a long lived active lava lake the nims pillan data exhibit the thermal signature of a pillanian eruption style a large vigorous eruption with associated open channel or sheet flows producing an extensive flow field by orbit c10 in september 1997 the high mass eruption rate high liquidus temperature at least 1870 k eruption at pillan is the best candidate so far for an active ultramafic magnesium rich komatiitic flow on io a style of eruption never before witnessed the thermal output per unit area from pillan is however consistent with the emplacement of large open channel flows magma temperature at pele is 1600 k if the magma temperature is 1600 k it suggests a komatiitic basalt composition the power output from pele is indicative of a magma volumetric eruption rate of 250 to 340 m3 s 1 although the pele lava lake is considerably larger than its terrestrial counterparts the power and mass fluxes per unit area are similar to active terrestrial lava lakes

the summer 1997 eruption at pillan patera on io implications for ultrabasic lava flow emplacement galileo data and numerical modeling were used to investigate the summer 1997 eruption at pillan patera on io this event now defined as pillanian eruption style keszthelyi et al this issue included a high temperature 1600 c possibly ultrabasic 140 km high plume eruption that deposited dark orthopyroxene rich pyroclastic material over 125 000 km2 followed by emplacement of dark flow like material over 3100 km2 to the north of the caldera we estimate that the high temperature energetic episode of this eruption had a duration of 52 167 days between may and september 1997 with peak eruption temperatures around june 28 1997 galileo 20 m pixel 1 images of part of the pillan flow field show a widespread rough pitted surface that is unlike any flow surface we have seen before we suggest that this surface may have resulted from 1 a fractured lava crust formed during rapid low viscosity lava surging perhaps including turbulent flow emplacement 2 disruption of the lava flow by explosive interaction with a volatile rich substrate or 3 a combination of 1 and 2 with or without accumulation of pyroclastic materials on the surface well developed flow lobes are observed suggesting that this is a relatively distal part of the flow field shadow measurements at flow margins indicate a thickness of 8 10 m we have modeled the emplacement of putative ultrabasic flows from the summer 1997 pillan eruption using constraints from new galileo data results suggest that either laminar sheet flows or turbulent channelized flows could have traveled 50 150 km on a flat unobstructed surface which is consistent with the estimated length of the pillan flow field 60 km our modeling suggests low thermal erosion rates 20 m erosion channels was unlikely especially distal to the source we calculate a volumetric flow rate of 2 7 103 m3 s 1 which is greater than those for typical mauna loa kilauea flows but comparable to those for the 1783 laki eruption and the inferred flow rates of the roza flows in the columbia river flood basalts the differences in ultrabasic eruption styles on earth and io appear to be controlled by the different eruption environments plumes at sites of ultrabasic eruptions on io suggest strong magma volatile interactions on a low gravity body lacking an atmosphere whereas the geology at sites of komatiite eruptions on earth suggest mostly submarine emplacement of thick flows with a pronounced lack of subaerial explosive activity