formation of an a ā lava delta insights from time lapse multibeam bathymetry and direct observations during the stromboli 2007 eruption five consecutive multibeam bathymetries collected before during and after the 2007 stromboli eruption combined with visual inspections allowed us to document the morphological evolution of an a lava fed delta and to reconstruct the main processes acting during its submarine emplacement the 2007 stromboli delta extended down to 600 m water depth and covered an area of 420 103 m2 with a maximum thickness of 65 m and a total estimated volume of 7 106 m3 i e three times larger than its subaerial counterpart the lava delta grew mainly through the emplacement of discrete lobes about 50 150 m in size lobes were fed from point sources along the paleoshoreline and their subaqueous pathways seem to be mainly controlled by the submarine morphology with flows mostly filling in depressions left by previous lobes the main controlling factors on the lobe morphology and thickness are the effusion rates and the pre eruption morphology i e the geometry and gradients of the basal surface data also shows that sudden slope failure of portions of the submarine delta may occur simultaneously with accretion implying that a significant part of the delta material can be transported to greater depths by submarine gravity flows the present study is relevant for future monitoring and hazard assessment during the growth of active lava fed deltas as well as for a better interpretation of ancient volcaniclastic successions inland

volcanic investigations of the puna ridge hawai i relations of lava flow morphologies and underlying slopes abstract previous investigators have demonstrated that submarine lava flow morphologies are the result of a complex interplay between lava rheology effusion rate and underlying slope here we specifically investigate the relation between underlying slope and submarine lava flow morphology along three study sites of the puna ridge kilauea volcano hawai i using electronic still camera esc images and detailed bathymetry collected by argo ii we can compare the lava morphology and the associated underlying slope our results indicate that rubble is most common on the steepest slopes 25 and that pillowed and lobate flows dominate on slopes 20 sheet flows were only seen on relatively shallow slopes 15 these observations disagree with the results obtained from previous laboratory analog experiments suggesting that the laboratory results are directly applicable for lavas emplaced on relatively low

underwater observations of active lava flows from kilauea volcano hawaii underwater observation of active submarine lava flows from kilauea volcano hawaii in march june 1989 revealed both pillow lava and highly channelized lava streams flowing down a steep and unconsolidated lava delta the channelized streams were 0 7 1 5 m across and moved at rates of 1 3 m s the estimated flux of a stream was 0 7 m 3 s jets of hydrothermal water and gas bubbles were associated with the volcanic activity the rapidly moving channelized lava streams represent a previously undescribed aspect of submarine volcanism

deposition of harmattan dust and its influence on base saturation of soils in northern ghana ferruginous soils formed from volta shale deposits in northern ghana are highly weathered have high iron and aluminium oxide contents and a mineralogy dominated by quartz and low activity clays with low effective cec despite their advanced weathering state base saturation values of top soils are generally above 80 and deficiencies of basic cations are uncommon we postulated that the annual deposition of dust from the sahara carried by the harmattan weather system may be responsible for the high base saturation therefore we collected dust material for two entire dry seasons at nyankpala surrounded by highly weathered volta shale deposits and during several events of harmattan and local dust storms at bolgatanga surrounded by a variety of parent materials long distance harmattan dust had a clearly finer particle size distribution than dust collected during local storms but angularity and evidence of weathering on dust particles did not distinguish dust from different sources in bolgatanga soils contained unweathered minerals derived from local parent materials and both local storm and harmattan dust contained large amounts of bases significant amounts of micas and feldspars and k contents up to 3 in the dust collected at nyankpala showed harmattan dust to be the source of k and other bases found on volta shale soils short distance dust in nyankpala was mostly quartz and vegetation ashes dust deposition during one harmattan season at nyankpala amounted to about 15 g m 2 and carried a total of 140 400 300 and 60 mg m 2 of mg ca k and na respectively these amounts could account for the high base saturation of the low cec in volta shale soils

airborne dust and its significance to soils abstract movement of mineral dust by the atmosphere has been underway for ages but efforts to assess its magnitude and significance have come largely in the last century attempts to identify and understand effects of the dust on soils are even more recent mostly in the last 30 years airborne movements have several forms dust is transported by large storms that can be spectacular dust is also moved by smaller pulses and in a rather continuous flux most movement is within continents or from continents to nearby oceans but fine dust fine silt and clay is carried from one continent to another prime sources of the dust are the deserts and semi arid regions of the world for example large quantities of dust are carried out of the sahara every year quantities of dust carried by individual pulses from the small ones to the massive storms extend from a few thousand to 150 million metric tons during the course of a year the total quantities can be large one example is an estimate that on the average 770 million metric tons originating in the western united states are carried 2300 km each year that amount would add roughly 3000 kg ha 1 yr 1 to soils between the rocky mountains and the mississippi river small pulses and the near continuous flux add between 100 and 200 kg ha 1 yr 1 to soils of the eastern united states on the average comparable quantities are being added to soils in other parts of the world as well airborne accessions of dust have a variety of effects in soil development and on soils after they have been formed dust dominates processes of genesis in a few soils affects horizon differentiation appreciably in many more is a primary source of constituents essential to some horizons and layers in a number of soils provides the bulk of the material for silty surface horizons in many soils and can contribute supplies of nutrient elements for plants examples of all such effects are covered in this review first among these effects to be recognized even though not understood were the silty surface layers that failed to match underlying horizons later recognized was airborne dust as a source of calcium carbonate for calcic horizons that the dust could add significant quantities of nutrient elements as for example south of the sahara came into the picture even later the beneficial effects of airborne dust to many soils raises an interesting question is the dust more or less useful in its new location than it was in its source area an adequate answer to that question would provide an improved basis for assessing the effects of wind erosion

desert loess versus glacial loess quartz silt formation source areas and sediment pathways in the formation of loess deposits abstract pathways are presented which show the proposed sequence of events involved in the formation of loess deposits both hypothetical deposits and those of central china hungary nigeria and tunisia these pathways illustrate the potential role of and inter relationships between a variety of silt generating mechanisms in the formation of loess using these pathways the existence of desert loess is discussed and it is concluded that this depends on how the terms glacial loess and desert loess are applied if desert loess is taken either to signify nonglacial mechanisms of silt production or to characterise the environment from which aeolian entrainment took place then desert loess is a very real and widely distributed deposit however if the term glacial loess is used to refer to the global climatic regime under which the loess deposit has formed rather than the geomorphic mechanisms responsible for silt generation then desert loess would not be an appropriate term for the classification of loess deposits it is suggested that classifying loess deposits with reference to the global climatic regime under which they accumulated would facilitate a greater understanding of the role of environmental conditions at all stages in the formation of loess deposits

using 14c dating of stable humin fractions to assess upbuilding pedogenesis of a buried holocene humic soil horizon towada volcano japan the genesis of a 40 cm thick buried holocene humic soil horizon in a 6 m high sequence near towada volcano japan was examined by dating stable plant derived humin particles by ams based radiocarbon 14c and by analyzing stable carbon isotope ratios 13c phytolith composition and soil chemical properties the ams dating yielded calibrated ages ranging from 7570 7679 to 6180 6313 cal yr bp we obtained a strong correlation r 0 99 p 0 001 between sample depth and the mean age the now buried humic soil was formed by the incremental accumulation of tephric loess and aeolian dust at a constant rate of 30 mm per century for at least 1200 years whilst the soil surface was slowly rising graminaceous vegetation was supplied at a constant rate so that developmental upbuilding pedogenesis ensued the soil was buried and isolated by the fall of the towada chuseri tephra about 6200 cal yr bp thus the tephra soil sequence near towada volcano represents both developmental and retardant upbuilding pedogenesis

dust flux estimates for the last glacial period in east central europe based on terrestrial records of loess deposits a review loess paleosol sequences are significant records of the mineral dust cycle of glacial interglacial periods as dust particles give rise to direct and indirect radiative forcing obtaining a reliable picture of the global and regional patterns of mineral dust fluxes during glacial periods can lead to a better understanding of the contribution of mineral dust to past climate changes recent progress in absolute dating of loess deposits in the carpathian basin in east central europe made it possible to provide correct aeolian flux estimates for the last glacial period marine isotope stage mis 2 mass accumulation rates mars from chronological data of 33 loess sites exhibited a wide range of values from 150 to 1422 g m 2 a 1 centered around median and mean values of 338 and 417 g m 2 a 1 marpm10marpm10 and marpm2marpm2 estimates have been also calculated using grain size measurements of many loess samples and loess mars in order to facilitate comparison with models and since particles larger than 10 m have a negligible radiative effect here we show that some previous model simulations of the dust cycle at the last glacial maximum lgm significantly underestimated the real aeolian flux ranges of our estimates marpm10 34 324marpm10 34 324 and marpm2 9 3 88 2gm 2a 1 in east central europe for this reason some simulations of dust induced direct radiative forcing of the lgm climate failed to yield reliable results for this mid latitude region as they have been based on three dimensional dust field models that are not capable of estimating the real aeolian fluxes in central europe a recent global model of top of the atmosphere toa radiative forcing by mineral aerosols at the lgm that has been based on more realistic parameterization of dust sources transport and deposition revealed zonally averaged surface cooling of 2 c for the latitudes of our study area this surface cooling and toa radiative forcing 2 to 3 w m 2 are greater than recognized in other models and draws our attention to the importance of further modeling the impact of mineral dust on lgm climate in order to gain insight into the spatial pattern of radiative forcing and better understand resulting climate response in mid latitude loess regions such as east central europe

pedogenic modification of loess significance for palaeoclimatic reconstructions abstract this review considers the role of pedogenic processes in modifying wind blown dust loess concentrating particularly on the ways that resulting properties may be interpreted as indicators of past climatic conditions and changes emphasis is placed on the sequences of palaeosols developed within loess deposits that are frequently regarded as some of the best terrestrial equivalents of marine sediment records of long term global climatic change a palaeosol is generally interpreted in terms of the broad pedogenic processes and environments assumed to be currently responsible for that type of soil forming at the present surface even the very presence of a palaeosol may have palaeoclimatic significance however in that it is often taken to indicate a period of relative land surface stability and warmer and or moister conditions between cold and or arid phases of loess accumulation in reality it may be more useful to consider many loess palaeosol sequences in terms of changing balances between pedogenesis and loess accumulation over geological time in most regions it seems that the balance swings towards pedogenesis during interglacials or interstadials when sediment supply and transport are limited and the climate is warmer and or wetter where accumulation rates are still appreciable during these soil forming intervals however the soils and palaeosols may be accretionary with surface build up keeping pace with pedogenesis welding may also occur where covering sediments are insufficiently thick to isolate an underlying palaeosol from the effects of pedogenesis active at a new land surface further complications occur due to reworking of palaeosols and syndepositional pedogenic alteration of loess units generally such pedocomplexes can only be deciphered if the different pedogenic geomorphic and sedimentary processes are identified and ordered within a pedosedimentary reconstruction a recent trend has been to treat some loess palaeosol sequences as quasi continuous time series particularly when comparing depth functions of climatic proxy properties such as magnetic susceptibility and grain size with marine and ice core isotope curves

seismic attenuation and velocity dispersion in fractured rocks the role played by fracture contact areas the presence of fractures in fluid saturated porous rocks is usually associated with strong seismic p wave attenuation and velocity dispersion this energy dissipation can be caused by oscillatory wave induced fluid pressure diffusion between the fractures and the host rock an intrinsic attenuation mechanism generally referred to as wave induced fluid flow geological observations suggest that fracture surfaces are highly irregular at the millimetre and sub millimetre scale which finds its expression in geometrical and mechanical complexities of the contact area between the fracture faces it is well known that contact areas strongly affect the overall mechanical fracture properties however existing models for seismic attenuation and velocity dispersion in fractured rocks neglect this complexity in this work we explore the effects of fracture contact areas on seismic p wave attenuation and velocity dispersion using oscillatory relaxation simulations based on quasi static poroelastic equations we verify that the geometrical and mechanical details of fracture contact areas have a strong impact on seismic signatures in addition our numerical approach allows us to quantify the vertical solid displacement jump across fractures the key quantity in the linear slip theory we find that the displacement jump is strongly affected by the geometrical details of the fracture contact area and due to the oscillatory fluid pressure diffusion process is complex valued and frequency dependent by using laboratory measurements of stress induced changes in the fracture contact area we relate seismic attenuation and dispersion to the effective stress the corresponding results do indeed indicate that seismic attenuation and phase velocity may constitute useful attributes to constrain the effective stress alternatively knowledge of the effective stress may help to identify the regions in which wave induced fluid flow is expected to be the dominant attenuation mechanism

rapid mass wasting following nearshore submarine volcanism on kilauea volcano hawaii abstract the rapid mass wasting of shallow submarine basalts was documented during scuba dives along the flanks of kilauea volcano hawaii during the kii lava entry of the current eruption 19 20 5 n 154 59 8 w lava entered the ocean at this site from mid february to late march 1990 with several pauses dives on 19 20 march 1990 confirmed the widespread formation of lava pillows at this site over a water depth range of 20 40 m and visual observations suggested that the resulting volcanic deposits were generally stable despite the steep 40 incline of the seafloor the pre eruptive nearshore seafloor slope was 14 however dives on 2 april 1990 revealed that nearly all submarine volcanic features had been subject to mass wasting as the offshore area had been transformed into a debris field composed of material ranging in size from fine sand to boulder fragments this generally featureless seascape extended uniformly to beyond the visual range of divers 60 m water depth high resolution multibeam bathymetry and sidescan imaging indicate that steeply sloped coarse sediment extends down the flanks of kilauea in this area to abyssal depths implying a linkage between nearshore submarine volcanism and deep water deposits

loess accumulation and soil formation in central kansas united states during the past 400 000 years based on interpolation of thermoluminescence dates and the mean accumulation rate of 0 034 mm yr 1 four cycles of pedogenic caco3 accumulation are found within the loveland loess 415 325 ka 325 250 ka 250 195 ka and 195 95 ka the four caco3 peaks correspond chronologically to marine oxygen isotope stages 11 9 7 and 5 respectively the early wisconsin 95 70 ka was characterized by sand dune activity the reddish pedocomplex was formed from 70 to 35 ka under relatively warm and moist climatic conditions with a very slow rate of silt accumulation 0 016 mm yr 1 the gilman canyon pedocomplex enriched in organic matter and dated at 35 20 ka was formed under a strong physical weathering regime and a relatively high rate of silt accumulation 0 15 mm yr 1 indicating a windy relatively moist probably cool environment it developed when the laurentide ice sheet was advancing and dust content in greenland ice core was low the peoria loess was accumulated at a rate of 0 3 mm yr 1 in central kansas under cold dry conditions when the ice sheet fluctuated around its maximum position and the dust content in the greenland ice core was the highest even the warm substage around 13 ka has some corresponding evidence in the central great plains the well developed brady soil dated at 10 5 8 5 ka indicates that the early holocene was the optimal time for soil development since 20 ka the poorly weathered bignell loess might have been deposited during the altithermal period from 8 5 to 6 ka

thermoluminescence ages of post glacial loess rakaia river south island new zealand abstract we applied the partial bleach r beta thermoluminescence tl dating technique to two samples from massive post glacial loess overlying the last major aggradation gravel burnham formation near barrhill on the south bank of the rakaia river this site is roughly midway between the coast and the front range of canterbury previously the time of initiation of deposition of such loess in the region was only poorly constrained to somewhere between the interval 16 32 ka and ca 11 ka loess deposition has continued until today along margins of major braided rivers sample bhl 5 30 cm above the gravel gave a tl age of 11 7 1 9 1 ka and sample bhl 1 1 35 m above bhl 5 and 1 9 m below the surface gave an age of 5 49 0 70 ka thus age depth extrapolation at the barrhill site implies that loess deposition began at 13 2 ka and continued through the holocene to the present the average rate of deposition between the two tl samples was 0 22 0 07 mm year analytical error only and possibly greater thereafter the presence of the loess wedge dating from 13 2 ka indicates that the rakaia river began to entrench at about this time in this middle segment of the piedmont plain

rivers and loess the significance of long river transportation in the complex event sequence approach to loess deposit formation abstract rivers are essential for loess deposit formation river systems which relate directly to loess deposit formation include the danube and the rhine the mississippi and the missouri the thames and the medway the indus ganges and brahmaputra the dnepr don and volga the clutha mataura and rakaia new zealand rivers the yellow river rivers in south america siberian rivers flowing north the odra and the wisla between the mountains and the ice the syr darya and amu darya into the desert the contention is that rivers are not just important in major loess deposit formation they are mandatory necessary imperative obligatory essential indispensable requisite for a complete and satisfactory study of a loess deposit we need to know how the material is produced how it is transported and distributed across the landscape how intermediate deposits are formed how transportation provides the defining properties i e open structure collapsibility draping across the landscape and what may happen post deposition e g chernozemisation fragipan formation increased collapsibility etc if rivers are essential then it would appear that the british loess is probably alpine material delivered by the proto rhine and the polish loess is not derived from the ice sheet to the north but from the mountains to the south the lack of loess in canada is explained by the absence of suitable rivers the loess in russia and neighbouring countries can be classified as jefferson et al jefferson i f evstatiev d karastenev d mavlyanova n g smalley i j 2003b the engineering geology of loess and loess like deposits a commentary on the russian literature engineering geology 68 333 351 suggested on the basis of associated rivers a new deposit of glacial loess is recognised associated with the dnepr don and volga rivers the uswr loess the smalley leach smalley i j leach j a 1978 the origin and distribution of the loess in the danube basin and associated regions of east central europe a review sedimentary geology 21 1 26 available from www geo edu ro sgr mod downloads pdf smalley sedgeo 1978 pdf vision of the loess in the danube basin and east central europe is probably misconceived they assigned a great significance to glacial action and put loess in a northern band it appears that this proposed glacial influence is minimal and that the danube loess is essentially mountain loess derived from the alps the carpathians the sudeten mountains and other high regions the danube system is a classic example of a river controlling loess distribution

interaction between aggrading geomorphic surfaces and the formation of a late pleistocene paleosol in the palouse loess of eastern washington state abstract variable rates of loess deposition contributed to dramatic regional variation in a soil stratigraphic unit the washtucna soil in the palouse loess deposits in the channeled scabland of eastern washington state throughout most of the channeled scabland the morphology of the washtucna soil is that of a single buried soil but it bifurcates into two well developed and pedologically distinct buried soils in areas immediately downwind of the major source of loessial sediment regional loess stratigraphy confirms that the two well developed soils formed during the same interval of time during which only one soil formed in areas that are distal to loess source areas the variable and perhaps rapid rates of soil formation suggested by the stratigraphy resulted from an interaction between variable rates of loess deposition and the formation of superimposed calcic soils petrocalcic horizons with weak stage iv morphology formed as the zone of carbonate accumulation moved up into former a and cambic horizons that had been profusely burrowed by cicadas the development of cicada burrows in one phase of soil development that were subsequently engulfed by pedogenic carbonate under a rising land surface seems to have greatly accelerated the development of the petrocalcic horizons accelerated rates of formation of the petrocalcic horizons occurred when extrinsic pulses of loess deposition and intrinsic engulfment of burrowed horizons thresholds were exceeded stratigraphic evidence suggests that the soil formation that accompanied the rise in the land surface due to additional loess deposition may have occurred during the late wisconsin glaciation when giant glacial outburst floods in the channeled scabland triggered a new cycle of loess deposition

structures and facies associated with the flow of subaerial basaltic lava into a deep freshwater lake the sulphur creek lava flow north cascades washington abstract the ca 8800 14c yrs bp sulphur creek lava flowed eastward 12 km from the schriebers meadow cinder cone into the baker river valley on the southeast flank of mount baker volcano the compositionally zoned basaltic to basaltic andesite lava entered crossed and partially filled the 2 km wide and 100 m deep early holocene remnant of glacial lake baker the valley is now submerged beneath a reservoir but seasonal drawdown permits study of the distal entrant lava as a lava volume that may have been as much as 180 106 m3 entered the lake the flow invaded the lacustrine sequence and extended to the opposite east side of the drowned baker river valley the volume and mobility of the lava can be attributed to a high flux rate a prolonged eruption or both basalt exposed below the former level of the remnant glacial lake is glassy or microcrystalline and sparsely vesicular with pervasive hackly or blocky fractures together with pseudopillow fractures these features reflect fracturing normal to penetrative thermal fronts and quenching by water a fine grained hyaloclastite facies was probably formed during quench fragmentation or isolated magma water explosions although the structures closely resemble those developed in lava ice contact environments establishing the depositional environment for lava exhibiting similar intense fracturing should be confirmed by geologic evidence rather than by internal structure alone the lava also invaded the lacustrine sequence forming varieties of peperite including sills that are conformable within the invaded strata and resemble volcaniclastic breccias the peperite is generally fragmental and clast or matrix supported fine grained and rounded fluidal margins occur locally the lava formed a thickened subaqueous plug that as the lake drained in the mid holocene was exposed to erosion the baker river then cut a 52 m deep gorge through the shattered highly erodible basalt

loess in europe mass accumulation rates during the last glacial period abstract upper pleistocene loess palaeosol sequences provide excellent high resolution terrestrial archives of climate forcing due to improvements in numerical age determinations especially in luminescence dating methods a more reliable time based reconstruction of the past climate and environmental change has become available for the loess record in europe chronological information was collected from 43 sites along a northwest to southeast transect in europe thirty three of these sites had sufficient age information to allow estimation of mass accumulation rates and it was possible to isolate the mass accumulation rates of primary loess during the last glacial period 28 13 ka bp at 21 of these locations these sites fall along a coarse climatic gradient from the relatively coastal climate of belgium and france to the drier more continental climate of central europe interpreting mass accumulation rates of loess in terms of this climatic gradient is not straightforward as these deposits are dominated by sources in floodplains and large river systems thus accumulation rates are influenced strongly by regional wind and precipitation patterns but mostly by the availability of glacially derived material from the alps and the periglacial terrains that characterized european fluvial systems during and immediately following glaciation

a remarkable late saalian mis 6 loess dust accumulation in the lower danube at harletz bulgaria abstract while numerous high resolution studies concerning last glacial aeolian sequences are available for europe the approach of the penultimate glacial in this geographical area is still poorly developed in order to bridge this gap this study focuses on the bulgarian sequence of harletz along the danube river where extremely high sedimentation rates allow the depiction of high resolution signals during mis 6 at harletz in nw bulgaria on the western bank of the ogosta river tributary of the danube a 20 m thick loess palaeosols section was cleaned and sampled for a multi disciplinary study and detailed pedostratigraphic approach high resolution continuous bulk sampling 5 cm was carried out to characterise sedimentary grain size magnetic properties including magnetic susceptibility and its frequency dependence colour reflectance 1 cm and organic carbon geochronological control is based on 16 samples collected for osl and met pirir dating using a cyclo stratigraphic approach of the sequence combined with dating constraints provided by both met pirir dates and the age of a tephra layer occurring at a depth of 12 m within the main loess unit we can demonstrate that the harletz section exhibits a 10 m thick late saalian marine isotope stage 6 mis 6 loess accumulation unique in europe the lower part of the main loess unit is 4 m thick and overlies a basal brown soil complex allocated to mis 7 which includes an exceptionally thick 4 m and detailed succession of loess and four incipient soil horizons never described in european loess until now the closest and best dated high resolution palaeoenvironmental archive suitable for comparison comes from lake ohrid located about 400 km to the sw of harletz the ohrid palynological record shows a progressive step by step evolution in climate and in environmental change during the transition between mis 7 and mis 6 from which a parallel with the harletz pedosedimentary succession can be proposed during the younger part of mis 6 160 129ka steppe vegetation with abundant herbs artemisia is dominant in the lake ohrid record in good accordance with a global enhancement of aeolian dynamics especially well recorded in sections located close to the danube river from serbia to bulgaria and romania l2 loess according to interpretations stemming from this study the silts and fine sands building the harletz loess section would have been transported from the danube braided river system located at that time at about 4 5 km to the nw based on our data the main loess units are characterised by a very low to a total absence of coarse sand particles by contrast during the eemian interglacial mis 5e and to a lesser extent throughout mis 5 and during mis 3 interstadials the long distance transport of silt and fine sand particles is stopped and a weak aeolian sedimentation is likely driven by north easterly winds transporting coarse sand grains from the proximal ogosta river sandy banks finally the weak development of last glacial loess 4 m max likely results from a rapid infilling of the sedimentary trap during the saalian then followed by a strong anthropogenic erosion of the topsoil and of the upper part of the loess profile since the early holocene neolithic

stratigraphy and palaeoclimatic significance of late quaternary loess palaeosol sequences of the last interglacial glacial cycle in central alaska abstract loess is one of the most widespread subaerial deposits in alaska and adjacent yukon territory and may have a history that goes back 3 ma based on mineralogy and major and trace element chemistry central alaskan loess has a composition that is distinctive from other loess bodies of the world although it is quartz dominated central alaskan loess was probably derived from a variety of rock types including granites metabasalts and schists detailed stratigraphic data and pedologic criteria indicate that contrary to early studies many palaeosols are present in central alaskan loess sections the buried soils indicate that loess sedimentation was episodic or at least rates of deposition decreased to the point where pedogenesis could keep ahead of aeolian input as in china loess deposition and pedogenesis are likely competing processes and neither stops completely during either phase of the loess soil formation cycle loess deposition in central alaska took place before and probably during the last interglacial period during stadials of the mid wisconsin period during the last glacial period and during the holocene an unexpected result of our geochronological studies is that only moderate loess deposition took place during the last glacial period our studies lead us to conclude that vegetation plays a key role in loess accumulation in alaska factors favouring loess production are enhanced during glacial periods but factors that favour loess accumulation are diminished during glacial periods the most important of these is vegetation boreal forest serves as an effective loess trap but sparsely distributed herb tundra does not thus thick accumulations of loess should not be expected where tundra vegetation was dominant and this is borne out by modern studies near the treeline in central alaska much of the stratigraphic diversity of north american loess including that found in the central lowlands the great plains and alaska is explained by a new model that emphasizes the relative importance of loess production factors versus loess accumulation factors

lava seawater interactions at shallow water submarine lava flows hydrothermal plumes associated with nearshore lava flows from kilauea volcano hawaii were studied on five occasions during 1989 1990 to address the current lack of data on direct lava seawater interactions the following enrichments were found in the sea surface hydrothermal plumes above the active underwater lava flows h2 15 000x ambient seawater concentrations mn 250x and si 20x water temperatures reached 46 c lower concentrations and temperatures were observed in the plumes with increasing distance from shore with h2 si and mn concentrations linearly related to seawater temperature unlike deep sea spreading center hydrothermal plumes no ch4 enrichment was observed the elevated h2 is likely to be from water rock reactions rather than from the release of magmatic gas the plume mass heat ratios presented here suggest that submarine flood basalts although aerially large should be relatively small immediate contributors to oceanic geochemical cycles compared to hydrothermal circulation through the crust

hydrography and geochemistry of sea surface hydrothermal plumes resulting from hawaiian coastal volcanism the entry of lava into the ocean at kilauea volcano hawaii has produced extensive sea surface hydrothermal plumes studies at this site over 1989 1991 showed that particle rich chemically altered thermal plumes of 1 3 m thickness can be mapped for distances up to 2 km from the entries using an array of physical and chemical tracers particle concentrations in the plumes were as high as 65 mg l 1 and produced light attenuation anomalies exceeding 11 m 1 the maximum observed seawater temperature was 69 c the following extremes in plume chemical markers were measured h2 2 1 m dissolved mn 320 nm dissolved si 55 m co2 1 6 mm alkalinity 1 5 meq l 1 and ph 7 1 dissolved h2 linearly increased and co2 ph and total alkalinity decreased with increasing seawater temperature dissolved mn and si also increased with increasing temperature but were better correlated with each other indicating that heat is not conserved in the surface plumes heat and mass inputs to the ocean are comparable to those from mid ocean ridge crest vent fields

lava flows from a mid 1980s submarine eruption on the cleft segment juan de fuca ridge a series of lava flows with a total volume of 0 05 km3 were erupted in the mid 1980s along 17 km of the northern cleft segment of the juan de fuca ridge observations from camera tows and submersible dives show that the new flows are all similar in appearance and consist entirely of pillow lava with a mixture of smooth and striated surface textures suggesting a relatively uniform eruption rate approaching 1 m3 s at point source vents the flows vary in size from small patches to large steep sided ridges and were probably erupted from a dike intruded along the ridge axis because they are aligned along a linear fissure graben system observations at north cleft show that the physical appearance of new flows changes more rapidly than previously realized and that earlier qualitative dating of young lavas based on sediment cover and glassy surface texture were probably overestimates by an order of magnitude sediment accumulation on the lavas is quite variable and locally surprisingly substantial mainly due to hydrothermal deposits that formed while the lava flows were cooling biological vent communities photographed on the new flows in 1989 show that vent animals can colonize new vent sites rapidly but that warm water was still venting only in a few places nonvent animals are much slower to colonize the new flows and rates of colonization observed at north cleft may be useful for making improved age estimates of young 10 years lava flows elsewhere the north cleft eruption represents about 2 of the estimated average annual volcanic output along the global mid ocean ridge implying that many other submarine eruptions are occurring undetected

a terrestrial palynological record for the last two glacial cycles from southwestern new zealand abstract a pollen profile from okarito pakihi bog in south westland new zealand extending from near present back to marine isotope stage mis 6 provides a continuous record of vegetation and climate change for the past two glacial cycles independent chronological control was obtained by ams radiocarbon dating of organic sediments in the upper part of the sequence and osl dating of inorganic silts in the lower part with a unique tie point provided by the ca 26 5 cal ka kawakawa tephra as was probably a common occurrence in this region the basin developed as a moraine dammed proglacial lake and remained lacustrine until the early holocene when a peat bog developed survival of the depositional site through subsequent multiple ice advances unusual in a glaciated landscape was probably assisted by lateral displacement of the basin relative to its source area across the alpine fault there is good correspondence between inferred periods of substantial treeline depression in the pollen profile and the record for ice advance in this region more cooling events are evident in the pollen record however presumably due to the fragmentary nature of glacial geomorphology the pollen record also shows broad consistency with the mis record and hence with the milankovitch orbital forcing model but with some departures including an early onset to the last glacial maximum lgm several sub milankovitch scale events are also evident including a mid lgm warming and lateglacial reversals during both the last and the penultimate deglaciation

mid latitude trans pacific reconstructions and comparisons of coupled glacial interglacial climate cycles based on soil stratigraphy of cover beds abstract south westland new zealand and southern chile are two narrow continental corridors effectively confined between the pacific ocean in the west and high mountain ranges in the east which impart significant influence over regional climate vegetation and soils in both these southern mid latitude regions evidence for extensive and repeated glaciations during cold phases of the quaternary is manifested by arrays of successively older glacial drift deposits with corresponding outwash plain remnants in south westland these variably aged glacial landforms are mantled by layered multisequal soils characterised by slow loess accretion and pedogenesis in an extreme leaching and weathering environment these cover bed successions have undergone repeated coupled phases of topdown and upbuilding soil formation that have been related to fluctuating cycles of interglacial warm and glacial cold climate during the quaternary in this study we recognise multisequal soils overlying glacial landforms in southern continental chile but unlike the spodic podzolic soil sequences of south westland these are of dominantly volcanigenic andic provenance and are very similar to multisequal soils of andic provenance that predominate in and adjacent to areas of rhyolitic to andesitic volcanism in north island new zealand here we develop a soil stratigraphic model to explain the observed occurrence of multisequal soils mantling dominantly glacial landforms of southern continental chile based on proxy data from southern chile we propose that persistent vegetation cover and high precipitation on the western side of the andes during colder than present episodes tended to suppress the widespread production of glacially derived loessial materials despite the pervasive occurrence of glacial and glacio fluvial deposits that have frequently inundated large tracts of this landscape during the quaternary given the lack of loess cover beds that have traditionally assisted in the relative dating of glacial episodes prior to the late quaternary surface exposure dating techniques could provide another chronological alternative to address this issue however there have been two main obstacles to successfully apply this dating technique in patagonia first minimum exposure ages may be obtained on moraines older than the last glacial cycle due to erosion although dating outwash plains is more robust second on the wet western side adjacent to the andes persistent vegetation cover during both glacial and post glacial times as well as widespread inundation by volcanic mass flows appear preventive we make a case that soil genesis within this region appears to be dominated by a constant flux of intermittently erupted andean sourced tephra which has continued to upbuild soils at the ground surface separated by intervals where topdown weathering processes are intensified as already demonstrated by new zealand studies multisequal soil successions have a clear implied connection to coupled glacial and interglacial climate cycles of the quaternary on this basis similar sequences in northwest patagonia provide a relatively untapped archive to enable quaternary glacial and environmental changes in this pervasively glaciated volcanic region to be constructed

introduction to this special section fractures naturally occurring fractures in hydrocarbon reservoirs may increase the porosity and permeability of the reservoir and knowledge of the orientation and density of fractures is required to optimize production in reservoirs having low matrix permeability areas of high fracture density may represent sweet spots of high permeability and it is desirable to be able to target such locations for infill drilling because fractures show preferred orientations this may result in significant permeability anisotropy in the reservoir and it is important for optimum drainage that the separation of producers should be more closely spaced along the direction of minimum permeability than along the direction of maximum permeability numerically generated discrete fracture networks are being used increasingly to simulate flow through fractured reservoirs and need to be constrained using quantitative geophysical geologic and reservoir engineering data the hydraulic conductivity of fractures varies strongly with ap

using formation micro imaging wireline logs and onshore analogues to distinguish volcanic lithofacies in boreholes examples from palaeogene successions in the faroe shetland basin ne atlantic

submarine growth and internal structure of ocean island volcanoes based on submarine observations of mauna loa volcano hawaii a recent model for the submarine growth of hawaiian volcanoes indicates that these volcanoes are composed mainly of fragmental lava debris formed as lavas enter the ocean this model has major implications for locating earthquake hypocenters and for the landslide hazard potential of these and other ocean island volcanoes observations from submersible dives and analyses of volcanic glasses collected from the western submarine flank of mauna loa indicate that subaerially erupted pillow lavas are abundant at depths of 950 to 1900 m below sea level fragmental lava is an important component of ocean island volcanoes as witnessed during the most recent eruption of kilauea volcano but probably is the dominant lithology only in the upper 1 km of the submarine section a submarine dike complex was discovered 17 km west of the assumed axis of mauna loa9s southwest rift which indicates that its intrusive complex is much broader than previously suspected 20 km vs 8 km the great width of this dike complex may be a consequence of crustal unloading following the south kona landslide or a normal feature of hawaiian rift zones that was previously unrecognized

non hawaiian lithostratigraphy of louisville seamounts and the formation of high latitude oceanic islands and guyots guyots are large seamounts with a flat summit that is generally believed to form due to constructional biogenic and or erosional processes during the formation of volcanic islands however despite their large abundance in the oceans there are still very few direct constraints on the nature and formation of guyots in particular those formed at high latitude that lack a thick cap of shallow marine carbonate rocks it is largely accepted based on geophysical constraints and surficial observations sampling that the summit platform of these guyots is shaped by wave abrasion during post volcanic subsidence of volcanic islands here we provide novel constraints on this hypothesis and the summit geology of guyots with a lithostratigraphic analysis of cores from three louisville seamounts south pacific collected during expedition 330 of the integrated ocean drilling program iodp thirteen lithofacies of sedimentary and volcanic deposits are described which include facies not previously recognized on the top of guyots and offer a new insight into the formation of high latitude oceanic islands on a fast moving plate our results reveal that the lithostratigraphy of louisville seamounts preserves a very consistent record of the formation and drowning of volcanic islands with from bottom to top i volcaniclastic sequences with abundant lava fed delta deposits ii submarine to subaerial shield lava flows iii post volcanic shallow to deeper marine sedimentary rocks lacking thick reef deposits iv post erosional rejuvenated volcanic rocks and v pelagic sediments recognition of erosional boundaries between subaerial lava flows and shallow marine sedimentary rocks provides novel support for post volcanic wave planation of guyots however the summit geology of louisville seamounts is dissimilar to that of high latitude hawaiian emperor guyots that have emplaced in a similar tectonic and environmental setting and that include thicker lava stacks with apparently little lava fed delta deposits to explain observed lithostratigraphic discrepancy we propose that louisville seamounts represent a distinct type of intraplate ocean volcano characterized by formation of a smaller island with a central shield volcano surrounded by extended shallow marine shelves formed by lava fed deltas in this interpretation the summit platform of louisville type guyots results from early syn volcanic subaerial to shallow marine constructional volcanic processes and marine erosion enhanced by later post volcanic wave planation this contrasts with larger hawaiian edifices that are capped by thicker shield volcanoes and that develop an extended wave planation surface during post volcanic subsidence in the absence of efficient coral growth the difference between hawaiian and louisville type volcanic islands and guyots can be explained by contrasted dynamic disequilibrium between magmatic growth erosion and subsidence during the island building stage unlike hawaiian type volcanoes louisville seamounts are characterized by alkaline magmatism that extends from the late seamount to island stages this supports more limited magmatic growth during the formation of louisville islands and we hypothesize that this promotes the formation of ephemeral shallow marine platforms and extended lava fed deltas hawaiian type volcanoes and guyots are unusually large in the population of intraplate ocean volcanoes louisville type guyots as defined in this study could therefore represent a very common but yet poorly documented mode of oceanic island formation in the pacific ocean and other similar fast moving plate settings

the contemporary physical and chemical flux of aeolian dust a synthesis of direct measurements of dust deposition abstract the deposition of aeolian or windblown dust is widely recognized as an important physical and chemical flux to ecosystems dust deposition adds exogenous mineral and organic material to terrestrial surfaces and can be important for the biogeochemical cycling of nutrients there have been many studies that characterize the physical and chemical composition of dust however few studies have synthesized these observations in order to examine patterns geochemical fluxes we have compiled observations of dust deposition rates particle size distributions psd mineralogy and bulk elemental and organic chemistry the rates of dust deposition observed across the globe vary from almost 0 to greater than 450 g m 2 yr 1 sites receiving dust deposition can be partitioned into broad categories based on there distance from dust source regions when compared to global dust models our results suggest some models may underestimate dust deposition rates at the regional and local scales the distance from the source region that dust is deposited also influences the particle size distributions mineralogy and chemical composition of dust however more consistent dust sampling and geochemical analyses are needed to better constrain these spatial patterns on average the concentrations of most major elements si al fe mg ca k in aeolian dust tend to be similar 20 to the composition of the upper continental crust ucc but there is substantial variability from sample to sample in contrast some elements tend to be depleted na or enriched ti in dust likely as a result of soil weathering processes prior to dust emissions trace elements especially heavy metals are consistently enriched in dust relative to the ucc ecologically important nutrients such as n and p are also present in dust deposition the geochemical flux attributable to dust deposition can be substantial in ecosystems located proximal to dust source regions we calculate estimates of elemental flux rates based on the average chemical composition of aeolian dust and varying rates of deposition these estimated flux rates are useful as a rough gauge of the degree to which dust deposition may influence biogeochemical cycling in terrestrial ecosystems and should be utilized to better constrain deposition estimates of global dust models

dust transport and the question of desert loess formation although contemporary dust storms are frequent in arid and semi arid areas desert loess deposits are poorly developed much of the world s loess occurs in mid latitude areas which experienced glaciation during the pleistocene ocean core evidence indicates that dust transport from sub tropical deserts increased during cold stages of the pleistocene but loess formed only on certain desert margins for reasons which have not been fully explained this paper re examines the mechanisms of dust transport and deposition and the circumstances leading to the accumulation of thick loess typical loess is composed mainly of medium silt grains which are transported in short term suspension a few metres above the ground significant thicknesses of loess form only when dust is trapped within a limited area often relatively close to the source dust particles finer than 20 m are transported mainly in long term suspension over a greater height range and may be widely dispersed the availability of silt and the frequency magnitude and direction of dust transporting winds are important factors governing the potential for loess formation but the existence of a suitable dust trap is particularly important traps may be formed by topographic obstacles areas of moist ground or vegetated surfaces vegetation adjacent to glacial outwash plains and braided meltwater streams trapped dust in mid latitudes during the pleistocene dust blown during glacial periods from certain deserts notably in sinai soviet central asia and china accumulated as loess in neighbouring semi arid regions on the margins of other deserts loess formation was inhibited partly by the absence of vegetation traps during most of the holocene net dust deposition rates in all desert marginal areas have been too low for significant loess accumulation this is mainly due to a reduction in silt availability and a tendency towards landscape stability reported dust storm frequencies during the past 50 years over estimate the longer term holocene dust flux due to the effects of human activities much modern dust owes its origin to erosion of cultivated soils in semi arid areas and is finer than typical loess

elastic wave propagation in fractured media using the discontinuous galerkin method abstractwe have formulated and implemented a discontinuous galerkin method dgm for elastic wave propagation that allows for discontinuities in the displacement field to simulate fractures or faults the approach is based on the interior penalty formulation of dgm and the fractures are simulated using the linear slip model which is incorporated into the weak formulation by including an additional term that is similar to the penalty term but uses the fracture compliance instead of an arbitrary penalty parameter we have calibrated our results against an analytic solution of fracture induced anisotropy for a set of elongated horizontal fractures and we have evaluated numerical examples that simulate the reflection and transmission of waves at a fracture and at fracture interface waves this method can further be used with models containing intersecting fractures and multiple fracture sets in 2d or 3d domains

dust accumulation in the new zealand region since the last glacial maximum abstract loess is widespread in new zealand deposits 1 m thick cover 10 of the land area it has mainly been derived from dust deflated from river floodplains during the last glacial maximum lgm dust accumulation continues today downwind of major river floodplains most loess is quartzofeldspathic having its origins in mesozoic and neogene rocks of the axial ranges and hill country in the central north island there are deposits of volcanic loess derived from aeolian reworking of tephras loess morphology and properties vary greatly due to diverse parent materials post depositional climates and drainage conditions the widespread 26 170 cal yr kawakawa tephra provides a datum for calculating mass accumulation rates mars rates are mostly within the range 70 150 g m 2 yr 1 but enhanced deposition at one site gave a rate of 360 g m 2 yr 1 contemporary mars of 40 100 g m 2 yr 1 were determined for distances of 1 75 0 4 km downwind of the rakaia river lgm mars of quartz for two marine cores p69 q858 drilled 100 300 km east of new zealand are 40 70 g m 2 yr 1 the mar of the aeolian component of p69 is estimated to be ca 15 g m 2 yr 1

growth history of kilauea inferred from volatile concentrations in submarine collected basalts abstract major element and volatile h2o co2 s compositions of glasses from the submarine flanks of kilauea volcano record its growth from pre shield into tholeiite shield stage pillow lavas of mildly alkalic basalt at 2600 1900 mbsl on the upper slope of the south flank are an intermediate link between deeper alkalic volcaniclastics and the modern tholeiite shield lava clast glasses from the west flank of papau seamount are subaerial mauna loa like tholeiite and mark the contact between the two volcanoes h2o and co2 in sandstone and breccia glasses from the hilina bench and in alkalic to tholeiitic pillow glasses above and to the east were measured by ftir volatile saturation pressures equal sampling depths 10 mpa 1000 m water for south flank and puna ridge pillow lavas suggesting recovery near eruption depths and or vapor re equilibration during down slope flow south flank glasses are divisible into low pressure co2 0 5 wt s 1000 1700 ppm and high pressure groups co2 40 ppm s 1000 ppm corresponding to eruption sea level at moderate water depths 300 1000 m or shallower but in disequilibrium and in deep water 1000 m saturation pressures range widely in early alkalic to strongly alkalic breccia clast and sandstone glasses establishing that early k lauea s vents spanned much of mauna loa s submarine flank with some vents exceeding sea level later south flank alkalic pillow lavas expose a sizeable submarine edifice that grew concurrent with nearby subaerial alkalic eruptions the onset of the tholeiitic shield stage is marked by extension of eruptions eastward and into deeper water to 5500 m during growth of the puna ridge subaerial and shallow water eruptions from earliest kilauea show that it is underlain shallowly by mauna loa implying that mauna loa is larger and kilauea smaller than previously recognized

three dimensional lithofacies variations in hyaloclastite deposits analysis of the spatial lithofacies variability within lava fed delta formations in southern iceland has revealed complex three dimensional volcanic architectures in hyaloclastite deposits in non glacial settings two depositional environments are studied a lava entering a marine embayment stori nupur and b lava advancing into a body of water of the flanks of a surtseyan cone hjorleifshof i interaction between environmental factors such as shoreline geomorphology water depth wave energy levels the nature of the lava transport system lava supply rate all affect the resulting lava deltas creating complex lithofacies arrangements and stacking patterns recognised here are two types of hyaloclastite deltas one of syn sedimentary origin hjorleifshof i and one derived from primary fragmentation processes stori nupur syn sedimentary systems are dominated by destabilisation of the hyaloclastite pile leading to reworking downslope and share similarities to alluvial delta systems conversely primary fragmented systems are controlled by waxing and waning cycles in volcanic effusivity whereby the hyaloclastite unit recorded is not the product of one lava flow rather than one eruptive event

how fast are soil forming processes in quaternary sediments of a tropical floodplain a case study in southeast brazil abstract floodplains are depositional features of a channel valley associated with a specific climatic and hydrologic regime of a drainage basin in tropical conditions sediments can be quickly weathered by soil forming processes and tend to obliterate pre existing sedimentary structures therefore the objective of many studies on floodplains is to identify and discuss such sedimentary features mostly those related to the morphology of channel deposits additionally a qualitative approach to identify aspects of pedological evolution in these environments has been attempted in few studies the purpose of this study was to interpret the intensity and the time of alluvial sediment weathering by pedogenetic processes in tropical humid conditions soil profiles were analyzed in different environments of deposition in the pardo river floodplain southeast brazil by accounting for sedimentary facies and pedological features supported by multi proxy data provided from geochemistry macro and micromorphology grain size total carbon total nitrogen 13 c isotopic analysis and 14 c osl optically stimulated luminescence dating based on the results we identified that pedogenetic features and soil horizon distributions were closely related to sediment architecture grain size and position in the floodplain in the pardo floodplain fluvic gleysols loamic and clayic with moderately to strongly developed structures were identified in overbank fine sediments fluvic cambisols clayic were found in abandoned paleomeanders fluvic cambisols loamic in sandy scrollbars gleyic acrisols clayic cutanic differentic in channel deposits which presented a 130 cm thick bt horizon with illuvial clay coatings and histosols fluvic with high contents of total carbon 11 9 and 26 8 in histic horizons in small scale avulsive systems deposits were dated to between 35 000 and 700 years bp 13 c isotopic data revealed a trend toward enriched values in older samples 14 21 in which c 4 plants dominated and a relative impoverishment of the values in more recent samples 26 9 to 27 9 this result was consistent with the tendency of the distribution of c 3 plants to increase over that of c 4 plants favored by the warmer and wetter climate since the upper holocene in this study a fluvic gleysol profile of

pedogenesis by upbuilding in an extreme leaching and weathering environment and slow loess accretion south westland new zealand abstract soil formation is usually envisaged as acting from the surface downwards in many environments however the accumulation of sediment and soil formation are contemporaneous it is only where the rate of one process far exceeds the rate of the other that assumptions of topdown pedogenesis are appropriate the aspect of upbuilding pedogenesis that distinguishes it from topdown pedogenesis is that each increment of soil below the a horizon has experienced processes characteristic of all horizons above it this study examines the influence of upbuilding soil formation in a high rainfall environment of rapid soil formation and slow loess accretion an environment where upbuilding could have a noticeable influence on soil properties soils formed by topdown soil formation topdown soils are compared with soils formed in loess that accumulated from early last glaciation to the holocene upbuilding soils soils are compared in two environments alaquods on poorly drained terraces and placorthods or dystrochrepts on well drained moraine crests we have assumed that properties of the upbuilding soils inherited during the current topdown phase of pedogenesis beginning in the holocene are analogous to those in the topdown soils in this manner soil properties evolved during upbuilding are distinguished in well drained upbuilding soils on moraines subsoil organic carbon has mineralised so that profile trends are very similar to corresponding topdown soils upbuilding has enhanced weathering in subsoils which is reflected in lower ph lower total p and lower primary inorganic p than in topdown soil counterparts total p concentrations in upbuilding soils are much lower than unweathered loess and constant throughout the subsoil and there is almost no p in primary forms in contrast total p in c horizons of topdown soils reaches concentrations typical of the parent material and more than 30 of this is in a primary inorganic form the differences are attributed to each subsoil increment of upbuilding soils having been part of acid a and e horizons oxalate extractable fe and al data indicate that podzolisation was active during upbuilding poorly drained upbuilding soils on terraces have higher subsoil organic carbon inherited from former a or o horizons than comparable topdown soils buried a and o horizons inherited during upbuilding and preserved in the reducing conditions have acted as sinks for mobile al and now resemble podzolic illuvial bh horizons upbuilding through addition of loess to soils promotes a pedogenic pathway distinct from topdown pedogenesis consequently soil chronosequence studies that include soils on old loess mantled surfaces do not strictly satisfy the assumptions of soil chronosequences the nature and rate of soil processes inferred from these studies need revisiting the findings of this study are transferable to other environments where the rate of soil formation and sediment accumulation are comparable

rock fracture compliance derived from time delays of elastic waves the purpose of this study is to compare the reliability of various methods of estimating normal rock fracture compliance from elastic wave measurements we compare ultrasonic through transmission laboratory measurements for a smooth fracture in a westerly granite specimen with numerical simulations and analytical solutions the focus is on deriving compliance from time delays the influence of specimen and source transducer width was constrained using numerical wave simulations we find that measured ultrasonic phase delays are better suited to estimate the fracture compliance than group delays using the frequency domain instead of the time domain increases the accuracy of the fracture compliance estimates we further show that for cases where precise phase delay measurements are unavailable employing first break times in conjunction with numerical simulations can be considered as an alternative

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

diversity and peculiarities of soil formation in eolian landscapes insights from the mineral magnetic records abstract magnetic properties of loess paleosol sequences are widely utilized as sensitive easily obtained and reliable proxy archives of past climate change in continental settings however soil formation in aeolian landscapes may occur under different and changing conditions of dust sedimentation which will affect the growth and development of the pedogenic magnetic component this phenomenon is explored in our study by analyzing depth variations of the following magnetic characteristics frequency dependent magnetic susceptibility anhysteretic magnetic susceptibility and the ratio between anhysteretic susceptibility and isothermal remanent magnetization acquired in a 100 mt back field arm irm 100 mt along three loess paleosol profiles from ne bulgaria a conceptual model for the time evolution of the grain size of the pedogenic magnetic fraction with soil depth is proposed which is build upon the mechanism of soil formation accretional or in stable land surfaces or a combination of the two another magnetic ratio isothermal remanence acquired in a 300 mt back field divided by low field magnetic susceptibility irm 300 mt is utilized as a proxy for the changes in the ratio of silt to clay fractions indicative of changes in dust sedimentation regimes during glacial interglacial transitions according to the proposed conceptual model verified by the magnetic signature of three holocene soils from ne bulgaria discrimination between accretional soils and soils developed without dust additions during soil forming period can be done accretional soils are characterized by parallel changes in grain size sensitive magnetic proxies soils developed at stable landscape conditions show gradation of the depths at which maximum enhancement of various proxies occurs with deepest occurrence of the maximum in fd followed by depth of maximum arm and arm irm 100 mt another implication of the new conceptual model is that the mean coercivity of the pedogenic component of accretional soils will be higher than that of soils developed without eolian input at equal temperature conditions because of the soils thermal gradient and different depths at which pedogenic minerals form in the two settings the results revealed that the holocene soils so has developed under different soil forming conditions than paleosols from the same sites

sulfur accumulation in melanudands during development by upbuilding pedogenesis since 14 15cal ka to understand the contribution of upbuilding pedogenesis to the accumulation of sulfur s in melanudands we investigated the vertical distribution of s species using k edge x ray absorption near edge structure xanes spectroscopy of s species and vertical variation of 34s values of total s in two japanese melanudands developed above tephra nt s dated at 14 15 cal ka these soils have been developed by upbuilding pedogenesis in which episodic accumulations of volcanic ash and eolian dust transported from the asian continent are added incrementally to the soil surface while topdown pedogenesis occurs concomitantly forming soil horizons the oxidation states of s compounds determined by xanes analysis varied widely in the soil profiles the predominant s species was highly oxidized s in ester sulfates and inorganic sulfates 6 oxidation state proportions of s with reduced and intermediate oxidation states increased episodically to as much as 66 ester sulfate s was found in the soil horizons with estimated ages less than 10 cal ka a close correlation was found between ester sulfate s concentrations and al associated organic s concentrations p 0 05 indeed the concentrations themselves were roughly similar the 34s values of total s increased with depth in the two soil profiles these results suggest that episodic deposits of volcanic ash and eolian dust trapped detritus and humus beneath them during the buildup of the soil surface the organic s compounds in this material might be decayed as topdown pedogenic processes in the soils production of ester sulfate s may be related to the warm and humid climate of the holocene which may have accelerated microbial activity responsible for transformation of reduced to highly oxidized s ester sulfate s might have become al associated forms and accumulated in the soils due to their high pedogenic mineral contents

the last glacial maximum lgm in western south island new zealand implications for the global lgm and mis 2 abstract the morainic and outwash deposits of the larrikins la and moana mn formations in north westland are correlated with the m5 t5 and m6 t6 deposits in south westland the la m5 deposits resulted from two separate otira glaciation glacial advances la 1 m5 1 la 2 m5 2 of essentially similar extents pollen sequences in peats and coverbeds extending from before to after the kawakawa tephra 26 500 cal yr bp indicate an extensive period of cold with a slight amelioration beginning shortly before tephra deposition this amelioration which is supported by interpretation of coverbed sequences in south westland separates the la 1 m5 1 and la 2 m5 2 advances the three westland glacial advances la 1 m5 1 la 2 m5 2 and mn m6 culminated at ca 28 000 21 500 and 19 000 cal yr bp the last being followed by major rapid glacier retreat pollen and caco 3 records from dsdp 594 east of the south island reflect contemporary glacier fluctuations on the east side of the southern alps they show the last major cold period as lasting from ca 34 000 to ca 16 000 years ago a period starting before the culmination of the la 1 m5 1 advance and ending later than the beginning of glacier retreat from the mn m6 advance the period from the la 1 m5 1 culmination to the mn m6 culmination represents the lgm in new zealand a slightly longer lgm is recorded in chile and a long lgm may also be indicated in australia a long lgm in the southern hemisphere is supported by the global sea level curve and by the regional antarctic temperature criteria of the vostok ice core these different records indicate a southern hemisphere lgm beginning at least as early as 27 000 years ago much earlier than the ocean last isotope maximum lim from 21 500 to 18 000 years ago the beginning of mis 2 defined primarily from deep sea benthic 18 o at 24 000 years is well after the beginning of ice advances leading to the southern hemisphere lgm a review of global land and ocean correlations is desirable

magma emission rates from shallow submarine eruptions using airborne thermal imaging abstract the effusion rate is the most important parameter to gather when a volcanic eruption occurs because it controls the way in which a lava body grows extends and expands influencing its dimensional properties calculation of lava flow volume from thermal images collected by helicopter surveys has been largely used during the last decade for monitoring subaerial effusive eruptions however due to the depths where volcanic activity occurs monitoring submarine volcanic eruptions is a very difficult task the 2011 2012 submarine volcanic eruption at el hierro canary islands has provided a unique and excellent opportunity to monitor eruptive processes occurring on the seabed the use of a hand held thermal camera during daily helicopter flights allowed us to estimate for the first time the daily and total erupted magma volumes from a submarine eruption the volume of magma emitted during this eruption has been estimated at 300 mm3 giving an average effusion rate of 25 m3 s 1 thermal imagery by helicopter proved to be a fast inexpensive safe and reliable technique of monitoring volcanic eruptions when they occur on the shallow seabed

pedogenesis soil mass balance phosphorus dynamics and vegetation communities across a holocene soil chronosequence in a super humid climate south westland new zealand abstract this study quantifies progressive pedogenesis under a super humid climate on the west coast of south island new zealand it focuses on soil morphology pedogenic oxides soil mass balance phosphorus transformation and linking pedogenesis trajectories to vegetation communities the study comprises a set of dune ridges of a coastal sand dune complex covered by unmodified conifer podocarp angiosperm forest the surface ages of the chronosequence range from 370 y to 6500 y rapid podzolisation is characteristic for the study area within 1000 y soils reach the spodosol stage with typical eluvial illuvial horizons and mobilisation of fe and al this period is also characterised by the most rapid losses of total phosphorus at a rate of 110 g m 2 ky 1 a relative loss of 41 beyond 3000 y changes in soil chemistry and losses for all nutrients markedly slow soil mass balance shows that the 6500 y soil has lost 75 total p 62 k 52 ca and 54 na soil p fractions substantially change across the gradient high leaching losses of apatite and non occluded p in the first hundreds of years coincide with accumulation of organic and occluded inorganic forms in the topsoil and subsoil which mitigate total p loss beyond 1000 y of pedogenesis all p fractions decline at similar rates to low more persistent levels with apatite non occluded p being the dominant p form after 6500 y of pedogenesis this incipient steady state is assumed to be sustained by the advection of parent material derived p through surface lowering and reduced biological cycling vegetation communities change from more diverse communities on young and less impoverished soils in the first 1000 y to less diverse and less variable communities beyond 1000 y of ecosystem development the soil evolution correlated vegetation changes documented in this study are consistent with general schemes of vegetation succession for the west coast of south island

last glacial loess in the conterminous usa the conterminous united states contains an extensive and generally well studied record of last glacial loess the loess occurs in diverse physiographic provinces and under a wide range of climatic and ecological conditions both glacial and non glacial loess sources are present and many properties of the loess vary systematically with distance from loess sources united states midcontinent last glacial loess is probably the thickest in the world and our calculated mass accumulation rates mars are as high as 17 500 g m 2 yr at the bignell hill locality in nebraska and many near source localities have mars greater than 1500 g m 2 yr these mars are high relative to rates calculated in other loess provinces around the world recent models of last glacial dust sources fail to predict the extent and magnitude of dust flux from the mid continent of the united states a better understanding of linkages between climate ice sheet behaviour routing of glacial meltwater land surface processes beyond the ice margin and vegetation is needed to improve the predictive capabilities of models simulating dust flux from this region r 2003 elsevier ltd all rights reserved

dust transportation and deposition in a superhumid environment west coast south island new zealand contemporary rates of dust deposition monitored along a 300 km section of the superhumid west coast of new zealand s south island are presented in this setting dust is entrained primarily from the dry channels of braided glaciofluvial rivers that drain the western slopes of the southern alps measured dust deposition ranged between 0 21 and 118 9 kg 1 ha 1 month 1 which is similar to dust deposition rates monitored in arid and semiarid environments however these are not considered to be sufficient for present day loess genesis dust deposition was highest in summer because of the greater frequency of favourable dust transporting winds and the effect of rainfall was secondary dust transportation occurred mainly during the passage of nonprecipitating cold fronts or postfrontal southwesterlies transportation also occurred during prefrontal conditions and in winter fohn southeasterlies were the predominant dust transporting winds to affect the west coast

volcanic eruption of the mid ocean ridge along the east pacific rise crest at 9 45 52 n direct submersible observations of seafloor phenomena associated with an eruption event in april 1991 in april 1991 we witnessed from the submersible alvin a suite of previously undocumented seafloor phenomena accompanying an in progress eruption of the mid ocean ridge on the east pacific rise crest at 9 45 n 52 n the volume of the eruption could not be precisely determined although comparison of pre and post eruption seabeam bathymetry indicate that any changes in ridge crest morphology resulting from the eruption were 10 m high effects of the eruption included 1 increased abundance and redistribution of hydrothermal vents disappearance of numerous vent communities and changes in characteristics of vent fauna and mineral deposits within the eruption area since december 1989 2 murkiness of bottom waters up to tens of meters above the seafloor due to high densities of suspended mineral and biogenic particulates 3 destruction of a vent community by lava flows mass wasting and possible hydrovolcanic explosion at a site known as tubeworm barbecue in the axial summit caldera asc at 9 50 6 n 4 near critical temperatures of hydrothermal vent fluids ranging up to 403 c 5 temporal variations over a 2 week interval in both temperatures and chemical isotopic compositions of hydrothermal fluids 6 unusual compositions of end member vent fluids with ph values ranging to a record low of 2 5 salinities ranging as low as 0 3 wt nacl one twelfth that of seawater and dissolved gases reaching high concentrations 65 mmol l for both co2 and h2s 7 venting at temperatures above 380 c of visually detectable white vapor that transformed to plumes of gray smoke a few centimeters above vent orifices 8 disorganized venting of both high temperature fluids black and gray smoke and large volumes of cooler diffuse hydrothermal fluids directly from the basaltic seafloor rather than from hydrothermal mineral constructions 9 rapid and extensive growth of flocculent white bacterial mats species unknown on and under the seafloor in areas experiencing widespread venting of diffuse hydrothermal fluid and 10 subseafloor downslope migration of magma normal to the ridge axis in a network of small scale 1 5 m diameter lava tubes and channels to distances at least 100 200 m outside the asc we suggest that in april 1991 intrusion of dikes in the eruption area to 200 m beneath the asc floor resulted in phase separation of fluids near the tops of the dikes and a large flux of vapor rich hydrothermal fluids through the overlying rubbly cavernous lavas low salinities and gas rich compositions of hydrothermal fluids sampled in the eruption area are appropriate for a vapor phase in a seawater system undergoing subcritical liquid vapor phase separation boiling and phase segregation hydrothermal fluids streamed directly from fissures and pits that may have been loci of lava drainback and or hydrovolcanic explosions these fissures and pits were lined with white mats of a unique fast growing bacteria that was the only life associated with the brand new vents the prolific bacteria which covered thousands of square meters on the ridge crest and were also abundant in subseafloor voids may thrive on high levels of gases in the vapor rich hydrothermal fluids initially escaping the hydrothermal system white bacterial particulates swept from the seafloor by hydrothermal vents swirled in an unprecedented biogenic blizzard up to 50 m above the bottom the bacterial proliferation of april 1991 is likely to be a transient bloom that will be checked quickly either by decline of dissolved gas concentrations in the fluids as rapid heat loss brings about cessation of boiling and or by grazing as other organisms are re established in the biologically devastated area

seismic and acoustic signals detected at lo ihi seamount by the hawai i undersea geo observatory 1 the hawai i undersea geo observatory hugo is an ocean bottom observatory located on the summit of lo ihi seamount hawai i an electro optical cable connects the hugo junction box to a shore station on the big island of hawaii thereby enabling the first real time monitoring of a submarine volcano hugo was active for 3 months in 1998 collecting nearly continuous real time data on a high rate hydrophone signals detected during that time include local as well as teleseismic earthquakes t phases from pacific wide earthquakes landslides on the submarine flank of kilauea and eruption sounds from the current kilauea eruption the data do not indicate a lo ihi eruption during the time that hugo was active the variety and quality of signals detected by the hugo hydrophone confirms that a real time observatory can serve a valuable role in studies of oceanic acoustics local and teleseismic earthquakes and submarine eruption mechanics

upbuilding pedogenesis under active loess deposition in a super humid temperate climate quantification of deposition rates soil chemistry and pedogenic thresholds abstract although the importance of dust deposition as an integral component of terrestrial biogeochemical cycles is well recognised few studies have directly addressed pedogenic processes associated with dust deposition on the land surface itself and if so mainly as relict features this work addresses this gap by looking at the pedogenic response to an active loess flux gradient in a super humid strong weathering environment on the west coast of new zealand s south island along the gradient seven soil pits were examined for a range of soil physical colour texture bulk density structure roots and chemical properties ph fe o fe d al o soil organic carbon measured to a depth of 50 cm to capture the transitional changes arising from minimal to maximal loess deposition rates maximal deposition rate was estimated to be 28 4 g m 2 y 1 along the gradient towards the highest deposition rate loess free sandy spodosols changed to increasingly more finely textured soils ultimately featuring a two fold increase of silt the pedogenic oxides fe o fe d and al o gradually increased each by 50 and soil organic carbon by 60 these increases were facilitated by continuous accession of loess the loess mixed with organic matter at the surface and became increasingly weathered and leached with the time that it had spent undergoing eluviation subsequently the loess increments were buried within the subsoil as part of an upwardly thickening spodic horizon upbuilding pedogenesis because of the high deposition rates under maximum loess flux spodosol formation became ultimately retarded and an inceptisol formed because loess supply overwhelmed topsoil leaching having also an illuvial subsoil horizon this inceptisol showed the strongest chemical indicators for podzolisation of the gradient soil data from supplementary sites suggested that more developed soils required lower loess fluxes to retard further pedogenic differentiation than younger soils the existence of a loess gradient that is capable of forming distinctive deposits in a super humid environment gives evidence that not only dry arid climates e g during glacials are potentially suitable for the formation of aeolian substrates loess the study indicates enhanced soil organic carbon storage in soils as a result of loess deposition and concomitant pedogenesis

distribution of present day vertical deformation across the southern alps new zealand from 10 years of gps data 1 we use ten years of gps data from nine continuous and six semi continuous gps stations in a transect across the southern alps to measure rates of relative vertical movement with typical 1 uncertainties of 0 3 0 5 mm yr the estimated vertical rates define a fairly smooth profile across the range with the highest rates of 5 mm yr found near the crest of the mountains and 20 30 km southeast of the alpine fault the distribution of vertical rates supports models based on horizontal velocities from gps surveys in which interseismic coupling on the alpine fault decreases from 100 near the surface to zero by 13 18 km depth

late pleistocene buried humic soils within a tephra soil sequence near unzen volcano kyushu japan abstract relatively few late pleistocene buried humic soils in volcanic areas have been studied to date because they are not common worldwide the present study examined the origin of soil organic matter som in mainly late pleistocene buried humic soils within a tephra soil sequence near unzen volcano northeastern shimabara peninsula kyushu sw japan the buried humic soil horizons were divided into seven horizons in a tephra soil sequence the total carbon contents were very high for late pleistocene soils with a value of 60 g kg 1 obtained for the oldest buried humic soil 8ab horizon the main phytolith types in the buried humic soils are pleioblastus sect nezasa in a and 2ab and sasa sect crassinodi in 3ab 4ab 5ab 6ab 7ab c and 8ab som was derived mainly from gramineae in the oldest buried humic soil 8ab horizon the 13c values indicate that c3 plants contributed more than 50 of the plant derived carbon in the som and the phytoliths indicate the dominance of c3 grasses e g sasa sect crassinodi in the ne and se of the peninsula the late pleistocene humic soils formed due to an abundant supply of organic matter from mainly grass vegetation such as sasa sect crassinodi regardless of climate change at 30 ka or earlier in the unzen volcano area the present study contributes to the paleoenvironmental reconstruction for the late pleistocene

holocene loess deposition and soil formation as competing processes matanuska valley southern alaska although loess paleosol sequences are among the most important records of quaternary climate change and past dust deposition cycles few modern examples of such sedimentation systems have been studied stratigraphic studies and 22 new accelerator mass spectrometry radiocarbon ages from the matanuska valley in southern alaska show that loess deposition there began sometime after f6500 14 c yr b p and has continued to the present the silts are produced through grinding by the matanuska and knik glaciers deposited as outwash entrained by strong winds and redeposited as loess over a downwind distance of f40 km loess thickness sand content and sand pluscoarse silt content decrease whereas fine silt content increases loess deposition was episodic as shown by the presence of paleosols at distances 10 km from the outwash plain loess source stratigraphic complexity is at a maximum i e the greatest number of loesses and paleosols at intermediate 10 25 km distances from the loess source surface soils increase in degree of development with distance downwind from the source where sedimentation rates are lower proximal soils are entisols or inceptisols whereas distal soils are spodosols ratios of mobile cao k2o and fe2o3 to immobile tio2 show decreases in surface horizons with distance from the source thus as in china where loess deposition also takes place today eolian sedimentation and soil formation are competing processes study of loess and paleosols in southern alaska shows that particle size can vary over short distances loess deposition can be episodic over limited time intervals and soils developed in stabilized loess can show considerable variability under the same vegetation d 2004 university of washington all rights reserved

coastal dunes in westland new zealand provide a record of paleoseismic activity on the alpine fault regional episodes of coastal progradation and dune formation in south westland new zealand have quickly followed all known alpine fault earthquakes since a d 1200 this reflects rapid transport of large postseismic sediment pulses from mountain catchments to the coast and accumulation of this material as a dune ridge this study provides the first demonstration of this link for multiple events over a region the dune sequences also provide evidence of another previously unrecognized regional aggradation event which may be earthquake related and which occurred just 50 yr after a large alpine fault earthquake coastal dunes have great potential for paleoseismic application because the spatial separation of earthquake induced sediment pulses on a prograding coast allows identification of events closely spaced in time coastal dune systems have the potential to improve paleoseismic understanding over the holocene for many plate boundary faults near coastal areas

elucidating the geogenic and pedogenic pathways of formation of soils of peninsular india signatures of past landscape modifications abstract the soils of modified landforms of peninsular india present an opportunity to unearth soil and landscape evolution we explore the potential of vertical texture contrast vtc soils as signatures of past landscape modifications and associated soil formation in peninsular india we studied six vtc soils occurring on different geological formations for their morphology geochemistry and mineralogy in order to interpret the geogenic and pedogenic pathways of their formation the presence of a lithological discontinuity with sharp contrast in particle size in pedons p1 and p3 suggested that fluvial sedimentary layering led to their formation pedons p2 and p5 are examples of buried soils where basaltic alluvium of varying thickness is overlying the soils of granitic and gneissic complex origin these soils are potential proxies of landform changes attributable to paleo alluvial mass deposition possibly during the late pleistocene pedon p4 is a relict paleosol in which the presence of a ck horizon between the argillic bt and bc horizons indicates sedimentation of stratified rocks geogenic followed by clay illuviation pedogenic during the past wet climate the occurrence of smectite dominant shrink swell s w soil pedon p6 over the shale parent material suggests that the s w soil is from a transported alluvium of weathering deccan basalt our results demonstrate the usefulness of vtc soils in interpreting the climate shift driven soil landscape evolution in peninsular india and elsewhere

submarine eruption near socorro island mexico geochemistry and scanning electron microscopy studies of floating scoria and reticulite abstract products of an underwater eruption near socorro island in the ne pacific were observed directly on january 29 1993 ten days after precursors were first recorded by sofar sound fixing and ranging hydrophones located in hawaii and tahiti eruptive activity was noticed from boats and ships as small steam plumes rising from the sea at an area centered at 18 48 n 111 05 w 2 4 km nw of punta tosca and 4 6 km ssw of cape henslow on socorro island the observed steam was produced by 1 3 m large blocks of hot dark grey highly vesiculated basalt rising buoyantly to the surface from two submarine shallow vents at 210 and 30 m depth tens of blocks accompanied by bubbles could be observed rising to the surface in irregular pulses these scoriaceous blocks remained floating at the surface until they would crack into smaller pieces by thermal contraction emitting hissing noises from vapourizing seawater in contact with the hot interior of the blocks steam jets several metres in height were produced and occasionally blocks were propelled laterally by the steam jet depending on vesicularity and permeability blocks remained floating and drifting with the surface current for 1 15 minutes before sinking back floating rocks covered an area of about 6000 m2 this intermittent activity has been observed ever since and has not stopped as of april 1994 buoyant scoria and reticulite are indicative of volatile mostly co2 supersaturation and exsolution in the magma prior to rapid quenching which inhibits loss of volatiles by bubble escape a high velocity ascent of low viscosity magma in a relatively narrow conduit is also required to prevent substantial gas escape and allow formation of reticulite the buoyant scoria is most probably ejected by intermittent lava fountaining at fixed vents as a result of changes in eruption velocities due to changes in the exsolved gas content of the lava between january and july 1993 floating blocks of scoria and reticulite were collected on several occasions from the surface of the sea for chemical and mineralogical analyses major and minor element analyses including ree as well as electron microprobe analyses of different phases revealed that the composition of the emitted lava has not changed through time blocks of basalt sio2 45 47 are highly vitric and vesicular with tabular anorthite phenocrysts up to 3 mm in length and minor grains of forsteritic olivine ree and trace element composition of these rocks suggest an anomalous mantle source for the erupted alkali basalt lava the ongoing eruption will either continue in a similar fashion as described and eventually cease or built up a mound that reaches the surface and forms an island with accompanying change in eruptive style

emplacement and erosion by archean komatiite lava flows at kambalda revisited we have developed a mathematical model to evaluate the flow and erosional potential of submarine channelized komatiite lavas at kambalda western australia field data from kambalda were used to constrain the choice of important input parameters and model results were compared with data from field studies and geochemical analyses our results suggest that thermal erosion is strongly dependent upon the nature and behavior of the substrate if the substrate is treated as an unconsolidated hydrous sediment that can be fluidized by vaporized seawater then our model predicts that an initially 10 m thick basal kambalda komatiite lava could have produced very high thermo mechanical erosion rates 23 10 m day crustal thicknesses of 5 20 cm at distances of 5 35 km from the source and a high degree of lava contamination 3 12 in contrast if the substrate is treated as a more consolidated anhydrous sediment that could not be fluidized then our model predicts that a kambalda komatiite flow would have had much lower thermal erosion rates 1 2 0 4 m day and degrees of contamination 1 3 and would have had crustal thicknesses of 5 20 cm at longer flow distances of 30 165 km field constraints are generally consistent with our predictions for a non fluidized substrate the reentrant embayments at kambalda are thought to form from either erosion of deep channels in a flat basaltic seafioor huppert et al 1984 or erosion of a thin 5 m sediment with minor undercutting of basalt in pre existing topography lesher et al 1984 our modeling indicates that the former was possible for long eruption durations months whereas the latter was possible for short eruption durations 2 weeks as the latter hypothesis is more consistent with the existing field evidence for thermal erosion at kambalda we believe it is the preferred interpretation

identifying hazards associated with lava deltas lava deltas formed where lava enters the ocean and builds a shelf of new land extending from the coastline represent a significant local hazard especially on populated ocean island volcanoes such structures are unstable and prone to collapse events that are often accompanied by small explosions that can deposit boulders and cobbles hundreds of meters inland explosions that coincide with collapses of the east lae apuki lava delta at k lauea volcano hawai i during 2005 2007 followed an evolutionary progression mirroring that of the delta itself a collapse that occurred when the lava ocean entry was active was associated with a blast of lithic blocks and dispersal of spatter and fine glassy tephra shortly after delta growth ceased a collapse exposed hot rock to cold ocean water resulting in an explosion composed entirely of lithic blocks and lapilli further collapse of the delta after several months of inactivity by which time it had cooled significantly resulted in no recognizable explosion deposit seaward displacement and subsidence of the coastline immediately inland of the delta was measured by both satellite and ground based sensors and occurred at rates of several centimeters per month even after the lava ocean entry had ceased the anomalous deformation ended only after complete collapse of the delta monitoring of ground deformation may therefore provide an indication of the potential for delta collapse while the hazard associated with collapse can be inferred from the level of activity or the time since the last activity on the delta

emplacement of subaerial pahoehoe lava sheet flows into water 1990 kūpaianaha flow of kilauea volcano at kaimū bay hawai i episode 48 of the ongoing eruption of kilauea hawai i began in july 1986 and continuously extruded lava for the next 5 5 years from a low shield k paianaha the flows in march 1990 headed for kalapana and inundated the entire town under 15 25 m of lava by the end of august as the flows advanced eastward they entered into kaim bay replacing it with a plain of lava that extends 300 m beyond the original shoreline the focus of our study is the period from august 1 to october 31 1990 when the lava buried almost 406 820 m2 of the 5 m deep bay when lava encountered the sea it flowed along the shoreline as a narrow primary lobe up to 400 m long and 100 m wide which in turn inflated to a thickness of 5 6 m the flow direction of the primary lobes was controlled by the submerged delta below the lavas and by damming up lavas fed at low extrusion rates breakout flows through circumferential and axial inflation cracks on the inflating primary lobes formed smaller secondary lobes burying the lows between the primary lobes and hiding their original outlines inflated flow lobes eventually ruptured at proximal and or distal ends as well as mid points between the two ends feeding new primary lobes which were emplaced along and on the shore side of the previously inflated lobes the flow lobes mapped with the aid of aerial photographs were correlated with daily observations of the growing flow field and 30 primary flow lobes were dated excluding the two repose periods that intervened while the bay was filled enlargement of the flow field took place at a rate of 2 440 22 640 square meters per day in the bay lobe thickness was estimated to be up to 11 m on the basis of cross sections of selected lobes measured using optical measurement tools measuring tape and hand level the total flow lobe volume added in the bay during august 1 october 31 was approximately 3 95 million m3 giving an average supply rate of 0 86 m3 s

no depth limit to hydrovolcanic limu o pele analysis of limu from lō ihi seamount hawai i deep sea limu o pele are shards of basaltic glass commonly described as bubble walls when first identified they were inferred to form in submarine fire fountains but were then reinterpreted as the products of hydrovolcanic volcanism formed when submarine lava flows entrapped and vaporised seawater limu discovered below the c 3 km critical depth of seawater where superheated water exists as a supercritical fluid instead of a vapour led to the hydrovolcanic model of limu o pele formation being discarded in favour of a magmatic co2 driven strombolian like model this revised magmatic mechanism has been widely accepted by the scientific community we describe a newly discovered limu o pele rich deposit at 1 052 mbsl on the northeast summit plateau region of l ihi seamount hawai i the limu at this site is concentrated in a chemically monomict ash lens interbedded with thin lava sheets that are separated from overlying volcaniclastic material by a discontinuity the geometry and geochemistry of the deposit provide compelling evidence for a hydrovolcanic sheet flow related origin the exceptional abundance and preservation of limu at this site allows 4 morphologic subtypes of limu thin film plateau border convex film and pele s hair to be identified and linked to portions of the isolated rupturing bubbles from which they are derived we extend our discussion to beyond this new l ihi deposit by including a review of limu o pele occurrences and thermodynamic considerations that demonstrate the hydrovolcanic model of limu formation to be more tenable than the magmatic model at all depths including below the critical depth of seawater

morphometric study of pillow size spectrum among pillow lavas measurements of h and v dimensions in the horizontal and vertical directions of pillows exposed in vertical cross section were made on 19 pillow lavas from the azores cyprus iceland new zealand tasmania the western usa and wales the median values of h and v plot on a straight line that defines a spectrum of pillow sizes having linear dimensions five times greater at one end than at the other basaltic toward the small size end and andesitic toward the large size end the pillow median size is interpreted to reflect a control exercised by lava viscosity pillows erupted on a steep flow foot slope in lava deltas can however have a significantly smaller size than pillows in tabular pillowed flows inferred to have been erupted on a small depositonal slope indicating that the slope angle also exercised a control pipe vesicles generally abundant in the tabular pillowed flows and absent from the flow foot pillows have potential as a paleoslope indicator pillows toward the small size end of the spectrum are smooth surfaced and grew mainly by stretching of their skin whereas disruption of the skin and spreading were important toward the large size end disruption involved increasing skin thicknesses with increasing pillow size and pillows toward the large size end are more analogous with toothpaste lava than with pahoehoe and are inferred from their thick multiple selvages to have taken hours to grow pseudo pillow structure is also locally developed an example of endogenous pillow lava growth that formed intrusive pillows between normal pillows is described from sicily isolated pillow like bodies in certain andesitic breccias described from iceland were previously interpreted to be pillows but have anomalously small sizes for their compositions it is now proposed that they may lack an essential attribute of pillows namely the development of bulbous forms by the inflation of a chilled skin and are hence not true pillows para pillow lava is a common lava type in the flow foot breccias it forms irregular flow sheets that are locally less than 5 cm thick and failed to be inflated to pillows perhaps because of an inadequate lava supply rate or too high a flow velocity