flowgo a kinematic thermo rheological model for lava flowing in a channel we present a kinematic self adaptive numerical model to describe the down flow thermal and rheological evolution of channel contained lava as our control volume of lava advances down a channel it cools and crystallizes an increasingly thick and extensive surface crust grows and its heat budget and rheology evolve by estimating down flow heat and velocity loss our model calculates the point at which the control volume becomes stationary giving the maximum distance lava flowing in the channel can extend modeled effusion rates velocities widths surface crust parameters heat budget cooling temperature crystallinity viscosity and yield strength all compare well with field data collected during eruptions at mauna loa k lauea and etna modeled lengths of 25 27 2 5 5 7 and 0 59 0 83 km compare with measured lengths of 25 27 4 and 0 75 km for the three flows respectively over proximal flow portions we calculate cooling crystallization viscosity and yield strength of 1 10 c km 1 0 001 0 01 volume fraction km 1 103 104 pa s and 10 3 102 pa respectively at the flow front cooling crystallization viscosity and yield strength increase to 100 c km 1 0 1 volume fraction km 1 106 107 pa s and 103 104 pa respectively all of which combine to cause the lava to stop flowing our model presents a means of a analyzing lava flow thermo rheological relationships b identifying important factors in determining how far a channel fed flow can extend c assessing lava flow hazard and d reconstructing flow regimes at prehistoric unobserved or remote flows

modeling flood dynamics along the superelevated channel belt of the yellow river over the last 3000 years the yellow river china experienced 1000 levee breaches during the last 3000 years a reduced complexity model is developed in this study to explore the effects of climate change and human activity on flood levels levee breaches and river avulsions the model integrates yearly morphological change along a channel belt with daily river fluxes and hourly evolution of levee breaches model sensitivity analysis reveals that under natural conditions superelevation of the channel belt dominates flood frequency when there is significant human accelerated basin erosion and breach repair the dominant factors shift to a combination of mean annual precipitation superelevation critical shear stress of weak channel banks and the time interval between breach initiation and its repair the effect of precipitation on flood frequency is amplified by land use changes in the hinterland particularly in the erodible loess plateau uncertainty analysis estimates the most likely values of the dominant factors for six historical periods between 850 b c and a d 1839 which are used to quantitatively reconstruct flood dynamics during 850 b c to a d 1839 when the sediment load increased fourfold the breach recurrence interval was shortened from more than 500 years to less than 6 years and the breach outflow rate increased 27 times river management practices during a d 1579 to a d 1839 focused on levees and triggered a severe positive feedback of increased levee heights and flood hazard exacerbation raising the levee heights proved to be ineffective for sustainable flood management

influence of volatile loss on thickness and density profiles of active basaltic flow lobes a bulk density increase due to degassing during emplacement may have a significant influence on the thickness of a lava flow and the rate at which it advances we present a theoretical model of a lava flow that loses enough volatiles to cause density changes along the path of the flow we assume that the flow is emplaced as a single isolated unit and the bulk rheology e g viscosity is a function of distance from the vent this type of model is applicable to solitary lobes of basaltic aa and isolated sheets of pahoehoe that advance as a fluid continuum with bulk lava density changes as a function of distance along the flow path equations for the flow thickness and the bulk density profiles are derived from mass and volume conservation formulas are tabulated for thickness and density profiles for various combinations of flow rates rheologic changes and degassing rate functions we also tabulate formulas for estimating parameters associated with the form and rate of degassing from field data the mauna loa 1984 1 flow is a typical example of a flow showing evidence of a bulk density increase and is used to estimate the model parameters thickness and density profiles are then computed for a range of plausible lava densities two different rate functions for the loss of volatiles and two different models of viscosity change results indicate that the thickness profile of a lava flow can be significantly affected when there is a large difference between the density at the vent and at the flow front for relatively high rates of degassing the flow profile has a maximum thickness located progressively closer to the vent as the rate of degassing increases for depth dependent degassing an increase in viscosity acts to thicken the flow which increases the rate of degassing thus mitigating the thickening influence of the increasing viscosity degassing while a flow is active can increase the duration of emplacement by as much as 60 we find that the flow thickness profiles are sensitive to the choice of flow rate and the initial density regardless of the form of the degassing function the nature of the flow rate can significantly affect the shape of the profile as well as the flow front thickness when the rate of volatile loss depends on the flow thickness the density profile depends explicitly on the way the rheology changes along the flow path in all cases density increases during emplacement counter the tendency of a flow to thicken due to increases in viscosity or resistance to flow with distance thus the parameters that define the rate of degassing and the consequent density change along the path of a flow emerge as important variables for a quantitative understanding of flow emplacement

rheology of bubble bearing magmas the rheology of bubble bearing suspensions is investigated through a series of three dimensional boundary integral calculations in which the effects of bubble deformation volume fraction and shear rate are considered the behaviour of bubbles in viscous flows is characterized by the capillary number ca the ratio of viscous shear stresses that promote deformation to surface tension stresses that resist bubble deformation estimates of ca in natural lava flows are highly variable reflecting variations in shear rate and melt viscosity in the low capillary number limit e g in carbonatite flows bubbles remain spherical and may contribute greater shear stress to the suspension than in high capillary number flows in which bubble deformation is significant at higher ca deformed bubbles become aligned in the direction of flow and as a result contribute less shear stress to the suspension calculations indicate that the effective shear viscosity of bubbly suspensions at least for ca 0 5 is a weakly increasing function of volume fraction and that suspensions of bubbles are shear thinning field observations and qualitative arguments however suggest that for sufficiently large ca ca greater than about 1 the effective shear viscosity may be less than that of the suspending liquid bubbles reach their quasi steady deformed shapes after strains of order one for shorter times the continuous deformation of the bubbles results in continual changes of rheological properties in particular for small strains the effective shear viscosity of the suspension may be less than that of the liquid phase even for small ca results of this study may help explain previous experimental theoretical and field based observations regarding the effects of bubbles on flow rheology

the anthropocene and the landscape of confucius a historical ecology of landscape changes in northern and eastern china during the middle to late holocene the yellow river catchment of northern china was central to the rise of complex societies from the first neolithic farmers through to early states and empires these cultural developments brought with them rising populations and increasing intensity of land use this region provides an important record of landscape changes that mark the development of the anthropocene in china geoarchaeological research in the middle reaches of the yellow river catchment of henan province and eastward to the si river drainage of shandong province illustrates human impact on vegetation and hydrological systems dating back at least until the middle neolithic yangshao period in the mid holocene ca 7000 yr bp this research provides geomorphological evidence that early human impact began in the yangshao period with deforestation soil erosion and increased alluviation in the upper catchment of the yiluo river the increased alluviation allowed small scale neolithic farmers to intensify and supplement their production with

trends and controls of holocene floodplain sedimentation in the rhine catchment article i nfo holocene floodplain sedimentation in the rhine catchment is controlled by human and climate impacts intricate river behaviour modifies the fluvial response to the external impacts making cause effect analysis difficult especially on large spatial scales to better understand the relative importance and interdependencies of external and internal controls temporally resolved floodplain sedimentation rates are established using three different methods i floodplain storage studies on the trunk stream ii depth age analysis of overbank deposits from different parts of the catchment and iii cumulative frequency distributions of 14 c ages from floodplain deposits from various parts of the catchment the applied methodology strongly differs with the available temporal resolution and the size of the corresponding catchment all three methods show a strong increase in sedimentation rate for more recent periods that can be linked to increasing human impact evidences for climate impacts and intricate river behaviour are less clear and hindered by insufficient temporal resolution of the currently available data

sedimentation rates in the lower yellow river over the past 2300 years as influenced by human activities and climate change analysis of the sedimentary record has been used to determine the historical sedimentation rate in the lower yellow river and the historical literature has been studied to obtain information on climate change and human activities based on the data obtained the temporal variation in the sedimentation rate in the lower yellow river over the past 2300 years has been studied in relation to climate change and the impact of human activities the results indicate that the response of the sedimentation zone of yellow river system to changes in the erosion zone are consistent with existing understanding changes in vegetation and land use both related to climate change and human activities are two major controls responsible for the increase in sedimentation rates additionally the changing strategies for harnessing of the lower yellow river are also responsible for such acceleration with the trend of accelerated sedimentation in the past 2300 years the period from the 7th to 10th centuries and the period since the mid 19th century have been identified as two periods in which abrupt changes occurred copyright c 2003 john wiley sons ltd

pahoehoe and aa in hawaii volumetric flow rate controls the lava structure the historical records of kilauea and mauna loa volcanoes reveal that the rough surfaced variety of basalt lava called aa forms when lava flows at a high volumetric rate 5 10 m3 s and the smooth surfaced variety called pahoehoe forms at a low volumetric rate 5 10 m3 s this relationship is well illustrated by the 1983 1990 and 1969 1974 eruptions of kilauea and the recent eruptions of mauna loa it is also illustrated by the eruptions that produced the remarkable paired flows of mauna loa in which aa formed during an initial short period of high discharge rate associated with high fountaining and was followed by the eruption of pahoehoe over a sustained period at a low discharge rate with little or no fountaining the finest examples of paired lava flows are those of 1859 and 1880 1881 we attribute aa formation to rapid and concentrated flow in open channels there rapid heat loss causes an increase in viscosity to a threshold value that varies depending on the actual flow velocity at which when surface crust is torn by differential flow the underlying lava is unable to move sufficiently fast to heal the tear we attribute pahoehoe formation to the flowage of lava at a low volumetric rate commonly in tubes that minimize heat loss flow units of pahoehoe are small usually 1 m thick move slowly develop a chilled skin and become virtually static before the viscosity has risen to the threshold value we infer that the high discharge rate eruptions that generate aa flows result from the rapid emptying of major or subsidiary magma chambers rapid near surface vesiculation of gas rich magma leads to eruptions with high discharge rates high lava fountains and fast moving channelized flows we also infer that long periods of sustained flow at a low discharge rate which favor pahoehoe result from the development of a free and unimpeded pathway from the deep plumbing system of the volcano and the separation of gases from the magma before eruption achievement of this condition requires one or more episodes of rapid magma excursion through the rift zone to establish a stable magma pathway

new statistics for estimating the bulk rheology of active lava flows puu oo examples downstream changes in lava rheology due to cooling crystallization and vesiculation have a strong influence on the final length and morphology of a lava flow three statistics are proposed to estimate the change in lava rheology with distance along the path of an active flow these statistics correspond to three separate models of the volumetric flow rate dependence on the thickness of the flow each statistic is based on flow dimensions and topographic data that are often available from field measurements or remote sensing one model assumes an elementary laminar newtonian flow a second empirical model often used to describe the flow of complex geologic materials such as lahars sediment laden floods and debris flows is also investigated for comparison a new volume loss model is also proposed to account for stationary components such as levees and stagnant areas the three statistics derived from these flow rate models are applied and interpreted for two well defined lobes from episodes 2 and 18 of the 1983 1984 puu oo eruption the power law dependence of the first two models results only in modest differences in the estimates of rheologic change along the flow path however the removal of lava from the active flow to construct stationary components produces significant differences in both the magnitude of computed rheologic changes and the ability to discern trends in rheologic changes along the path of the flow

anthropocene archaeology of the yellow river china 5000 2000 bp in this paper we use geoarchaeological and paleoenvironmental data from three localities in the yellow river valley china taosi sanyangzhuang and the yiluo valley to argue that human activi

development of lava tubes in the light of observations at mauna ulu kilauea volcano hawaii during the 1969 1974 mauna ulu eruption on kilauea s upper east rift zone lava tubes were observed to develop by four principal processes 1 flat rooted crusts grew across streams within confined channels 2 overflows and spatter accreted to levees to build arched roofs across streams 3 plates of solidified crust floating downstream coalesced to form a roof and 4 pahoehoe lobes progressively extended fed by networks of distributaries beneath a solidified crust still another tube forming process operated when pahoehoe entered the ocean large waves would abruptly chill a crust across the entire surface of a molten stream crossing through the surf zone these littoral lava tubes formed abruptly in contrast to subaerial tubes which formed gradually all tube forming processes were favored by low to moderate volume rates of flow for sustained periods of time tubes thereby became ubiquitous within the pahoehoe flows and distributed a very large proportionof the lava that was produced during this prolonged eruption tubes transport lava efficiently once formed the roofs of tubes insulate the active streams within allowing the lava to retain its fluidity for a longer time than if exposed directly to ambient air temperature thus the flows can travel greater distances and spread over wider areas even though supply rates during most of 1970 1974 were moderate ranging from 1 to 5 m3 s large tube systems conducted lava as far as the coast 12 13 km distant where they fed extensive pahoehoe fields on the coastal flats some flows entered the sea to build lava deltas and add new land to the island the largest and most efficient tubes developed during periods of sustained extrusion when new lava was being supplied at nearly constant rates tubes can play a major role in building volcanic edifices with gentle slopes because they can deliver a substantial fraction of lava erupted at low to moderate rates to sites far down the flank of a volcano we conclude therefore that the tendency of active pahoehoe flows to form lava tubes is a significant factor in producing the common shield morphology of basaltic volcanoes

simulating the thermorheological evolution of channel contained lava flowgo and its implementation in excel flowgo is a one dimensional model that tracks the thermorheological evolution of lava flowing down a channel the model does not spread the lava but instead follows a control volume as it descends a line of steepest descent centred on the channel axis the model basis is the jeffreys equation for newtonian flow modified for a bingham fluid and a series of heat loss equations adjustable relationships are used to calculate cooling crystallization and down channel increases in viscosity and yield strength as well as the resultant decrease in velocity here we provide a guide that allows flowgo to be set up in excel in doing so we show how the model can be executed using a slope profile derived from google tm earth model simplicity and ease of source term input from google tm earth means that this exercise allows i easy access to the model ii quick global application and iii use in a teaching role output is tested using measurements made for the 2010 eruption of piton de la fournaise la reunion island the model is also set up for rapid syneruptive hazard assessment at piton de la fournaise as we show using the example of the response to the june 2014 eruption

neodymium isotopes as tracers in marine sediments and aerosols north atlantic nd and sm concentrations and nd isotopic compositions were measured on the detrital fraction of deep sea surface sediments and on aerosols sampled over the north atlantic and mediterranean sea the data expressed asend 0 and as model ages ranged from 14 5 end 0 4 9 and from 0 01 to 2 21 ga respectively two areas where the sediments contain relatively less radiogenic nd are to the west off north africa and eastward of the canadian shield this distribution is consistent with other tracers in suggesting that a significant fraction of the sediments are derived from aeolian material transported by major wind systems saharan dust transported in the equatorial trade winds belt and north american soil material transported in the latitudes of the westerlies between these aeolian dominated belts along an axis from the azores to gibraltar and the mediterranean lies a zone of more radiogenicend 0 values in sediments and aerosols influenced by the recent volcanism of this region previously reported distributions of nd isotopes in bottom formed iron manganese crusts and coatings are similar to distributions of nd isotope values in detrital sediments and aerosols this suggests that the detrital fraction has undergone partial dissolution and desorption in the water column and or in the pore waters of near surface sediments and that a significant proportion of nd in the authigenic ferromanganese phases is derived from this source and may therefore not represent strictly dissolved seawater nd isotope ratios useful as watermass tracers

textural and rheological evolution of basalt flowing down a lava channel the muliwai a pele lava channel was emplaced during the final stage of mauna ulu s 1969 1974 eruption kilauea hawaii the event was fountain fed and lasted for around 50 h during which time a channelized flow system developed in which a 6 km channel fed a zone of dispersed flow that extended a further 2 6 km the channel was surrounded by initial rubble levees of a a capped by overflow units of limited extent we sampled the uppermost overflow unit every 250 m down the entire channel length collecting and analyzing 27 air quenched samples bulk chemistry density and textural analyses were carried out on the sample interior and glass chemistry and microlite crystallization analyses were completed on the quenched crust thermal and rheological parameters cooling crystallization rate viscosity and yield strength were also calculated results show that all parameters experience a change around 4 5 km from the vent at this point there is a lava surface transition from pahoehoe to a a lava density microlite content viscosity and yield strength all increase down channel but vesicle content and lava temperature decrease cooling rates were 6 7 c km with crystallization rates increasing from 0 03 c km proximally to 0 14 c km distally modeling of the channel was carried out using the flowgo thermo rheological model and allowed fits for temperature microlite content and channel width when run using a three phase viscosity model based on a temperature dependent viscosity relation derived for this lava the down flow velocity profile suggests an initial velocity of 27 m s declining to 1 m s at the end of the channel down channel lava underwent cooling that induced crystallization causing both the lava viscosity and yield strength to increase moreover lava underwent degassing and a subsequent vesicularity decrease this aided in increasing viscosity with the subsequent increase in shearing promoting a transition to a a

the effects of shape on crystal settling and on the rheology of magmas the effects of the shape of phenocrysts on their settling velocity and on the rheology of magmas are discussed spherical crystals fall at a velocity given by stokes law and need to be present in large concentrations before they have a marked effect on the viscosity of a suspension elongate crystals fall at a much smaller velocity which may be determined from the formulas and graphs given herein such elongate crystals can have a dramatic effect on the viscosity of a suspension even at low volume fractions suspended crystals and bubbles will not impart a yield stress to the magma unless they form a touching network across the entire suspension it is suggested therefore that most previous inferences of a yield stress in subliquidus magmas are erroneous measurements of the subliquidus rheology of magmas need to be accompanied by careful characterization of the microstructure and distribution of the solid phase on which such rheologies critically depend

hydroclimatic conditions and fishing practices at late paleolithic makhadma 4 egypt inferred from stable isotope analysis of otoliths abstract the late paleolithic site of makhadma 4 located along the nile river in upper egypt yielded an important ichthyofauna characterized by a very high proportion of tilapia oreochromis niloticus we used isotopic analysis 18o of well preserved otoliths ear stones of tilapia to reconstruct the former hydrological conditions as well as the fishing strategies of the site s inhabitants otoliths from two modern fish captured in the nile river near esna were also examined to test how accurately tilapia otoliths reflect their ambient environment all otoliths were sequentially micromilled to recover high resolution isotopic profiles along the main growth axis comparison of the modern otolith profiles with environmental data shows that tilapia 18o values record seasonal variations of the modern nile hydroclimate but that their values are offset the archaeological otoliths record very large intra individual cyclical variations in 18o values with relatively consistent amplitude as well as very high seasonal maximum values up to 8 3 compared with the modern otoliths the hydrological regime of the water body in which the archaeological fish lived was characterized by a reduced nile water inflow that could not negate the effect of local evaporation during spring the reconstructed hydrological conditions are in accordance with a new model of nilotic behavior that assumes the creation of lakes by damming of the nile as a result of a high eolian activity during hyper arid periods of the late pleistocene although large seasonal evaporation may have resulted in a severe seasonal reduction in the lake s volume and extent the lake was nevertheless maintained for several years cyclic variations in otolith 18o values permit reconstruction of the period of the hydrological cycle during which the fish were captured fishing of young individuals occurred mostly after the maximum input of inflow water from the nile when evaporitic conditions were at their lowest i e during fall

rheological behavior of bubble bearing magmas abstract the vesiculation of the rising magma in a volcanic conduit results in a large change in the viscosity of magma understanding the effect of bubbles on the viscous behavior of bubble melt mixtures over a wide range of bubble volume fractions is essential for accurate modeling of the volcanic processes in this study new equations for the relative viscosity of concentrated bubble bearing suspensions are developed using a differential scheme along with the solution of an infinitely dilute suspension of bubbles out of the four models developed in the paper two models predict the relative viscosity to be a function of only two variables capillary number and volume fraction of bubbles there are no adjustable parameters in these models the remaining two models include an additional parameter that is the maximum packing volume fraction of bubbles the proposed models are evaluated using published numerical and experimental data on the relative viscosity of concentrated suspensions of bubbles the viscosity models for bubble bearing suspensions developed in this study are useful in modeling of the volcanic processes

using satellite imagery to identify and analyze tumuli on earth and mars abstract tumuli are small dome like features that form when magmatic pressures build within a subsurface lava pathway causing the overlying crust to bulge upwards as the appearance of these features has been linked to lava flow structure e g underlying lava flow tubes and conditions there is interest in identifying such features in satellite images so they can be used to expand our understanding of lava flows within regions difficult to access such as on other planets here we define a methodology for identifying and measuring tumuli within satellite imagery and validate it by comparing our results with fieldwork results of terrestrial tumuli reported in the literature and with independent measurements we made within amboy field ca in addition we present aggregated results from the application of our methodology to satellite images of six terrestrial fields and seven martian fields with 2100 tumuli identified per planet comparisons of tumuli morphometrics on earth and mars yield similarities in size and overall shape which were surprising given the many differences in the environmental and planetary conditions within which these features have formed given our measurements we identify constraints for tumulus formation models and drivers that would yield similar shapes and sizes on two different planets furthermore we test a published hypothesis regarding the number of tumuli that form per a square kilometer and find it unlikely that a diagnostic tumuli density value exists

textural characterization of the pāhoeho a a transition in hawaiian basalt p hoehoe and a are the most common surface morphologies in basaltic lava flows yet no predictive models exist to link physical parameters of flow emplacement to changes in their surface textures and rheological properties we have characterized changes of vesicularity vesicle deformation and crystallinity across the p hoehoe a transition as preserved in two different eruptions a brief high velocity effusion of lava from k lauea volcano on 1 february 1996 and a small breakout from an ephemeral vent within a larger channel produced during the 1868 eruption of mauna loa this allowed us to compare conditions leading to the p hoehoe a transition for both open channel flow k lauea 1996 and reactivation of lava from an ephemeral vent mauna loa 1868 textural changes across the transition include a decrease in vesicularity and vesicle number density b increase in microlite crystallinity and crystal number density and c increase in vesicle deformation the results support past qualitative descriptions of the transition and highlight the importance of plagioclase crystallinity in controlling lava rheology and surface morphology

the length of channelized lava flows insight from the 1859 eruption of mauna loa volcano hawai i a r t i c l e i n f o the 1859 eruption of mauna loa volcano hawai i produced paired a and p hoehoe ows of exceptional length 51 km the a ow eld is distinguished by a long n36 km and well de ned p hoehoe lined channel indicating that channelized lava remained uid to great distances from the vent the 1859 eruption was further unusual in initiating at a radial vent on the volcano s northwest ank instead of along the well de ned rift zone that has been the source of most historic activity as such it presents an opportunity both to examine controls on the emplacement of long lava channels and to assess hazards posed by future ank eruptions of mauna loa here we combine evidence from historical chronicles with analysis of bulk compositions glass geothermometry and microlite textures of samples collected along the 1859 lava ows to constrain eruption and ow emplacement conditions the bulk compositions of samples from the a and p hoehoe ow elds are bimodally distributed and indicate tapping of two discrete magma bodies during eruption samples from the p hoehoe ow eld have bulk compositions similar to those of historically erupted lavas b8 wt mgo lava that fed the a channel is more primitive n8 wt mgo nearly aphyric and was erupted at high temperatures 1194 1216 c we suggest that the physical properties of proximal channel fed lava i e high temperature low crystallinity and low bulk viscosity promoted both rapid ow advance and development of long p hoehoe lined channels critical for the latter was the large temperature decrease 50 c required to reach the point at which plagioclase and pyroxene started to crystallize the importance of phase constraints are emphasized by our dif culty in replicating patterns of cooling and crystallization recorded by high temperature eld samples using common models of ow emplacement placement of the 1859 eruption within the context of historic activity at mauna loa suggests that the formation of radial vents and eruptions of high temperature magma may not only be linked but may also be a consequence of periods of high magma supply e g 1843 1877 flank eruptions could therefore warrant special consideration in models and hazard mitigation efforts

a centennial tribute to g k gilbert s hydraulic mining debris in the sierra nevada abstract g k gilbert s 1917 classic monograph hydraulic mining debris in the sierra nevada is described and put into the context of modern geomorphic knowledge the emphasis here is on large scale applied fluvial geomorphology but other key elements e g coastal geomorphology are also briefly covered a brief synopsis outlines key elements of the monograph followed by discussions of highly influential aspects including the integrated watershed perspective the extreme example of anthropogenic sedimentation computation of a quantitative semidistributed sediment budget and advent of sediment wave theory although gilbert did not address concepts of equilibrium and grade in much detail the rivers of the northwestern sierra nevada were highly disrupted and thrown into a condition of nonequilibrium therefore concepts of equilibrium and grade for which gilbert s early work is often cited are discussed gilbert s work is put into the context of complex nonlinear dynamics in geomorphic systems and how these concepts can be used to interpret the nonequilibrium systems described by gilbert broad basin scale studies were common in the period but few were as quantitative and empirically rigorous or employed such a range of methodologies as pp105 none demonstrated such an extreme case of anthropogeomorphic change

channel overflows of the pōhue bay flow mauna loa hawai i examples of the contrast between surface and interior lava a number of overflows from a large lava channel and tube system on the southwest rift zone of mauna loa were studied initial overflows were very low viscosity gas rich p hoehoe evidenced by flow unit aspect ratios and vesicle sizes and contents calculated volumetric flow rates in the channel range between 80 and 890 m3 s and those of the overflows between 35 and 110 m3 s after traveling tens to hundreds of meters the tops of these sheet like overflows were disrupted into a surface composed of clinker and p hoehoe fragments after these a overflows came to rest lava from the interiors was able to break out on to the surface as p hoehoe the surface structure of a lava flow records the interaction between the differential shear rate usually correlated with the volumetric flow rate and viscosity induced resistance to flow however the interior of a flow being better insulated may react differently or record a later set of emplacement conditions clefts of toothpaste lava occurring within fields of clinker on proximal type a flows also record different shear rates during different times of flow emplacement the interplay between viscosity and shear rate determines the final morphological lava type and although no specific portion of lava ever makes a transition from a back to p hoehoe parts of a flow can appear to do so

how shear helps lava to flow understanding the thermo rheological regime and physical character of lava while it is flowing is crucial if we are to adequately model lava flow emplacement dynamics we present measurements from simultaneous sampling and thermal imaging across the full width of an active channel at piton de la fournaise la reunion france our data set involves measurements of flow dynamics at three sites down channel from the vent quantification of flow velocities cooling rates sample texture and rheology allows all thermo rheological parameters to be linked and down as well as cross channel variations to be examined within 150 m from the vent we recorded an unexpected velocity increase from 0 07 to 0 1 m s in spite of cooling rates of 0 19 to 0 29 degree sign c m and constant slope this change requires a switch from a newtonian dominated regime to a bingham plug dominated regime sample analysis reveals that the plug comprises foam like lava and the shear zones involve vesicle poor low viscosity lava with distance from the vent shear zones develop carrying the vesicular plug between them this causes flow to initially accelerate helped by bubble shearing in narrow lateral shear zones until cooling takes over as the main driver for viscosity increase and hence velocity decrease

the history of human induced soil erosion geomorphic legacies early descriptions and research and the development of soil conservation a global synopsis abstract this paper presents a global synopsis about the geomorphic evidence of soil erosion in humid and semihumid areas since the beginning of agriculture historical documents starting from ancient records to data from the mid twentieth century and numerous literature reviews form an extensive assortment of examples that show how soil erosion has been perceived previously by scholars land surveyors farmers land owners researchers and policy makers examples have been selected from ancient greek and roman times and from central europe southern africa north america the chinese loess plateau australia new zealand and easter island furthermore a comprehensive collection on the development of soil erosion research and soil conservation has been provided with a particular focus on germany and the usa geomorphic evidence shows that most of the agriculturally used slopes in the old and new worlds had already been affected by soil erosion in earlier prehistoric times early descriptions of soil erosion are often very vague with regard to the roman times geomorphic evidence shows seemingly opposing results ranging from massive devastation to landscapes remaining stable for centuries unfortunately historical documentation is lacking in the following centuries historical records become more frequent and more precise and observations on extreme soil erosion events are prominent sometimes they can be clearly linked to geomorphic evidence in the field the advent of professional soil conservation took place in the late eighteenth century the first extensive essay on soil conservation known to the western world was published in germany in 1815 the rise of professional soil conservation occurred in the late nineteenth and early twentieth centuries soil remediation and flood prevention programs were initiated but the long term success of these actions remains controversial in recent years increasing interest is to recover any traditional knowledge of soil management in order to incorporate it into modern soil conservation strategies the study shows that local and regional variations in natural settings cultural traditions and socioeconomic conditions played a major role for the dynamics and the rates of soil erosion on a long term perspective geomorphic evidence and historical sources can often complement each other but there should be also an awareness of new pitfalls when using them together

a three dimensional bingham model for channeled lava flows we propose a three dimensional 3 d bingham model for channeled lava flow unlike from the 3 d newtonian models this model can be applied also far from the vent where the bingham rheology cannot be neglected as a consequence of the lava cooling we assume the lava to be an isothermal bingham liquid flowing in a rectangular channel down a constant slope the flow velocity is calculated by solving semianalytically the steady state navier stokes equation together with the 3 d bingham constitutive equation the flow vorticity is evaluated and used to define the plug shape and position for different flows a completely filled conduit a partially filled conduit and an open channel each component of the flow vorticity vector satisfies the laplace equation and has been evaluated by using the relaxation method the mass flow rate is evaluated for different values of the yield stress it appears that the bingham rheology causes a significant reduction in flow rate as the yield stress increases for the highest yield stress values the plug in the center of the flow welds with the plugs in the flow corners suggesting a possible rheological mechanism for the lava tube formation

cooling and crystallization of lava in open channels and the transition of pāhoehoe lava to a ā samples collected from a lava channel active at kilauea volcano during may 1997 are used to con strain rates of lava cooling and crystallization during early stages of flow lava erupted at near liquidus tem peratures f1150 7c cooled and crystallized rapidly in upper parts of the channel glass geothermometry indi cates cooling by 12 14 7c over the first 2 km of trans port at flow velocities of 1 2 m s this translates to cooling rates of 22 50 7c h cooling rates this high can be explained by radiative cooling of a well stirred flow consistent with observations of non steady flow in proximal regions of the channel crystallization of plag ioclase and pyroxene microlites occurred in response to cooling with crystallization rates of 20 50 per hour crystallization proceeded primarily by nucleation of new crystals and nucleation rates of f10 4 cm 3 s are similar to those measured in the 1984 open channel flow from mauna loa volcano there is no evidence for the large nucleation delays commonly assumed for plagioclase crystallization in basaltic melts possibly a reflection of enhanced nucleation due to stirring of the flow the transition of the flow surface morphology from pahoehoe to a aoccurred at a distance of 1 9 km from the vent at this point the flow was thermally stratified with an interior temperature of f1137 7c and crystallinity of f15 and a flow surface tempera ture of f1100 7c and crystallinity of f45 a afor mation initiated along channel margins where crust was continuously disrupted and involved tearing and clotting of the flow surface both observations suggest that the transition involved crossing of a rheological threshold we suggest this threshold to be the develop ment of a lava yield strength sufficient to prevent vis cous flow of lava at the channel margin we use this concept to propose that a aformation in open chan nels requires both sufficiently high strain rates for con tinued disruption of surface crusts and sufficient groundmass crystallinity to generate a yield strength equivalent to the imposed stress in hawai i where lava is typically microlite poor on eruption these combined requirements help to explain two common observations on a aformation a a aflow fields are generated when effusion rates are high thus promoting crustal disruption and b under most eruption conditions lava issues from the vent as pahoehoe and changes to a aonly after flowing some distance thus permitting sufficient crystallization

a study of physico geographical factors for formation of hyperconcentrated flows in the loess plateau of china semi arid climate poor vegetation cover and highly erodible loess can be regarded as the main natural factors responsible for the formation of hyperconcentrated flows on the loess plateau china the degree to which the hyperconcentrated flows develop especially their extreme suspended concentration shows a significant areal differentiation this is closely related to the grainsize composition of suspended sediment an optimal grainsize composition of suspended sediment has been identified which leads to the highest value of extreme concentration among different river basins this optimal composition is related to the combination of three surface material types i e loess wind blown sand and weathered bedrock and it occurs as a result of seasonally alternating wind and water processes operating in this area

extreme flooding of the lower yellow river near the northgrippian meghalayan boundary evidence from the shilipu archaeological site in southwestern shandong province china abstract understanding the societal impacts of past climate changes may deepen our insight into human adaptation and resilience against potential climate changes in the future however the degree and nature of climate civilization link are still a matter of debate fluvial deposits preserved within a cultural stratigraphical context at archaeological sites in the lower yellow river area may offer an exceptional framework for evaluating the role of climate changes in the rise and fall of ancient civilizations here we show evidence for great lower yellow river floods during the neolithic bronze age transition about 4000 3500 years ago comparing with existing terrestrial and marine records suggests that they were a downstream manifestation of flooding in the middle reaches of the yellow river most likely triggered by excessive summer precipitation while a weak el nino condition prevailed the floods substantially modified the preexisting landscape and altered the agricultural conditions thereby driving people dwelling on the higher mounds to move upward our results provide a past analogue of the linked climatic environmental and societal changes at a time when large and rapid climate changes occurred

channel adjustments in response to the operation of large dams the upper reach of the lower yellow river the yellow river in china carries an extremely large sediment load river channel form and lateral shifting in a dynamic partly meandering and partly braided reach of the lower yellow river have been significantly influenced by construction of sanmenxia dam in 1960 liujiaxia dam in 1968 longyangxia dam in 1985 and xiaolangdi dam in 1997 using observations from huayuankou station 128 km downstream of xiaolangdi dam this study examines changes in the river before and after construction of the dams the temporal changes in the mean annual flow discharge and mean annual suspended sediment concentration have been strongly influenced by operation of theses dams observations of sediment transport coefficient ratio of sediment concentration to flow discharge at a station hydraulic geometry and bankfull channel form observed from 1951 to 2006 have shown that although variations in flow and sediment load correspond to different periods of dam operation changes in channel form are not entirely synchronous with these the channel has been subject to substantial deposition due to the flushing of sediment from sanmenxia dam resulting in a marked reduction in bankfull cross sectional area flows below bankfull had a greater impact on channel form than higher flows because of very high sediment load at a station hydraulic geometry shows that the variation of channel cross sectional area below bankfull in this wide and relatively shallow system largely depends on changes in width such at a station changes are significantly influenced by 1 events below bankfull and 2 overbank floods bankfull depth is the main component of channel adjustment in that depth adjusts synchronously with channel area the channel adjusts its size by relatively uniform changes in depth and width since 1981 channel morphology is not the product of single channel forming flow frequency it is determined by the combination of relatively low flows that play an important role in fine sediment transport and bed configuration as with relatively high flows that are effective at modifying the channel s morphology the sediment transport coefficient is a useful index for efficiently guiding the operation of the dams in a way that would minimize channel changes downstream sedimentation over the nearly 60 years of study period caused the lower yellow river to aggrade progressively the only significant exception being the two years following completion of sanmenxia dam

volatiles in glasses from mauna loa volcano hawai i implications for magma degassing and contamination and growth of hawaiian volcanoes glasses from mauna loa pillow basalts recent subaerial vents and inclusions in olivine were analyzed for s cl f and major elements by electron microprobe select submarine glasses were also analyzed for h2o and co2 by infrared spectroscopy the compositional variation of these tholeiitic glasses is dominantly controlled by crystal fractionation and they indicate quenching temperatures of 1 115 1 196 c submarine rift zone glasses have higher volatile abundances except f than nearly all other submarine and subaerial glasses with the maximum concentrations increasing with water depth the overwhelming dominance of degassed glasses on the submarine flanks of mauna loa implies that much of volcano s recent submarine growth involved subaerially erupted lava that reached great water depths up to 3 1 km via lava tubes anomalously high f and cl in some submarine glasses and glass inclusions indicate contamination possibly by fumarolic deposits in ephemeral rift zone magma chambers the relatively high co2 but variable h2o k2o and s k2o in some submarine rift zone glasses indicates pre eruptive mixing between degassed and undegassed magma within mauna loa s rift system volatile compositions for mauna loa magmas are similar to other active hawaiian volcanoes in s and f but are less cl rich than l ihi glasses however cl k2o ratios are similar mauna loa and l ihi magmas have comparable but lower h2o than those from kilauea thus kilauea s source may be more h2o rich the dissimilar volatile distribution in glasses from active hawaiian volcanoes is inconsistent with predictions for a simple concentrically zoned plume model

geochemistry of the 1984 mauna loa eruption implications for magma storage and supply the 1984 eruption of mauna loa volcano hawaii produced about 220 106 m3 of lava of remarkably homogeneous composition no significant compositional changes occurred during the 22 day eruption and along the 20 km vent system even though crystallinity increased substantially accompanying a decline in the eruption rate such homogeneity in lava composition is typical of many historic mauna loa eruptions the 1984 lava along with most other homogeneous mauna loa lavas is multiply saturated crystallizing olivine clinopyroxene and plagioclase bulk compositions are perched at the intersection of an olivine control trend with a trend for more differentiated lavas there is no evidence to indicate that the 1984 lava is a differentiate of the 1975 magma or that it results from mixing a new batch of magma with differentiated melt remaining in the magmatic plumbing system after the 1975 eruption it is proposed that these lavas are erupted directly from a small continuously replenished magma reservoir located about 3 4 km beneath the summit caldera successive eruptions therefore provide a sampling of magma chamber processes and small but discernible changes in lava composition reflect the competing processes of magma supply differentiation and eruption

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

crystallization history of the 1984 mauna loa lava flow during a 3 week eruption in 1984 mauna loa produced vent lavas that increased in crystallinity from 1 to 30 and 27 km long flows that increased in crystallinity as they moved downstream we examined the crystallization history of these lavas using crystal size distribution csd analysis to study the rates of crystallization viscosity increase and latent heating typical average growth and nucleation rates were 5 10 9 cm s 1 and 5 cm 3 s 1 for microphenocrysts 20 to 500 m size crystals nucleated in the rift zone and 5 10 8 cm s 1 and 5 104 cm 3 s 1 for microlites 1 to 20 m size crystals nucleated in the channel these crystallization rates are high compared with those found in other csd studies of igneous rocks probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel growth and nucleation rates decreased with time at the vent and with distance downstream the maximum downstream total crystallinity measured is 39 25 microlites 14 microphenocrysts in a quenched sample 14 km from the vent growth and nucleation rates cannot be calculated for postemplacement samples but they place upper limits of 53 58 on the amount of crystallization in the channel 9 20 km from the vent crystallization could have been mostly responsible for the 105 fold downstream increase in apparent viscosity although degassing and increasing incorporation of solid lava fragments also contributed another effect of crystallization on the lava flow was the sizeable latent heating 0 01 j g 1 s 1 over the first half of the flow length if the crystallinity of downstream quench samples is representative of the hot fluid core which may have been counteracted by entrainment of cooler material measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics

comparative geothermometry of recent hawaiian eruptions in this paper we compare lava temperatures measured using cr a1 thermocouples or infrared spectrometry with estimated quenching temperatures based on the glass geothermometry calibration of helz and thornber 1987 comparative data are available for the april 1982 and september 1982 summit eruptions the pu u o o east rift eruption 1983 1986 all three eruptions at kilauea and the 1984 mauna loa eruption the results show that quenching temperatures based on the mgo contents of kilauean glasses tmgo lie within 10oc of field measurements using the infrared spectrometer for 85 of the samples where a cr a1 thermocouple was used 90 of the field measurements lie within 1 o to 11oc of tmg o for samples with tfiel d 1130oc samples where tfiel d 1130oc show larger divergence the uncertainty in tmg o by itself is 10oc so the level of agreement between field measurements and tmg o is very good for kilauean lavas systematic comparison of field measurements of temperature with glass geothermometry for the 1984 mauna loa eruption suggests that although the field and glass temperatures lie within 10oc of each other the kilauean tmg o calibration is nevertheless not appropriate for mauna loa glasses and that actual quenching temperatures for mauna loa samples will lie 10o 20oc higher than would be predicted from the kilauea calibration curve consideration of possible effects of variable volatile content suggest that in most cases these are small samples erupted early in an eruption may reflect preeruptive water contents different enough to affect tmg o significantly but later spatter samples and all flow samples appear to have equilibrated at low enough water contents for the calibration to be applicable we conclude that the mgo based geothermometer can be applied to glassy kilauean samples to give temperatures that generally will lie within 10oc of a field measurement plots of glass mgo content versus time if a suitable sample base is available should give a thorough quantitative record of the thermal history of any kilauean eruption

hawaiian lava flows in the third dimension identification and interpretation of pahoehoe and a a distribution in the kp 1 and soh 4 cores 1 hawaiian lava flows are classified as pahoehoe or a a by their surface morphology as surface morphology reflects flow emplacement conditions the surface distribution of morphologic flow types has been used to study the evolution and eruptive history of basaltic volcanoes we extend this analysis to the third dimension by determining the distribution of flow types in two deep drill cores the scientific observation hole 4 soh 4 core drilled near kilauea s east rift zone erz and the pilot hole kahi puka 1 kp 1 for the hawaiian scientific drilling project hsdp drilled through distal flows from mauna loa and mauna kea flows are classified using both internal structures and groundmass textures with the latter useful when identification based on mesoscopic flow features e g surface morphology and vesicle content and distribution is ambiguous we then examine the temporal distribution of pahoehoe and a a flows in proximal soh 4 and distal kp 1 settings sequence analysis shows that the two flow types are not randomly distributed in either core but instead are strongly clustered the proximal soh 4 core is dominated by thin pahoehoe flows 60 by volume consistent with the common occurrence of surface fed pahoehoe flows in near vent settings the distal kp 1 core has a high proportion of a a 58 by volume although the proportion of pahoehoe and a a varies dramatically throughout the mauna kea sequence thick inflated pahoehoe flows dominate when the drill site was near sea level consistent with the numerous inflated pahoehoe fields on the current coastal plains of kilauea and mauna loa a a flows are abundant when the site was far above sea level as slope increases from the coastal plains to mauna kea s flank this correlation may reflect the combined effect of long transport distances and increased slopes on flow emplacement these results demonstrate that flow type and thickness variations in cores provide valuable information about both vent location and local site environment observed variations in flow type within the kp 1 core raise interesting questions about feedback between volcano evolution and flow morphology and suggest that flow type is an important variable in models of volcano growth and related models for lava flow hazard assessment

observations on basaltic lava streams in tubes from kilauea volcano island of hawai i from 1986 to 1997 the pu u o o kupaianaha eruption of kilauea produced a vast pahoehoe flow field fed by lava tubes that extended 10 12 km from vents on the volcano s east rift zone to the ocean within a kilometer of the vent tubes were as much as 20 m high and 10 25 m wide on steep slopes 4 10 a little farther away from the vent some tubes formed by roofing over of lava channels lava streams were typically 1 2 m deep flowing within a tube that here was typically 5 m high and 3 m wide on the coastal plain 1 tubes within inflated sheet flows were completely filled typically 1 2 m high and several tens of meters wide tubes develop as a flow s crust grows on the top bottom and sides of the tubes restricting the size of the fluid core the tubes start out with nearly elliptical cross sectional shapes many times wider than high broad flat sheet flows evolve into elongate tumuli with an axial crack as the flanks of the original flow were progressively buried by breakouts temperature measurements and the presence of stalactites in active tubes confirmed that the tube walls were above the solidus and subject to melting sometimes the tubes began downcutting progressive downcutting was frequently observed through skylights a rate of 10 cm d was measured at one skylight for nearly 2 months

anthropogenic origins of a late holocene basin wide unconformity in the middle reaches of the yellow river the luoyang basin henan province china we evaluate the relative importance of climate change fluvial dynamics and anthropogenic environmental modification in forming the holocene sedimentary record of the luoyang basin a tributary drainage basin of the yellow river located in western henan province china our 2011 fieldwork south of the erlitou site in the luoyang basin indicates that an unconformity dating to ca ad 1100 is roughly coincident with a major southward shift in the lower course of the yellow river in ad 1128 the governor of kaifeng breached the dikes of the yellow river to impede an advancing army causing the yellow river to flow south out to the yellow sea we argue that the dike breach not only changed the fluvial dynamics of the yellow river but also switched the rivers in the luoyang basin from an aggrading to an incising system the resumption of sedimentation in the luoyang basin is roughly coincident with the next major shift of the yellow river s main course northward to the bohai sea in ad 1855 the unconformity found in the luoyang basin may be a legacy of historically contingent human agency rather than climatic shifts or gradual environmental modification

shear rate dependence of the pāhoehoe to a ā transition analog experiments hawaiian lava flows typically erupt as pahoehoe and transform to a aas they travel away from eruptive vents although the exact conditions that govern this transformation are not well constrained here we describe a set of laboratory experiments that use corn syrup and ellipsoidal rice grains as an analog to lava with crystals to examine the depen dence of the transition on shear rate and particle concentration at a particle volume fraction of 0 3 increasing the shear rate produces a sequence of deformation regimes defined by increasing amounts of shear localization the same regimes may be traversed at constant shear rate by varying the particle concentration at high shear rates the onset of nonlaminar deformation corresponds to the percolation threshold thus providing a link between suspension microstructure and deformation behavior together these results high light the combined importance of shear rate and crystallinity in determining the flow behavior of basaltic lava

formation of channelized lava flows on an unconfined slope 1 the formation of channelized lava flows on a wide uniform slope is investigated both theoretically and experimentally when a lava is released at a constant flow rate from a point source we predict that it flows both down and across the slope at the same rate in a early time regime before undergoing a transition to a long time regime where down slope flow is faster than lateral flow eventually the lateral flow is stopped by the strength of the growing surface crust and the flow then travels down slope in a channel of constant width using scaling analysis we derive expressions for the final channel width in both flow regimes as a function of the flow rate the slope the density difference driving the flow the lava viscosity the thermal diffusivity and the yield strength of the crust we also find a dimensionless flow morphology parameter that controls whether the subsequent channel flow occurs in a mobile crust regime or in a tube regime these theoretical predictions are in good agreement with laboratory experiments in which polyethylene glycol wax flows down a wide uniform slope under cold water the theory is also applied to the understanding of the formation of a basaltic sheet flow lobe in hawaii which had an estimated crust yield strength of order 6 104 pa

sediment deposition and erosion during the extreme flood events in the middle and lower reaches of the yangtze river abstract floods often are accompanied by intensified soil erosion and thus high sediment supply from the catchment into the main channel of the river this paper examined the sediment processes especially deposition and erosion during the two extreme flood years in 1954 and 1998 in the middle and low reaches of the yangtze river the total amount of sediment supplied to the middle and lower reaches from yichang hankou and hankou datong was 1095 mt in 1954 and 855 9 mt in 1998 or 176 and 137 of the averaged 622 mt a from 1950 to 2006 a high deposition occurred in the floodplains lakes and channels along the section yichang hankou both in 1954 and 1998 the total deposition reached 635 mt and 499 mt in 1954 and 1998 or 138 and 124 of the sediment load measured at the datong station respectively however different processes in the downstream section hankou datong during the two flood events were found severe erosion 140 mt happened in 1954 but only a slight erosion occurred 22 mt in 1998 thus the floodplains and channels in the middle and lower reaches of the yangtze river play an important role in regulating sediment discharge during extreme flood events the heavy deposition in the middle reaches effectively reduced the amount of sediment discharged into the river mouth and thus acted as a major depocenter in the extreme flood year the results also suggested that the yichang hankou tended to shift from a depositional section to an erosional section whereas the hankou datong changed from an erosion dominated section to a deposition dominated section even before the three gorges reservoir infilling in 2003 it is anticipated that this tendency would be accelerated and the historical role of sediment regulation by the two reaches could eventually be changed due to the reduced sediment supply from the upper yangtze

lengths and hazards from channel fed lava flows on mauna loa hawai i determined from thermal and downslope modeling with flowgo using the flowgo thermo rheological model we have determined cooling limited lengths of channel fed i e a lava flows from mauna loa we set up the program to run autonomously starting lava flows from every 4th line and sample in a 30 m spatial resolution srtm dem within regions corresponding to the ne and sw rift zones and the n flank of the volcano we consider that each model run represents an effective effusion rate which for an actual flow coincides with it reaching 90 of its total length we ran the model at effective effusion rates ranging from 1 to 1 000 m3 s 1 and determined the cooling limited channel length for each keeping in mind that most flows extend 1 2 km beyond the end of their well developed channels and that our results are non probabilistic in that they give all potential vent sites an equal likelihood to erupt lava coverage results include the following sw rift zone flows threaten almost all of mauna loa s sw flanks even at effective effusion rates as low as 50 m3 s 1 the average effective effusion rate for sw rift zone eruptions since 1843 is close to 400 m3 s 1 n flank eruptions although rare in the recent geologic record have the potential to threaten much of the coastline s of keauhou with effective effusion rates of 50 100 m3 s 1 and the coast near anaeho omalu if effective effusion rates are 400 500 m3 s 1 the 1859 a flow reached this coast with an effective effusion rate of 400 m3 s 1 if the ne rift zone continues to be active only at elevations 2 500 m in order for a channel fed flow to reach hilo the effective effusion rate needs to be 400 m3 s 1 the 1984 flow by comparison had an effective effusion rate of 200 m3 s 1 hilo could be threatened by ne rift zone channel fed flows with lower effective effusion rates but only if they issue from vents at 2 000 m or lower populated areas on mauna loa s se flanks e g p hala could be threatened by sw rift zone eruptions with effective effusion rates of 100 m3 s 1

emplacement history and inflation evidence of a long basaltic lava flow located in southern payenia volcanic province argentina abstract the el corcovo lava flow from the huanul shield volcano in the southern mendoza province central western argentina traveled a distance of 70 km and covered a minimum area of 415 km 2 the flow emplacement was controlled both by extrinsic e g topography and intrinsic e g lava supply rate lava physicochemical characteristics factors the distal portion of the lava flow reached the colorado river valley in la pampa province where it spread and then was confined by earlier river channels cross sections through the flow surveyed at several localities show two vesicular layers surrounding a dense central section where vesicles are absent or clustered in sheet shaped and cylindrical shaped structures lavas of the el corcovo flow are alkaline basalts with low values of viscosity the morphological and structural characteristics of the flow and the presence of landforms associated with lava accumulation are the evidence of inflation this process involved the formation of a tabular sheet flow up to 4 m of thick with a large areal extent in the proximal sectors while at terminal sectors frontal lobes reached inflation values up to 10 m the numerous swelling structures present at these portions of the flow suggest the movement of lava in lava tubes we propose that this aspect and the low viscosity of the lava allowed the flow travel to a great distance on a gentle slope relief

a developmental model of olivine morphology as a function of the cooling rate and the degree of undercooling we performed dynamic crystallization experiments in the cmas system at 1 atm to investigate the evolution of the morphology of forsterite crystals as a function of cooling rate and degree of undercooling in sections parallel to the 010 plane we observed the evolution of the forsterite morphology from tablets to hopper skeletal crystals and then to swallowtail shapes dendritic morphology for increased degree of undercooling the other shapes described in the literature can be interpreted as particular sections of those three shapes the onset of dendritic growth is due to a competition between the growth of the faces of the initial hopper crystal and dendrite overgrowths the forsterite dendrites are formed by a succession of units which look like hopper shapes this result has been tested by an additional set of experiments

the petrology of some picrites from mauna loa and kilauea volcanoes hawaii the mineralogy and chemistry of picrites from mauna loa and kilauea have been investigated to evaluate for hawaiian tholeiitic picrites the contrasting genetic models which have been proposed for these mg rich volcanics namely products of direct crystallization of high mg melts 20 25 mgo or the result of accumulation of olivine phenocrysts into less mg rich melts genetic interpretations rely heavily on mg fe partitioning relations between olivines and their picrite hosts although the 100 mg mg fe2 ratios m of picrites are wide ranging m 73 6 82 9 for fe2o3 feo 0 15 with mgo as high as 27 8 the average 100 mg mg fe ratios mg of the cores of olivine phenocrysts megacrysts show only restricted compositional variation mg 87 2 89 0 successive olivine generations are progressively more fe rich olivine liquid mg fe partitioning data and the mn and ni abundances in olivine phenocrysts collectively indicate that they were precipitated by mg rich basaltic melts with 12 14 mgo spinel compositions range from liquidus magnesiochromites occurring mainly as inclusions in olivine phenocrysts to groundmass titanomagnetites which crystallized at nearsolidus temperatures the cr2o3 contents and m values of liquidus magnesiochromites suggest that their parent melts were neither mg rich picritic mgo 20 nor relatively mg poor basaltic types