soil weathering and accumulation rates of oxalate extractable phases derived from alpine chronosequences of up to 1 ma in age abstract in this study we compare newly developed chemical weathering data with previously published data from soils developed along two chronosequences of glacial deposits in the european alps and the rocky mountains wind river range usa by combining these chronosequences we are able to present a comprehensive dataset that represents a time period of 1 ma we describe weathering trends of important elements using a number of weathering indices e g k ca ti ratio the weathering index b of kronberg and nesbitt 1981 and the open mass transport function further we describe the accumulation of al fe si and mn oxyhydroxides including partially organic phases as a function of time and derive the corresponding accumulation rates we calculated pedogenetically formed oxyhydroxides using an approach based on immobile elements our study represents one of only a few studies that describe rates of soil chemical weathering over a period as long as 1 ma results show that rates of chemical weathering clearly decrease along the chronosequences with increasing age of the soils we find weathering rates are nearly four orders of magnitude lower in the 1 ma old soils than in the young soils our results suggest that the older soils may be reaching a steady state for these chemical properties in their present environments a power function best explains the measured time trends of the index b and k ca ti ratios in the soils the best time trend model for pedogenic weakly to poorly crystalline phases and the relative losses gains based on the open system mass transport function were obtained with an exponential decay model function in terms of the soil system the decreases in the accumulation rate of the oxyhydroxides appears to be influenced not only by the factor of time but by climate as well increased precipitation at higher altitudes slows the decrease in weathering rate over time thus our 1 ma chronosequences also become pedogenic gradients since we describe variations in soil properties along biogenic gradients

erosional and climatic effects on long term chemical weathering rates in granitic landscapes spanning diverse climate regimes abstract we used cosmogenic nuclide and geochemical mass balance methods to measure long term rates of chemical weathering and total denudation in granitic landscapes in diverse climatic regimes our 42 study sites encompass widely varying climatic and erosional regimes with mean annual temperatures ranging from 2 to 25 c average precipitation ranging from 22 to 420 cm year 1 and denudation rates ranging from 23 to 755 t km 2 year 1 long term chemical weathering rates range from 0 to 173 t km 2 year 1 in several cases exceeding the highest granitic weathering rates on record from previous work chemical weathering rates are highest at the sites with rapid denudation rates consistent with strong coupling between rates of chemical weathering and mineral supply from breakdown of rock a simple empirical relationship based on temperature precipitation and long term denudation rates explains 89 95 of the variation in long term weathering rates across our network of sites our analysis shows that for a given precipitation and temperature chemical weathering rates increase proportionally with fresh material supply rates we refer to this as supply limited weathering in which fresh material is chemically depleted to roughly the same degree regardless of its rate of supply from breakdown of rock the temperature sensitivity of chemical weathering rates is two to four times smaller than what one would expect from laboratory measurements of activation energies for feldspar weathering and previous inter comparisons of catchment mass balance data from the field our results suggest that climate change feedbacks between temperature and silicate weathering rates may be weaker than previously thought at least in actively eroding unglaciated terrain similar to our study sites to the extent that chemical weathering rates are supply limited in mountainous landscapes factors that regulate rates of mineral supply from erosion such as tectonic uplift may lead to significant fluctuations in global climate over the long term

10be inventories in alpine soils and their potential for dating land surfaces abstract to exploit natural sedimentary archives and geomorphic landforms it is necessary to date them first landscape evolution of alpine areas is often strongly related to the activities of glaciers in the pleistocene and holocene at sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating using in situ produced cosmogenic nuclides are absent dating of soils could give information about the timing of landscape evolution this paper explores the applicability of soil dating using the inventory of meteoric 10be in alpine soils for this purpose a set of 6 soil profiles in the swiss and italian alps was investigated the surface at these sites had already been dated using the radiocarbon technique or the surface exposure determination using in situ produced 10be consequently a direct comparison of the ages of the soils using meteoric 10be and other dating techniques was made possible the estimation of 10be deposition rates is subject to severe limitations and strongly influences the obtained results we tested three scenarios using a the meteoric 10be deposition rates as a function of the annual precipitation rate b a constant 10be input for the central alps and c as b but assuming a pre exposure of the parent material the obtained ages that are based on the 10be inventory in soils and on scenario a for the 10be input agreed reasonably well with the age using surface exposure or radiocarbon dating the ages obtained from soils using scenario b produced ages that were mostly too old whereas the approach using scenario c seemed to yield better results than scenario b erosion calculations can in theory be performed using the 10be inventory and 10be deposition rates an erosion estimation was possible using scenario a and c but not using b the calculated erosion rates using these scenarios seemed to be plausible with values in the range of 0 57 mm ky the dating of soils using 10be has several potential error sources analytical errors as well as errors from other parameters such as bulk soil density and soil skeleton content have to be taken into account the error range was from 8 up to 21 furthermore uncertainties in estimating 10be deposition rates substantially influence the calculated ages relative age estimates and under optimal conditions absolute dating can be carried out age determination of alpine soils using 10be gives another possibility to date surfaces when other methods fail or are not possible at all it is however not straightforward quite laborious and may consequently have some distinct limitations

the temperature dependence of feldspar dissolution determined using a coupled weathering climate model for holocene aged loess soils abstract soils developed over the last 10 13 ky on peoria loess along a transect parallel to the mississippi river spanning 1600 km from north to south were investigated to estimate the effects of climate on rates of chemical weathering in the 22 soils na concentrations generally decreased from parent composition to the surface defining depletion profiles that document the weathering of plagioclase the integrated fraction of na f dissolved from each profile varied from 0 in the north to 26 in the south this variation is attributed to an increase in average precipitation and temperature from the north today s average values 0 5 m y 7 5 c to the south 1 2 m y 20 3 c we used the output from the genesis v2 global climate model gcm to calculate the mean annual temperature precipitation and porefluid advection velocity v through the soils for three time points during the last 13 000 y in order to quantify the effect of temperature on na depletion to interpret the soils quantitatively the na concentration depth profiles were fit to a sigmoidal model equation that yielded three fit parameters i a lumped kinetic parameter related to the reaction front thickness k ii the na concentration in soil at the surface c z 0 and iii the na concentration at depth in the parent c o the product kv the fraction f and the concentration difference c o c z 0 were all observed to vary with temperature along the transect according to the derivation and assumptions of the sigmoidal model these values are all functionally related to the dissolution rate constant of albite the variation in temperature can be explained for kv and c o c z 0 based on laboratory values of the activation energy e a for albite dissolution in contrast for the case of f the temperature dependence is larger than e a because it incorporates contributions from both e a and the reaction enthalpy h of albite dissolution furthermore the temperature dependence determined from c o c z 0 yields the best estimate of activation energy for albite dissolution e a 75 14 kj mol because it is not dependent upon the assumptions of soil texture such quantitative interpretations of soil profiles will be useful in predicting the effects of climate on soil chemistry

products of subglacial volcanic eruptions under different ice thicknesses two examples from antarctica late cenozoic subglacially erupted volcanic sequences are scattered throughout the antarctic peninsula two of the best preserved examples at mount pinafore alexander island c 5 5 6 ma and brown bluff graham land c 1 ma are complete enough to be regarded as sequence holotypes for this uncommonly preserved eruptive depositional setting despite a common glacial association the sedimentary lithofacies in the two outcrops suggest flowing and ponded water conditions respectively indicating significant differences in the depositional palaeoenvironments the original ice thicknesses exerted a major control on the lithofacies which resulted from each eruptive phase at mount pinafore the lithofacies were confined within a steep sided valley during successive eruptions beneath thin 100 150 m wet based ice the much thicker succession at brown bluff is a tindar tuya edifice which formed within a small basin probably 15 km across confined by ice 400 m thick

short and long term delivery rates of meteoric 10be to terrestrial soils well constrained long term average meteoric 10be deposition rates are important when meteoric 10be is used as a chronometer or tracer of earth surface processes to constrain meteoric 10be delivery to terrestrial soils we estimate time integrated 10be deposition rates from meteoric 10be inventories measured in dated soils and compare these results to a new synthesis of short term measurements of 10be in precipitation comparison of these long term rates to short term measurements suggests that short term measurements likely predict long term meteoric 10be deposition rates within uncertainties of 20 in precipitation measurements it is possible to deconvolve the contribution of atmospherically produced primary meteoric 10be from recycled meteoric 10be delivered by terrestrial dust if a second isotope is measured that quantifies either the recycled or primary components of meteoric 10be deposition we use dust concentration dependent differences between 7be and 10be measurements to make new estimates of the recycled contribution to total meteoric 10be flux delivered to the earth s surface these dust corrected data show a strong linear dependence between precipitation amount and primary meteoric 10be flux concentrations of primary meteoric 10be in mid and low latitude precipitation vary predictably by latitude between 0 63 104 and 2 05 104 atoms cm3 of precipitation providing a first order estimate of primary meteoric 10be deposition for a given latitude and precipitation rate

exhumation paths of high pressure low temperature metamorphic rocks from the lycian nappes and the menderes massif sw turkey a multi equilibrium approach the menderes massif and the overlying lycian nappes occupy an extensive area of sw turkey where high pressure low temperature metamorphic rocks occur precise retrograde p t paths reflecting the tectonic mechanisms responsible for the exhumation of these highpressure low temperature rocks can be constrained with multiequilibrium p testimatesrelyingonlocalequilibria whereasasimple isothermal decompression is documented for the exhumation of highpressure parageneses from the southern menderes massif various p t paths are observed in the overlying karaova formation of the lycian nappes in the uppermost levels of this unit far from the contact with the menderes massif all p t estimates depict cooling decompression paths these high pressure cooling paths are asso

late pleistocene holocene surface processes and landscape evolution in the central swiss alps abstract the european alps are a geomorphologically active region and experience a number of gravity driven hillslope processes soil and landscape formation in the alps has consequently undergone several minor and major traceable changes of developmental trajectories during the holocene soil development is hypothesised to be often non linear with time and characterised by stages of progressive and regressive evolution caused by upbuilding formation profile deepening and erosion profile shallowing several cold and warm climate phases are identified during the holocene but it is largely unknown which effects these might have had on slope processes by using datable moraines 10 be and mires 14 c we have constructed a temporal framework for these processes using the geochemical imprint of mires in the alpine setting of the goschener valley of the central swiss alps we reconstructed general mostly erosional landscape processes for the last ca 10 ka as this is the type locality for the goschener cold phase we assumed that this phase goschener cold phase i and ii 1 5 and 2 5 ka bp should have left easily recognizable traits after deglaciation 11 12 ka bp soil evolution was progressive beginning around 8 ka bp we detect a distinct increase in erosion here together with a vegetation change towards tundra vegetation and the highest measured rates of carbon sequestration other phases of high geomorphic activity were recognised ca 5 6 ka bp 4 ka bp and to a lesser extent 1 3 ka ago the cold phase at 5 6 ka bp corresponds to a less distinct change in vegetation and lessened erosion human impact is increasingly obvious since about 2 4 ka bp which overlaps with the goschener cold phase nonetheless erosion processes were not extraordinarily high during this period and a climate effect cannot be distinguished we detect evidence of increasing human disturbance regressive soil evolution for about the last 1 ka we also detect an increase in dust flux during the last ca 4 5 ka presumably due to the landscape change s in the sahara during this time

morphometry of glaciovolcanic edifices from iceland types and evolution abstract the morphology of many glaciovolcanoes is considered one of the distinctive characteristics of their ice confining eruption environment however a thorough morphometric analysis of a large number of glaciovolcanic edifices has never been performed based on a semi automatic geomorphometric mapping of glaciovolcanic edifices of the icelandic neovolcanic zones we present a morphometric database of 155 glaciovolcanic edifices formed during the last 0 78 ma this database enables a comprehensive analysis of the morphometric diversity of a large suite of glaciovolcanic edifices sheet like formations however are not considered due to lack of data using three planimetric measurements basal length average basal width and average summit plateau width and their ratios three main morphometric groups can be distinguished in a ternary diagram 1 conical edifices with no or small summit plateaus 2 linear ridges and 3 flat topped edifices subdivided into equidimensional and elongated all three groups contain edifices with and without lava caps these morphometric groups can be fitted to the commonly accepted terminology for cone mound tindar and tuya however since lava caps occur in all morphometric groups a grouping based on its existence is not practical this suggests that by adding the descriptor lava capped to any of the three classes may be a useful way to refine the classification based on the ternary diagram ridges are the most morphometrically distinct glaciovolcanic edifice because of their very extreme elongation followed by flat topped edifices and finally conical edifices however morphometric parameters cannot be used singlehanded to identify glaciovolcanic edifices from other types of volcanic edifices such as composite volcanoes shields or submarine volcanoes and should always be complemented with other observations the glaciovolcanic edifice volumes range from 0 15 10 2km3 to 32 km3 conical edifices are the smallest 1 km3 overall with growth three morphological evolutions can be considered a an initial eruptive fissure concentrates into one vent generating an equidimensional edifice that either can be a conical or a flat topped edifice b the edifice maintains its elongation suggesting that a fissure is the dominating vent structure and during continued eruption develops significant summit plateaus generating elongated flat topped edifices and c the edifice increases in elongation because the fissure lengthens during the eruption and a plateau building stage does not occur producing increasingly elongated ridges

melting of the glacier base during a small volume subglacial rhyolite eruption evidence from blahnukur iceland abstract although observations of recent volcanic eruptions beneath vatnajokull iceland have improved the understanding of ice deformation and meltwater drainage little is known about the processes that occur at the glacier base we present observations of the products of a small volume effusive subglacial rhyolite eruption at blahnukur torfajokull iceland lava bodies typically 7 m long have unusual conical morphologies and columnar joint orientations that suggest emplacement within cavities melted into the base of a glacier cavities appear to have been steep walled and randomly distributed these features can be explained by a simple model of conductive heat loss during the ascent of a lava body to the glacier base the released heat melts a cavity in the overlying ice the development of vapour escape pipes in the waterlogged permeable breccias surrounding the lava allows rapid heat transfer between lava and ice the formed meltwater percolates into the breccias recharging the cooling system and leaving a steam filled cavity the slow ascent rates of intrusive rhyolitic magma bodies provide ample time for a cavity to be melted in the ice above even during the final 10 m of ascent to the glacier base an equilibrium cavity size is calculated at which melting is balanced by creep closure this is dependent upon the heat input and the difference between glaciostatic and cavity pressure the cavity sizes inferred from blahnukur are consistent with a pressure differential of 2 4 mpa suggesting that the ice was at least 200 m thick this is consistent with the volcanic stratigraphy which indicates that the ice exceeded 350 m in thickness although this is the first time that a subglacial cavity system of this type has been reconstructed from an ancient volcanic sequence it shares many characteristics with the modern firn cave system formed by fumarolic melting within the summit crater of mount rainier washington at both localities it appears that localised heating at the glacier base has resulted in heterogeneous melting patterns despite the different rheological properties of ice and firn similar patterns of cavity roof deformation are inferred the development of low pressure subglacial cavities in regions of high heat flux may influence the trajectory of rising magma with manifold implications for eruptive mechanisms and resultant subglacial volcanic landforms

a model for submarine rhyolite dome growth ponza island central italy abstract the late pliocene rhyolitic submarine volcanic rocks of ponza island italy can be interpreted as the subaqueous equivalent of subaerial dome complexes in terms of geometry and structure three coalescing domes of about 1 km radius and aligned along a ne trending regional fracture have been identified the main difference between subaqueous and subaerial lava domes is that in a subaqueous environment lava is likely to undergo pervasive hyaloclastic brecciation so that domes are mainly composed of variously brecciated in situ to clast rotated hyaloclastite rather than coherent lava we suggest that the shape and rheologic behaviour through time of submarine domes are closely controlled by the development and thickness of the particulate hyaloclastic carapace which assumes the role of the solid crust of domes in subaerial environment the thickness of the hyaloclastic carapace at ponza is greater than 150 m and emplaced during several different pulses or eruptions in the earliest pulses lava is directly extruded on the seafloor and produces hyaloclastite the degree of brecciation of which decreases inward to the coherent flow banded rhyolite lava of the feeder dike once the hyaloclastic carapace is formed further pulses of magma combined with increase in height of the dome result in a local stress pattern characterised by a vertical 1 2 3 producing concentric and radial fractures and normal faults the newly rising magma shielded by the hyaloclastic carapace can intrude along these fault and fracture systems and invade previously emplaced but still water saturated hyaloclastite this produces the characteristic pattern of dikes observed at ponza as a series of concentric dikes that are progressively less inclined outward with respect to the dome centre these late stage dikes in turn produce hyaloclastite at their margins but generally less fragmented than the embedding hyaloclastite probably because the ascending magma is better shielded from direct contact with sea water periodic gravity collapses of the dome maintain the equilibrium between height and radius of the dome as suggested at ponza by the presence of mass flow deposits and the development of small topographic basins on top of the domes probably related to debris removal some of these topographic depressions host subaqueous pyroclastic deposits suggesting that if due to vertical growth of the dome water depth above the dome becomes shallower hydromagmatic explosions may occur

the control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment the study of a sample of river sediment enables the determination of spatially averaged denudation rates that provide an exceptional perspective on erosion and weathering processes that have taken place within a landscape these measurements are done with in situ produced cosmogenic nuclides e g 10be 26al mostly in quartz from alluvial sediment cosmogenic nuclides are produced when secondary cosmic rays interact with the very uppermost layer of the earth s surface they are produced within a characteristic depth scale of about 1 m which means that the measured concentrations record an integrated denudation history while material passed through this depth interval depending on the denudation rate the resulting integration time scales are 103 to 105 years and one obtains a robust long term estimate of natural denudation that is relatively insensitive to short term changes the last 10 years have seen significant research activity using these methods and an array of fascinating tectono geomorphologic and geochemical insights are emerging amongst these is the ability to identify the physical and chemical processes with which a landscape responds to tectonic activity or climate change a compilation of world wide denudation rates in non glaciated areas that however does not yet include some of the world s most active mountain belts has resulted in the following findings some of which have been unexpected 1 no obvious relationship between precipitation or mean annual temperature and total denudation is apparent 2 topographic relief alone does not result in high rates of denudation 3 denudation rates are high in areas of landscape rejuvenation that is triggered and controlled by tectonic activity faulting escarpment formation and retreat rifting surface uplift 4 rates of weathering using a combination of cosmogenic nuclides and zirconium normalised cation loss balances co vary primarily with physical erosion rates and much less with temperature or precipitation 5 in some areas of high land use short term rates from river load gauging exceed those from cosmogenic nuclides by several orders of magnitude which serves to highlight the severity of geomorphic change caused by human action in the future the control mechanisms over denudation will be determined on all spatial scales ranging from the single soil section to entire river basins the same analysis can be done back through time on well dated terraces lake records and marine sediment cores which is possible with 10be for the past 1 2 my the rates obtained will be used to develop a quantitative understanding of tectonic geomorphologic and geochemical landscape processes which in turn is a prerequisite to design and calibrate models of the response of landscapes to tectonic climate and anthropogenic forcing

large variations in holocene solar activity constraints from 10be in the greenland ice core project ice core 1 cosmogenic radionuclides extracted from ice cores hold a unique potential for reconstructing past solar activity changes beyond the direct instrumental period taking the geomagnetic modulation into account the solar activity in terms of the heliospheric modulation function can quantitatively be reconstructed in high resolution throughout the holocene for this period our results reveal changes in heliospheric modulation of galactic cosmic rays significantly larger than the variations reconstructed on the basis of neutron monitor measurements of galactic cosmic rays for the last 50 years moreover the 10be data from the greenland ice core project ice core as well as 14c support a high current solar activity however although the reconstruction of solar activity on long timescales is difficult our result suggests that the modern activity state of the sun is not that exceptional regarding the entire holocene this extended solar activity record provides the basis for further detailed investigations on solar and cosmic ray physics as well as on solar forcing of the earth s climate whose importance is suggested by increasing paleoclimatic evidences

application of cosmogenic 10be to dating soils on the raised coral reef terraces of kikai island southwest japan 10be concentrations of six soils on the raised coral reef terraces of kikai island southwest japan range from 0 80 to 7 17 109 atoms g 1 the annual deposition rate of 10be from the atmosphere to kikai island from 2000 to 2002 ranges from 2 0 to 3 5 106 atoms cm 2 year 1 with a mean of 2 8 0 7 106 atoms cm 2 year 1 minimum absolute ages calculated from the inventory of meteoric 10be in the soils and the annual deposition rate of 10be are initial rendzina like soil 8 ka rendzina like soil 18 ka brown rendzina like soil 56 ka terra fusca like soil 127 ka terra rossa like soil 136 ka and intergrade between terra rossa like and red yellow soil 102 ka therefore it was concluded that soil formation during the first 60 000 years would be as rendzina like soils and more than 100 000 years would be required for red yellow soils to develop on raised coral reef terraces under subtropical humid climatic conditions

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

subglacial lava propagation ice melting and heat transfer during emplacement of an intermediate lava flow in the 2010 eyjafjallajokull eruption during the 2010 eyjafjallajokull eruption in south iceland a 3 2 km long benmoreite lava flow was emplaced subglacially during a 17 day effusive explosive phase from april 18 to may 4 the lava flowed to the north out of the ice filled summit caldera down the outlet glacier gigjokull the flow has a vertical drop of about 700 m an area of ca 0 55 km2 the total lava volume is ca 2 5 107 m3 and it is estimated to have melted 10 13 107 m3 of ice during the first 8 days the lava advanced slowly 100 m day 1 building up to a thickness of 80 100 m under ice that was initially 150 200 m thick faster advance up to 500 m day 1 formed a thinner 10 20 m lava flow on the slopes outside the caldera where the ice was 60 100 m thick this subglacial lava flow was emplaced along meltwater tunnels under ice for the entire 3 2 km of the flow field length and constitutes 90 of the total lava volume the remaining 10 belong to subaerial lava that was emplaced on top of the subglacial lava flow in an ice free environment at the end of effusive activity forming a 2 7 km long a a lava field about 45 of the thermal energy of the subglacial lava was used for ice melting 4 was lost with hot water about 1 was released to the atmosphere as steam heat was mostly released by forced convection of fast flowing meltwater with heat fluxes of 125 310 kwm 2

ridge forming ice bounded lava flows at mount rainier washington large 0 3 4 km3 andesite and dacite lava flows at mount rainier washington sit atop or are perched along the sides of high ridges separating deep valleys early researchers proposed that these ridge forming lavas flowed into paleovalleys and displaced rivers to their margins entrenchment of the rivers then left the lavas atop ridges on the basis of exceptional flow thickness ice contact features and eruption age measurements we propose that the lavas flowed beside and between valley glaciers that filled the adjacent valleys in the pleistocene when the glaciers retreated the flows were left high on the adjacent ridges these lavas were never situated at valley floors and do not represent products of reversed topography instead ridge forming and perched lava flows at mount rainier and at many other high stratovolcanoes illustrate the ability of ice to dam deflect and confine flowing lava

subglacial and ice contact volcanism at the oraefajokull stratovolcano iceland eruptions of oraefajokull have produced mafic and silicic magmas and have taken place in both glacial and interglacial periods the geology of the volcano records the differing response of magmas of contrasting composition to interaction with ice of variable thickness and gives insight into the development of a long lived ice covered stratovolcano vatnafjall a ridge on the southeast flank of oraefajokull is the first area of the volcano to have been mapped in detail and the geological map is presented here alongside descriptions of each erupted unit the oldest units comprise pillow lavas hyaloclastite and jointed lava flows that were formed during subglacial basaltic eruptions involving abundant meltwater the products of a subsequent explosive initially phreatomagmatic subglacial rhyolite eruption were confined by ice to form a tephra pile over 200 m thick that was intruded by dense rhyolite magma towards the end of the eruption confinement by ice caused a later trachydacite lava flow to form buttresses and a steep pillar whilst some of the meltwater produced infiltrated the lava to generate red and black glassy breccias and cause localised steam explosions it is likely that much of it drained down the steep topography the most recently erupted units are subaerial basaltic lava flows the oldest of which were erupted during an interglacial period and have subsequently been partially eroded and scoured by advancing ice ice has been important in shaping the edifice by confining eruptive products to form constructional features and by later eroding parts of them to form deep valleys reconstructions of volcano ice interaction allowed the local thickness of the glacier at the time of each eruption to be estimated and demonstrates that the upper surface of the ice has varied in elevation by over 700 m

the global average production rate of10be precipitation collected in continuously open containers for about a year at seven sites around the united states was analyzed for10be 90sr 210pb and238u based on these data and long term precipitation 90sr and210pb delivery patterns the stratospheric tropospheric and recycled10be components in the collections were estimated and the global10be production rate was assessed single station production rate estimates range from 0 52 106 atoms cm 2 yr 1 to 2 64 106 atoms cm 2 yr 1 the mean value is 1 21 106 atoms cm 2 yr 1 with a standard error of 0 26 106 atoms cm 2 yr 1

ice volcano interaction of the 1996 gjalp subglacial eruption vatnajokull iceland volcanic eruptions under glaciers can cause dangerous floods and lahars1 2 3 and create hyaloclastite fragmented glassy rock mountains4 5 6 7 8 but processes such as the rate of heat transfer between ice and magma edifice formation and the response of the surrounding glacier are poorly understood because of the lack of data here we present observations from the fissure eruption at vatnajokull ice cap iceland in october 1996 in the 13 days of the eruption 3 km3 of ice were melted and the erupted magma fragmented into glass forming a hyaloclastite ridge 6 7 km long and 200 300 m high under 500 750 m of ice meltwater of temperatures of 15 20 c flowed along a narrow channel at the glacier bed into the grimsvotn subglacial lake for five weeks before draining in a sudden flood or jokulhlaup subsidence and crevassing of the ice cap occurred over the eruptive fissure and the meltwater path whereas elsewhere the glacier surface remained intact suggesting that subglacial eruptions do not trigger widespread basal sliding in warm based glaciers

physical volcanology of a subglacial to emergent rhyolitic tuya at rauðufossafjoll torfajokull iceland we present the first modern volcanological study of a subglacial to emergent rhyolite tuya at se rau ufossafjoll torfajokull iceland a flat topped edifice with a volume of 1 km3 was emplaced in upper pleistocene time beneath a glacier 350 m thick although it shares morphological characteristics with basaltic tuyas the lithofacies indicate a very different eruption mechanism field observations suggest that the eruption began with vigorous phreatomagmatic explosions within a well drained ice vault building a pile of unbedded ash up to 300 m thick this was followed by a subaerial effusive phase in which compound lava flows were emplaced within ice cauldrons small volume effusive eruptions on the volcano flanks created several lava bodies with a variety of features columnar jointed sides subaerial tops peperitic bases that are used to reconstruct spatially heterogeneous patterns of volcano ice interaction volcaniclastic sediments exposed in a stream section provide evidence for channelised meltwater drainage and fluctuating depositional processes during the eruption we develop models for the evolution of se rau ufossafjoll and discuss the differences between subglacial rhyolitic and basaltic eruption mechanisms which are principally caused by contrasting hydrological patterns

large scale phreatomagmatic silicic volcanism a case study from new zealand abstract pyroclastic deposits of the 20 000 year old wairakei formation occur in the region surrounding lake taupo in the central north island of new zealand recent advances in the correlation of both proximal and distal equivalents of the wairakei deposits show that they were the result of one large eruption the ash layers once covered most of new zealand they are also present in deep sea cores from the sw pacific and on the chatham islands the dispersal and grain size parameters of the ash fall members indicate that their vent area was within the taupo volcano tectonic depression which for a long period has contained a large lake the wairakei eruption is interpreted to have been phreatomagmatic throughout each phase of the eruption sequence generated its own characteristic deposits the sequence of events can be summarized as follows 1 eruption and deposition of a white fine grained bedded fall deposit 2 eruption and deposition of a medium grained pumice fall deposit 3 generation of ultra fine wet ash clouds with a fall deposit accumulating largely as aggregates and accretionary lapilli accompanied by base surges 4 formation of water cooled pyroclastic flows and deposition of an extensive ignimbrite 5 return to a dominantly vertical eruption column and deposition of a medium grained bedded ash fall immediately followed by another wet ultra fine fall deposit charged with accretionary lapilli finally 6 an ignimbrite less widespread than that of phase 4 was produced co ignimbrite fall deposits of fine vitric dust and medium grained pumice were laid down over a huge area there may have been a short hiatus in activity between phases 4 and 5

cosmic ray produced 10be and 26al in antarctic rocks exposure and erosion history we have measured cosmic ray produced t1 2 1 5 million years 10be and t1 2 0 705 million years 26al in purified quartz fractions of selected rock samples from antarctic mountains from these data we calculate 1 mean erosion rates for the limiting case of steady state surface exposure to cosmic rays and 2 minimum exposure ages for the limiting case of no erosion calculated mean erosion rates are very low on the order of a few times 10 5 cm yr we believe the sampling to be sufficient to generalize this result to exposed bedrock in antarctica in favorable cases it is possible to distinguish between the limiting cases steady state erosion seems a better description in such cases most samples including some taken a few meters above the present ice level seem to have been exposed for millions of years without major episodes of burial or abrasion by ice

identifying magma water interaction from the surface features of ash particles the deposits from explosive volcanic eruptions those eruptions that release mechanical energy over a short time span1 are characterized by an abundance of volcanic ash2 3 this ash is produced by fragmentation of the magma driving the eruption and by fragmenting and ejecting parts of the pre existing crust host rocks interactions between rising magma and the hydrosphere oceans lakes and ground water play an important role in explosive volcanism4 5 because of the unique thermodynamic properties of water that allow it to very effectively convert thermal into mechanical energy although the relative proportion of magma to host rock fragments is well preserved in the pyroclastic rocks deposited by such eruptions it has remained difficult to quantitatively assess the interaction of magma with liquid water from the analysis of pyroclastic deposits2 3 4 5 here we report the results of a study of natural pyroclastic sequences combined with scaled laboratory experiments we find that surface features of ash grains can be used to identify the dynamic contact of magma with liquid water the abundance of such ash grains can then be related to the water magma mass ratios during their interaction

surges of glaciers in iceland surges are common in all the major ice caps in iceland and historical reports of surge occurrence go back several centuries data collection and regular obser vationover thelast several decadeshave permitteda detailed descriptionof several surges fromwhich it is possible to generalize onthe nature of surging in icelandic glaciers com bining the historical records of glacier front variations and recent field research we sum marize the geographic distribution of surging glaciers their subglacial topography and geology the frequency andduration of surges changes in glacier surface geometry during the surge cycle and measured velocity changes comparedto calculatedbalance velocities wenotetheindicatorsofsurgeonsetanddescribechangesinice waterandsedimentfluxes duringa surge surgesaccomplishasignificantfractionofthetotalmasstransportthrough the main outlet glaciers of ice caps in iceland and have important implications for their hydrology ouranalysisof the data suggeststhat surge type glaciersin icelandarecharac terizedbygentlysloping surfacesandthatthey movetoo slowlytoremain inbalance given their accumulation rate surge frequency is neither regular nor clearly related to glacier size or massbalance steeply sloping glaciers whetherhard or soft bedded seemto move sufficiently rapidly to keep inbalance with the annual accumulation

strong climate and tectonic control on plagioclase weathering in granitic terrain abstract investigations to understand linkages among climate erosion and weathering are central to quantifying landscape evolution we approach these linkages through synthesis of regolith data for granitic terrain compiled with respect to climate geochemistry and denudation rates for low sloping upland profiles focusing on na as a proxy for plagioclase weathering we quantified regolith na depletion na mass loss and the relative partitioning of denudation to physical and chemical contributions the depth and magnitude of regolith na depletion increased continuously with increasing water availability except for locations with mean annual temperature

fragmentation of magma during plinian volcanic eruptions the ratio of the volume of vesicles gas to that of glass liquid in pumice clasts v g v l reflects the degassing and dynamic history experienced by a magma during an explosive eruption v g v l in pumices from a large number of plinian eruption deposits is shown here to vary by two orders of magnitude even between pumices at a given level in a deposit these variations in v g v l do not correlate with crystallinity or initial water content of the magmas or their eruptive intensities despite large ranges in these variables gas volume ratios of pumices do however vary systematically with magma viscosity estimated at the point of fragmentation and we infer that pumices do not quench at the level of fragmentation but undergo some post fragmentary evolution on the timescale of plinian eruptions pumices with viscosities 109 pa s can expand after fragmentation as long as their bubbles retain gas at a rate inversely proportional to their viscosity once the bubbles connect to form a permeable network and lose their gas expansion halts and pumices with viscosities 105 pa s can collapse under the action of surface tension textural evidence from bubble sizes and shapes in pumices indicates that both expansion and collapse have taken place the magnitudes of expansion and collapse therefore depend critically on the timing of bubble connectivity relative to the final moment of quenching we propose that bubbles in different pumices become connected at different times throughout the time span between fragmentation and quenching after accounting for these effects we derive new information on the fragmentation process from two characteristics of pumices the most important is a relatively constant minimum value of v g v l of 1 78 64 vol vesicularity in all samples with viscosities 105 pa s this value is independent of magma composition and thus reflects a property of the eruptive mechanism the other characteristic is that highly expanded pumices 85 vol vesicularities are common which argues against overpressure in bubbles as a mechanism for fragmenting magma we suggest that magma fragments when it reaches a vesicularity of 64 vol but only if sheared sufficiently strongly the intensity of shear varies as a function of velocity in the conduit which is related to overpressure in the chamber so that changes in overpressure with time are important in controlling the common progression from explosive to effusive activity at volcanoes

scanning electron microscope method for rock varnish dating rock varnish coatings on cobbles from geomorphic surfaces and exposed deposits in arid environments are an effective medium for dating over a time range of several thousand to a few million years a new analytical method for dating of rock varnish is presented wherein the varnish cation ratio vcr is determined by a scanning electron microscope sem equipped with an energy dispersive x ray analyzer edax the experimental sem method is a nondestructive technique that has several potential advantages over the original method of analysis described by r i dorn that uses particle induced x ray emission pixe of varnish scraped from rock surfaces the sem method can potentially eliminate analytical errors due to contamination from rock substrate because variations in varnish thickness and irregularities on the substrate surface are examined before cation ratios are determined because varnish surfaces remain intact varnish sites that yield anomalous results may be reanalyzed or verified in addition the general accessibility of scanning electron microscopes will make rock varnish dating more widely available for use in quaternary studies cation ratios were calculated for rock varnish from espanola basin new mexico and the yucca mountain region nevada and were used to construct rock varnish dating curves for these areas

soil geomorphology and frozen ground conditions at a subalpine talus slope having permafrost in the eastern swiss alps at a subalpine site with permafrost below the timberline in the eastern swiss alps the complex interrelationship between different environmental factors was investigated by applying an integrated approach that combines soil mapping 3d near surface geophysics and surface and subsurface temperature monitoring the objectives of this approach were to explore the 3d extension of isolated permafrost bodies and to relate this to surface parameters such as soils and humus forms and other extrinsic factors using this procedure interdependencies between surface soil properties and humus forms and subsurface factors ground thermal regime and frozen ground conditions could be independently analysed although time consuming 3d eri electrical resistivity imaging demonstrated its ability for precise permafrost mapping despite climate warming super cooling in winter along the investigated scree slopes is still efficient enough for establishing permafrost conditions by comparing the spatial dimensions of the permafrost bodies with surface conditions we found that thick moss or organic litter layers had an insulating effect and prevented the permafrost from melting however the comparison of soil units and soil thickness with the permafrost distribution did not always show an obvious relationship this indicates that there is a complex evolution and behaviour of soils and permafrost at such sites

snow contact volcanic facies and their use in determining past eruptive environments at nevados de chillan volcano chile studies of the eruptive products from volcanoes with variable ice and snow cover and a long history of activity enable reconstruction of erupted palaeoenvironments as well as highlighting the hazards associated with meltwater production such as jokulhlaups and magma water interaction existing difficulties include estimation of ice snow thicknesses and discrimination between ice and snow contact lithofacies we present field evidence from the cerro blanco subcomplex of nevados de chillan stratovolcano central chile which has erupted numerous times in glacial and non glacial periods and most recently produced andesitic lava flows in the 1861 1865 eruption from the santa gertrudis cone on the northwest flank of the volcano the main period of lava effusion occurred during the winter of 1861 when the upper flanks of the volcano were reportedly covered in snow and ice the bases and margins of the first lava flows produced are cut by arcuate fractures which are interpreted as snow contact features formed when steam generated from the melting of snow entered tensional fractures at the flow base in contrast the interiors and upper parts of these flows as well as the overlying flow units have autobrecciated and blocky textures typical of subaerial conditions due to insulation by the underlying lava similar textures found in a lava flow dated at 90 0 0 6 ka that was emplaced on the northwest flank of cerro blanco are also inferred to be ice and snow contact features these textures have been used to infer that a small valley glacier overlain by snow existed in the santa gertrudis valley at the time of the eruption such reconstructions are important for determining the long term evolution of the volcano as well as assessing future hazards at seasonally snow covered volcanoes

icelandic pseudocraters as analogs to some volcanic cones on mars pseudocraters are rootless vents formed by the interaction of lava flows with surface or near surface water this interaction can produce mild explosions and the accumulation of scoria and spatter into small constructs pseudocraters in several localities in iceland were examined in the field and compared to similar appearing features observed on mars the icelandic pseudocrater cones in this study range in size from 6 to 70 m in diameter have summit craters which range from 2 to 28 m in diameter many cones lack craters entirely and have flanks that are either concave up or convex up the size and spacing of icelandic pseudocraters might be a function of the availability of water in which larger closely spaced features result from efficient lava water interaction as suggested by the environments in which the features formed possible martian pseudocrater cones in amazonis planitia range in diameter from 30 to 180 m and have craters 12 to 80 m in diameter a numerical model for volcanic explosions was adapted to study the formation of pseudocraters under terrestrial and martian conditions the results suggest that explosions forming martian cones require significantly less water calculated masses are less by a factor of 4 to 16 than those forming icelandic pseudocraters despite their larger sizes this is attributed to the low gravity and atmospheric pressure in the mars environment and is consistent with the likely lower abundance of water which might be present as interstitial ice at shallow depths in the regolith locations of potential pseudocraters on mars at latitudes as low as 8 n imply the presence of crustal ice stores at the time of their formation

glacial interglacial history of the skaftafell region southeast iceland 0 5 ma volcanic strata in the skaftafell region southeast iceland record a sequence of at least 16 glacial and interglacial intervals since 5 ma two composite sections of 2 to 2 8 km thickness have been constructed from multiple overlapping cliff profiles the timing of alternating sequences of subaerial lava flows pillow basalts and hyaloclastite deposits is provided by magnetostratigraphic mapping and k ar radiometric dating we find that the frequency and intensity of glaciations increased significantly at ca 2 6 ma and particularly since 0 8 ma amplifying topographic relief in this area from

peperite a review of magma sediment mingling the study of peperite is important for understanding magma water interaction and explosive hydrovolcanic hazards this paper reviews the processes and products of peperite genesis peperite is common in arc related and other volcano sedimentary sequences where it can be voluminous and dispersed widely from the parent intrusions it also occurs in phreatomagmatic vent filling deposits and along contacts between sediment and intrusions lavas and hot volcaniclastic deposits in many environments peperite can often be described on the basis of juvenile clast morphology as blocky or fluidal but other shapes occur and mixtures of different clast shapes are also found magma is dominantly fragmented by quenching hydromagmatic explosions magma sediment density contrasts and mechanical stress as a consequence of inflation or movement of magma or lava magma fragmentation by fluid fluid shearing and surface tension effects is probably also important in fluidal peperite fluidisation of host sediment hydromagmatic explosions forceful intrusion of magma and sediment liquefaction and shear liquification are probably the most important mechanisms by which juvenile clasts and host sediment are mingled and dispersed factors which could influence fragmentation and mingling processes include magma host sediment and peperite rheologies magma injection velocity volatile content of magma total volumes of magma and sediment involved total volume of pore water heated presence or absence of shock waves confining pressure and the nature of local and regional stress fields sediment rheology may be affected by dewatering compaction cementation vesiculation fracturing fragmentation fluidisation liquefaction shear liquification and melting during magma intrusion and peperite formation the presence of peperite intraclasts within peperite and single juvenile clasts with both sub planar and fluidal margins imply that peperite formation can be a multi stage process that varies both spatially and temporally mingling of juvenile clast populations formed under different thermal and mechanical conditions complicates the interpretation of magma fragmentation and mingling mechanisms

products of an effusive subglacial rhyolite eruption blahnukur torfajokull iceland we present field observations from blahnukur a small volume 400 m thick lithofacies associations attest to complex patterns of volcano ice interaction erosive channels at the base of the subglacial sequence are filled by both eruption derived material and subglacial till which show evidence for deposition by flowing meltwater this suggests that meltwater was able to drain away from the vent area during the eruption much of the subglacial volcanic deposits consist of conical to irregularly shaped lava lobes typically 5 10 m long set in poorly sorted breccias with an ash grade matrix a gradational lavabreccia contact at the base of lava lobes represents a fossilised fragmentation interface driven by magma water interaction as the lava flowed over poorly consolidated waterlogged debris sets of columnar joints on the upper surfaces of lobes are interpreted as ice contact features the morphology of the lobes suggests that they chilled within conically shaped subglacial cavities 2 5 m high avalanche deposits mantling the flanks of blahnukur appear to have been generated by the collapse of lava lobes and surrounding breccia a variety of deposit characteristics suggests that this occurred both prior to and after quenching of the lava lobes collapse events may have occurred when the supporting ice walls were melted back from around the cooling lava lobes and breccias much larger lava flows were emplaced in the latter stages of the eruption columnar joint patterns suggest that these flowed and chilled within subglacial cavities 20 m high and 100 200 m in length there is little evidence for magma water interaction at lava flow margins which suggests that these larger cavities were drained of meltwater as rhyolite magma rose to the base of the glacier the nature of the subglacial cavity system played an important role in governing the style of eruption and the volcanic facies generated we present evidence that the cavity system evolved during the eruption reflecting variations in both melting rate and edifice growth that are best explained by a fluctuating eruption rate

the role of climate and vegetation in weathering and clay mineral formation in late quaternary soils of the swiss and italian alps nteractions between climate and soil remain ambiguous particularly when silicate weathering and clay mineral formation and transformation rates are considered in relation to global climate changes recent studies suggest that climate affects weathering rates much less than previously thought here we show that the climate in the central european alps has a significant but indirect influence on the weathering of soils through vegetation the pattern of element leaching and mineral transformations is not only due to precipitation and temperature element leaching was greatest in subalpine forests near the timberline weathering is lessened at higher and lower altitudes vegetation therefore contributes significantly to weathering processes the highest accumulation of organic matter was found in climatically cooler sites subalpine range where the production of organic ligands which enhance weathering is greatest patterns of smectite formation and distribution had strong similarities to that of the elemental losses of fe and al r 0 69 p 0 01 or base cations r 0 58 p 0 05 higher precipitation rates and the production of organic chelating compounds in the soil promoted the appearance of smectites the relationship between climate element leaching fe al ca mg k na and smectite formation is strongly nonlinear and driven by the podzolisation process which is more pronounced near the timberline because of the bioclimatic constellation climate warming will probably in the future lead to a decrease in som stocks in the subalpine to alpine range because of more favourable conditions for biodegradation that would also affect weathering processes

cryptotephrochronology of the eemian and the last interglacial glacial transition in the north east atlantic the eemian interglacial and the onset of the subsequent glacial period serve as the most recent analogue for the natural operation of the climate system during the current interglacial pronounced climatic oscillations occurred during this period but their nature and pattern are poorly understood due to dating limitations and unknown phase relationships between different regions and archives tephrochronology offers considerable potential for precise correlation of disparate palaeoclimatic archives preserving evidence of these rapid climatic transitions through the tracing of common isochronous tephra horizons we outline the identification of three previously unknown cryptotephra horizons within a marine core from the rockall trough north east atlantic this sequence preserves a high resolution record of this interval and shard size geochemical heterogeneity and the co variance of shard concentrations with ice rafted debris data are utilized to demonstrate that primary airfall was the most likely transport and depositional pathway the main geochemical populations of these horizons have similar transitional alkali major and trace element compositions suggesting that they were derived from a common icelandic source potentially the oraefajokull volcanic system these tephra horizons represent additions to the north atlantic event stratigraphy for this period and tentative correlations to icelandic terrestrial deposits are proposed for two horizons

cosmogenic nuclide derived rates of diffusive and episodic erosion in the glacially sculpted upper rhone valley swiss alps denudation rates of small tributary valleys in the upper rhone valley of the swiss central alps vary by more than an order of magnitude within a very small distance tens of kilometers morphometric data indicate two distinct erosion processes operate in these steep mountain valleys we determined the rates of these processes using cosmogenic beryllium 10 10be in pooled soil and stream sediment samples denudation in deep glacially scoured valleys is characterized by rapid non uniform processes such as debris flows and rock falls in these steep valleys denudation rates are 760 2100 mm kyr 1 in those basins which show minimal previous glacial modification denudation rates are low with 60 560 mm kyr 1 the denudation rate in each basin represents a binary mixture between the rapid non uniform processes and soil creep the soil production rate measured with cosmogenic 10be in soil samples averages at 60 mm kyr 1 mixing calculations suggest that the debris flows and rock falls are occurring at rates up to 3000 7000 mm kyr 1 these very high rates occur in the absence of baselevel lowering since the tributaries drain into the rhone trunk stream up stream of a knickzone the flux weighted spatial average of denudation rates for the upper rhone valley is 1400 mm kyr 1 which is similar to rock uplift rates determined in this area from leveling the pace and location of erosion processes are determined by the oscillation between a glacial and a non glacial state preventing the landscape from reaching equilibrium copyright 2010 john wiley sons ltd

meteoric 10be dating of highly weathered soils from fluvial terraces in taiwan abstract stream terraces are geomorphic markers that can be used to gauge surface deformation in response to tectonic uplift the surface deposits of the terraces form a chronosequence that indicates the rate and process of soil development placing a time or age constraint upon soil development has become one of the most important factors in the disciplines of soil science and fluvial geomorphology the radiocarbon 14c method is unable to date old terraces or soils but the longer half life of cosmogenic beryllium 10 10be permits this isotope to be useful to determine soil ages and rates of formation red soils redder than 7 5yr are commonly distributed on old high altitude stream terraces throughout taiwan in this study three pedons of alluvium related red soils were sampled from the taoyang ty ym pakua pk 1 and chiayi terraces cy 1 respectively located in northern central and southern taiwan according to field morphology and chemical analyses these red soils are characterized in soil taxonomy as being highly weathered and they are classified as typic hapludox ty ym and pk 1 and typic paleudult cy 1 meteoric 10be dating shows ages of 261 ka for ty ym 124 ka for pk 1 and 386 ka for cy 1 however the trend of these ages does not agree with the degree of soil development the former two ages are likely underestimated through loss of 10be due to strong leaching and considerable erosion the age obtained from cy 1 may represent the required time for soils develop into oxisols in taiwan

chemical weathering response to tectonic forcing a soils perspective from the san gabriel mountains california abstract what controls the chemical weathering of soils in tectonically active landscapes recent field and modeling studies suggest that tectonic forcing and associated increases in erosion rates may either promote or hinder soil chemical weathering these competing trajectories are dependent on two primary controls the availability of fresh minerals and their residence time on the landsurface here we explore rates and extents of soil weathering in the san gabriel mountains of california where previous work has measured clear tectonic fingerprints on rates of long term exhumation hillslope erosion and landscape morphology we quantify chemical weathering across this landscape by elemental analysis of soils saprolites and bedrock on six sites that bracket the low gradient hillslopes of the relict upland plateau and the high gradient hillslopes at the margins of the tectonically driven incising landscape average chemical depletion fractions which measure weathering losses from soil relative to unweathered parent material decrease with increasing elevation and decreasing temperature reflecting a combination of climate influence and potential dust inputs from the mojave desert weathering fluxes from non dust affected sites with similar elevations climates and lithology correlate with both erosion rates and hillslope gradient on low gradient hillslopes 25 weathering intensities and rates both decrease as erosion rates increase and soils thin at the highest denudation rates 300 t km 2 y 1 saprolite production is outpaced and soils are produced directly from fractured rock these patterns are consistent with those predicted by a previously published model for denudation weathering relationships based on mineral weathering kinetics variable weathering extents in soils indicate that weathering in the sgm is largely kinetically limited this study is the first to quantify decreases in both rates and extents of soil chemical weathering with increasing erosion rates and suggests tectonic uplift in rapidly eroding and incising landscapes may not stimulate increased silicate weathering

initial stages of weathering and soil formation in the morteratsch proglacial area upper engadine switzerland investigations in alpine soils indicate that mineral weathering is much faster in young soils 1000 yr than in old soils 10 000 yr however little is known about the initial stages of weathering and soil formation i e during the first decades of soil genesis in this study we investigated rock forming minerals weathering at very early stages of soil formation due to the continuous retreat of the morteratsch glacier upper engadine swiss alps the proglacial area offers a full time sequence from 0 to 150 yr old surfaces a low slope and the absence of glacier which might have interrupted soil formation processes contributed to the choice of the morteratsch proglacial valley for this case study the area is well documented regarding vegetation and soils the tectonic unit is the bernina crystalline which is mainly constituted of granitoid rocks consequently the glacial till has an acidic character mineralogical measurements were carried out on the soil fraction 2 mm using xrd and drift for qualitative and quantitative phase analysis in addition chemical analyses of the stream water from the main channel tributaries and of rainwater were performed with a special focus on ca sr and sr isotope ratios 87sr 86sr furthermore the accumulation of organic matter within the time sequence and physical soil properties were measured decreasing grain size with time shows active physical weathering processes soil organic matter has been accumulated during 150 yr at very high rates special emphasis has been given to chemical weathering and to the formation and transformation mechanisms of minerals of special interest were biotite chlorite epidote plagioclase and calcite biotite has been continuously transformed into illite like components within 150 yr the concentration of epidote significantly decreased the high ca sr as well as 87sr 86sr ratios in the stream and spring waters confirmed that ca bearing minerals are weathering and transforming at very high rates in the proglacial area also in cryic ice free environments chemical weathering rates are high leading to the formation and transformation of minerals disseminated calcite in granitoid rocks not confined to sedimentary carbonate rocks also plays a role in subglacial environments it is however not known for how long such an influence is significant and measurable the high ca na and ca sr ratio in the stream and tributary waters showed that calcite contributes to the supply of soluble ca although the ion activity product calculations clearly demonstrated that the waters were undersaturated with respect to this mineral

the glaciovolcanic evolution of an andesitic edifice south crater tongariro volcano new zealand abstract unusual deposits mapped and logged in detail around the summit area of tongariro volcano tongariro volcanic centre new zealand indicate that the construction and evolution of a substantial portion of this andesitic stratovolcano was beneath a significant ice cap or summit glacier as the edifice was built under and through the overlying ice the style of volcanism evolved in a complex history of growth initially a 100 m thick widespread hyaloclastite deposit was emplaced within a subglacial eruption formed meltwater lake this was followed by several phases of effusive and explosive eruptions producing lava flows and primary volcaniclastic deposits emplaced along channels carved into the ice by heated meltwater the clastic deposits contain quenched bombs and structural features that indicate waterlain transport and emplacement and soft sediment deformation such accumulation of water on a steep sided edifice without evidence for a subaerial crater lake along with lava flow features indicating confinement suggest that a substantial summit glacier was responsible for the production and retention of water and the architecture of these deposits recent studies at nearby ruapehu volcano have provided good evidence for glaciovolcanic interactions during the last glacial period however until now little was known of the physical lava ice interactions in the centre during the last interglacial period and the earlier part of the last glacial period 110 64 ka these new data support a reinterpretation for the volcanic evolution of the older tongariro edifice and the emplacement mechanisms of primary volcaniclastic deposits they also help to constrain local ice thicknesses and extents at the times of eruption in addition this study contributes to a sparse global catalogue of glaciovolcanic deposits of andesitic composition particularly of primary volcaniclastics preserved at mid latitude stratovolcanoes the variety of deposit types indicates a volcano building and evolving with glaciation and is an outstanding example of the types of glaciovolcanic interaction that can occur at one volcano

explosive rhyolite tuya formation classic examples from kerlingarfjoll iceland rhyolite eruptions in iceland mostly take place at long lived central volcanoes examples of which are found associated with each of the present day rift zone ice caps subglacial eruptions at kerlingarfjoll central volcano produced rhyolite tuyas that are notable for their exposures of early erupted pyroclastic material observations from a number of these edifices are synthesised into a general model for explosive rhyolite tuya formation eruptions begin with violent phreatomagmatic explosions that generate massive tuff mt but the influence of water quickly declines leading to the formation of massive lapilli tuffs mlt containing magmatically fragmented vesicular pumice and ash these are deposited rapidly near the vent probably by moist pyroclastic density currents confined by ice but not within a meltwater lake the explosive effusive transition is controlled by the ascent rate and gas content of the magma an unusual obsidian rich massive lapilli tuff lithofacies omlt is identified and interpreted as pyroclastic material that was intruded into gas fluidised deposits at the explosive effusive transition the effusive phase of eruption involves the emplacement of intrusions and lava caps intrusions of lava into the early erupted phreatomagmatic deposits are characterised by peperitic margins and the formation of hyaloclastite intrusions into stratigraphically higher levels of the pyroclastic material show more limited interaction with the host tephra and have microcrystalline cores large lava bodies with columnar jointed margins cap the tuyas and have intrusive basal contacts with the tephras the main influence of the ice is to confine the rhyolite eruptive products to immediately above the vent region this is in contrast to subglacial basaltic tuya forming eruptions which are characterised by the formation of meltwater lakes phreatomagmatic fragmentation and subaqueous deposition the lack of meltwater storage may reduce the potential for large jokulhlaups

the 1969 subglacial eruption on deception island antarctica events and processes during an eruption beneath a thin glacier and implications for volcanic hazards a short lived eruption of basaltic andesite to andesite on deception island in 1969 occurred from a series of fissures underneath a glacier the glacier was thin c 100 m and the eruption created a large and sudden discharge of meltwater that overflowed the glacier severely damaging buildings on the island the eruption was unusually well documented and it illustrates several features of subglacial eruptions that are only poorly known and not well understood in particular overflowing meltwater is contrary to predictions based on existing simple hydrological models for eruptions beneath thin glaciers the eruption is analysed in this paper and used as a model for the fluid dynamics and thermodynamics of eruptions beneath a thin glacier mainly composed of impermeable ice it is suggested that in eruptions of relatively fluid magmas with a low magma rise rate volatiles and magma are able to decouple and subglacial melting is strongly influenced by the superheated magmatic and hydrothermal gases mainly steam thus melting is much faster than that due solely to coupled conductive magma and convective meltwater heat transfer the influence of gasdriven melting also has an important effect on the shape of the meltwater cavity and may be at least partly responsible for the cylindrical ice chimneys developed above vents on deception island the results of the study are important for reconstructing the shapes of englacial cavities melted above a vent they also highlight the importance of glacier structure and densification rather than simply glacier thickness in determining the hydraulic evolution of an eruption even eruptions beneath thin glaciers can generate significant meltwater floods

clay mineralogy chemical weathering and landscape evolution in arctic alpine sweden abstract the purpose of this research was to 1 characterize the clay mineralogy of soils in and adjacent to karkevagge a recently deglaciated valley in arctic sweden 2 document chemical weathering in a periglacial environment and 3 use the mineralogy to help explain landscape evolution soil samples were analyzed from 11 sites that differ in elevation parent material drainage slope and vegetation parent materials include residuum alluvium colluvium and glaciofluvial material derived from garnet mica schist plus in one locality a till of granitic origin x ray diffraction xrd was used to characterize the clay size fraction

magma water interactions in subaqueous and emergent basaltic in the subaqueous growth and emergence of a basaltic volcano clasts are formed by one or a combination of 1 explosive release of magmatic volatiles 2 explosive expansion and collapse of steam formed at magma water contact surfaces 3 explosive expansion of steam following enclosure of water in magma or entrapment of water close to magma and 4 cooling contraction these processes named respectivelymagmatic explosivity contact surface steam explosivity bulk interaction steam explosivity andcooling contraction granulation can be enhanced by mutual interaction and feedback the first three explosive processes are limited at certain water depths hydrostatic pressures and become increasingly vigorous at shallower levels the depth of onset of magmatic explosivity depends largely on juvenile volatile content it is up to 200 m for tholeiitic magmas and up to 1 km for alkalic magmas at the depth where formation of clastic deposits becomes predominant over effusion of lavas magmatic explosivity is subordinate to steam explosivity as a clast forming process the upward transition to accumulation of dominantly clastic deposits is not simply related to the onset of substantial exsolution of magmatic volatiles and can occur without it contact surface explosivity commonly requires initiation by a vigorous impact between magma and water and although no certain depth limit is known likelihood of such explosivity decreases rapidly with depth clast generation by bulk interaction explosivity appears to be restricted to depths much shallower than that of the critical pressure of water which in sea water is at about 3 km cooling contraction granulation can occur in any depth of water but at shallow levels may be replaced by contact surface explosivity during continuous eruption under water tephra can be ejected and deposited within a cupola of steam such that rapid quenching does not occur emergent volcanoes are characterized by distinctive steam explosive activity that results primarily from a bulk interaction between rapidly ascending magma and a highly mobile slurry of clastic material water and steam the water gets into the vent by flooding across or through the top of the tephra pile and violent explosions cease when this access is sealed the eruptions during emergence of surtsey and capelinhos typify the distinctive explosive activity the style and controls of which are different from those of maar volcanoes

the nature and dynamics of frozen ground in alpine and subarctic periglacial environments a spatial assessment of the complex discontinuous and sporadic permafrost distribution and characteristics in high altitude alpine and high latitude subarctic permafrost environments was achieved u

weathering rates as a function of climate results from a climosequence of the val genova trentino italian alps a soil sequence in northern italy along an elevational gradient ranging from moderate 950 m a s l to high alpine 2440 m a s l climate zones was investigated with respect to element losses ca mg k na fe al si mn and the development of clay minerals element losses were derived from mass balance calculations that are based on enrichment depletion factors using immobile element contents ti mass balance calculations indicated that extensive mineral weathering resulted in significant leaching losses of major base cations with losses up to 80 of the initial content in the parent material al particularly from upper horizons and si element denudation was greatest in subalpine forests near the timberline weathering rates decreased with both higher and lower altitudes the pattern of smectite distribution along the climosequence has strong similarities to the al si na and k losses while an inverse trend could be detected for clay minerals with a high amount of interlayered al highest smectite contents with up to 30 of the clay fraction and also highest weathering rates were found at sites in subalpine forest near the timberline higher precipitation rates and the production of chelating compounds in the soil are believed to promote the appearance of smectites weathering rates of na and k were additionally modelled as a function of precipitation and temperature the relationship between climate and element weathering is strongly nonlinear and is thought to be overshadowed by the pronounced podzolisation effect near the timberline

permafrost thaw and destabilization of alpine rock walls in the hot summer of 2003 1 exceptional rockfall occurred throughout the alps during the unusually hot summer of 2003 it is likely related to the fast thermal reaction of the subsurface of steep rock slopes and a corresponding destabilization of ice filled discontinuities this suggests that rockfall may be a direct and unexpectedly fast impact of climate change based upon our measurements in alpine rock faces we present model simulations illustrating the distribution and degradation of permafrost where the summer of 2003 has resulted in extreme thaw we argue that hotter summers predicted by climate models for the coming decades will result in reduced stability of many alpine rock walls

the 1996 eruption at gjalp vatnajokull ice cap iceland efficiency of heat transfer ice deformation and subglacial water pressure the 13 day long gjlp eruption within the vatnajkull ice cap in october 1996 provided important data on ice volcano interaction in a thick temperate glacier the eruption produced 0 8 km 3 of mainly volcanic glass with a basaltic icelandite composition equivalent to 0 45 km 3 of magma ice thickness above the 6 km long volcanic fissure was initially 550 750 m the eruption was mainly subglacial forming a 150 500 m high ridge only 2 4 of the volcanic material was erupted subaerially monitoring of the formation of ice cauldrons above the vents provided data on ice melting heat flux and indirectly on eruption rate the heat flux was 5 6 10 5 wm 2 in the first 4 days this high heat flux can only be explained by fragmentation of magma into volcanic glass the pattern of ice melting during and after the eruption indicates that the efficiency of instantaneous heat exchange between magma and ice at the eruption site was 50 60 if this is characteristic for magma frag mentation in subglacial eruptions volcanic material and meltwater will in most cases take up more space than the ice melted in the eruption water accumulation would therefore cause buildup of basal water pressure and lead to rapid release of the meltwater continuous drainage of meltwater is therefore the most likely scenario in subglacial eruptions under temperate glaciers deforma tion and fracturing of ice played a significant role in the eruption and modified the subglacial water pressure it is found that water pressure at a vent under a subsiding cauldron is substantially less than it would be during static loading by the overlying ice since the load is partly compensated for by shear forces in the rapidly deforming ice in addition to intensive crevassing due to subsidence at gjlp a long and straight crevasse formed over the southernmost part of the volcanic fissure on the first day of the eruption it is suggested that the feeder dyke may have overshot the bedrock ice interface caused high deformation rates and fractured the ice up to the surface the crevasse later modified the flow of meltwater explaining surface flow of water past the highest part of the edifice the dominance of magma fragmentation in the gjlp eruption suggests that initial ice thickness greater than 600 700 m is required if effusive eruption of pillow lava is to be the main style of activity at least in similar eruptions of high initial magma discharge

evidence of volcanic and glacial activity in chryse and acidalia planitiae mars abstract chryse and acidalia planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water ice rich geologic history these landforms include giant polygons bounded by kilometer scale arcuate troughs bright pitted mounds and mesa like features to investigate the significance of the last we have analyzed in detail the region between 60 n 290 e and 10 n 360 e utilizing hirise high resolution imaging science experiment images as well as regional scale data for context the mesas may be analogous to terrestrial tuyas emergent sub ice volcanoes although definitive proof has not been identified we also report on a blocky unit and associated landforms drumlins eskers inverted valleys kettle holes consistent with ice emplaced volcanic or volcano sedimentary flows the spatial association between tuya like mesas ice emplaced flows and further possible evidence of volcanism deflated flow fronts volcanic vents columnar jointing rootless cones and an extensive fluid rich substratum giant polygons bright mounds rampart craters allows for the possibility of glaciovolcanic activity in the region landforms indicative of glacial activity on chryse acidalia suggest a paleoclimatic environment remarkably different from today s climate changes on mars driven by orbital obliquity changes or giant outflow channel activity could have resulted in ice sheet related landforms far from the current polar caps

resolving the integral connection between pedogenesis and landscape evolution abstract soil is central in the terrestrial ecosystem linking and providing feedback responses to the other components i e water atmosphere and vegetation however the role of soil in landscape evolution is usually not well acknowledged in modeling landscape evolution soil is only treated as a residue of weathering that is transported and redistributed along the hillslope weathering is considered as a process that produces clays and generates unconsolidated materials available for erosion while pedology has been debating the form of qualitative factorial models for 75 years models for soil water heat solute gas and chemical reactions in a profile have matured as soils are distributed continuously in three dimensions across landscapes the profile models need to consider lateral fluxes this review outlines the role of soil in landscape modeling first we review the role of soil in the current landscape evolution models we then review data and models on soil weathering rates and transport processes we discuss soil profile models that simulate soil formation processes and combined soil landscape evolution models finally we discuss how the models can be tested and validated in the real world and suggest how both soil scientists and landscape modelers can work together to address the grand challenges in modeling earth surface processes

clay mineral evolution along a soil chronosequence in an alpine proglacial area abstract as a consequence of global warming additional areas will become ice free and subject to weathering and soil formation the most evident soil changes in the alps will occur in proglacial areas where young soils will continuously develop due to glacier retreat little is known about the initial stages of weathering and soil formation i e during the first decades of soil genesis in this study we investigated clay minerals formation during a time span 0 150 years in the proglacial area of morteratsch swiss alps the soils developed on granitic till and were lithic leptosols mineralogical measurements of the clay the detected clay mineral formation and transformation mechanisms within this short time span confirmed the high reactivity of freshly exposed sediments even in a cryic environment

the critical role of climate and saprolite weathering in landscape evolution landscapes evolve in response to external forces such as tectonics and climate that influence surface processes of erosion and weathering internal feedbacks between erosion and weathering also play an integral role in regulating the landscapes response our understanding of these internal and external feedbacks is limited to a handful of field based studies only a few of which have explicitly examined saprolite weathering here we report rates of erosion and weathering in saprolite and soil to quantify how climate influences denudation by focusing on an elevation transect in the western sierra nevada mountains california we use an adapted mass balance approach and couple soil production rates from the cosmogenic radionuclide crn 10be with zirconium concentrations in rock saprolite and soil our approach includes deep saprolite weathering and suggests that previous studies may have underestimated denudation rates across similar landscapes along the studied climate gradient chemical weathering rates peak at middle elevations 1200 2000 m averaging 112 3 9 7 t km 2 y 1 compared to high and low elevation sites 46 8 5 2 t km 2 y 1 measured weathering rates follow similar patterns with climate as those of predicted silica fluxes modeled using an arrhenius temperature relationship and a linear relationship between flux and precipitation furthermore chemical weathering and erosion are tightly correlated across our sites and physical erosion rates increase with both saprolite weathering rates and intensity unexpectedly saprolite and soil weathering intensities are inversely related such that more weathered saprolites are overlain by weakly weathered soils these data quantify exciting links between climate weathering and erosion and together suggest that climate controls chemical weathering via temperature and moisture control on chemical reaction rates our results also suggest that saprolite weathering reduces bedrock coherence leading to faster rates of soil transport that in turn decrease material residence times in the soil column and limit soil weathering copyright 2009 john wiley sons ltd

cosmogenic nuclide based investigation of spatial erosion and hillslope channel coupling in the transient foreland of the swiss alps abstract transient landscape disequilibrium is a common response to climatic fluctuations between glacial and interglacial conditions such landscapes are best suited to the investigation of catchment wide response to changes in incision the geomorphology of the trub and grosse fontanne adjacent stream systems in the napf region of the swiss molasse was analyzed using a 2 m lidar dem the two catchments were impacted by the last glacial maximum lgm even though the glaciers never overrode this region they did however cause base levels to drop by as much as 80 m despite their similar tectonic lithologic and climatic settings these two basins show very different responses to the changing boundary conditions stream profiles in the trub tend to be smooth while in the fontanne numerous knickzones are visible similarly cut and fill terraces are abundant in the trub watershed but absent in the fontanne where deep valleys have been incised the trub appears to be a coupled hillslope channel system because the morphometrics throughout the basin are uniform the morphology of hillslopes upstream of the knickzones in the fontanne is identical to that of the trub basin but different downstream of the knickzones suggesting that the lower reaches of the fontanne have been decoupled from the hillslopes however the rapid incision of the fontanne is having little effect on the adjacent upper hillslopes we tested this interpretation using cosmogenic 10 be derived basin averaged denudation rates and terrace dating the coupled nature of the trub basin is supported by the similarity of denudation rates 350 50 mm ky 1 at a variety of spatial scales upstream of the knickzones rates in the fontanne 380 50 mm ky 1 match those of the trub downstream of the knickzones denudation rates increase to 540 100 mm ky 1 the elevated rates in the downstream areas of the fontanne are due to rapid incision causing a decoupling of the hillslope from the channel basin response time and the magnitude of base level drop exert the principal control over the difference in geomorphic response between the two basins the timing of the filling of the trub valley 17 2 ka and the initial incision of the fontanne 16 3 ka were calculated verifying that these are responses to late glacial perturbations unique lithologic controls allow for one of the fastest regolith production rates yet to be reported 380 mm ky 1

the table a flat topped volcano in southern british columbia revisited more than 65 years ago w h mathews published a seminal paper in american journal of science describing the table an iconic flat topped volcano in southern british columbia canada the table is recognized as the type example of a glaciovolcanic lava dominated tuya we use field mapping 3 d photogrammetry lithofacies identification and 40ar 39ar geochronology to re examine the emplacement origins of this unique volcanic edifice the table is a steep sided flat topped mass of dense porphyritic andesite preserving a near original outer surface of hackly fractured aphanitic material the age of the edifice is 100 12 ka a new model for the emplacement involves dike injection and endogenous inflation within an overlying ice mass that is estimated to have been 250 to 350 m thick the model assumes that the edifice expanded outwardly as an elliptical cylinder endogenously inflating and melting an equal volume of ice the thermal exchange between the expanding massif and the melting ice operates across a subvertical well drained enveloping carapace of quench breccia for effusion rates of 0 5 to 2 m3 s 1 marginal heat fluxes are 43 to 186 w m 2 implying low overall heat transfer coefficients 0 04 to 0 18 w m 2 k 1 the total volume of ice melted serves as a calorimeter and constrains the average thickness 3 m and properties thermal conductivity 0 1 0 4 w m 1 k 1 of the breccia carapace the heat transfer efficiency of intermediate lava dominated tuyas is significantly lower 2 than reported for other glaciovolcanic systems commonly 45 77 but similar to that found for block lava flows and lava tubes

from a black to a gray box a mass balance interpretation of pedogenesis we utilize chemical elements as tracers in a mass balance analysis that provides functional relationships among soil chemical composition bulk density and volume change in relation to parent material these analytical functions are based on the principle of conservation of mass and include a term quantifying mass flux into out of the soil and between horizons we apply the technique to the oldest member of a chronosequence developed on marine terraces in northern california it is an alfisol that evolved from beach sand to its present state nearly one third of its weight is composed of secondary clay minerals in about 240 ky aside from large increases in organic carbon desilication is the dominant factor in soil evolution 29 50 83 g cm 2 si was leached from the beach sand during pedogenesis the rate of desilication is roughly 2 1 t km 2 yr 1 0 21 g cm 2 ky 1 an order of magnitude slower than that implied by the si denudation rate calculated for the mattole river watershed weathering of primary minerals and synthesis of secondary minerals is relatively well advanced suggesting that the rate of desilication may be declining the local beach is composed of quartz and sodic plagioclase with smaller amounts of chlorite mica and kaolinite the soil has substantially different mineralogy sand is dominated by quartz and clay is dominated by kaolinite halloysite chloritic intergrades and gibbsite bases are also leached though the total mass was much less 57 2 55 g cm 2 of na in the beach sand was lost as plagioclase weathered by focusing on elemental and mineralogical gains and losses we emphasize the essential connection between the pedologic environment and the external hydrochemical environment

glaciovolcanic landsystems and large scale glaciotectonic deformation along the brekknafjoll jarlhettur iceland abstract this paper documents the glaciovolcanic landsystem of the brekknafjoll jarlhettur ridge in central iceland glaciolacustrine diamict is found beneath and in association with a complex assemblage of pillow lava lava breccias and hyaloclastites three depositional environments are identified glaciolacustrine fan pillow lava dome and hyaloclastite fan these subaqueous environments occurred both simultaneously and at different times along the volcanic fissures which underlie the ridge and have given rise to a complex facies architecture this facies architecture provides evidence that the ridge evolved in a time transgressive fashion during several episodes of volcanism some of which may have been punctuated by periods of ice erosion associated with the ridge are large diapiric folds in diamict and gravel which form by the loading and lateral displacement of saturated diamict beneath the developing volcanic pile a depositional model is presented which emphasises the glaciolacustrine component and the time transgressive nature of the glaciovolcanic landsystem much of the eruption occurred in subglacial to englacial lakes or vaults which were probably linked by water and sediment exchange the initial subglacial vaults appear to have extended beyond the fissure limits and were infilled by glaciolacustrine diamicts subaqueous outwash and the eruption of pillow lava this was followed by the eruption of hyaloclastite sand and breccia forming an elongated fan

formation rates of smectites derived from two holocene chronosequences in the swiss alps the formation rate of smectitic components in alpine soils is derived from two chronosequences in the swiss alps covering a time span of 11 500 years the soils developed on granitic parent material the lithologies between the two chronosequences investigation areas however showed some distinct differences with respect to the main mineralogy and to a lower extent to the chemistry the chronofunctions of smectitic phase formation g kgclay year were fitted to data using an exponential formation model extensive mineral weathering resulted in significant losses of chlorite and mica and the corresponding formation of smectite and regularly and irregularly interstratified mica smectite this formation is especially pronounced in the early stages of soil formation our investigations reveal that the greatest changes in soil clay mineralogy of alpine soils on granitic or gneiss host material occur within the first 1000 3000 years of soil development at both investigation sites the annual formation rates are in a similar order of magnitude with 0 1 g kg year or even higher at the start of soil formation and with values 0 01 g kg year after about 7000 years the pedogenetic smectites from the e or bs horizons included several populations with various interlayer charges this heterogeneity seems to be related to the nature of their precursors

evolution of a subglacial basaltic lava flow field tennena volcanic center mount edziza volcanic complex british columbia canada abstract studies of terrestrial glaciovolcanic deposits have elucidated the utility of these deposits as tools to constrain ice conditions at the time of their emplacement very few studies however have documented the emplacement of effusion dominated basaltic glaciovolcanic eruptions the tennena volcanic center tvc located at 57 40 57 705 n 130 39 43 138 w on the western flank of mount edziza volcanic complex mevc in northwestern british columbia canada preserves a detailed record of interactions between coherent basaltic lavas and a local regional ice sheet inferred to be associated with the last glacial maximum lgm here we describe the field characteristics of five primary volcanic lithofacies and five associated glaciogenic lithofacies and discuss their spatial distribution within the volcanic center we find that 1 the distribution of primary hydrovolcanic clastic deposits tuff breccias and lapilli tuffs is confined to tennena cone 2 pillow lavas are present throughout the extent of the surrounding lava field with morphologies that include distinctive structures comprising vertically oriented distended pillows 3 multiple lobes of massive non pillowed lavas that represent high initial magma discharge rates are confined to medial distances from the cone and 4 associated glaciogenic facies that underlie or onlap the tvc lavas indicate a variable sediment water ratio during subglacial meltwater drainage at the time of the eruption or shortly afterwards analyses of h 2 o co 2 in pillow rim samples give broad constraints for emplacement pressures equivalent to 500 1400 m of overlying ice no subaerial lava morphologies are found on the cone or in the proximal medial and distal lithofacies and the sequence is interpreted as documenting an eruption of basaltic lava flows beneath either the lgm cordilleran ice sheet or a younger dryas expansion of the still extant edziza ice cap the tvc lavas especially medial and distal ones display excellent examples of textures and morphologies that can be used to 1 help identify other terrestrial and martian basaltic lava flows emplaced beneath ice and 2 further our understanding on how sub ice lava flows are emplaced

lava and ice interaction at stratovolcanoes use of characteristic features to determine past glacial extents and future volcanic hazards structures resulting from lava and ice interaction are common at glaciated stratovolcanoes during summit eruptions at stratovolcanoes meltwater is produced and travels freely down steep slopes and thin permeable valley glaciers eroding the ice and enlarging preexisting glacial drainages as a result eruptions in this environment have produced few catastrophic floods lava flowing into the open channels and voids in the glaciers becomes confined and grows thicker filling the available space and producing steep sided bodies with smooth bulbous contact surfaces quenching of lava against ice or by water forms small scale features such as tensional fractures and glass as the amount of meltwater in contact with the lava increases the type and abundance of smaller scale features become similar to those produced during subglacial eruptions into meltwater lakes identification of large and small scale lava ice contact features in the field can be used to reconstruct paleoglacial extent and combined with geochronology of lavas to determine past paleoclimate an understanding of lava ice interaction allows us to better assess the hazards posed by future eruptions at glaciated volcanoes

continental scale temperature variability during the past two millennia past global climate changes had strong regional expression to elucidate their spatio temporal pattern we reconstructed past temperatures for seven continental scale regions during the past one to two millennia the most coherent feature in nearly all of the regional temperature reconstructions is a long term cooling trend which ended late in the nineteenth century at multi decadal to centennial scales temperature variability shows distinctly different regional patterns with more similarity within each hemisphere than between them there were no globally synchronous multi decadal warm or cold intervals that define a worldwide medieval warm period or little ice age but all reconstructions show generally cold conditions between ad 1580 and 1880 punctuated in some regions by warm decades during the eighteenth century the transition to these colder conditions occurred earlier in the arctic europe and asia than in north america or the southern hemisphere regions recent warming reversed the long term cooling during the period ad 1971 2000 the area weighted average reconstructed temperature was higher than any other time in nearly 1 400 years

pseudopillow fracture systems in lavas insights into cooling mechanisms and environments from lava flow fractures abstract detailed field observations of structures within the flow front of a holocene trachyandesite lava from snaefellsnes iceland are presented the lava provides exceptional three dimensional exposure of complex brittle and ductile deformation textures that record processes of lava fracture and quenching driven by external water the flow front interior is characterised by structures consisting of a large metre scale curviplanar master fracture with many smaller centimetre scale subsidiary fractures perpendicular to the master fracture such structures have previously been recognised in a range of lava compositions from basalt to dacite and called pseudopillows or pseudopillow fractures we propose the term pseudopillow fracture systems to emphasise the consistent package of different fracture types occurring together all documented occurrences of pseudopillow fracture systems are in lavas that have been inferred to interact with an aqueous coolant i e liquid water ice or snow we use fracture surface textures and their orientation in relation to flow banding to identify three distinct types of master fracture and two types of subsidiary fractures master fracture surface textures used to identify fracture mechanisms include chisel marks striae cavitation dimples river lines and rough smooth fracture surface textures these indicate both brittle and ductile fracture happening on different types of master fracture chisel marks on subsidiary fractures indicate comparative cooling rates cooling directions and isotherm orientations at the time of fracture we propose a model for pseudopillow fracture system formation taking into account all the various fracture types textures and fracture propagation mechanisms and discuss their implications for interaction mechanisms between lava flows and external coolants

soil formation rates on silicate parent material in alpine environments different approaches different results abstract high mountain soils develop in particularly sensitive environments consequently deciphering and predicting what drives the rates of soil formation in such environments are a major challenge in terms of soil production or formation from chemical weathering the predominating perception for high mountain soils and cold environments is often that the chemical weathering portion of soil development is temperature inhibited often to the point of non occurrence several concepts exist to determine long term rates of soil formation and development we present three different approaches 1 quantification of soil formation from minimally eroded soils of known age using chronosequences known surface age and soil thickness sast 2 determination of soil residence times srt and production rates through chemical weathering using un stable isotopes e g 230 th 234 u activity ratios and 3 a steady state approach using cosmogenic isotopes e g 10 be for each method data from different climate zones and particularly from high mountains alpine environment are compared the sast and steady state approach give quite similar results for alpine environments european alps and the wind river range rocky mountains usa using the srt approach soil formation rates in mountain areas but having a temperate climate do not differ greatly from the sast and steady state approaches independent of the chosen approach the results seem moderately comparable soil formation rates in high mountain areas alpine climate range from very low to extremely high values and show a clear decreasing tendency with time very young soils have up to 3 4 orders of magnitude higher rates of development than old soils 10 5 to 10 6 yr this apparently is a result of kinetic limits on weathering in regions having young surfaces and supply limits to weathering on old surfaces due to the requirement for chemical weathering to occur soil production rates cannot be infinitely high consequently a speed limit must exist in the literature this limit has been set at about 320 to 450 t km 2 a our results from the sast approach show however that in alpine areas soil formation easily reaches rates of up to 800 2000 t km 2 a these data are consistent with previous studies in mountain regions demonstrating that particularly young soils intensively weather even under continuous seasonal snowpack and thus that the concept of temperature controlled soil development soil forming intervals in alpine regions must be reconsidered

strong tectonic and weak climatic control of long term chemical weathering rates the relationships among climate physical erosion and chemical weathering have remained uncertain because long term chemical weathering rates have been difficult to measure here we show that long term chemical weathering rates can be measured by combining physical erosion rates inferred from cosmogenic nuclides with dissolution losses inferred from the rock to soil enrichment of insoluble elements we used this method to measure chemical weathering rates across 22 mountainous granitic catchments that span a wide range of erosion rates and climates chemical weathering rates correlate strongly with physical erosion rates but only weakly with climate implying that by regulating erosion rates tectonic uplift may significantly accelerate chemical weathering rates in granitic landscapes

soil formation and weathering in a permafrost environment of the swiss alps a multi parameter and non steady state approach spatially discontinuous permafrost conditions frequently occur in the european alps how soils under such conditions have evolved and how they may react to climate warming is largely unknown this study focuses on the comparison of nearby soils that are characterised by the presence or absence of permafrost active layer thickness 2 3 m in the alpine tundra and subalpine forest range of the eastern swiss alps using a multi method geochemical and mineralogical approach moreover a new non steady state concept was applied to determine rates of chemical weathering soil erosion soil formation soil denudation and soil production long term chemical weathering rates soil formation and erosion rates were assessed by using immobile elements fine earth stocks and meteoric 10be in addition the weathering index k ca ti the amount of fe and al oxyhydroxides and clay minerals characteristics were considered all methods indicated that the differences between permafrost affected and non permafrost affected soils were small furthermore the soils did not uniformly differ in their weathering behaviour a tendency towards less intense weathering in soils that were affected by permafrost was noted at most sites weathering rates the proportion of oxyhydroxides and the weathering stage of clay minerals were lower in permafrost soils in part erosion rates were higher at the permafrost sites and accounted for 79 97 of the denudation rates in general soil formation rates 8 8 86 7 t km2 y were in the expected range for alpine soils independent of permafrost conditions it seems that the local microenvironment particularly vegetation and subsequently soil organic matter has strongly influenced denudation rates as the climate has varied since the beginning of soil evolution the conditions for soil formation and weathering were not stable over time soil evolution in high alpine settings is complex owing to among others spatio temporal variations of permafrost conditions and thus climate this makes predictions of future behaviour very difficult this article is protected by copyright all rights reserved

rhyolitic volcano ice interactions in iceland iceland contains an abundance and diversity of rhyolitic edifices produced during volcano ice interactions glaciovolcanism that is unmatched by any other volcanic province with an estimated 350 km3 erupted during the past 0 8 ma from at least fifteen volcanic systems this review summarises research undertaken during the past decade and provides a new summary of the distribution of rhyolitic glaciovolcanic rocks erupted during the past 0 8 ma descriptions of effusion dominated edifices focus on the two best studied edifices the c 0 6 km3 and 570 m high prestahnukur edifice and the smaller volume 0 1 km3 drape of blahnukur both show little or no evidence of magmatic fragmentation i e driven by volatile exsolution but both show abundant evidence of quench fragmentation and meltback of ice walls a particular feature of prestahnukur is its sheet like lava bodies which are interpreted as sills that intruded the ice edifice interface rhyolitic tuyas are products of sustained eruptions into thick ice and form distinctive steep sided edifices with flat or broad dome like tops they are 300 700 m high with volumes up to 2 km3 though 0 5 1 0 km3 is more typical initial vigorous phreatomagmatic eruptions within well drained ice vaults build steep sided piles of tephra confined by ice walls gradual upwards increases in inflated clasts point to the decreasing involvement of meltwater and the increasing ability of the magma to vesiculate as the eruption progresses and terminates non explosive degassing produces lava caps up to 300 m thick oraefajokull is a stratovolcano illustrating complex volcano ice interactions generated when rhyolitic lavas erupt onto steeper slopes and encounter ice of variable thickness and properties e g fracturing eruptive units record dramatic ice thickness fluctuations of up to 500 m in valley glaciers between eruptions which emphasises that useful palaeoenvironmental information can be gleaned from detailed studies of volcano ice interactions considerable value is added when palaeoenvironmental information is combined with ar ar dating for example ar ar dating of two rhyolitic tuyas at torfajokull reveal that they erupted prior to the last glacial maximum when temperatures were at least 4 c cooler than the present day ar ar dating of prestahnukur suggests it erupted during the last interglacial glacial transition into over 700 m of ice which corroborates studies arguing for rapid accumulation of land based ice during global cooling

facies analysis of proximal subglacial and proglacial volcaniclastic successions at the eyjafjallajokull central volcano southern iceland

sediments and landforms at kviarjokull southeast iceland a reappraisal of the glaciated valley landsystem abstract eyles identified kviarjokull an outlet of the icecap oraefajokull southeast iceland as an exemplar of the glaciated valley landsystem emphasising rockfall debris supply passive transport and reworking of a thick cover of supraglacial morainic till in this paper we take a fresh look at the sediments and landforms of kviarjokull focusing on clast form analysis to reconstruct primary transport pathways new data demonstrate the importance of active transport of debris derived from the glacier bed substantial portions of the supraglacial debris cover can be traced back to englacial channel fill deposits or anomalously thick exposures of basal ice these two types of sediments also make up much of kviarjokull s large neoglacial moraine rampart we attribute the abundance of these non rockfall sediments to the presence of a terminal overdeepening and the switch from predominantly subglacial to predominantly englacial drainage that this induces this hydrological switch enhances retention of debris within ice transport preventing it from being washed away and making it available to feed ice marginal moraine formation the complexity of sediment transport processes observed at kviarjokull and the contrast between it and alpine glaciers undermines any single concept of the glaciated valley landsystem accordingly we propose kviarjokull as the type example of a distinct subclass defined by its moderate relief high debris turnover and drainage behaviour characteristic of an overdeepened basin

subglacial intermediate volcanism at kerlingarfjoll iceland magma water interactions beneath thick ice the products of andesite and dacite glaciovolcanism at kerlingarfjoll are unlike others previously described in the literature three sequences of lithofacies are described and interpreted here the andesitic deposits at campsite gully are divided into massive vitriclastic lapilli tuff with intrusions fluidal clast bearing vitriclastic lapilli tuff and stratified pumice rich vitriclastic lapilli tuff at tindur andesitic eruptions produced contorted pillow fragment breccia and the clast supported lithic breccia finally pillow lava with intrusions and crudely bedded vitriclastic lapilli tuff of dacitic composition are described at haraldur abundant vitriclasts the presence of pillow lavas hackly fracturing of lava bodies and lack of oxidation of clasts demonstrate that each of these lithofacies formed in the presence of abundant water this contrasts with all other descriptions of subglacially erupted intermediate magmas which are characterised by jointed and glassy lava flows and domes with a marked scarcity of fragmental material the kerlingarfjoll sequences therefore demonstrate that it is possible for intermediate magmas to generate and interact with significant volumes of water at the base of a glacier preliminary estimates of volatile contents in glassy clasts correspond to quenching pressures equivalent to 500 m water or 550 m ice this is consistent with eruption beneath an ice sheet that was thick enough to overwhelm the underlying topography and where meltwater drainage was controlled by the morphology of the glacier surface it is argued that the drainage of water due to steep topography and or thin and fractured ice as opposed to thermodynamic considerations is the most likely explanation for the absence of evidence for significant magma water interaction in previously described instances of intermediate glaciovolcanism the apparent low viscosity of the kerlingarfjoll magmas may relate to relatively high eruption temperatures and or the inhibition of degassing of the magma due to high ambient pressures and the consequent limitation of groundmass crystallisation

last glacial to post glacial 10be fluctuations in a sediment core from the academician ridge lake baikal 10be concentrations sediment composition and sediment accumulation rates were determined in a sediment core from the academician ridge of lake baikal the 10be concentrations vary from 5 07 108 atoms g in the last glacial section to 11 25 108 atoms g in the section representing the post glacial climate stage 10be fluxes on the other hand increase toward the last glacial stage coinciding with an increase of the sediment accumulation rate these facts imply that climate related sedimentation is related to both flux and concentration of the nuclide in the sediment core during the last glacial stage arid conditions in the lake s watershed caused a marked increase in flux of clay particles with low 10be content to the lake resulting in an increased flux but lowered concentration of 10be in the sediments it is suggested that the 10be record of the bottom sediments of lake baikal can be used as a proxy indicator of climate change in central asia

application of a combination of dating techniques to reconstruct the lateglacial and early holocene landscape history of the albula region eastern switzerland landforms in val mulix and the albula region in eastern switzerland offer a detailed insight into the period between the oldest dryas until the early holocene to better understand lateglacial and holocene climate change in the central alps glacial moraines polished bedrock and periglacial rock glacier landforms were dated using a combined approach of numerical cosmogenic 10be and relative schmidt hammer weathering rind thickness dating techniques at high elevation sites near the last glacial maximum lgm trimline 10be exposure ages of glacially modified bedrock are between 11 2 ka and 13 5 ka this suggests the persistence of long lasting small local ice caps after the breakdown of the lgm ice domes or alternatively a reformation of ice perhaps during the younger dryas in val mulix we obtained one of the first ages for the daun stadial 14 7 ka moraines 14 9 1 8 ka supporting a pre bolling chronological position the age is in excellent agreement with the age of a boulder from an egesen i moraine located up valley which we postulate may be a daun moraine that was re occupied during the egesen stadial a boulder from an egesen ii moraine gave an age of 10 7 ka which is similar to ages of egesen ii moraines at other sites in the alps 10be ages from boulders found on a relict rock glacier in val mulix indicate that the main active phase lasted from the lateglacial until the early holocene the derived mean annual flow rate is of the order of decimetres which is in accordance with values stated in the literature based on measuring active rock glaciers in the alps exposure ages from a glacially polished rock barrier showed that this area was ice free at the end of the younger dryas 9 0 0 7 ka and 11 9 0 9 ka the polished bedrocks are located a few hundred meters down valley from the little ice age lia moraines this gives direct evidence of a fast ice retreat towards the end of the younger dryas with glacier length variations that did not exceed the 1850 ad extension little ice age maximum surface exposure dating is however limited by several methodological constraints the choice of suitable snow depths plays a crucial role in the calculation of the 10be ages shielding of surfaces from cosmic rays by snow can significantly influence the exposure age and variations in the estimated annual snowfall in the albula region since the lgm is therefore a potential source of considerable uncertainty in our measurements while the measurement of weathering rind thicknesses turned out to be an appropriate tool to support the reconstruction of lateglacial landscape evolution schmidt hammer r values were less helpful the r values enabled a temporal distinction of landforms within the holocene lia moraine active rock glaciers but not within the lateglacial from a methodological point of view the different dating methods enabled a cross checking an extended interpretation of the data and a more accurate estimate of the possible sources of error

how fast does soil grow abstract quantifying the rate of soil formation has become important in response to the consideration of soil as a renewable resource the availability of new sophisticated laboratory techniques has opened up the possibility of addressing the demand of quantifying processes of soil landscape evolution in the critical zone here we investigated the rate of soil formation of world soils based on published results of tcn derived terrestrial cosmogenic nuclides 10 be soil production rates spr the compilation of published tcn derived spr for different climatic zones and lithologic conditions showed exponentially decreasing spr with increasing soil thickness for the majority of the discussed studies this implies that the presence of a soil mantle protects the bedrock from further weathering we found that rates of soil production in australia appear to be similar in range when compared with other parts of the world we concluded that we can formulate an average quantitative estimate of global soil production based on tcn soil production rate mm kyr 1 114 11 exp 2 05 soil thickness in mm such a rate is useful for global modelling of soil formation to better understand the role of soils in landscape evolution

thermodynamics and fluid dynamics of effusive subglacial eruptions we consider the thermodynamic and fluid dynamic processes that occur during subglacial effusive eruptions subglacial eruptions typically generate catastrophic floods jokulhlaups due to melting of ice by lava and generation of a large water cavity we consider the heat transfer from basaltic and rhyolitic lava eruptions to the ice for typical ranges of magma discharge and geometry of subglacial lavas in iceland our analysis shows that the heat flux out of cooling lava is large enough to sustain vigorous natural convection in the surrounding meltwater in subglacial eruptions the temperature difference driving convection is in the range 10 100 c average temperature of the meltwater must exceed 4 c and is usually substantially greater we calculate melting rates of the walls of the ice cavity in the range 1 40 m day indicating that large subglacial lakes can form rapidly as observed in the 1918 eruption of katla and the 1996 eruption of gjalp fissure in vatnajokull the volume changes associated with subglacial eruptions can cause large pressure changes in the developing ice cavity these pressure changes can be much larger than those associated with variation of bedrock and glacier surface topography previous models of water cavity stability based on hydrostatic and equilibrium conditions may not be applicable to water cavities produced rapidly in volcanic eruptions energy released by cooling of basaltic lava at the temperature of 1200 c results in a volume deficiency due to volume difference between ice and water provided that heat exchange efficiency is greater than approximately 80 a negative pressure change inhibits escape of water allowing large cavities to build up rhyolitic eruptions and basaltic eruptions with less than approximately 80 heat exchange efficiency cause positive pressure changes promoting continual escape of meltwater the pressure changes in the water cavity can cause surface deformation of the ice laboratory experiments were carried out to investigate the development of a water cavity by melting ice from a finite source area at its base the results confirm that the water cavity develops by convective heat transfer

the convenient fiction of steady state soil thickness abstract steady state regolith or soil thickness ssst whereby surface removals are approximately balanced by production of new soil by bedrock weathering is a common assumption in most models of hillslope and landscape evolution ssst is also a fundamental assumption in the use of cosmogenic radionuclides crn to estimate erosion and weathering rates the steady state concept is based on feedbacks between soil thickness and weathering at the base of the regolith such that sometimes after an optimal or threshold thickness is achieved thicker soils lead to lower weathering rates and vice versa ssst is thus only applicable to soils formed chiefly from weathering of the underlying bedrock where sufficient time has elapsed for regolith accumulation and where effects of processes other than weathering and surface removals on thickness are negligible even within this domain the widespread occurrence of deep weathering profiles regolith stripping and inherited regolith features makes ssst problematic as a conceptual model for pedogenesis or weathering profile development the ratio of soil thickness to total weathering profile thickness is proposed as a simple index of steady state steady state profiles formed on weathered bedrock should exhibit ratios close to unity data from the cumberland plateau region of eastern kentucky show that soil weathering profile ratios in shallow 20 m and generally significantly greater than soil thicknesses in the region suggesting ratios convenient fiction facilitating the use of some models and tools the potential pitfalls arise from the possibility that the utility of ssst as a convenient fiction in some contexts may be mistaken for a realistic representation of the dynamics of pedogenesis and weathering profile evolution