formal definition and dating of the gssp global stratotype section and point for the base of the holocene using the greenland ngrip ice core and selected auxiliary records the greenland ice core from northgrip ngrip contains a proxy climate record across the pleistocene holocene boundary of unprecedented clarity and resolution analysis of an array of physical and chemical parameters within the ice enables the base of the holocene as reflected in the first signs of climatic warming at the end of the younger dryas greenland stadial 1 cold phase to be located with a high degree of precision this climatic event is most clearly reflected in an abrupt shift in deuterium excess values accompanied by more gradual changes in d 18 o dust concentration a range of chemical species and annual layer thickness a timescale based on multi parameter annual layer counting provides an age of 11 700 calendar yr b2 k before ad 2000 for the base of the holocene with a maximum counting error of 99 yr a proposal that an archived core from this unique sequence should constitute the global stratotype section and point gssp for the base of the holocene series epoch quaternary system period has been ratified by the international union of geological sciences five auxiliary stratotypes for the pleistocene holocene boundary have also been recognised copyright 2008 john wiley sons ltd

paleointensity assisted chronostratigraphy of detrital layers on the eirik drift north atlantic since marine isotope stage 11 1 four piston cores collected in 1999 and 2002 from the eirik drift southern labrador sea off se greenland provide paleomagnetic environmental magnetic and oxygen isotope records back to marine isotope stage 11 age models for the cores are based on a combination of planktonic oxygen isotope data relative geomagnetic paleointensity proxies and the identification of geomagnetic excursions laschamp and iceland basin environmental magnetic data delineate two distinct detrital signals interpreted to reflect the behavior of the surrounding ice sheets greenland and laurentide to orbital and millennial scale climate forcing broad decimeter scale intervals of increased magnetic concentration and grain size occur during the early part of interglacial marine isotopic stages mis 1 5 7 9 and 11 discrete centimeter scale layers recognized by magnetic concentration and grain size sensitive parameters gamma ray attenuation gra bulk density and carbonate content are observed in glacial and interglacial stages as well as during terminations on the basis of glacial reconstructions on greenland during the last termination the broad decimeter scale coarser grained intervals can be attributed to detrital influx associated with the retreat of the terrestrial based greenland ice sheet in the early holocene a similar magnetic signal observed within interglacial mis 5 7 9 and 11 indicates similar greenland ice sheet behavior during these time intervals two types of centimeter scale detrital layers are also recognized back to mis 11 detrital carbonate dc layers reflect predominately ice rafted debris ird deposition while the low detrital carbonate ldc layers reflect mass movement as evidenced by sharp basal contacts graded bedding and traction structures likely from the greenland slope some detrital layers on eirik drift particularly the dc layers can be tentatively correlated to detrital layers observed in the central north atlantic and to those documented on the southern side of the labrador sea at orphan knoll

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

estimation of locations and migration of debris flows on izu oshima island japan on 16 october 2013 by the distribution of high frequency seismic amplitudes abstract in the early morning on 16 october 2013 large debris flows resulted in over 30 people dead on izu oshima island japan which were induced by heavy rainfall from the approaching typhoon 1326 wipha we successfully estimated the locations and migration processes of five large events of the debris flows using the spatial distribution of high frequency seismic amplitudes recorded by a seismic network on the island the flows occurred on the western flank of the island almost at the same place as the site where large traces of debris flows were identified after the disaster during each event of debris flows the estimated locations migrated downstream with increasing time from the caldera rim of miharayama volcano in the center of the island to its western side with a speed of up to 30 m s the estimated time series of source amplitudes are different from event to event exhibiting a large variety of flow sequences while they seem to have repeated at a relatively narrow area over several tens of minutes the present approach may be utilized for early detection and warning for prevention and reduction of the present type of disasters in the future

improving the amplitude source location asl method using multicomponent seismic data an assessment with active source seismic dataimproving the asl method using multicomponent seismic data an assessment with active source seismic data improving the amplitude source location asl method using multi component seismic data an assessment with active source seismic data

precursory characteristics of the seismicity before the 6 august 2012 eruption of tongariro volcano north island new zealand abstract the 6 august 2012 eruption from the upper te maari crater of tongariro volcano followed approximately three weeks of precursory seismic activity earthquake relocations including data from extra temporary stations indicated that nearly all events were in a small area very close to upper te maari most of these relocated events were very shallow with nearly all events being between 1000 and 1500 m below the ground surface the pre eruption seismicity occurred in three main swarms during the first swarm on 12 13 july 2012 all the earthquakes had consistent inter event times of 71 8 min while in the later swarms 17 20 and 29 30 july many events had a similar pattern of consistent inter event times the stationary quasi periodic clockwork earthquake process suggests that a single fracture point was excited by a nearly constant rate flux process the dominant type of earthquake observed in these swarms had a sharp onset and a broad spectrum with strong energy from 2 to 10 hz most events seen had a local magnitude of 1 5 to 2 5 with virtually no smaller events most of these earthquakes appeared to belong to a main earthquake family whose characteristics included a strong spectral component at about 2 hz and three bursts of energy spaced at intervals of about 1 5 s of the 116 located earthquakes 75 had a correlation coefficient greater than 0 70 with a master event the spectra of these events did not change with size with matching frequency peaks for all the events with a high correlation the last event of this type was the day before the 6 august 2012 eruption none have been seen since and there has been very little seismicity under tongariro this seismicity alerted gns science and other organisations to the unrest of tongariro and the volcanic alert level and aviation colour code were raised to publicise this gns science also increased its monitoring of tongariro and discovered that the magmatic gas concentrations had increased compared to previous measurements in may 2012 however the seismicity did not show any accelerating trend that suggested an immediate eruption threat indicating the difficulty of predicting small eruptions in tongariro and similar volcanoes

trees in the subalpine belt since 11 700 cal bp origin expansion and alteration of the modern forest high altitude alpine ecosystems are likely to be highly sensitive to future climate change understanding long term tree stand dynamics may be a key requirement for forecasting such changes here we present a high resolution record of paleobotanical macroremains covering the last 11 700 years from a small subalpine pond situated in the inner french alps at 2035 m a s l the early presence of larch larix decidua arolla pine pinus cembra and birch betula at this elevation just after the end of the younger dryas cold transition suggests the occurrence of either glacial tree refugia located nearby in the northwestern alps or a previously unrecorded early and rapid tree migration the 8200 cal bp cooling event is characterized by a rapid and limited expansion of mountain pine pinus mugo uncinata type mixed stands of larch birch and arolla pine established at 8300 cal bp and were present through the mid holocene after the holocene climatic optimum at 5600 cal bp recurrent fires led to the

migration of tremor locations before the 2008 eruption of meakandake volcano hokkaido japan abstract we estimate the locations of three tremor sequences denoted a b and c that occurred before the 2008 eruption at meakandake volcano eastern hokkaido japan using the spatial distribution of seismic amplitudes of volcanic tremor although we used only five seismic stations we could estimate the locations of three tremor sequences we find two different tremor source areas those of tremor a located about 2 km southwest of the erupted crater area a and the other about 1 km southeast to south of the crater as that of the tremor c area b the location of an early phase of the tremor b is estimated in area a while the location of its later phase appears to connect the two areas this location migration during tremor b occurred simultaneously with other important geophysical phenomena before the eruption event as suggested by geodetic and geomagnetic studies our findings of the two tremor locations of the tremor sequences and location migration during tremor b may be important for future monitoring activities at meakandake volcano particularly to forecast the location of a possible phreatic eruption

dual polarisation c band weather radar imagery of the 6 august 2012 te maari eruption mount tongariro new zealand abstract the 6 august 2012 eruption of mt tongariro from upper te maari crater in the central north island of new zealand was the first volcanic eruption observed by an operational weather radar in new zealand and is believed to be one of only a small number of eruptions observed by a dual polarisation radar worldwide the eruption was also observed by a geonet webcam and detailed ash deposit studies have permitted analysis of the plume characteristics a combination of radar and webcam imagery show 5 pulses within the first 13 min of the eruption and also the subsequent ash transport downwind comparison with ash samples show the radar was likely detecting ash particles down to about 0 5 mm diameter the maximum plume height estimated by the radar is 7 8 1 0 km above mean sea level amsl although it is possible this may be a slight under estimation if very small ash particles not detected by the radar rose higher and comprised the very top of the plume the correlation coefficient and differential reflectivity fields that are additionally measured by the dual polarisation radar provide extra information about the structure and composition of the eruption column and ash cloud the correlation coefficient easily discriminates between the eruption column and the ash plume and provides some information about the diversity of ash particle size within both the ash plume and the subsequent detached ash cloud drifting downwind the differential reflectivity shows that the larger ash particles are falling with a horizontal orientation and indicates that ice nucleation and aggregation of fine ash particles was probably occurring at high altitudes within 20 25 min of the eruption

evolution of the central nordic seas over the last 20 thousand years the deep and surface water paleoceanographic evolution of the central nordic seas over the last 20 thousand years was reconstructed using various micropaleontological isotopic and lithological proxy data these show a high spatial and temporal complexity of the oceanic circulation when compared with other records from the region during early deglaciation a collapse of ice sheets surrounding the nordic seas released large amounts of freshwater that affected both the surface and bottom water circulation and significantly contributed to heinrich stadial 1 during the younger dryas the central nordic seas were affected by a last major freshwater plume which probably originated from the arctic ocean when major ice rafting had ceased around 11ka subsurface temperatures started to rise however atlantic water advection and subsurface temperatures reached their maximum in the central nordic seas later than along the eastern continental margin that spatio temporal offset is explained by a gradual re routing and westward expansion of the atlantic water flow during times when the greenland sea gyre system became more steadily established in the greenland basin the holocene thermal maximum ended c 5 5ka and time coeveal with an increase in sea ice export from the arctic in the lofoten basin the cooling occurred later after 4ka and together with a weakening of the overturning processes the neoglacial cooling was reached c 3ka together with low solar irradiance expanding sea ice and a slight decrease in deep convection at c 2ka subsurface temperatures began to rise again due to an increasing influence of atlantic waters

relative partitioning of acoustic and seismic energy during strombolian eruptions the relative elastic energy partitioning during strombolian eruptions can be estimated from acoustic pressure and seismic velocity records we outline methods for determining acoustic and seismic energies for sensors deployed within several kilometers of erupting vents we use these energies to introduce the concept of the volcano acoustic seismic ratio g or vasr which is the ratio of elastic energy propagated through the atmosphere and into the earth eruption vasr is a physical diagnostic of explosive degassing that is appropriate for comparing eruption mechanisms at individual and between various volcanoes here we assess acoustic and seismic energies and corresponding vasr for discrete strombolian explosive events at karymsky and erebus volcanoes we attribute the relatively high and stable vasr at erebus g 8 standard deviation 41 to repeatable source conditions occurring at the surface of a persistent lava lake with accompanying strong coupling to the atmosphere lower and more variable vasr at karymsky g 0 18 in 1998 to g 1 51 in 1991 with standard deviations of 93 and 313 respectively is attributed to changing conditions within a narrow partially choked conduit variable seismoacoustic energy partitioning for karymsky as manifested by the large vasr standard deviation suggests that conduit conditions affecting vasr which include magma properties conduit obstruction or fragmentation depths can evolve both during the course of an explosion and between successive events d 2005 elsevier b v all rights reserved

needle accumulation rate model based reconstruction of palaeo tree biomass in the western subalpine alps an appropriate bioproxy is required to decipher holocene tree biomass dynamics from the stand scale in relation to local processes such as disturbance or global climate change here we used plant litter collected in traps placed in subalpine forests and data on the surrounding stands to develop calibration equations for converting the observed macroremain accumulation rates to tree biomass basal area values the needle accumulation rate nar was modeled for larix decidua and pinus cembra we then used the calibration equation developed from the trapped macroremains to reconstruct past tree biomass for sedimentary holocene series from two subalpine lakes in the alps our data show that nar is significantly correlated with basal area we found a clear overrepresentation of l decidua nar compared with its real basal area this distortion potentially masks the occurrence of p cembra another important functional species of subalpine ecosystems when macroremains are not calibrated without calibration

using the spatial distribution and lithology of ballistic blocks to interpret eruption sequence and dynamics august 6 2012 upper te maari eruption new zealand the ballistic ejection of blocks during explosive eruptions constitutes a major hazard near active volcanoes fields of ballistic clasts can provide important clues towards quantifying the energy dynamics and directionality of explosive events but detailed datasets are rare during the 6 august 2012 hydrothermal eruption of upper te maari tongariro new zealand three explosions occurred in rapid succession within less than 20 s the first two produced laterally directed pyroclastic density currents pdc and the final vertical explosion generated an ash plume each of these explosions was associated with the ejection of ballistic blocks we present detailed maps of the resulting 5 1 km2 block impact field and the distribution of the 2200 impact craters with diameters 2 5 m there are two distinct regions of high crater concentration where crater densities reach more than six times the average background density these occur at distances of 500 700 m east and 1000 1350 west of a 430 m long fissure that was created during the eruption the high density fields are characterized by a narrow radial spread of 45 and are located along the proximal transport direction of the pyroclastic density currents a provenance analysis of ballistic blocks allowed us to reconstruct two different eruptive vents for the explosions the first two laterally directed explosions were sourced from the fissure while the third explosion occurred through the pre existing upper te maari crater generating a roughly axisymmetric shower of ballistics stratigraphic relationships between impact craters pdc and fall deposits suggest that the ballistic blocks were initially coupled with the rapidly expanding gas particle mixtures that produced the pdcs ballistic trajectory modeling reproducing the lateral extent and main impact density pattern of the western impact field allows estimation of the vertical expansion angle of the second and largest explosion the calculations show that the largest proportion of the explosion energy was strongly focused as a narrow and extremely shallow from 3 to 15 from the horizontal laterally expanding hydrothermal blast the results presented here constitute an important data set for ballistic hazard assessment at tongariro volcano and they can provide further clues towards better understanding highly energetic laterally directed volcanic explosions at similar hydrothermal fields

integrating multidisciplinary science modelling and impact data into evolving syn event volcanic hazard mapping and communication a case study from the 2012 tongariro eruption crisis new zealand abstract new zealand s tongariro national park volcanoes produce hazardous eruptions every few years to decades on 6 august 2012 the te maari vent of tongariro volcano erupted producing a series of explosions and a fine ash of minor volume which was dispersed rapidly to the east this manuscript presents a summary of the eruption impacts and the way these supported science communication during the crisis particularly in terms of hazard map development the most significant proximal impact was damage from pyroclastic surges and ballistics to the popular and economically important tongariro alpine crossing track the only hazard to affect the medial impact zone was a few mms of ashfall with minor impacts field testing indicated that the te maari ash had extremely low resistivity when wetted implying a very high potential to cause disruption to nationally important power transmission networks via the mechanism of insulator flashover this was not observed presumably due to insufficient ash accumulation on insulators virtually no impacts from distal ashfall were reported post event analysis of pm10 data demonstrates the additional value of regional air quality monitoring networks in quantifying population exposure to airborne respirable ash while the eruption was minor it generated a high level of public interest and a demand for information on volcanic hazards and impacts from emergency managers the public critical infrastructure managers health officials and the agriculture sector meeting this demand fully taxed available resources we present here aspects of the new zealand experience which may have wider applicability in moving towards improved integration of hazard impact information mapping and communication these include wide use of a wiki technical clearinghouse and email listservs a focus on multi agency consistent messages and a recently developed environment of collaboration and alignment of both research funding and technical science advice hazard maps were integral to science communication during the crisis but there is limited international best practice information available on hazard maps as communication devices as most volcanic hazard mapping literature is concerned with defining hazard zones we propose that hazard maps are only as good as the communications framework and inter agency relationships in which they are embedded and we document in detail the crisis hazard map development process we distinguish crisis hazard maps from background hazard maps and ashfall prediction maps illustrating the complementary nature of these three distinct communication mechanisms we highlight issues that arose and implications for the development of future maps

dynamics of surges generated by hydrothermal blasts during the 6 august 2012 te maari eruption mt tongariro new zealand abstract the 6 august 2012 te maari eruption produced violent and widespread cold pyroclastic density currents pdcs following unroofing of the pressurized hydrothermal system despite an erupted volume of only 5 10 5 m 3 and lacking any juvenile component the 340 000 m 3 of pdcs spread over an area of 6 1 km 2 and had mobilities that were on the order of volcanic blasts or blast like pdcs this great mobility was due to strong lateral focussing of explosion energy producing jets with initial velocities 100 m s we present a type stratigraphy for these hydrothermal derived low temperature pdcs that show a tripartite deposit sequence each of the deposit units dominates respectively three outward gradational sedimentary facies reflecting transitions in the propagating pdc transport and depositional mechanisms the largest pdcs directed west and east of the upper te maari area were generated from outer cone breccias and tuffs that were mostly highly hydrothermally altered landsliding and the geometry of the hydrothermal area led to the directed jetting initial particle laden jets laid sheets grading into lobes of proximal massive sand to gravel rich facies dominated by unit a and extending up to 1 km from the vents as the jets were collapsing a vertically and longitudinally stratified pdc developed within the first few hundred metres from source exponential thinning and coarse tail grading dominated fining with radial distance of massive unit a resulted from fast deposition and progressive depletion of the most concentrated flow region behind the pdc head markedly slower tractional sedimentation from the passing pdc body and tail deposited the highly stratified and ripple bedded fine coarse ash of unit b this formed distinctive dune fields of the medial dune bedded ash rich facies upwards in depositional sequences the waning of the current can be seen by replacement of higher energy bedforms to progressively lower ones downstream progressive waning and further depletion are characterised by the development of the distal wavy to planar bedded ash rich facies this is increasingly dominated by the uppermost deposition unit c of laminated fine med ash deposited by gently turbulent dilute phoenix clouds these high energy pdcs sourced from flank hydrothermal systems should be regarded as a serious threat in any multihazard assessment of a stratovolcano even though they may not be one of the major magmatic vent sites in addition further detailed studies of these hydrothermal jetting events and their deposits should be pursued in order to better understand large volume volcanic blasts which appear to be a larger scale sibling phenomenon

seismo acoustic evidence for an avalanche driven phreatic eruption through a beheaded hydrothermal system an example from the 2012 tongariro eruption abstract the 6 august 2012 te maari eruption comprises a complex eruption sequence including multiple eruption pulses a debris avalanche that propagated 2 km from the vent and the formation of a 500 m long arcuate chasm located 300 m from the main eruption vent the eruption included 6 distinct impulses that were coherent across a local infrasound network marking the eruption onset at 11 52 18 all times utc an eruption energy release of 3 1012 j was calculated using a body wave equation for radiated seismic energy a similar calculation based on the infrasound record shows that 90 of the acoustic energy was released from three impulses at onset times 11 52 20 20 of total eruption energy 11 52 27 50 and 11 52 31 20 these energy impulses may coincide with eyewitness accounts describing an initial eastward directed blast followed by a westward directed blast and a final vertical blast pre eruption seismic activity includes numerous small unlocatable micro earthquakes that began at 11 46 50 two larger high frequency earthquakes were recorded at 11 49 06 and 11 49 21 followed directly by a third earthquake at 11 50 17 the first event was located within the scarp based on an arrival time location from good first p arrival times and probably represents the onset of the debris avalanche the third event was a tornillo characterised by a 0 8 hz single frequency resonance and has a resonator attenuation factor of q 40 consistent with a bubbly fluid filled resonator this contrasts with a similar tornillo event occurring 2 5 weeks earlier having q 250 1000 consistent with a dusty gas charged resonator we surmise from pre eruption seismicity and the observed attenuation change that the debris avalanche resulted from the influx of fluids into the hydrothermal system causing destabilisation and failure the beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity

the younger dryas cold interval as viewed from central greenland abstract greenland ice core records provide an exceptionally clear picture of many aspects of abrupt climate changes and particularly of those associated with the younger dryas event as reviewed here well preserved annual layers can be counted confidently with only 1 errors for the age of the end of the younger dryas 11 500 years before present ice flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty glaciochemical and particulate data record atmospheric loading changes with little uncertainty introduced by changes in snow accumulation confident paleothermometry is provided by site specific calibrations using ice isotopic ratios borehole temperatures and gas isotopic ratios near simultaneous changes in ice core paleoclimatic indicators of local regional and more widespread climate conditions demonstrate that much of the earth experienced abrupt climate changes synchronous with greenland within thirty years or less post younger dryas changes have not duplicated the size extent and rapidity of these paleoclimatic changes

analysis of long period seismic waves excited by the may 18 1980 eruption of mount st helens a terrestrial monopole long period 100 to 260 s love and rayleigh waves excited by the eruption of mount st helens on may 18 1980 and recorded by ida sro and asro stations were analyzed to determine the mechanism of the eruption the amplitude radiation patterns of both rayleigh and love waves are two lobed with a nodal direction in e5 s for rayleigh waves and in n5 e for love waves these radiation patterns preclude any double couple mechanism the radiation pattern the initial phase the relatively large amplitude ratio of love to rayleigh waves and the existence of clear nodes in the radiation patterns of fundamental mode and higher mode rayleigh waves suggest that the source is represented by an almost horizontal less than 15 from the horizontal single force pointed toward s5 w the surface wave spectra fall off very rapidly at periods shorter than 75 s suggesting a very slow source process although the details of the source time history could not be determined a smooth bell shaped time function f o s t 1 2 f o l cos t for 0 t 2 and f o s t 0 for t 2 with 75 s is considered appropriate on the basis of comparison between synthetic and observed seismograms and of the shape of the source spectrum the peak value of the force f 0 is about 10 18 dynes the tailing end of the source time function could not be resolved and some overshoot may be added the magnitude and the time history of the force can be explained by a northward landslide followed by a lateral blast observed at the time of the eruption two distinct events about 110 s apart can be identified on body wave and short period surface wave records the first event may correspond to the earthquake which triggered the landslide and the lateral blast the second event appears to correspond to a second large earthquake and explosion which took place about 2 minutes after the first earthquake

high impact mass drops from helicopter a new active seismic source method applied in an active volcanic setting 1 we obtain estimates of the seismic velocity and attenuation for white island volcano by use of high impact sand bag drops from helicopter three drops were attempted two at either end of a 6 station linear array within the crater floor and the third in the volcano s crater lake the bags were dropped from 310 380 m height and contained 700 kg of sand the impact velocity was estimated at 60 70 m s yielding a kinetic energy of about 106 nm giving p wave onsets to a distance of 1 km we obtained a seismic velocity estimate ofvp 1 2 km s for the unconsolidated crater floor and vp 2 2 km s for rays traversing through consolidated rock outside the crater attenuation was very strong q 10 for both consolidated and unconsolidated parts of the volcano this trial shows that low cost helicopter mass drops can be successfully applied to safely determine sub surface properties at hazardous volcanoes

experimental estimates of the energy budget of hydrothermal eruptions application to 2012 upper te maari eruption new zealand sudden hydrothermal eruptions occur in many volcanic settings and may include high energy explosive phases ballistics launched by such events together with ash plumes and pyroclastic density currents generate deadly proximal hazards the violence of hydrothermal eruptions or explosive power depends on the energy available within the driving fluids gas or liquid which also influences the explosive mechanisms volumes durations and products of these eruptions experimental studies in addition to analytical modeling were used here to elucidate the fragmentation mechanism and aspects of energy balance within hydrothermal eruptions we present results from a detailed study of recent event that occurred on the 6th of august 2012 at upper te maari within the tongariro volcanic complex new zealand the eruption was triggered by a landslide from this area which set off a rapid stepwise decompression of the hydrothermal system explosive blasts were directed both westward and eastward of the collapsed area with a vertical ash plume sourced from an adjacent existing crater all explosions ejected blocks on ballistic trajectories hundreds of which impacted new zealand s most popular hiking trail and a mountain lodge 1 4 km from the explosion locus we have employed rocks representative of the eruption source area to perform rapid decompression experiments under controlled laboratory conditions that mimic hydrothermal explosions under controlled laboratory conditions an experimental apparatus for 34 by 70 mm cylindrical samples was built to reduce the influence of large lithic enclaves up to 30 mm in diameter within the rock the experiments were conducted in a temperature range of 250 degrees c 300 degrees c and applied pressure between 4 mpa and 6 5 mpa which span the range of expected conditions below the te maari crater within this range we tested rapid decompression of pre saturated samples from both liquid dominated conditions and the vapor dominated field further we tested dry samples at the same pressure and temperature conditions results showed that host rock lithology and state of the interstitial fluid was a major influence on the fragmentation and ejection processes as well as the energy partitioning clasts were ejected with velocities of up to 160 m s as recorded by high speed camera in addition to rare large clasts analogous to ballistics a large amount of fine and very fine 63 mu m ash was produced in all experiments the efficiency of transformation of the total explosive energy into fragmentation energy was estimated between 10 to 15 depending on the host rock lithology while less than 0 1 of this was converted into kinetic energy our results suggest that liquid to vapor flashing expansion provides an order of magnitude higher energy release than steam expansion which best explains the dynamics of the westward and most energetic directed blast at te maari considering the steam flashing as the primary energy source the experiments suggested that a minimum explosive energy of 7 x 10 10 to 2 x 10 12 j was involved in the te maari blast experimental studies under controlled conditions compared closely to a field example are thus highly useful in providing new insights into the energy release and hazards associated with eruptions in hydrothermal areas c 2016 the author s published by elsevier b v

evidence for early warming and cooling in north atlantic surface waters during the last interglacial in depth analysis of planktic foraminiferal census data paired with 18o records of specific indicator species provides new insight into the surface ocean evolution of the northeast atlantic during the previous interglacial warm period oxygen isotope stage ois 5e full interglacial conditions existed at the study site for a maximum of only 8 kyr between 125 and 117 ka highest sea surface temperatures ssts occurred during early ois 5e concomitant with high summer insolation but after the main phase of ice sheet melting of the preceding glaciation saalian this early peak sst interval is marked by the appearance of tropical subtropical species and lasted for 4 kyr until 121 ka as corroborated by a major change in planktic 18o relative stability in global ice volume continued for another 3 4 kyr before ssts dropped further toward the next stadial during early ois 5e the situation of the surface water vertical structure appears to have been different from the early holocene for ois 5e it is therefore suggested that the particular melting history of late saalian ice had a long lasting and profound effect on both postdeglacial surface water mass configuration in the north atlantic and heat moisture transfer into europe

calendar dated glacier variations in the western european alps during the neoglacial the mer de glace record mont blanc massif holocene glacier records from the western european alps are still sparse although a number of sites are well suited to constraining pre and early little ice age lia glacier advances the present study provides the first dendrochronologically based and calendar dated neoglacial glacier chronology for the mont blanc massif french alps it is based on the analysis of over 240 glacially buried pinus cembra subfossil logs and wood remains found either embedded in till or as detrital material in the mer de glace right lateral moraine only a few of the samples were found to be formally in situ but we show that some logs were virtually in situ not rooted but showing little or no evidence of reworking and could be used to accurately reconstruct past glacier margin behavior in space and time uncertainties regarding the other samples may relate to original growth location and or to outer wood decay the resulting dates followed by a were therefore considered maximum limiting ages for glacier advances the main burial events interpreted as glacier advances occurred between ca 1655 and 1544 bc between ca 1230 and 1105 bc between ca 1013 and 962 937 bc at ca 802 777 bc after 608 bc between 312 and 337 ad between ca 485 ad and 606 ad between 1120 and 1178 ad between ca 1248 and 1278 1296 ad and after 1352 ad these advances predate the late lia maxima known from historical sources the magnitude of the advances gradually increased to culminate in three near neoglacial maxima during the 7th 12th and 13th centuries ad followed by a first lia neoglacial maximum in the second half of the 14th century ad the pattern of neoglacial events described here is coherent with central and eastern alpine glacier chronologies this indicates marked synchronicity of late holocene glacier variability and forcing at a regional scale although occasional differences could be detected between western and eastern records the mer de glace record also confirms the link between the timing of sediment erosion in a high elevation glaciated alpine catchment and subsequent deposition in the sub alpine lake bourget

late eemian warming in the nordic seas as seen in proxy data and climate models 1 we analyze a transient simulation of the last glacial inception in a climate model of intermediate complexity focusing on sea ice ocean circulation dynamics in the north atlantic and nordic seas as northern high latitude summer insolation decreases toward the end of the eemian interglacial arctic sea ice export to the north atlantic increases this surface fresh water transport weakens deep water formation in the north atlantic and the near surface circulation of the subpolar gyre as a consequence the relative contribution of subpolar gyre waters to the atlantic inflow into the nordic seas is reduced giving way to more warm and saline subtropical waters from the north atlantic current we thus find an episode of relatively high heat and salt transport into the nordic seas during the last glacial inception between 119 000 and 115 000 years before present this stabilizes deep ocean convection in the region and warms scandinavia during a phase of low insolation these findings are in good agreement with proxy data from the nordic seas and north atlantic at the end of the warm interval sea surface temperature drops by about 3 c marking the onset of large scale glacier growth over scandinavia

multicentury glacier fluctuations in the swiss alps during the holocene subfossil remains of wood and peat from six swiss glaciers found in proglacial fluvial sediments indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed vegetation growth in now glaciated basins an extended data set of swiss glacier recessions consisting of 143 radiocarbon dates is presented to improve the chronology of glacier fluctuations a comparison with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850 9600 93008650 85508050 77007550 74506550 61505950 57005500 52004400 43003400 28002700 21501850 14001200 cal yr bp it is proposed that major glacier fluctuations occurred on a multicentennial scale with a changing pattern during the course of the holocene after the younger dryas glaciers receded to a smaller extent and prolonged recessions occurred repeatedly culminating around 7 cal kyr bp after a transition around 6 cal kyr bp weak fluctuations around the present level dominated after 3 6 cal kyr bp less frequent recessions interrupted the trend to advanced glaciers peaking with the prominent little ice age this trend is in line with a continuous decrease of summer insolation during the holocene

modern and ancient pedogenesis as revealed by holocene fire northern apennines italy abstract soil needs a long time for its development and traces of the past effects of climate vegetation cover and human activity can persist through time thus paleosols are widely studied for paleo environmental reconstructions so to understand the effects of climate changes and or human activities that for millennia transformed the land and interacted with soil formation the aim of this work was to assess the influence of both ancient and modern environmental conditions on the pedogenesis at mt cimone northern apennines italy in particular we compared buried paleosols and the overlying modern soils separated by a charcoal enriched horizon aub along an altitudinal climatic sequence from 1553 to 1939 m above sea level the radiocarbon age of the aub horizon was 3040 2940 calibrated years before present therefore it was taken as a chronological marker for the beginning of soil formation of the modern soil unit the horizons thickness of the modern soil varied among the sites suggesting the occurrence of accumulation erosion processes with a differential redistribution over the aub horizon of the soil material transported by surface water runoff the soil horizon sequence in the paleosol at lower altitudes 1553 1700 m was rather simple bw c horizons indicating the occurrence of a moderately intense paleo pedogenesis instead from 1700 to 1900 m mostly above the actual tree line the paleosol showed well expressed processes of eluviation illuviation of organic matter and fe al oxyhydroxides which led to the formation of e bs or bhs c horizons sequences podzols these findings agree with previous studies dealing with climatic and palynological changes occurred in this area in the last seven millennia at altitudes 1700 m the ancient pedogenetic phase occurred during the atlantic climatic period with a cryic soil temperature regime no permafrost presence of seasonal snow and a progressive tree species transition from abies alba to oaks of warm temperate climate the modern pedogenetic phase seemed to be affected by local wetter conditions and human induced forest disturbance as it is testified by the change in the pollen abundance

seismic tracking of lahars using tremor signals debris flows or lahars frequently occur in volcanic regions and cause serious disasters to nearby communities lahars are commonly observed as long lasting high frequency tremor in seismic records we propose a seismic technique to locate the source of tremor originating from lahars by using waveform data from a seismic network in this method we fit the surface wave amplitudes from point sources positioned over the surface of a volcano to the observed tremor amplitudes and estimate the spatial distributions of the normalized residuals in successive time windows the observed tremor amplitudes at individual stations are corrected by site amplification factors independently estimated from coda waves of tectonic earthquakes the positions of time windows applied to the observed tremor signals are corrected for the travel times of individual source and receiver pairs we track the source of tremor or lahars as temporal changes of the best fit locations in the residual distributions this method is an extension of the existing methods used to locate seismic events and tremor associated with volcanic eruptions we applied this technique to tremor signals of lahars observed by a seismic network at cotopaxi volcano ecuador our analysis showed regions with small residuals on the ne flank of the volcano this suggests that lahars descended on this flank which is consistent with the result of a field survey that found fresh lahar deposits on the ne flank our method which can be easily automated may be useful for the rapid detection and monitoring of lahars

search for temporal changes in shear wave splitting associated with the 2012 te maari eruptions at mount tongariro new zealand abstract we investigate changes in shear wave splitting and vp vs ratios of local earthquakes from the geonet catalogue during a 16 month period beginning a year before the first te maari eruption at mount tongariro on august 6 2012 focusing on four permanent seismographs located in proximity to the volcano we identify four time periods bounded by sharp transitions that comprise the study period during which moving averages of the shear wave splitting parameters fast direction and t delay time are fairly constant at all stations vp vs is steady throughout most of the study period at 1 75 small variations occur during the earthquake swarm at the volcano which started a month before the first eruption and for some low magnitude events occurring after a change in earthquake location method analysis of data sets in which epicentre location hypocentre depth and event magnitude are restricted illustrates that observed temporal changes in shear wave splitting parameters are likely due to the spatial variation of paths this in turn is governed by the spatial distribution of seismicity and measurement quality we think the short term variation in vp vs ratios is due to event origin time uncertainty of low magnitude earthquakes or incorrect s phase arrival timing for events in the tongariro swarm these results suggest that any volcanic processes able to cause changes in shear wave splitting or vp vs associated with the two eruptions during our study period were too localised to te maari to be observed at the seismographs studied using our methods dominant observed during the study period are oriented approximately tangential to the tongariro ngauruhoe massif at all four stations we suggest that this may result from gravitational loading of tongariro and ngauruhoe mountains inducing fracturing or dilatation of tangentially oriented microcracks there may also be some effect from layered material causing horizontal propagating rays yielding faster speed sh waves than sv at station ngz measurements from shallow earthquakes in immediate proximity to the seismographs indicate the potential presence of a shallow highly anisotropic body in the volcano

seismic monitoring and modeling of an active volcano for prediction we describe seismic monitoring and modeling of an active volcano for the purpose of predicting the magma transport process in real time we selected the piton de la fournaise which has been monitored by an observatory since the early 1980s and is active with 28 eruptions from 1980 until august 1992 it erupted on march 9 1998 after an unusually long quiet period the eruption lasted until september 21 1998 before the march eruption we completed the initial construction of a model of a magma system based primarily on long period lp events and coda localization we found that lp events are associated with the lateral movement of magma to the rift zone and not with the vertical movement to the summit we also found that the source of 2 hz lp events is located below that of 1 hz lp events the coda localization is a newly discovered phenomenon that helped to locate a magma body this model was used for interpreting the incoming information from the precursory seismic crisis and the eruption tremor during the 6 months of the eruption the simultaneous monitoring and modeling of an active volcano led us to a quantitative simulation of the eruption process computing excess pressure and flow rate in a system of reservoirs connected by channels

changes in erosion patterns during the holocene in a currently treeless subalpine catchment inferred from lake sediment geochemistry lake anterne 2063 m a s l nw french alps the role of climate and human activities a high resolution sedimentological and geochemical study was performed on a 20 m long core from the alpine lake anterne 2063 m a s l nw french alps spanning the last 10 ka sedimentation is mainly of minerogenic origin the organic matter quantity toc as well as its quality hydrogen hi and oxygen oi indices both indicate the progressive onset and subsequent stabilization of vegetation cover in the catchment from 9950 to 5550 cal bp during this phase the pedogenic process of carbonate dissolution is marked by a decrease in the calcium content in the sediment record between 7850 and 5550 cal bp very low manganese concentrations suggest anoxic conditions in the bottom water of lake anterne these are caused by a relatively high organic matter terrestrial and lacustrine content a low flood frequency and longer summer stratification triggered by warmer conditions from 5550 cal bp a decrease in toc stabilization of hi and higher sedimentation rates together reflect increased erosion rates of leptosols and developed soils probably due to a colder and wetter climate then three periods of important soil destabilization are marked by an increased frequency and thickness of flood deposits during the bronze age and by increases in topsoil erosion relative to leptosols hi increases during the late iron age roman period and the medieval periods these periods are also characterized by higher sedimentation rates according to palynological data human impact deforestation and or pasturing activity probably triggered these periods of increased soil erosion

shear wave velocity structure of the tongariro volcanic centre new zealand fast rayleigh and slow love waves indicate strong shallow anisotropy abstract models of the velocity structure of volcanoes can help define possible magma pathways and contribute to calculating more accurate earthquake locations which can help with monitoring volcanic activity however shear wave velocity of volcanoes is difficult to determine from traditional seismic techniques such as local earthquake tomography let or refraction reflection surveys here we use the recently developed technique of noise cross correlation of continuous seismic data to investigate the subsurface shear wave velocity structure of the tongariro volcanic centre tgvc of new zealand focusing on the active ruapehu and tongariro volcanoes we observe both the fundamental and first higher order modes of rayleigh and love waves within our noise dataset made from stacks of 15 min cross correlation functions we manually pick group velocity dispersion curves from over 1900 correlation functions of which we consider 1373 to be high quality we subsequently invert a subset of the fundamental mode rayleigh and love wave dispersion curves both independently and jointly for one dimensional shear wave velocity vs profiles at ruapehu and tongariro volcanoes vs increases very slowly at a rate of approximately 0 2 km s per km depth beneath ruapehu suggesting that progressive hydrothermal alteration mitigates the effects of compaction driven velocity increases at tongariro we observe larger vs increases with depth which we interpret as different layers within tongariro s volcanic system above altered basement greywacke slow vs on the order of 1 2 km s are compatible with p wave velocities using a vp vs ratio of 1 7 from existing velocity profiles of areas within the tgvc and the observations of worldwide studies of shallow volcanic systems that used ambient noise cross correlation methods most of the measured group velocities of fundamental mode love waves across the tgvc are 0 1 0 4 km s slower than those of fundamental mode rayleigh waves in the frequency range of 0 25 1 hz first higher mode love waves are similarly slower than first higher mode rayleigh waves this is incompatible with synthetic dispersion curves we calculate using isotropic layered velocity models appropriate for ruapehu and tongariro in which love waves travel more quickly than rayleigh waves of the same period the love rayleigh discrepancy is likely due to structures such as dykes or cracks in the vertical plane having increased influence on surface wave propagation however several measurements at ruapehu have love wave group velocities that are faster than rayleigh wave group velocities the differences between the love and rayleigh wave dispersion curves also vary with the azimuth of the interstation path across ruapehu and tongariro volcanoes significant azimuthal dependence of both love and rayleigh wave velocities are also observed this suggests azimuthal anisotropy within the volcanic structures which coupled with radial anisotropy makes the vs structures of ruapehu and tongariro volcanoes anisotropic with orthorhombic or lower order symmetry we suggest that further work to determine three dimensional volcanic structures should include provisions for such anisotropy

seismic analysis of the 13 october 2012 te maari new zealand lake breakout lahar insights into flow dynamics and the implications on mass flow monitoring abstract on 6 august 2012 an eruption of the upper te maari vent tongariro volcano and subsequent debris flow in the mangatetipua channel created a debris dam and ephemeral lake the lake reached its maximum volume of 50 000 m3 by 13 october initiating dam breaching at 22 30 nzdt 11 30 utc after a period of intense rainfall the breach eventually grew to 29 12 m causing eroded debris flow sediment and water to remobilize as a lahar the event comprising multiple surges lasted 30 min and displaced 57 000 m3 of remobilized sediment up to 4 5 km downstream to determine the dynamics of the event the seismic signals generated by the lahar were compared with active seismic source data collected in february 2013 the comparison used a common frequency band range of 3 10 hz to compute amplitude for four near field seismic stations for periods with signal to noise ratios above 2 0 we obtained lahar amplitude distributions that match best the equivalent active source amplitudes within 0 5 km of the dam breakout the accumulated seismic energy of the lahar was estimated at 1 93 109 nm whereas the peak energy was 6 88 107 nm results of this work may improve the characterization of future mass flow events in the te maari mangatetipua area through the calibration of seismic stations used in this study

seismic and acoustic signatures of surficial mass movements at volcanoes abstract surficial mass movements such as debris avalanches rock falls lahars pyroclastic flows and outburst floods are a dominant hazard at many volcanoes worldwide understanding these processes cataloging their spatio temporal occurrence and detecting tracking and characterizing these events would advance the science of volcano monitoring and help mitigate hazards seismic and acoustic methods show promise for achieving these objectives many surficial mass movements generate observable seismic and acoustic signals and many volcanoes are already monitored significant progress has been made toward understanding modeling and extracting quantitative information from seismic and infrasonic signals generated by surficial mass movements however much work remains in this paper we review the state of the art of the topic covering a range of scales and event types from individual rock falls to sector collapses we consider a full variety of volcanic settings from submarine to subaerial shield volcano to stratovolcano finally we discuss future directions toward operational seismo acoustic monitoring of surficial mass movements at volcanoes

the abrupt termination of the younger dryas climate event previous studies on two deep greenland ice cores have shown that a long series of climate oscillations characterized the late weichselian glaciation in the north atlantic region1 and that the last glacial cold period the younger dryas ended abruptly 10 700 years ago2 here we further focus on this epoch defining event and present detailed heavy isotope and dust concentration profiles which suggest that in less than 20 years the climate in the north atlantic region turned into a milder and less stormy regime as a consequence of a rapid retreat of the sea ice cover a warming of 7 c in south greenland was completed in about 50 years

locating pyroclastic flows on soufriere hills volcano montserrat west indies using amplitude signals from high dynamic range instruments pyroclastic flows are located using amplitude signals from a seven station high dynamic range seismograph array located 1 9 6 1 km from soufriere hills volcano in montserrat west indies locations are determined by measuring the seismograph signal amplitude for an event recorded at several stations in a moving time window analysis for a given window the measured amplitudes are corrected to a trial source location by removing the effect of the surface wave geometric spreading instrument gain and the attenuation at calculated travel times the trial source location is then compared to other trial locations via an iterative localised grid search where the root mean squared amplitude residual a is minimised the process is repeated for subsequent time steps resulting in a best fit event location and size through time the method has been tested on four small events occurring on april 8 1999 august 12 1999 february 25 2001 and july 4 2001 when visual observations of pyroclastic flows coincided with good seismograph station coverage number of stations 5 azimuthal gap 160 based on the location results the four events propagated 0 5 1 4 1 3 and 1 0 km from the dome and had maximum attenuation corrected reduced displacements drq of 9 0 2 8 6 9 and 2 3 cm2 and maximum pyroclastic flow velocities of 7 30 20 and 8 ms 1 respectively a time lapse video of the event of august 12 1999 shows that amplitude based location through time closely matches the observed run out distance and velocity in contrast amplitude based locations for the events of april 8 1999 and july 4 2001 underestimated the actual flow run out by 1 5 km underestimation of the true run out distance is probably due to both the increased distribution of sources as coherent dome material disaggregates into many blocks and signal contamination from other sources results indicate that pyroclastic flows and rockfalls can be located using amplitude signals from high dynamic range seismograph stations yielding estimates of size and trajectory regardless of visibility conditions on the volcano this new method is being tested as a hazard mitigation and research tool on montserrat

late glacial chironomid based temperature reconstructions for lago piccolo di avigliana in the southwestern alps italy chironomid headcapsules were used to reconstruct late glacial and early holocene summer temperatures at lago piccolo di avigliana lpa two training sets northern sweden north america were used to infer temperatures the reconstructed patterns of temperature change agreed well with the grip and ngrip 18o records inferred temperatures were high during the bolling ca 19 c slowly decreased to ca 17 5 c during the allerod reached lowest temperatures ca 16 c during the younger dryas and increased to ca 18 5 c during the preboreal the amplitudes of change at climate transitions i e oldest dryas bolling 3 c allerod younger dryas 1 5 c and younger dryas preboreal 2 5 c were smaller than in the northern alps but similar to those recorded at another site in northeastern italy our results suggest that 1 allerod temperatures were higher in the southern alps and 2 higher during the preboreal 1 c than during the allerod these differences might provide an explanation for the different responses of terrestrial vegetation to late glacial and early holocene climatic changes in the two regions other sites on both sides of the alps should be studied to confirm these two hypotheses

the cold event 8200 years ago documented in oxygen isotope records of precipitation in europe and greenland stable oxygen isotope ratios of ostracod valves in late glacial and holocene sediments of core as 92 5 from deep lake ammersee southern germany reflect variations of mean oxygen isotope ratios in past atmospheric precipitation the record reconfirms the strong similarity of climate evolution in europe and greenland during the last deglaciation for the first time in europe we find a 200 year long negative 18o excursion which is contemporaneous with the strongest negative 18o excursion in the greenland ice around 8 2 ky before present the 8 2 ky isotopic event on both sides of the north atlantic ocean is interpreted as a cold period most probably induced by a perturbation of the north atlantic thermohaline circulation we discuss two possible triggering mechanisms 1 weak forcing as proposed by alley et al and 2 forcing by a strong and sudden freshwater pulse from the collapse of the hudson ice dome

source mechanism of long period events at kusatsu shirane volcano japan inferred from waveform inversion of the effective excitation functions abstract we investigate the source mechanism of long period lp events observed at kusatsu shirane volcano japan based on waveform inversions of their effective excitation functions the effective excitation function which represents the apparent excitation observed at individual receivers is estimated by applying an autoregressive filter to the lp waveform assuming a point source we apply this method to seven lp events the waveforms of which are characterized by simple decaying and nearly monochromatic oscillations with frequency in the range 1 3 hz the results of the waveform inversions show dominant volumetric change components accompanied by single force components common to all the events analyzed and suggesting a repeated activation of a sub horizontal crack located 300 m beneath the summit crater lakes based on these results we propose a model of the source process of lp seismicity in which a gradual buildup of steam pressure in a hydrothermal crack in response to magmatic heat causes repeated discharges of steam from the crack the rapid discharge of fluid causes the collapse of the fluid filled crack and excites acoustic oscillations of the crack which produce the characteristic waveforms observed in the lp events the presence of a single force synchronous with the collapse of the crack is interpreted as the release of gravitational energy that occurs as the slug of steam ejected from the crack ascends toward the surface and is replaced by cooler water flowing downward in a fluid filled conduit linking the crack and the base of the crater lake

a possible mechanism for the strong weakening of the north atlantic subpolar gyre in the mid 1990s 1 the extent and strength of the north atlantic subpolar gyre spg changed rapidly in the mid 1990s going from large and strong in 1995 to substantially weakened in the following years the abrupt change in the intensity of the spg is commonly linked to the reversal of the north atlantic oscillation nao index changing from strong positive to negative values in the winter 1995 96 in this study we investigate the impact of the initial spg state on the subsequent behavior of the spg by means of an ocean general circulation model driven by ncep ncar reanalysis fields our sensitivity integrations suggest that the weakening of the spg cannot be explained by the change in the atmospheric forcing alone rather for the time period around 1995 the spg was about to weaken irrespective of the actual atmospheric forcing due to the ocean state governed by the persistently strong positive nao during the preceding seven years 1989 1995 our analysis indicates that it was this preconditioning of the ocean in combination with the sudden drop in the nao in 1995 96 that lead to the strong and rapid weakening of the spg in the second half of the 1990s this hypothesis explains the diverging evolution of the strength of the spg and the atmospheric forcing winter nao after 1995 as has been suggested recently

simple scaling of catastrophic landslide dynamics catastrophic landslides involve the acceleration and deceleration of millions of tons of rock and debris in response to the forces of gravity and dissipation their unpredictability and frequent location in remote areas have made observations of their dynamics rare through real time detection and inverse modeling of teleseismic data we show that landslide dynamics are primarily determined by the length scale of the source mass when combined with geometric constraints from satellite imagery the seismically determined landslide force histories yield estimates of landslide duration momenta potential energy loss mass and runout trajectory measurements of these dynamical properties for 29 teleseismogenic landslides are consistent with a simple acceleration model in which height drop and rupture depth scale with the length of the failing slope

last interglacial mis5e hydrographic shifts linked to meltwater discharges from the east greenland margin abstract proximal evidence of the surface ocean response to size reduction of the greenland ice sheet gis during the last interglacial mis5e and preceding glacial termination t2 remains largely elusive using a new sediment record from the western iceland sea the behavior of the northeastern gis and its relation to the subpolar north atlantic surface hydrography is examined extremely light oxygen isotopic 18o values are found off central east greenland during early mis5e and point to enhanced meltwater release potentially from the northeastern sector of the gis data from downstream the cold east greenland current egc and its eastward branches suggest a far reaching effect of this meltwater not only in the nordic seas but also in the se labrador sea in particular whereas an early mis5e warming at 128 5 126 5 ka in the two regions coincided with the relative reduction of meltwater input into the egc the subsequent cooling noted at 126 5 ka followed a renewed major freshwater event off central east greenland our data further indicate persistent freshwater influence from the east greenland margin over the entire mis5e interval and in addition also reveal a late mis5e meltwater event the latter event occurred just prior to the last glacial inception and emphasizes the importance of greenland meltwater as forcing factor on interglacial climates

calibrating the amplitude source location asl method by using active seismic sources an example from te maari volcano tongariro national park new zealand a frequently applied amplitude source location asl method is here calibrated and optimized by using active seismic sources located at the surface of a dry stream channel the asl produced location discrepancies larger than 1 0 km laterally and 500 m in depth by using independently determined velocity model attenuation and site amplification factors afs sensitivity tests for asl input parameters show that attenuation and velocity have moderate influence on the location but are easy to independently constrain afs are shown to strongly influence the location and their application may introduce substantial location uncertainties model uncertainties are accommodated with either lateral or depth changes depending on the input parameters station corrections and the source station geometry

the application of a calibrated 3d ballistic trajectory model to ballistic hazard assessments at upper te maari tongariro abstract on 6 august 2012 upper te maari crater tongariro volcano new zealand erupted for the first time in over one hundred years multiple vents were activated during the hydrothermal eruption ejecting blocks up to 2 3 km and impacting 2 6 km of the tongariro alpine crossing tac hiking track ballistic impact craters were mapped to calibrate a 3d ballistic trajectory model for the eruption this was further used to inform future ballistic hazard orthophoto mapping revealed 3587 impact craters with a mean diameter of 2 4 m however field mapping of accessible regions indicated an average of at least four times more observable impact craters and a smaller mean crater diameter of 1 2 m by combining the orthophoto and ground truthed impact frequency and size distribution data we estimate that approximately 13 200 ballistic projectiles were generated during the eruption the 3d ballistic trajectory model and a series of inverse models were used to constrain the eruption directions angles and velocities when combined with eruption observations and geophysical observations the model indicates that the blocks were ejected in five variously directed eruption pulses in total lasting 19 s the model successfully reproduced the mapped impact distribution using a mean initial particle velocity of 200 m s with an accompanying average gas flow velocity over a 400 m radius of 150 m s we apply the calibrated model to assess ballistic hazard from the august eruption along the tac by taking the field mapped spatial density of impacts and an assumption that an average ballistic impact will cause serious injury or death casualty over an 8 m 2 area we estimate that the probability of casualty ranges from 1 to 16 along the affected track assuming an eruption during the time of exposure future ballistic hazard and probabilities of casualty along the tac are also assessed through application of the calibrated model we model a magnitude larger eruption and illustrate that the probability of casualty could reach 100 in localised areas of the track in contrast ballistics ejected from a smaller eruption did not reach the track as was the case with the 21 november 2012 eruption the calibrated ballistic model can therefore be used to improve management of ballistic hazards both at tongariro and also once recalibrated to other volcanoes worldwide

evolution of the northeast labrador sea during the last interglaciation 1 boreal summer insolation during the last interglaciation lig generally warmed the subpolar to polar northern hemisphere more than during the early holocene yet regional climate variations between the two periods remain we investigate northeast labrador sea subsurface temperature and hydrography across terminations t i and ii and during the lig to assess the impact of two different magnitudes of boreal summer insolation increase on the northeast labrador sea we use mg ca ratios in neogloboquadrina pachyderma sinistral as a proxy of calcification temperature to document changes in subsurface temperatures over eirik drift our corresponding record of d 18 o of seawater documents changes in water mass salinity mg ca calcification temperatures peak early in the holocene coincident with peak boreal summer insolation in contrast lig temperatures are relatively constant through the interglaciation and are no warmer than peak holocene temperatures during the first half of the lig d 18 o of seawater remains depleted likely from southern greenland ice sheet retreat and enhanced arctic freshwater and sea ice export to the labrador sea the consequent stratification of the labrador sea and attendant suppressed convection explains delayed deep ocean ventilation and a cooler subsurface in the northeast labrador sea during the lig

pollen inferred palaeoclimate reconstructions in mountain areas problems and perspectives transfer functions are an efficient tool for the quantitative reconstruction of past climate from low to mid elevation pollen sites however the application of existing methods to high altitude pollen assemblages frequently leads to unrealistic results in the aim of understanding the causes of these biases the standard best modern analogue method has been applied to two high altitude pollen sequences to provide quantitative climate estimates for the lateglacial and holocene periods both pollen sequences laghi dell orgials 2130 m sw aspect and lago delle fate 2240 m e aspect are located in the subalpine belt on opposing sides of the st anna di vinadio valley italian maritime alps different results were obtained from the two sequences the largest differences occurred in palaeotemperature reconstruction with notable differences in both the values and trends at each site these biases may be attributed to 1 a lack of high elevation best modern analogues in the database of modern samples 2 the problem of pollen taxa that have multiple climatic significance 3 problems related to the complexity of mountainous ecosystems such as the phenomenon of uphill transport of tree pollen by wind possible improvements to the reconstruction process are discussed copyright 2006 john wiley sons ltd

perils in distinguishing phreatic from phreatomagmatic ash insights into the eruption mechanisms of the 6 august 2012 mt tongariro eruption new zealand abstract the weak geophysical precursors of the 6 august 2012 te maari eruption of mt tongariro and a lack of obvious juvenile components in its proximal ballistic deposits imply that the eruption was caused by the sudden decompression of a sealed hot hydrothermal system strong magmatic signals in pre and post eruption gas emissions indicate that fresh magma had intruded to shallow levels shortly before this eruption here we examine the volcanic ash produced during the august eruption with the aim of determining whether juvenile magma was erupted or not the widely applied criteria for identifying fresh juvenile pyroclasts provided inconclusive results the te maari ash sorting and trend towards a unimodal grain size distribution increase with distance along the dispersal axis proximal to intermediate sites showing polymodal grain size distributions can be related to the re fragmentation of different pre existing lithologies overlapped erupted pulses and transport mechanisms and to particle aggregation between 69 and 100 vol of particles coarser than 3 and 45 75 vol of grains finer than 3 were sourced from the pre existing commonly hydrothermally altered vent area lavas and pyroclasts free crystals pyroxene plagioclase magnetite pyrite make up 0 23 vol of particles coarser than 3 and 22 41 vol of grains finer than 3 brown to black fragments of fresh glass are a small 1 15 vol but notable component under sem these blocky glassy particles are poorly vesicular and irregularly shaped some with fluidal or bubble wall surfaces and others with fragmented stepped surfaces and fine adhering ash in thin section they contain variable amounts of microlites within an isotropic groundmass the range in silica content of the microprobe analysed glass is very wide 56 77 wt and cannot be correlated to any specific particle textural type these chemically and texturally diverse glassy fragments are identical to mechanically broken pieces of country rock lavas and pyroclasts both their diversity and their match with vent country rocks argue strongly against a juvenile origin for the glassy fragments we conclude that rising magma provided only heat and gas into the overlying sealed vapour dominated hydrothermal system a landslide from this area led to a rapid decompression and ash was produced by top down hydrothermal explosions careful attention must be paid to the combination of compositions and textures of fine ash particles in such situations as well as to the context of their source vent in order to be confident that new magma has reached the surface

all age depth models are wrong but how badly the uncertainty and error associated with fitted age depth models were investigated by fitting a range of models to sets of simulated radiocarbon dates based on varved sediments and comparing the modelled relationship with the varve timescale with large numbers of dates cubic smooth splines out perform other models with few dates no model reliably provides a good fit to reality and calculated confidence intervals are over optimistic c 2003 elsevier ltd all rights reserved

measuring basal force fluctuations of debris flows using seismic recordings and empirical green s functions we present a novel method for measuring the fluctuating basal normal and shear stresses of debris flows by using along channel seismic recordings our method couples a simple parameterization of a debris flow as a seismic source with direct measurements of seismic path effects using empirical green s functions generated with a force hammer we test this method using two large scale 8 and 10 m experimental flows at the u s geological survey debris flow flume that were recorded by dozens of three component seismic sensors the seismically derived basal stress fluctuations compare well in amplitude and timing to independent force plate measurements within the valid frequency range 15 50 hz we show that although the high frequency seismic signals provide band limited forcing information there are systematic relations between the fluctuating stresses and independently measured flow properties especially mean basal shear stress and flow thickness however none of the relationships are simple and since the flow properties also correlate with one another we cannot isolate a single factor that relates in a simple way to the fluctuating forces nevertheless our observations most notably the gradually declining ratio of fluctuating to mean basal stresses during flow passage and the distinctive behavior of the coarse unsaturated flow front imply that flow style may be a primary control on the conversion of translational to vibrational kinetic energy this conversion ultimately controls the radiation of high frequency seismic waves thus flow style may provide the key to revealing the nature of the relationship between fluctuating forces and other flow properties

broadband seismic monitoring of active volcanoes using deterministic and stochastic approaches 1 we systematically used two approaches to analyze broadband seismic signals for monitoring active volcanoes one is waveform inversion of very long period vlp signals assuming possible source mechanisms the other is a source location method of long period lp events and tremor using their amplitudes the deterministic approach of the waveform inversion is useful to constrain the source mechanism and location but is basically only applicable to vlp signals with periods longer than a few seconds the source location method assumes isotropic radiation of s waves and uses seismic amplitudes corrected for site amplifications this simple approach provides reasonable source locations for various seismic signals such as a vlp event accompanying lp signals an explosion event and tremor associated with lahars and pyroclastic flows observed at five or fewer stations our results indicate that a frequency band of about 5 12 hz and a q factor of about 60 are appropriate for the determination of the source locations in this frequency band the assumption of isotropic radiation may become valid because of the path effect caused by the scattering of seismic waves the source location method may be categorized as a stochastic approach based on the nature of scattering waves systematic use of these two approaches provides a way to better utilize broadband seismic signals observed at a limited number of stations for improved monitoring of active volcanoes

rapid changes in the mechanism of ocean convection during the last glacial period high amplitude rapid climate fluctuations are common features of glacial times the prominent changes in air temperature recorded in the greenland ice cores1 2 are coherent with shifts in the magnitude of the northward heat flux carried by the north atlantic surface ocean3 4 changes in the ocean s thermohaline circulation are a key component in many explanations of this climate flickering5 here we use stable isotope and other sedimentological data to reveal specific oceanic reorganizations during these rapid climate change events deep water was generated more or less continuously in the nordic seas during the latter part of the last glacial period 60 to 10 thousand years ago but by two different mechanisms the deep water formation occurred by convection in the open ocean during warmer periods interstadials but during colder phases stadials a freshening of the surface ocean reduced or stopped open ocean convection and deep water formation was instead driven by brine release during sea ice freezing these shifting magnitudes and modes nested within the overall continuity of deep water formation were probably important for the structuring and rapidity of the prevailing climate changes

distinguishing subalpine soil types using extractible al and fe fractions and ree geochemistry article i nfo only a few paleoecological studies have attempted to use the geochemistry of lacustrine sediments to reconstruct the history of soil genesis the geochemical signatures of modern soils must firstly be determined before using them to investigate lake sediments our study explores the geochemical variability between eight subalpine soil profiles from the internal zone of the alps to find relevant sediment tracers for present day soils based on the concentrations of secondary al and fe bearing phases as well as major element and rare earth element ree geochemistry different subalpine soil types can be clearly differentiated in the study area although formed in similar geomorphological settings the soil typologies are diverse podzol group soils are developed under old growing coniferous forest whereas cambisols occur under present day old meadows by applying pca including pedological and geochemical parameters we can clearly discriminate between podzol and cambisol samples revealing differences that reflect the intensity of chemical weathering in contrast deep and surface samples can be distinguished using the degree of physical weathering the proportions of organic bound al and fe are significantly higher in podzols thus providing a sediment tracer to reconstruct the intensity and degree of podzolisation the increase of light ree fractionation from the c horizons to the topsoil horizons is explained in terms of soil processes the high field strength element nb is used to estimate enrichment or depletion relative to the unweathered parent material the resulting normalized ree patterns indicate that podzol profiles are more depleted than cambisols moreover normalized ree patterns of a and bw horizons are similar in the cambisol profiles whereas the e and bs horizons of podzols exhibit large variations normalized ree patterns may thus provide a precise tracer of the degree of weathering of materials hence we suggest that ree behaviour and soil weathering are clearly related this study also highlights the effects of millennial scale agricultural practices on soils e g the eventual depodzolization related to deforestation

sub surface structures and site effects extracted from ambient noise in metropolitan guangzhou china abstract in this paper ambient noise is used to investigate near surface structures and site effects in metropolitan guangzhou we deployed 94 short period stations across guangzhou area and later a dense linear array across the shougouling fault sf using more than one month s continuous data we invert three dimensional shear wave velocity structures of guangzhou area via ambient noise tomography results show low velocity near the guangzhou conghua fault gcf shougouling fault sf and beneath the alluvial plain in the south region meanwhile high velocity anomalies are beneath the mountain area in northeastern region moreover we obtain the sediment thickness and sub surface shear wave velocity structures around the shougouling fault sf by horizontal to vertical spectral ratio hvsr method hvsr results show a significant shift in the thickness of the sedimentary layer across the sf shear wave velocity derived from hvsr curves has a consistent trend of variation with the sediment thickness our results provide a better understanding of sub surface structures of metropolitan guangzhou and can be served as a reference model for geological disaster migration prediction in the city

energy growth in laharic mass flows lahars debris flows and sediment rich floods are frequent and deadly hazards at all mountain forming volcanoes their hazard potential is traditionally assessed through mass conserving closed system models where peak conversion rates of potential energy to mechanical energy and hence maximum destruction potential are predicted to occur on the steepest volcano flanks this belies evidence of extremely high energy and deadly catastrophes caused by such flows at large distances from volcanoes here we use the first high resolution record of a moving lahar to develop a new model of the temporally and spatially variable mass flow structure we show that bulk flow energy can grow dramatically in such systems over tens to hundreds of kilometers via momentum transfers from the lahar into water and particles along its path we also demonstrate that dynamic transformations of such flows and their ultimate runout are primarily controlled by the mass flow front

initiation and flow behavior of the 1980 pine creek and muddy river lahars mount st helens washington two large high velocity lahars volcanic debris flows were triggered by a pyroclastic surge during the first few minutes of the may 18 1980 eruption of mount st helens the initial surge cloud evolved progressively by gravity segregation from a gas mobilized highly inflated density flow to a dense water mobilized basal debris flow lahar and accompanying ash cloud as it flowed down the east flank of the volcano the main source of the water for the lahars was probably from eroded snow and ice incorporated into the flow by turbulent mixing but ground water expelled together with the rock debris by the initiating volcanic explosions also may have contributed peak lahar discharge from the pine muddy fan upper smith creek and ape canyon probably exceeded 250 000 m 3 s initially but decreased exponentially in the downstream direction total volume of the lahars was in excess of 1 4 10 7 m 3 initial peak flow velocities in excess of 30 m s also decreased markedly downstream where flow was not impeded velocity was strongly related to the depth slope term r 2 3 s 1 2 from the manning uniform flow equation as a power law function during much of the route traveled lahar flow appears to have been supercritical deposits left in channels were generally thin relative to flow depth 0 to 2 5 m particles up to small boulder size were randomly distributed in the poorly sorted nonstratified matrix indicating complete suspension in a fully developed debris flow slurry however much larger clasts were transported as bed load computed sediment concentrations of matrix slurry samples ranged from 84 to 91 solids by weight and were similar for the two lahars two indirect methods for computing peak flow velocity previously only tentatively applied to debris flows were tested for accuracy by comparing computed lahar arrival times with recorded arrival times at swift reservoir the computed velocities appear to be 15 slower than the recorded velocities which is consistent with the restriction that the velocity formulas produce only minimum values

vegetation dieback as a proxy for temperature within a wet pyroclastic density current a novel experiment and observations from the 6th of august 2012 tongariro eruption abstract the 6th of august 2012 eruption of te maari mt tongariro new zealand generated wet pyroclastic density currents pdcs which caused widespread dieback of vegetation singed brown foliage in their path an absence of significant charcoal formation suggests that pdc temperatures were mostly below 250 c textural evidence for liquid water being present in the matrices during emplacement vesicles suggests that temperatures were

the greenland ice sheet during the last glacial cycle current ice loss and contribution to sea level rise from a palaeoclimatic perspective abstract during the last interglacial lig period between 130 and 116 thousand years before present ka bp the greenland ice sheet gris was considerably reduced in size contributing to a global mean sea level msl rise of 0 5 4 2 m relative to the present this is not sufficient to explain the 6 9 m msl rise estimated for the lig which implies that a significant contribution to the lig highstand came from antarctica following the lig the gris grew and attained its maximum volume of about 12 m global sea level equivalents sles between 18 and 16 ka bp since then the gris margins have retreated on an order of several hundred km following a general pattern of lagged response to changes in high latitude summer insolation and global greenhouse gas concentrations on shorter timescales and over smaller spatial scales the combination of internal ice sheet dynamics and external climate dynamics has often resulted in a more complex and asynchronous behaviour of the ice sheet margin the gris probably reached its minimum holocene extent around 4 ka bp and modelling studies suggest that it contributed to a rise in global msl of less than 0 2 m relative to the present at this time a period of steady growth followed the holocene minimum and in many areas the ice sheet advanced beyond its present limits during the little ice age i e the last few centuries currently the gris occupies an area of 1 7 10 6 km 2 and features a volume of 2 96 10 6 km 3 which amounts to 7 4 m sle observations show that the rate of mass loss from the gris has been accelerating over the past few decades and ice sheet modelling indicates that we have to go back to the last deglaciation around 10 ka bp in order to find sustained melt rates that were higher than those experienced over the last decade the future development of the gris will have a profound influence on sea level both globally and regionally but there are large uncertainties related to how the gris will respond to future global warming based on a range of modelling studies employing different emission scenarios the gris is expected to contribute about 0 1 0 3 m to global msl rise by the end of the 21st century in a longer time perspective modelling suggests that melting of the gris may replace ocean thermal expansion as the most important factor in future sea level rise potentially contributing with 0 7 2 6 m sle within the next 500 years multi millennial simulations show that the entire ice sheet 7 4 m sle might disappear completely within less than three thousand years under high emission scenarios i e with atmospheric co 2 reaching four times preindustrial levels

distortion of the apparent s wave radiation pattern in the high frequency wavefield tottori ken seibu japan earthquake of 2000 summary the distortion properties of the apparent s wave radiation pattern in the high frequency seismic wavefield of over f 2 hz is investigated using a large number of waveform records of the main shock and 29 aftershocks of the tottori ken seibu japan magnitude mw 6 6 earthquake in 2000 the dense seismic records from the kik net strong motion network show a clear four lobe pattern in the apparent s wave radiation pattern in the low frequency wavefield of f 2 hz and shows an almost isotropic distribution in all directions as the frequency increases above 5 hz the distortion of the apparent s wave radiation pattern in the high frequency wavefield increases as travel distance increases therefore the path effect caused by the scattering of seismic waves due to small scale heterogeneities in the crust is a major cause of distortion of the radiation pattern this hypothesis is examined by a 2 d finite difference method simulation of seismic waves in heterogeneous structure models the results of simulations clearly demonstrate the collapse of the s wave front due to seismic wave scattering in the heterogeneous structure by comparing the observed wavefield and the results of simulations using different sorts of stochastic heterogeneous models the most preferable model that can explain the observation is described by a von karman autocorrelation function with correlation distance of a 3 5 km order of 0 5 and rms value of e 0 07 however our simple stochastic random heterogeneity model proposed herein somewhat overestimates the scattering of low frequency signals below 2 hz

origin of spurious single forces in the source mechanism of volcanic seismicity single forces are often observed in the source mechanism of volcanic seismicity however their underlying causative processes are still doubtful the reliability of single force observations must be assessed prior to analyzing them in terms of physical mechanisms using numerical examples we show that source mislocation and velocity mismodeling lead to strong spurious single forces layering in the velocity model produces converted s waves and source mislocations modify the wavefield at the free surface mainly through converted s and surface waves however these waves can also be accurately reproduced in a homogeneous model by adding a vertical single force in the source mechanism which mainly generates s waves for large take off angles hence approximate velocity models can lead to the appearance of strong single forces in source inversions we conclude that in moment tensor inversion while single forces can be used in some cases to accommodate mismodeling errors they cannot be reliably used to infer physical processes

active seismic sources as a proxy for seismic surface processes an example from the 2012 tongariro volcanic eruptions new zealand abstract the 6 august 2012 eruption from tongariro volcano s te maari vent comprised a complex sequence of events including at least 4 eruption pulses a large chasm collapse and a debris avalanche volume of 7 10 5 m 3 that propagated 2 km beyond the eruptive vent the eruption was poorly observed being obscured by night time darkness and the eruption timing must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity that marked the eruption onset we have discriminated the evolution of the complex surface activity by comparing active seismic source data to the seismic sequence in a new cross correlation source location approach we dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent chasm and debris avalanche areas we obtained 8 successful drops having an impact energy ranging from 3 to 9 10 6 nm producing observable seismic signals to a distance of 5 to 10 km and having good signal to noise characteristics in the 3 12 hz range for the 8 drops we picked first p arrival times and calculated amplitude spectra for a uniform set of four stations we then compared these proxy source excitations to the natural eruption and pre eruption data using a moving window cross correlation approach from the correlation processing we obtain a best matched source position in the near vent region for the eruption period and significant down channel excitations during both the pre and post eruption periods the total seismic energy release calculated from the new method is 8 10 11 nm similar to an independently estimated calculation based on the radiated seismic energy the new energy estimate may be more robust than those calculated from standard seismic radiation equations which may include uncertainties about the path and site effects the active source data carry this information directly in the waveforms yielding a simple conversion between seismic amplitude and energy

reconstruction of holocene climate in southern france and eastern spain using quantitative anatomy of olive wood and archaeological charcoal quantitative anatomical analysis of wild olive wood demonstrates that certain criteria are determined by climatic factors regression models developed from modern calibration samples located in french and spanish mediterranean regions and charred under controlled thermal and atmospheric conditions allow us to quantify the response of vessel density and hydraulic conductivity to mean annual temperature and mean annual precipitation respectively from these predictive models climatic conditions are compared with data from wild olive charcoal from three different archaeological sites la cova de l esperit and montou france la cova de les cendres spain although archaeological charcoal results from the partial combustion of wood collected by man around settlements the available samples are sufficiently numerous to infer regional palaeoclimatic conditions they allow us to estimate the climatic changes that occurred in southern france roussillon and eastern spain levante during the holocene period the reconstructed mean annual temperature conditions show low variations throughout each site an increase from 1 to 1 5 c is recorded in southern france at the beginning of the subatlantic chronozone and could be related to the expansion of thermophilous vegetation including olea which is traditionally attributed to anthropogenic influence the mean annual precipitation curves fluctuate to a much greater extent they show positive oscillations wet phases at the atlantic chronozone and at the transition between the subboreal and the subatlantic in spain bioclimatic conditions comparable to those of the present day are recorded during the subboreal chronozone in southern france the onset of modern thermic conditions seems to be reached only during the subatlantic chronozone finally at the latitudes 39 40 n and 43 44 n the onset of the modern mediterranean climate in terms of temperature and precipitation occurred simultaneously about 3000 years ago

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

holocene paleoecological changes and agro pastoral impact on the la narce du beage mire massif central france a paleoecological study macrofossils pollen cryptogam spores non pollen palynomorphs was performed to investigate environmental changes recorded on the peat deposits of the la narce du beage m

holocene climate variability vegetation dynamics and fire regime in the central pyrenees the basa de la mora sequence ne spain abstract high resolution multiproxy data pollen sedimentology geochemistry chironomids and charcoal from the basa de la mora bsm lake sequence 42 32 n 0 19 e 1914 m a s l show marked climate variability in the central southern pyrenees throughout the holocene a robust age model based on 15 ams radiocarbon dates underpins the first precise reconstruction of rapid climate changes during the holocene from this area during the early holocene increased winter snowpack and high snowmelt during summer as a consequence of high seasonality led to higher lake levels a chironomid community dominated by non lacustrine taxa orthocladiinae related to higher inlet streams and a forested landscape with intense run off processes in the watershed from 9 8 to 8 1 cal ka bp climate instability is inferred from rapid and intense forest shifts and high fluctuation in surface run off shifts among conifers and mesophytes reveal at least four short lived dry events at 9 7 9 3 8 8 and 8 3 cal ka bp between 8 1 and 5 7 cal ka bp a stable climate with higher precipitation favoured highest lake levels and forest expansion with spread of mesophytes withdrawal of conifers and intensification of fires coinciding with the holocene climate optimum at 5 7 cal ka bp a major change leading to drier conditions contributed to a regional decline in mesophytes expansion of pines and junipers and a significant lake level drop despite drier conditions fire activity dropped as consequence of biomass reduction two arid intervals occurred between 2 9 and 2 4 cal ka bp and at 1 2 0 7 cal ka bp 800 1300 ad the latter coincides with the medieval climate anomaly and is one of the most arid phases of the holocene in bsm sequence anthropogenic disturbances were small until 700 ad when human pressure over landscape intensified with olea cultivation in the lowlands and significant deforestation in highlands colder and unfavourable weather conditions during the second part of the little ice age caused a temporary cease of high land management the most intense anthropogenic disturbances occurred during the second half of 19th century last decades are characterized by recovery of the vegetation cover as a result of land abandonment and lowered lake levels probably due to higher temperatures

internal structure and volcanic hazard potential of mt tongariro new zealand from 3d gravity and magnetic models abstract a new 3d geophysical model of the mt tongariro volcanic massif tgvm new zealand provides a high resolution view of the volcano s internal structure and hydrothermal system from which we derive implications for volcanic hazards geologically constrained 3d inversions of potential field data provides a greater level of insight into the volcanic structure than is possible from unconstrained models a complex region of gravity highs and lows 6 mgal is set within a broader 20 mgal gravity low a magnetic high 1300 nt is associated with mt ngauruhoe while a substantial thick demagnetised area occurs to the north coincident with a gravity low and interpreted as representing the hydrothermal system the hydrothermal system is constrained to the west by major faults interpreted as an impermeable barrier to fluid migration and extends to basement depth these faults are considered low probability areas for future eruption sites as there is little to indicate they have acted as magmatic pathways where the hydrothermal system coincides with steep topographic slopes an increased likelihood of landslides is present and the newly delineated hydrothermal system maps the area most likely to have phreatic eruptions such eruptions while small on a global scale are important hazards at the tgvm as it is a popular hiking area with hundreds of visitors per day in close proximity to eruption sites the model shows that the volume of volcanic material erupted over the lifespan of the tgvm is five to six times greater than previous estimates suggesting a higher rate of magma supply in line with global rates of andesite production we suggest that our model of physical property distribution can be used to provide constraints for other models of dynamic geophysical processes occurring at the tgvm

early holocene afforestation processes in the lower subalpine belt of the central swiss alps as inferred from macrofossil and pollen records to reconstruct the vegetation history of the upper engadine continuous sediment cores covering the past 11 800 years from lej da champfer and lej da san murezzan upper engadine valley c 1800 m a s l southeastern switzerland have been analysed for pollen and plant macrofossils the chronologies of the cores are based on 16 and 22 radiocarbon dates respectively the palaeobotanical records of both lakes are in agreement for the holocene but remarkable differences exist between the sites during the period 11 100 to 10 500 cal bp when lej da champfer was affected by re sedimentation processes macrofossil data suggest that holocene afforestation began at around 11400 cal bp a climatic deterioration the preboreal oscillation stopped and subsequently delayed the establishment of trees until c 11000 cal bp when first betula then pinus sylvestrislmugo then larix 300 years later and finally pinus cembra expanded within the lake catchment treeline was at c 1500 m during the younger dryas 12 542 11 550 cal bp in the central alps our results along with other macrofossil studies from the alps suggest a nearly simultaneous afforestation e g by pinus sylvestris in the lower subalpine belt between 1500 and 2340 m a s l at around 11 400 to 11 300 cal bp we suggest that forest limit species e g pinus cembra larix decidua could expand faster at today s treeline c 2350 m a s l than 550 m lower earlier expansions at higher altitudes probably resulted from reduced competition with low altitude trees e g pinus sylvestris and herbaceous species comparison with other proxies such as oxygen isotopes residual a14c glacier fluctuations and alpine climatic cooling phases suggests climatic sensitivity of vegetation during the early holocene

debris flow evolution and the activation of an explosive hydrothermal system te maari tongariro new zealand abstract analysis of the pre and post eruption topography together with observations of the avalanche deposition sequence yields a triggering mechanism for the 6 august 2012 eruption of upper te maari the avalanche was composed of a wedge of c 683 000 774 000 m 3 of coarse breccia spatter and clay rich tuffs and diamictons which slid from the western flanks of the upper te maari crater the failure plane is considered to be a hydrothermally altered clay layer this landslide led to a pressure drop of up to 0 5 mpa enough to generate an explosive eruption from the hydrothermal system below which had been activated over the months earlier by additional heat and gas from a shallow intrusion the landslide transformed after c 700 m into a clay rich cohesive debris flow eroding soils from steep narrow stretches of channel before depositing on intermediate broad flatter reaches after each erosive reach the debris flow contained greater clay and mud contents and became more mobile at c 2 km flow distance however the unsaturated flow stopped due to a lack of excess pore pressure this volume controlled flow deposited thick steep sided lobes behind an outer levee accreting inward and upward to form a series of curved surface ridges

eruption source processes derived from seismic and acoustic observations of the 25 september 2007 ruapehu eruption north island new zealand abstract mt ruapehu erupted on 25 september 2007 at 20 26 pm nzdt 8 26 ut generating a steam column to about 15 000 ft 4600 m a directed ballistic and surge deposit of coarse blocks and ash to the north of the crater lake and initiated lahars in the whangaehu catchment and whakapapa ski field the eruption was recorded on three broadband seismometers and two acoustic pressure sensors which indicated broadly coherent waveform characteristics across the network the eruption had a duration of less than 1 min as indicated by strong seismic and acoustic pulses the acoustic wave coincided with observed very long period vlp seismic signal 2 25 s period the acoustic pulse had a positive pressure indicating an explosion and travelled at a velocity of 320 m s the syn eruptive vlp was composed of surface waves having strong radial and transverse components the immediate aftermath of the eruption produced about 4 min of continued high amplitude spasmodic tremor signals that probably resulted from post explosion phase associated vent backfill stabilisation the eruption was preceded by minor volcano tectonic earthquakes and tremor bursts which began 10 min before the main eruption two smaller vlp signals were associated with these tremor pulses at 20 17 and 20 25 these pre eruptive vlp signals had particle motions indicating body and surface waves from a sub surface source region modelling of the vlp sources using a 3d finite difference method shows that that the pre eruption vlp signals are consistent with a volume fluctuation at 3 7 km depth from a radially symmetric source the main eruption vlp was consistent with a south and downward directed single force in response to a northward directed jet and northward directed ballistic deposits

holocene climate fire and vegetation dynamics at the tree line in the northwestern swiss alps treelines are expected to rise to higher elevations with climate warming the rate and extent however are still largely unknown here we present the first multi proxy palaeoecological study from the treeline in the northwestern swiss alps that covers the entire holocene we reconstructed climate fire and vegetation dynamics at iffigsee an alpine lake at 2 065 m a s l by using seismic sedimentary surveys loss on ignition visible spectrum reflectance spectroscopy pollen spore macrofossil and charcoal analyses afforestation with larix decidua and tree betula probably b pendula started at 9 800 cal b p more than 1 000 years later than at similar elevations in the central and southern alps indicating cooler temperatures and or a high seasonality highest biomass production and forest position of 2 100 2 300 m a s l are inferred during the holocene thermal maximum from 7 000 to 5 000 cal b p with the onset of pastoralism and transhumance at 6 800 6 500 cal b p human impact became an important factor in the vegetation dynamics at iffigsee this early evidence of pastoralism is documented by the presence of grazing indicators pollen spores as well as a wealth of archaeological finds at the nearby mountain pass of schnidejoch human and fire impact during the neolithic and bronze ages led to the establishment of pastures and facilitated the expansion of picea abies and alnus viridis we expect that in mountain areas with land abandonment the treeline will react quickly to future climate warming by shifting to higher elevations causing drastic changes in species distribution and composition as well as severe biodiversity losses