sector collapse sedimentation and clast population evolution at an active island arc volcano stromboli italy sciara del fuoco is the subaerial part of a partially filled sector collapse scar that extends to 700 m below sea level on stromboli volcano the collapse occurred 2200 m and 10 km from the shore to the nnw a fan shaped mounded feature comprises debris avalanche deposits 4 km3 from two or more sector collapses volcaniclastic density currents originating from sciara del fuoco follow the topographic margin of the debris avalanche deposits although overbank currents and other unconfined currents widely cover the mounded feature with turbidites historical recorded eruptive activity in sciara del fuoco is considerably less than that which occurred earlier and much of the partial fill may have formed from eruptions soon after the sector collapse it is possible that a mass of eruptive products similar to that in the collapse scar is dispersed as volcanogenic sediment in deep water of the tyrhennian basin evidence that the early post collapse eruptive discharge was greater than the apparent recent flux 2kg s counters suggestions that a substantial part of stromboli s growth has been endogenous the partial fill of sciaria del fuoco is dominated by lava and spatter layers rather than by the scoria and ash layers classically regarded as main constituents of strombolian cinder cones much of the volcanic slope beneath the vents is steeper than the angle of repose of loose tephra which is therefore rapidly transported to the sea delicate pyroclasts that record the magmatic explosivity are selectively destroyed and diluted during sedimentary transport mainly in avalanches and by shoreline wave reworking and thus the submarine deposits do not record well the extent and diversity of explosive activity and associated clast forming processes considerable amounts of dense non vesicular fine sand and silt grains are produced by breakage and rounding of fragments of lava and agglutinate the submarine extension of the collapse scar and the continuing topographic depression to 2200 m below sea level are zones of considerable by passing of fine sand and silt which are transported in turbidity currents evidently volcanogenic sediments dispersed around island volcanoes by density currents are unlikely to record well the true spectrum and relative importance of clast forming processes that occurred during an eruption marine sedimentary evidence of magmatic explosivity is particularly susceptible to partial or complete obliteration unless there is a high rate of discharge of pyroclastic material into the sea

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

spectral and dynamical hints on the time scale of preparation of the 5 april 2003 explosion at stromboli volcano stromboli volcano is well known for its continuous strombolian activity moreover the volcano occasionally shows effusive phases the latest in 1985 1986 on 28 december 2002 stromboli entered a new effusive phase accompanied by different paroxysmal events that led to considerable hazards for inhabitants and tourists on the island of stromboli on 30 december 2002 a major sector collapse affected the sciara del fuoco slope and initiated a tsunami on 5 april 2003 a powerful explosion which can be compared in size with the most recent explosion in 1930 covered a large part of the normally tourist accessible summit area with bombs as this explosion was not forecasted although the island was by then effectively monitored by a dense deployment of instruments in this paper we tackle the problem of highlighting the time scale of preparation of this event and conduct a search for possible precursors for this purpose we analyze the seismic data preceding the paroxysm with spectral and dynamical methods

the 1995 1998 eruption of the soufriere hills volcano montserrat wi eruption of the soufriere hills volcano began on 18 july 1995 after three years of elevated seismic activity four months of increasingly vigorous phreatic activity culminated in mid november 1995 with the initiation of dome growth growth rates increased unevenly through early march 1996 with fluctuations on time scales from hours to months since march 1996 gravitational collapse of the unstable dome flank has affected an ever increasing area with pyroclastic flows surges and ashfalls major collapse of the eastern flank on 17 september 1996 resulted in a sub plinian explosive eruption later that day by february 1997 the dome had outgrown the confines of the crater and begun to spill into the surrounding valleys a large collapse on 25 june 1997 caused pyroclastic flows and surges on the northern flanks and resulted in the only deaths of the eruption in august september and october 1997 vulcanian explosions followed further collapses on the western and northern flanks the largest event of the eruption occurred on 26 december 1997 with failure of the southwestern flank of the volcano producing a debris avalanche and large dome collapse pyroclastic flows dome growth ceased in early march 1998 but residual volcanic activity has continued and consists of ash venting mild explosions and dome collapse pyroclastic flows

sector collapse at kick em jenny submarine volcano lesser antilles numerical simulation and landslide behaviour kick em jenny volcano is the only known active submarine volcano in the lesser antilles it lies within a horseshoe shaped structure open to the west northwest toward the deep grenada basin a detailed bathymetric survey of the basin slope at kick em jenny and resulting high resolution digital elevation model allowed the identification of a major submarine landslide deposit this deposit is thought to result from a single sector collapse event at kick em jenny and to be linked to the formation of the horseshoe shaped structure we estimated the volume and the leading edge runout of the landslide to be ca 4 4 km3 and 14 km respectively we modelled a sector collapse event of a proto kick em jenny volcano using volcflow a finite difference code based on depth integrated mass and momentum equations our models show that the landslide can be simulated by either a coulomb type rheology with low basal friction angles 5 5 6 5 and a significant internal friction angle above 17 5 or with better results by a bingham rheology with low bingham kinematic viscosity 0 b 30 m2 s and high shear strength 130 180 m2 s2 the models and the short runout distance suggest that the landslide travelled as a stiff cohesive flow affected by minimal granular disaggregation and slumping on a non lubricated surface the main submarine landslide deposit can therefore be considered as a submarine mass slide deposit that behaved like a slump

melanges magmatiques a la montagne pelee martinique origine des eruptions de type saint vincent au cours des 40 000 dernieres annees l activite de la montagne pelee a consiste en l emission de coulees de ponces nuees ardentes peleennes et de type merapi mettant en place des produits de composition andesitique a dacitique ainsi que de quelques nuees ardentes de type saint vincent responsables de l emission de produits plus basiques andesites basaltiques basaltes accompagnes par des phenomenes de melanges magmatiques deux eruptions de ce type sv1 et sv2 datees a 25700 1200 et 22300 1200 ans b p ont ete etudiees au point de vue du deroulement de l eruption de la composition chimique des produits et de la mineralogie elles suivent toutes les deux un meme scenario eruptif evoluant depuis un pole andesitique vers un pole plus basique avec un stade intermediaire de melange magmatique les volumes emis sont tres importants de l ordre de 1 km3 ou plus les differences chimiques peu marquees 3 a 6 sio2 les variations moderees et progressives de la mineralogie ainsi que des conditions physiques de cristallisation t 920 930 a 950 970 c indiquent le cogenetisme des differents magmas

real time seismic amplitude measurement rsam a volcano monitoring and prediction tool seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions although several real time earthquake detection and data acquisition systems exist few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent analog seismic records provide a quick visual overview of activity however continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders at the cascades volcano observatory an inexpensive 8 bit analog to digital system controlled by a laptop computer is used to provide 1 min average amplitude information from eight telemetered seismic stations the absolute voltage level for each station is digitized averaged and appended in near real time to a data file on a multiuser computer system raw realtime seismic amplitude measurement rsam data or transformed rsam data are then plotted on a common time base with other available volcano monitoring information such as tilt changes in earthquake activity associated with dome building episodes weather and instrumental difficulties are recognized as distinct patterns in the rsam data set rsam data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion mount st helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations weather related noise shows up as low level long term disturbances on all seismic stations regardless of distance from the volcano implemented in mid 1985 the rsam system has proved valuable in providing up to date information on seismic activity for three mount st helens eruptive episodes from 1985 to 1986 may 1985 may 1986 and october 1986 tiltmeter data the only other telemetered geophysical information that was available for the three dome building episodes is compared to rsam data to show that the increase in rsam data was related to the transport of magma to the surface thus if tiltmeter data is not available rsam data can be used to predict future magmatic eruptions at mount st helens we also recognize the limitations of rsam data two examples of rsam data associated with phreatic or shallow phreatomagmatic explosions were not preceded by the same increases in rsam data or changes in tilt associated with the three dome building eruptions

hydrothermal circulation beneath mount pelee inferred by self potential surveying structural and tectonic implications abstract self potential sp surveys were made on mount pelee volcano martinique island french west indies in 1991 and 1992 in order to recognize its hydrothermal system the associated groundwater channeling and the main superficial structures of the massif almost 70 km of profiles were carried out with an average sample spacing of 50 m measurements essentially reveal negative sp anomalies down to 1700 mv with high gradients 1 83 mv m due to the infiltration of meteoric water into the massif rims of summit calderas morne macouba and etang sec present sharp negative sp anomalies on the western northern and eastern flanks negative sp anomalies indicate no upward water flow beneath mount pelee summit on the southwestern volcano flank a 3 5 6 km horseshoe shaped structure corresponding to a southwest flank collapse event older than 25 000 years bp is clearly identified by the sp mapping high gradients border the inner southern rim from morne calebasse to st pierre town and the caribbean sea along the northern rim of the horseshoe shaped structure the negative sp anomalies give place to a positive sp anomaly up to 200 mv of sw ne trend this zone covers the area of two active hot springs sources chaudes and puits chaud 40 65 c marine magnetic surveys and bathymetry show that the horseshoe shaped structure spreads into the caribbean sea up to about 10 km from the coast buried structural discontinuities are evidenced inside the flank collapse structure the upper one deviates the groundwater flow coming from the summit toward the south flank where the flow finds an indentation to expand again downwards this discontinuity is either an old hypothetical caldera rim partly destroyed by the collapse of the south southwestern flank and covered by recent pyroclastic deposits or more probably the trace of a bulge landslide a circulation model of the hydrothermal waters is proposed rainfall 5 6 m year is partly drained inside the summital calderas and the flank collapse zone through pyroclastic flows down to an impermeable basement there the groundwater constitutes perched aquifers at the contact of the bulge landslide or of the hypothetical old caldera rim along the inner northern border of the flank collapse structure the phreatic water is reheated warm groundwater flows along the northern avalanche structure rim and discharges near the coast in ground and marine outcrops of medium temperature finally the main part of the meteoric water is channeled along the old caldera rim or along the bulge landslide towards the south flank of mount pelee where some gaps in the rim exist there the groundwater finds again a subhorizontal gravitational circulation along mount pelee slopes into the caribbean sea

cyclic eruptions and sector collapses at monowai submarine volcano kermadec arc 1998 2007 1 repeated multibeam bathymetric surveys at monowai cone a shallow submarine basaltic volcano and part of the monowai volcanic center in the northern kermadec arc were conducted in 1998 2004 and 2007 these surveys document dramatic depth changes at the volcano including negative changes up to 176 m from two sector collapses and positive changes up to 138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars one sector collapse occurred on the se slope between 1998 and 2004 with a volume of 0 09 km3 and another occurred on the sw slope between 2004 and 2007 with a volume of 0 04 km3 the volume of positive depth change due to addition of volcanic material by eruption is of the same order 0 05 km3 between 1998 and 2004 and 0 06 km3 between 2004 and 2007 during these time intervals monitoring by the polynesian seismic network detected frequent t wave swarms at monowai indicative of explosive eruptive activity every few months an unusual t wave swarm on 24 may 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys but no similarly anomalous t waves were detected between 2004 and 2007 probably because the polynesian seismic network stations were acoustically shadowed from the second slide event we interpret that the sector collapses on monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano 20 moreover there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano volumetric rate calculations suggest that these two processes may be more or less in equilibrium the repeated collapses at monowai are relatively modest in volume involving only 0 1 0 5 of the edifice volume have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes and may be characteristic of how persistently active shallow submarine arc volcanoes grow

villarrica volcano chile characteristics of the volcanic tremor and forecasting of small explosions by means of a material failure method villarrica volcano chile 39 42 s 71 93 w is one of the most active volcanoes in the andes it shows persistent strombolian activity in a small lava lake situated at the bottom of the summit crater from september to december 2000 the volcano exhibited anomalous behaviour after a regional tectonic seismic event on 22 september the eruption of a small volume of lava apparently plugged the conduit this situation then lasted for ten days on 5 and 8 october a series of explosions reopened the system this eruption behaviour has allowed us to study the evolution of the characteristic tremor in the open and closed states of the conduit a shift in the peak frequency from 1 hz open to 2 hz closed the explosions related to the opening of the conduit were forecasted by means of a material failure method

correlations between so2 flux seismicity and outgassing activity at the open vent of villarrica volcano chile 1 the characteristics of the open vent activity of villarrica volcano chile were studied in detail by integrating visual observations of the lava lake analysis of the seismic tremor and measurements of so2 flux the outgassing activity comprises a persistent gas plume emission from the bottom of the crater as well as frequent explosive events three main styles of bubble bursting were identified at the surface of the active lava lake seething magma small short lived lava fountains and strombolian explosions seething magma consists of continual burst of relatively small bubbles a few meters in diameter with varying strength over the entire surface of the lava lake small lava fountains seen as a vigorous extension of seething magma commonly have durations of 20 120 s and reach 10 40 m high above the lava lake correlations between seismicity and visual observations indicate that the seismic tremor is mostly caused by the explosive outgassing activity furthermore for different periods between 2000 and 2006 during which the activity remained comparable the real time seismic amplitude measurement system rsam and so2 emission rates show a very good correlation higher so2 emissions appeared to be related to higher levels of the lava lake stronger bubble bursting activity and changes in the morphology and texture of the crater floor background low levels of activity correspond to a lava lake located 80 m below the crater rim small and or blocky morphology of the roof seismic amplitude rsam lower than 25 units few volcano tectonic earthquakes and daily averages of so2 emissions lower than 600 mg d

caldera or flank collapse in the fogo volcano what age consequences for risk assessment in volcanic islands abstract the target of this study is the fogo island in cape verde where the hazards caldera and or flank collapse and the timing 120 ka or younger are still controversial using high resolution dem field geological and structural analysis and high precision k ar dating we produced an age calibrated volcanic stratigraphy of fogo s summit cha das caldeiras for the last ca 220 ka from this we infer the following evolution and associated processes 1 the fogo volcano formed during seven stages of construction and partial destruction 2 three flank collapses can be recognised the biggest of which occurred between 60 and 43 ka 3 this collapse occurred retrogressively producing at least two distinct collapse blocks 4 the innermost collapse was only partial forming a flat step where a new volcano pico do fogo grew and formed the cha das caldeiras literally flat of the calderas 5 the removal of the buttressing eastern flank by the outermost collapse can be responsible for the seemingly caldera structure 6 the growing load of the young volcano can produce a new flank failure following the innermost fault 7 the young and closely spaced collapse ages here reported indicate a significant risk for the inhabitants of fogo in particular and for the whole cape verde archipelago and atlantic seaboard if a tsunami is produced by a future catastrophic flank collapse

models of tremor and low frequency earthquake swarms on montserrat recent observations from soufriere hills volcano in montserrat reveal a wide variety of low frequency seismic signals we discuss similarities and differences between hybrid earthquakes and long period events and their role in explosions and rockfall events these events occur usually in swarms and occasionally merge into tremor an observation that can shed further light on the generation and composition of harmonic tremor we use a 2d finite difference method to model major features of low frequency seismic signatures and compare them with the observations a depth dependent velocity model for a fluid filled conduit is introduced which accounts for the varying gas content in the magma and the impact on the seismic signals is discussed we carefully analyse episodes of tremor that show shifting spectral lines and model those in terms of changes in the gas content of the magma as well as in terms of a time dependent triggering mechanism of low frequency resonances in this way we explain the simultaneous occurrence of low frequency events and tremor with a spectral content comprising integer harmonics

the off shore continuation of an active basaltic volcano piton de la fournaise reunion island indian ocean structural and geomorphological interpretation from sea beam mapping abstract in 1984 a sea beam survey of the submarine east flank of piton de la fournaise was performed with r v jean charcot three main types of volcanic or volcano tectonic features have been identified 1 1 the subaerial ne and se volcanic rift zones of piton de la fournaise do not extend more than about five kilometers offshore unlike typical hawaiian rift zones which form narrow 2 4 km ridges extending tens of kilometers from the summit the active rift zones of piton de la fournaise widen downslope attaining more than 10 km at their front 2 2 the submarine extension of the grand brule slide is larger than the subaerial portion the entire slide forms a 7 24 km scar bounded by two ramparts to the north and south the slumped material may have moved as a debris flow forming a large talus downslope of the slide however the submarine counterpart of the south area of the grand brule seems to be composed by a slumped block whose structure is apparently not disturbed 3 3 another prominent feature is a conspicuous topographic high that occupies nearly all the center of the surveyed zone this cast flank submarine plateau cannot be associated with any active structure of piton de la fournaise its surface generally dips gently 2 3 and its northern and southern flanks are extensively cut by landslides cones of variable dimensions are observed on the plateau and farther to the east three hypotheses are examined to account for the origin of this morphology a remnant flank of an ancestral fournaise volcano associated with a large buried intrusion found by drilling beneath the grand brule b distinct volcanic massif or c material of a huge and ancient landslide the geophysical data show that the western part of this submarine plateau is reversely magnetized and associated with a moderate positive gravity anomaly this confirms that as suggested by the bathymetric analysis this part of the plateau is relatively coherent conversely the eastern portion of the plateau appears to be poorly magnetized and composed of low density material probably chaotic materials derived from landslides the reversed magnetization of the western part shows that the whole structure is older than 0 7 ma these results show that the volcanic history of piton de la fournaise is more complex than previously thought

morne patates volcano southern dominica lesser antilles mornes patates is the youngest volcano in dominica occupying a depression on the southwestern flank of a larger stratovolcano morne plat pays within the depression an arcuate ridge apparently of acid andesite lavas has been cored and largely buried by the explosive emplacement of two acid andesite domes and their associated pyroclastic deposits mainly block and ash flow deposits a basaltic scoria horizon exposed on the northern side of the depression has a 14 c age of 28450 1500 years b p and is not seen on the volcano itself which suggests that the domes and pyroclastic rocks are younger than this a 14 c age of 450 90 years b p from a block and ash flow deposit from the morne patates dome apparently confirms this and the youthful morphology also suggests a young age the angular shape of the depression and the steep submarine slopes are consistent with an origin as a lateral gravity slide rather than a caldera collapse vigorous fumarolic activity and swarms of local earthquakes suggest that magma exists at depth several kilometres beneath the morne patates morne plat pays area

classification of seismic signals at villarrica volcano chile using neural networks and genetic algorithms each volcano has its own unique seismic activity the aim of this work is to construct a system able to classify seismic signals for the villarrica volcano one of the most active volcanoes in south america since seismic signals are the result of particular processes inside the volcano s structure they can be used to forecast volcanic activity this paper describes the different kinds of seismic signals recorded at the villarrica volcano and their significance three kind of signals were considered as most representative of this volcano s activity the long period the tremor and the energetic tremor signals a classifier is implemented to read the seismic registers at 30 second intervals extract the most relevant features of each interval and classify them into one of the three kinds of signals considered as most representative of this particular volcano to do so 1033 different kinds of 30 s signals were extracted and classified by a human expert a feature extraction process was applied to obtain the main characteristics of each of them this process was developed using criteria which have been shown by others to effectively classify seismic signals based on the experience of a human expert the classifier was implemented with a multi layer perceptron mlp artificial neural network whose architecture and training process were optimized by means of a genetic algorithm this technique searched for the most adequate mlp configuration to improve the classification performance optimizing the number of hidden neurons the transfer functions of the neurons and the training algorithm the optimization process also performed a feature selection to reduce the number of signal features optimizing the number of network inputs the results show that the optimized classifier reaches more than 93 exactitude identifying the signals of each kind the amplitude of the signals is the most important feature for its classification followed by its frequency content the described methodology can be used to classify more seismic signals to improve the study of the activity of this volcano or to extend the study to other active volcanoes of the region

submarine landslides around the canary islands the morphology and structure of the submarine flanks of the canary islands were mapped using the gloria long range side scan sonar system bathymetric multibeam systems and sediment echosounders twelve young 2 ma giant landslides have been identified on the submarine flanks of the canary islands up to now older landslide events are long buried under a thick sediment cover due to high sedimentation rates around the canary islands most slides were found on the flanks of the youngest and most active islands of la palma el hierro and tenerife but young giant landslides were also identified on the flanks of the older 15 20 ma but still active eastern islands large scale mass wasting is an important process during all periods of major magmatic activity the long lived volcanic constructive history of the islands of the canary archipelago is balanced by a correspondingly long history of destruction resulting in a higher landslide frequency for the canary islands compared to the hawaiian islands where giant landslides only occur late in the period of active shield growth the lower stability of the flanks of the canaries is probably due to the much steeper slopes of the islands a result of the abundance of highly evolved intrusive and extrusive rocks another reason for the enhanced slope instability is the abundance of pyroclastic deposits on canary islands resulting from frequent explosive eruptions due to the elevated volatile contents in the highly alkalic magmas dike induced rifting is most likely the main trigger mechanism for destabilization of the flanks flank collapses are a major geological hazard for the canary islands due to the sector collapses themselves as well as triggering of tsunamis in at least one case a giant lateral blast occurred when an active magmatic or hydrothermal system became unroofed during flank collapse

slope failures on the flanks of the western canary islands abstract landslides have been a key process in the evolution of the western canary islands the younger and more volcanically active canary islands el hierro la palma and tenerife show the clearest evidence of recent landslide activity the evidence includes landslide scars on the island flanks debris deposits on the lower island slopes and volcaniclastic turbidites on the floor of the adjacent ocean basins at least 14 large landslides have occurred on the flanks of the el hierro la palma and tenerife the majority of these in the last 1 million years with the youngest on the northwest flank of el hierro as recent as 15 thousand years in age older landslides undoubtedly occurred but are difficult to quantify because the evidence is buried beneath younger volcanic rocks and sediments landslides on the canary island flanks can be categorised as debris avalanches slumps or debris flows debris avalanches are long runout catastrophic failures which typically affect only the superficial part of the island volcanic sequence up to a maximum thickness of 1 to 2 km they are the commonest type of landslide mapped in contrast slumps move short distances and are deep rooted landslides which may affect the entire thickness of the volcanic edifice debris flows are defined as landslides which primarily affect the sedimentary cover of the submarine island flanks some landslides are complex events involving more than one of the above end member processes individual debris avalanches have volumes in the range of 50 500 km3 cover several thousand km2 of seafloor and have runout distances of up to 130 km from source overall debris avalanche deposits account for about 10 of the total volcanic edifices of the small relatively young islands of el hierro and la palma some parameters such as deposit volumes and landslide ages are difficult to quantify the key characteristics of debris avalanches include a relatively narrow headwall and chute above 3000 m water depth on the island flanks broadening into a depositional lobe below 3000 m debris avalanche deposits have a typically blocky morphology with individual blocks up to a kilometre or more in diameter however considerable variation exists between different avalanche deposits at one extreme the el golfo debris avalanche on el hierro has few large blocks scattered randomly across the avalanche surface at the other icod on the north flank of tenerife has much more numerous but smaller blocks over most of its surface with a few very large blocks confined to the margins of the deposit icod also exhibits flow structures longitudinal shears and pressure ridges that are absent in el golfo the primary controls on the block structure and distribution are inferred to be related to the nature of the landslide material and to flow processes observations in experimental debris flows show that the differences between the el golfo and icod landslide deposits are probably controlled by the greater proportion of fine grained material in the icod landslide this in turn relates to the nature of the failed volcanic rocks which are almost entirely basalt on el hierro but include a much greater proportion of pyroclastic deposits on tenerife landslide occurrence appears to be primarily controlled by the locations of volcanic rift zones on the islands with landslides propagating perpendicular to the rift orientation however this does not explain the uneven distribution of landslides on some islands which seems to indicate that unstable flanks are a weakness that can be carried forward during island development this may occur because certain island flanks are steeper extend to greater water depths or are less buttressed by the surrounding topography and because volcanic production following a landslide my be concentrated in the landslide scar thus focussing subsequent landslide potential in this area landslides are primarily a result of volcanic construction to a point where the mass of volcanic products fails under its own weight although the actual triggering factors are poorly understood they may include or be influenced by dyke intrusion pore pressure changes related to intrusion seismicity or sealevel climate changes a possible relationship between caldera collapse and landsliding on tenerife is not in our interpretation supported by the available evidence

changes in the diffuse co2 emission and relation to seismic activity in and around el hierro canary islands significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at el hierro canary islands before the occurrence of several seismic events during 2004 two precursory co2 efflux increases started thirteen and nine days before two seismic events of magnitude 2 3 and 1 7 which took place near el hierro island canary islands on march 23 and april 15 reaching a maximun value of 51 1 and 46 2 g m 2 d 1 respectively five and eight days before the two seismic events other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1 3 and 1 5 which took place on october 15 and 21 respectively reaching the maximum values four and one day before the earthquakes these changes were not related to variations in atmospheric or soil parameters the material failure forecast method ffm which analyzes the rate of precursory phenomena was successfully applied to forecast the first seismic event that took place in el hierro island in 2004

large scale flank collapse events during the activity of montagne pelee martinique lesser antilles 1 a horseshoe shaped structure already identified on the southwestern flank of montagne pelee martinique lesser antilles arc was previously interpreted as resulting of a flank collapse event but no debris avalanche deposits were observed at the time new offshore high resolution bathymetry and geophysical data aguadomar cruise december 1998 to january 1999 r v l atalante lead us to identify three debris avalanche deposits on the submarine western flank of montagne pelee extending down to the grenada basin they display morphological fronts and hummocky morphology on bathymetric data speckled pattern on backscatter data and hyperbolic facies on 3 5 khz and seismic profiles new on land geological studies lead us to identify two other horseshoe shaped structures on the same flank of the volcano the three submarine deposits have been traced back to the structures identified on land which confirms the occurrence of repeated flank collapse events during the evolution of montagne pelee the ages of the last two events are estimated at 9 ka and 25 ka on the basis of 14c and 238u 230th dates every flank collapse produced debris avalanches which flowed down to the caribbean sea we propose that the repeated instabilities are due to the large asymmetry of the island with western aerial and submarine slopes steeper than the eastern slopes the asymmetry results from progressive loading by accumulation of volcanic products on the western slopes of the volcano and development of long term gravitational instabilities meteoric and hydrothermal fluid circulation on the floor of the second flank collapse structure also creates a weakened hydrothermalized area which favors the recurrence of flank collapses

radiometric dating of three large volume flank collapses in the lesser antilles arc abstract it is now recognised that flank collapses are a recurrent process in the evolution of the lesser antilles arc volcanoes large magnitude debris avalanche deposits have been identified off the coast of dominica martinique and st lucia with associated volumes up to 20 km 3 deplus c le friant a boudon g komorowski j c villemant b harford c segoufin j cheminee j l 2001 submarine evidence for large scale debris avalanches in the lesser antilles arc earth planet sci lett 192 145 157 we present new radiometric dating of three major events using the k ar cassignol gillot technique in the qualibou depression of st lucia a collapse has been constrained by dome emplacement prior to 95 2 ka in dominica where repetitive flank collapse events have occurred le friant a boudon g komorowski j c deplus c 2002 l ile de la dominique a l origine des avalanches de debris les plus volumineuses de l arc des petites antilles c r geoscience 334 235 243 the plat pays event probably occurred after 96 2 ka inside the depression caused by this event scotts head which is interpreted as a proximal megabloc from the subsequent soufriere avalanche event has been dated at 14 1 ka providing an older bound for this event on martinique three different domes within the carbets structure dated at 337 5 ka constrain the age of this high magnitude event finally these results obtained from three of the most voluminous flank collapses provide constraints to estimate the recurrence of these events which represent one of the major hazards associated with volcanoes of the lesser antilles arc

precursory subsurface 222rn and 220rn degassing signatures of the 2004 seismic crisis at tenerife canary islands precursory geochemical signatures of radon degassing in the subsurface of the tenerife island were observed several months prior to the recent 2004 seismic volcanic crisis these premonitory signatures were detected by means of a continuous monitoring of 222rn and 220rn activity from a bubbling co2 rich gas spot located at 2 850 m depth inside a horizontal gallery for groundwater exploitation at tenerife multivariate regression analysis mra on time series of the radon activity was applied to eliminate the radon activity fluctuation due to external variables such as barometric pressure temperature and relative humidity as well as power supply material failure forecast method ffm was successfully applied to forecast the anomalous seismicity registered in tenerife island in 2004 the changes in the 222rn 220rn ratio observed after the period of anomalous seismicity might suggest a higher gas flow rate and or changes in the vertical permeability induced by seismic activity

new insights into the recent eruptive and collapse history of montagne pelee lesser antilles arc from offshore marine drilling site u1401a iodp expedition 340 abstract marine tephrochronology provides a good alternative to study the eruptive history of volcanic islands and overcome the problem of poorly preserved on land outcropping here we provide new observations on the recent volcanological evolution

varying seismic acoustic properties of the fluctuating lava lake at villarrica volcano chile villarrica volcano outgasses through an open lava lake with bubbles ranging in size from submillimeter to several meters the largest of which produce strombolian bursting events that are visible from the crater rim thousands of shallow strombolian events identified through seismic waveform cross correlation were found to produce discrete and repetitive long period seismic and infrasonic signals we identified variations of up to 0 7 s in seismic acoustic arrival delay times between april and july 2010 at a station 750 m from the vent which we interpret as due to fluctuations in the level of lava lake during time periods interpreted as having high lava lake levels based on reduced time delays interevent times were also reduced and average seismic amplitude measurements seismic and acoustic event energies and volcano acoustic seismic ratios were all high as compared to times when the lava lake was lower the crater is also a source of nearly continuous monotonic infrasonic tremor we found that the peak frequency of this infrasonic tremor typically around 0 5 1 0 hz was inversely correlated with seismic acoustic delay times and therefore an indicator of lava lake level we use this correlation to propose a new model for infrasonic tremor generation namely using crater geometry to approximate a bessel horn we interpret the two clearest cycles of elevated seismicity and lava lake level as due to an increase in exsolved gas resulting from an injection of volatile rich magma or an overturn in a deeper magma reservoir

the giant submarine alika debris slide mauna loa hawaii probably represent multiple subsidence events before during and after the debris avalanches lower slopes of the slide contain distinctive lobate terraced deposits that are interpreted as having been emplaced more slowly prior to the debris avalanches estimated thicknesses of 50 200 m suggest volumes of 200 600 km 3 for the two lobes the combined volume of the entire slide and slump terrane is probably 1500 2000 km 3 the slide deposits predate a 13 ka coral reef and probably postdate the block faulted ninole basalt roughly dated as a few hundred thousand years old the alika slide or a similar deposit recognized on gloria images further north along the hawaiian ridge probably triggered a giant wave that washed 325 m high on lanai at about 100 ka slumping on mauna loa has been most intense adjacent to the large arcuate bend in its southwest rift zone as the rift zone migrated westward away from the growing kilauea volcano slumping events were probably triggered by seismic activity accompanying dike injection along the rift zone such massive slumps landslides and distal submarine turbidity flows appear to be widespread on the flanks of hawaiian volcanoes

flank failure directed blast eruption at soufriere guadeloupe french west indies a 3 000 yr old mt st helens an extensive apparently monogenic debris flow deposit in the basse terre st claude area of southern guadeloupe is contemporaneous with pyroclastic surge deposits that cover an area of at least 60 km2 these 3 000 yr old deposits were emplaced by the avalanching of a sector of soufriere volcano and an associated directed blast similar to the 1956 bezymianni and the may 18 1980 mt st helens eruptions

does an inter flaw length control the accuracy of rupture forecasting in geological materials multi scale failure of porous materials is an important phenomenon in nature and in material physics from controlled laboratory tests to rockbursts landslides volcanic eruptions and earthquakes a key unsolved research question is how to accurately forecast the time of system sized catastrophic failure based on observations of precursory events such as acoustic emissions ae in laboratory samples or on a larger scale small earthquakes until now the length scale associated with precursory events has not been well quantified resulting in forecasting tools that are often unreliable here we test the hypothesis that the accuracy of the forecast failure time depends on the inter flaw distance in the starting material we use new experimental datasets for the deformation of porous materials to infer the critical crack length at failure from a static damage mechanics model the style of acceleration of ae rate prior to failure and the accuracy of forecast failure time both depend on whether the cracks can span the inter flaw length or not a smooth inverse power law acceleration of ae rate to failure and an accurate forecast occurs when the cracks are sufficiently long to bridge pore spaces when this is not the case the predicted failure time is much less accurate and failure is preceded by an exponential ae rate trend finally we provide a quantitative and pragmatic correction for the systematic error in the forecast failure time valid for structurally isotropic porous materials which could be tested against larger scale natural failure events with suitable scaling for the relevant inter flaw distances

late quaternary sedimentation in the lesser antilles island arc investigation of patterns and processes of late quaternary sedimentation in the lesser antilles island arc indicates that the major components of deep water sediment are volcaniclastic silt and clay redeposited shallow water carbonate mainly aragonite and high mg calcite pelagic carbonate mainly low mg calcite and windblown dust from africa although sediment derived from the adjacent south american continent is included in accreted trench deposits marine deposition of this sediment within the arc is insignificant except at the south end of the forearc distribution of sedimentary components within the lesser antilles arc is controlled primarily by arc volcanism a miocene shift in the locus of volcanism which caused the arc to bifurcate created two sedimentologic regimes in the southern part of the arc which is characterized by volcanically active islands with high relief deep water sediment is dominantly volcaniclastic in contrast in the northern part of the arc where a broad arc platform separates high relief active volcanoes from low relief extinct volcanoes surrounded by wide carbonate shelves deep water sediment is composed mainly of redeposited shallow water carbonate pelagic carbonate and eolian transported saharan dust superposed on the facies patterns determined by arc volcanism is a subtle but distinct record of quaternary climate change glacial interglacial periods are recorded in deep water sediment by variations in sedimentation rate composition and texture volcaniclastic sedimentation responded to lowstands of sea level by increased sedimentation rates and thicker and or more frequent turbidites reflecting intensified currents in interisland passages and increased erosion of exposed insular shelves deep water carbonate sedimentation records decreased carbonate productivity on exposed shelves and in the open ocean during glacial lowstands as well as variations in carbonate preservation associated with changes in ocean circulation deposition of saharan dust increased during glacial periods because of intensified wind strengths

seismological aspects of the 1988 1989 lonquimay chile volcanic eruption abstract more than 1600 earthquakes were recorded in a four month period on portable seismographic stations installed in the lonquimay area immediately after the initiation of the volcanic eruption of december 25 1988 hypocentral parameters were calculated on a subset of 150 events showing clear p and s arrivals seismic activity was restricted to a north south elongated region that included the main crater of the lonquimay volcano the new navidad crater lies along the eastern margin of the area of seismicity most of the hypocenters are located at depths shallower than 6 km and none have depths exceeding 10 km the largest earthquakes of the sequence took place on dec 28 m 4 7 jan 12 13 m 4 8 and 5 0 and feb 24 m 5 3 the number of events per day varied it peaked on dec 27 with more than 260 events and more than 200 events were recorded on jan 13 both of which corresponded to the days of large earthquakes the relation of large to small events given by the b value of the magnitude frequency distribution log n a bm is typical of volcanic sequences b 1 7 and much larger than the equivalent for tectonic environments the rate of decay of the number of aftershocks of each large earthquake is proportional to t p with p increasing from 0 63 to 1 08 as the eruption progressed in time initial low values of p indicate a slow stress release in the region larger absolute values of p are comparable with tectonic environments and might be indicators of the last stages of the eruption process the total seismic energy release is 9 6 10 19 ergs about five orders of magnitude less than the estimated thermal energy the spatial distribution of earthquakes suggests that the sources of stress change associated with the eruption are located under and possibly to the south of the main crater of the lonquimay volcano and that the evacuation channels of magma occupied a zone of weakness in the region of the new crater

the past 5 000 years of volcanic activity at mt pelee martinique f w i implications for assessment of volcanic hazards the history of mt pelee martinique was subdivided into three stages based on field geology and 14c data the two first stages constructed an ancient mt pelee and an intermediate cone between 0 4 m y and 19 500 y b p the third or present stage started 13 500 years ago after a repose of 6 000 years this paper focuses on the activity of mt pelee during the past 5 000 years as a means to assess and zone volcanic hazards of the 23 magmatic eruptions during the past 5 000 years the ages of 21 eruptions of this period are based on 75 new 14c dates the types of phenomena and distribution of pyroclasts relate to four main types of activity the first type consists of pumice and ash flows that are not preceded by a plinian fall two eruptions named p6 and p4 illustrate this type for which the mixture of gas ash and pumice simply overflow the vent and flood several valleys the second type differs from the first by the occurrence of a preliminary moderate plinian fall stage four eruptions p5 p31 p2 and p1 illustrate this type two eruptions p32 and p33 experienced cataclysmic plinian explosions and pumiceous surges the third type is related to dome growth with the rise of viscous spines and the production of related block and ash flows five eruptions 1929 sept 1902 1904 npm nab2 and nmp illustrate this type the fourth type is characterized by violent ejection of more or less heterogeneous nuees ardentes the direction of the blast dictated by the morphology of the crater has been towards the south several times at mt pelee four eruptions may 1902 nab1 nrp2 and nrp3 belong to this type future magmatic eruptions at mt pelee will very likely belong to one of these four types assessment of hazards at mt pelee is based upon the behavior of the volcano during the past 5 000 years because 1 recognition of past magmatic eruptions is quite complete and well dated and 2 no structural change has occurred in the volcano a probabilistic and statistical approach has been tentatively followed stochastic models of wickman indicate a the chance that contemporary abnormal seismic and or phreatic activity at the volcano would signal an impending magmatic eruption is 20 percent b mt pelee exhibits a complex loading time behavior that may be related to the buffering effect of a magma chamber time is needed following a single or several closely spaced eruptions to establish conditions to initiate a new eruption and c if the 1929 event can be regarded as the last episode of the major 1902 eruption the volcano could remain in a dormant stage with respect to magmatic events for another century

a giant landslide on the north flank of tenerife canary islands the extent of mass wasting along the north flank of tenerife has been mapped using swath bathymetry gloria side scan sonar and 3 5 khz echo sounder data the marine surveys show that north of tenerife a giant landslide is exposed over an area of 5500 km2 of the seafloor more than twice the surface area of the island the landslide truncates an older ridge and valley topography that is associated with the shield building basalts on tenerife we interpret the ridge and valley topography as the result of subaerial erosion the landslide is estimated to have a length of 100 km a width of up to 80 km and a volume of about 1000 km3 it extends onshore into the orotava and icod valleys which have been interpreted as of landslide origin k ar dating of basaltic flows in the steep headwall of orotava suggests an age of formation for the valley is younger than 0 78 ma and may even be younger than 0 27 ma the icod valley is located immediately to the north of the most recent volcano on tenerife las canadas and has been associated with the collapse of its caldera between 1 2 and 0 2 ma a young age for the landslide is supported by the 3 5 khz echo sounder data which show that the landslide is draped by a thin 10 m layer of younger sediment the landslide did not form however during a single catastrophic event but represents the amalgamation of a number of separate landslides the occurrence of the ridge and valley topography in water depths of up to 2 5 km suggests that the shield building basalts have subsided by at least this amount since they formed 3 3 8 0 ma we speculate that this subsidence is caused by some form of stress relaxation that occurs in the underlying lithosphere the giant landslide imaged in our sonar data is associated with the late stages in the development of the most recent volcano on tenerife las canadas which only began at about 1 8 ma thus landsliding may be a particular feature of the time soon after emplacement when because of incomplete isostatic adjustment oceanic volcanoes have their greatest elevations above sea level and therefore are most susceptible to slope failure

a new model for the evolution of la reunion volcanic complex from complete marine geophysical surveys results from recent marine geophysical surveys offer a new perspective for characterizing the evolution processes of volcanic islands in 2006 cruises forever and eroder 1 investigated the submarine flanks and the surrounding abyssal plain of la reunion indian ocean to obtain for the first time a complete geophysical survey of the area combined analyses of these data reveal major differences in the evolution of the two emerged volcanoes piton des neiges and piton de la fournaise we show that debris avalanche deposits extend on the abyssal plain only offshore the active piton de la fournaise volcano attesting the occurrence of large flank collapse events the absence of such deposits offshore piton des neiges and the presence of compressive structures within the sedimentary unit below the edifice support a mechanism of slow deformation of this volcano such as sliding or spreading the slow deformation of piton des neiges has led to numerous secondary submarine slope instabilities and favored some unconfined turbidity flows which generated large sediment waves running downward all around the island this study proposes a new model using the most complete marine data set available slow deformation controls the evolution of piton des neiges whereas piton de la fournaise formed on the flanks of a pre existing edifice experienced catastrophic large flank collapse events

precursory seismicity of the 1994 eruption of popocatepetl volcano central mexico popocatepetl volcano is located in the central mexican volcanic belt within a densely populated region inhabited by over 20 million people the eruptive history of this volcano indicates that it is capable of producing a wide range of eruptions including plinian events after nearly 70 years of quiescence popocatepetl reawakened in december 21 1994 the eruptive activity has continued up until the date of this submission and has been characterized by a succession of lava dome growth and destruction episodes similar to events that have apparently been typical for popocatepetl since the fourteenth century in this regime the episodes of effusive and moderately explosive activity alternate with long periods of almost total quiescence in this paper we analyze five years of volcano tectonic seismicity preceding the initial eruption of the current episode the evolution of the v t seismicity shows four distinct stages which we interpret in terms of the internal processes which precede an eruption after a long period of quiescence the thermal effects of a magma intrusion at depth the fracturing related to the slow development of magma related fluid pathways the concentration of stress causing a protracted acceleration of this process and a final relaxation or redistribution of the stress shortly before the initial eruption are reflected in the rates of v t seismic energy release a hindsight analysis of this activity shows that the acceleration of the seismicity in the third stage asymptotically forecast the time of the eruption the total seismic energy release needed to produce an eruption after a long period of quiescence is related to the volume of rock that must be fractured so imposing a characteristic threshold limit for polygenetic volcanoes limit that was reached by popocatepetl before the eruption

characteristics of seismic waves composing hawaiian volcanic tremor and gas piston events observed by a near source array a correlation method specifically designed for describing the characteristics of a complex wave field is applied to volcanic tremor and gas piston events recorded by a semicircular array of geos instruments set at the foot of the puu oo crater on the east rift of kilauea volcano hawaii the spatial patterns of correlation coefficients obtained as functions of frequency for the three components of motion over the entire array are similar for gas piston events and tremor and clearly depict dispersive waves propagating across the array from the direction of puu oo the wave fields are composed of comparable amounts of rayleigh and love waves propagating with similar and extremely slow phase velocities ranging from 700 m s at 2 hz to 300 m s at 8 hz the highly cracked solidified lava flow on which the array was deployed and subjacent structure of alternating lava and ash layers formed during repeated eruptions of puu oo since 1983 appear to be responsible for the low velocities observed the results from puu oo stand in sharp contrast to those obtained in an experiment conducted in 1976 on the partially solidified lava lake of kilauea iki rayleigh waves were not observed in kilauea iki but well developed trains of love waves were seen to propagate there with velocities twice as high as those observed near puu oo these differences in the propagation characteristics of surface waves at the two sites may be attributed to the presence of a soft horizontal layer of molten rock in kilauea iki which may have lowered the phase velocity of rayleigh waves more drastically than that of love waves resulting in severe scattering of the rayleigh wave mode on the other hand the thin superficial pahoehoe flow under our array at puu oo may have favored the development of vertical columnar joints more extensively at this location than at kilauea iki which may have reduced the shear moduli controlling the love wave mode the average phase velocities in the frequency band from 2 to 5 hz found at puu oo are roughly similar to those determined for tremor at klyuchevskoy volcano kamchatka but the frequency dependence appears much stronger at puu oo

the relative importance of gravity induced versus current controlled sedimentation during the quaternary along the mideast u s outer continental margin revealed by 3 5 khz echo character abstract a detailed echo character map based on more than 50 000 km of 3 5 khz echograms reveals the relative importance of contour currents turbidity currents and mass wasting processes for the upper 50 100 m of sea floor sediments along the u s continental margin between southern georges bank and cape hatteras nineteen individual echo types are mapped and interpreted as deposits produced either by current controlled or gravity induced processes based on echo type distribution analysis of selected sediment core samples and the published results of other workers turbidity currents and mass wasting have apparently been the primary depositional agents throughout 60 of the region in contrast contour currents alone appear to have influenced only 10 of the region however combined processes i e non separable interaction between downslope and parallel to contour processes have influenced an estimated 25 of the margin the remaining 5 of the study area constitutes the outermost continental shelf echo types here reflect the influence of fluvial deltaic and shallow marine sedimentary processes changes in the relative distributions of various echo types with sea floor depth indicate that the dominant sedimentary processes change downslope and are significantly different within each physiographic province deposits formed by mass wasting dominate the continental slope where 50 of the sea floor is eroded and gullied by slides slumps and the heads of debris flows deposits developed under the influence of combined processes are most wide spread on the upper continental rise and cover 40 of the sea floor primarily in the form of deep sea channel levees modified by contour currents on the lower continental rise turbidites form more than 50 of the sea floor deposits the downslope deposits turbidity currents slumps debris flows etc were emplaced primarily during the pleistocene glacioeustatic sea level lowering moved beaches and rivers across the exposed continental shelf to the shelf edge where massive fluxes of terrigenous sediment could be delivered to the continental slope and rise by turbidity currents significant amounts of this sediment were transported through submarine canyons and leveed deep sea channels to the lower continental rise and formed the lower continental rise terrace a flat turbidite basin ponded behind the hatteras outer ridge southwest of the wilmington channel this glacially derived influx was diminished however depositional patterns indicate that downslope processes continued to be dominant at least as far south as cape hatteras where rapid deposition on the continental slope and uppermost continental rise created instabilities slope failure produced slumps slides and debris flows and provided an additional volumetrically important redistribution of sediment downslope the influence of contour currents is clearly observed only in those areas topographically shielded from the masking effects of downslope processes in particular along the seaward side of the buried chesapeake drift and the hatteras outer ridge

an overview of the palaeoproterozoic geology of peninsular india and key stratigraphic and tectonic issues abstract the archaean proterozoic rock successions in india have the potential to enrich the global database on precambrian stratigraphic development and to offer valuable clues to global tectonic reconstructions built over four distinct archaean cratonic nuclei the major palaeoproterozoic supracrustal belts cover sequences include the dhanjori group the singhbhum group including the dalma volcanics and the chandil formation in eastern india the cuddapah supergroup and the adjoining nellore schist belt bordering the eastern dharwar craton the aravalli supergroup in the aravalli delhi fold belt in nw india the lower vindhyan semri group and the mahakosal sausar betul belts close to the central indian tectonic zone citz and possibly the dongargarh supergroup in bastar a major erosional unconformity separates the archaean tonalite trondjhemite gneiss basement in these cratons from the overlying volcano sedimentary successions an overview of palaeoproterozoic stratigraphic development in these cratonic blocks is presented to bring out the salient features for global comparison and to highlight issues requiring further attention multiple metamorphic magmatic and deformation events are recorded in the fold belts at the join of the cratons or their margins inviting application of the plate tectonic paradigm however a comprehensive tectonic model for the amalgamation of the indian archaean nuclei is yet to emerge and is crucial for our understanding of palaeoproterozoic supercontinent development

first seismic record for intra arc strike slip tectonics along the liquine ofqui fault zone at the obliquely convergent plate margin of the southern andes a temporal seismic network recorded local seismicity along a 130 km long segment of the transpressional dextral strike slip liquine ofqui fault zone lofz in southern chile seventy five shallow crustal events with magnitudes up to m tief w 3 8 and depths shallower than 25 km were observed in an 11 month period mainly occurring in different clusters those clusters are spatially related to the lofz to the volcanoes chaiten michinmahuida and corcovado and to active faulting on secondary faults further activity along the lofz is indicated by individual events located in direct vicinity of the surface expression of the lofz focal mechanisms were calculated using deviatoric moment tensor inversion of body wave amplitude spectra which mostly yield strike slip mechanisms indicating a ne sw direction of the p axis for the lofz at this latitude the seismic activity reveals the present day activity of the fault zone the recent m tief w 6 2 event near puerto aysen southern chile at 45 4 s on april 21 2007 shows that the lofz is also capable of producing large magnitude earthquakes and therefore imposing significant seismic hazard to this region

features of volcanic tremors on mt etna sicily during the march august 1983 eruption the seismic analysis of the volcanic tremors preceding and accompanying the etnean eruption of march august 1983 has shown a significant variation in the spectral content before the beginning of the eruption the tremor peaks at 1 4 and 1 6 hz which might be associated with the feeding pipes of the ne crater schicket al 1982a being the dominant feature of the spectra

synchronous degassing patterns of the neighbouring volcanoes llaima and villarrica in south central chile the influence of tidal forces the neighbouring volcanoes villarrica and llaima are two of the most active volcanoes in chile and both currently degas continuously we present a semi continuous time series of so2 fluxes for villarrica and llaima volcanoes the time series was obtained using five scanning mini differential optical absorption spectrometers mini doas uv spectrometers over 6 months 13 february to 31 july 2010 and is based on 6 829 scans for villarrica and 7 165 scans for llaima statistical analyses of the so2 flux time series reveal a periodicity of degassing maxima about every 7 days and further a conspicuous synchronicity of the degassing maxima and minima between the two volcanoes intra day variations in so2 fluxes also show a striking correlation between villarrica and llaima all these patterns correlate well with the trend of the modelled solid earth tide curves where the 7 day degassing maxima correspond with both the fortnightly tidal maxima and minima the intra day degassing peaks mostly correlate well with the periods of maximum deformation rates during the diurnal tidal cycle and further with semidiurnal minima in atmospheric pressure a phenomenon we refer to as the tidal pump as there is little time lag between the tidal action and the changes in degassing rates we infer that degassing at both volcanoes is controlled by conduit convection involving physical separation between gas and magma at comparatively shallow levels variations in daily degassing rates were up to a factor of ca 12 and 10 for villarrica and llaima respectively without any noticeable changes in the periodicity we thus suggest that the described cyclic variations must be taken into account for all comparable volcanoes when using gas monitoring as a tool for volcanic hazard mitigation

the primitive volcano of mount pelee its construction and partial destruction by flank collapse abstract the geology of mount pelee the active volcano of martinique lesser antilles has been actively studied during the past decade this paper reviews the current knowledge about the oldest least well known part of the volcano here called paleo pelee and the relations between paleo pelee and the mont conil volcanic complex paleo pelee consists mostly of volcanic breccias with a few lava flows it differs in this respect from neighbouring active volcanoes such as the grande decouverte soufriere in guadeloupe and the soufriere in st vincent the oldest products of which are mainly lava flows paleo pelee initially formed a regular cone which was comparable in size with the present edifice it is now largely eroded and its products form prominent radial ridges on the western flank of mount pelee these are buried under younger deposits on the eastern flank the uniformly andesitic breccias of paleo pelee are for the most part brecciated lava flows it is inferred that the activity of mount pelee was less explosive at this stage than during following periods neo pelee the paleo pelee formations overlap those of mont conil the geology of mont conil is poorly known however its lowest exposed products are submarine andesitic breccias cut by many dikes this contrasts with paleo pelee where all breccias are of subaerial origin pleistocene limestones are interbedded within the mont conil breccias between 120 and 150 m above sea level though mont conil seems to be closely linked to mount pelee on the basis of available petrological data a major uplift must have occurred sometime during or after the construction of mont conil and forms a recognizable geological boundary between the two volcanic systems the paleo pelee edifice was partially destroyed by a flank collapse event that occurred on the southwest flank during the early stage 40 000 20 000 y b p of neo pelee this event is evidenced by a large 6 2 5 km horseshoe shaped structure which is limited by well preserved morphological scarps on land and by a 300 m offshore scarp as shown by seabeam bathymetry paleo pelee breccias and lava flows are truncated by the boundary of the collapse structure lava domes occupied the upslope part of the structure at a later time these domes are intersected by the present crater etang sec which has probably been the active vent for at least 2000 years the active crater is located at the intersection between the flank failure depression and an older caldera formed at the paleo pelee stage but probably enlarged later the flank failure structure appears as a major structure of the volcano and creates a strong structural asymmetry in the edifice this fact should be considered when dealing with such various aspects as the hydrogeology of the volcano the structural control of past and future eruptions and the volcanic hazards

lateral collapses and active sedimentary processes on the northwestern flank of stromboli volcano italy abstract the marine volcaniclastic system extending to 3 km water depth on the northwest flank of stromboli volcano has been surveyed using seismo acoustic profiling multibeam bathymetry deep towed long range side scan sonar imaging and box core sampling deposits and sea floor topography record repeated flank collapses that have occurred during the last 13 ka and created the present sciara del fuoco scar an extensive 170 km2 debris avalanche deposit characterized by subdued hummocks megablocks is buried by turbidites formed from gravity currents that originated in sciara del fuoco the currents were mainly deflected along the margin of the avalanche deposit but also spilt over onto it the turbidites reflect topographic flow stripping and their thinning towards slightly steeper slopes indicates that some material that settled there drained further downslope as secondary higher concentration flows the estimated volume of the entire fan shaped bulge amounts to 12 2 5 km3 about 3 5 km3 of which is attributed to the post collapse sedimentation the remaining 8 5 2 5 km3 is in the order of the volume computed for the material removed by the multiple sector collapses that affected the nw stromboli flank two units are identified in the distal part of the bulge through the recognition of their fronts and these indicate a layered structure for successive debris avalanche deposits granulometric and particle type characterization of seabed samples shows clast population evolution with sedimentary transport distance from the main entrance point of debris in sciara del fuoco to the confluence with the stromboli canyon and into the marsili basin some 45 km from the island changes in particle populations are due to selective sedimentation and also mixing with a wide range of terrigenous detritus brought by currents that descended the main stromboli canyon from the continental shelf abundant fine sand and silt is produced at the volcano and occurrence of mainly coarse grained material along the channel to the marsili basin indicates that a considerable volume of volcaniclastic material from stromboli lies in the sedimentary succession accumulating on the distal basin floor where a deep sea fan is growing

source mechanism of volcanic earthquakes a description and classification of seismic sources found in active zones of volcanism are given the main sources of seismic wave energy are caldera collapse shear fractures with comparatively low spectral corner frequencies shallow gas explosions hydraulic pressure transients and non stationary magma flew

seismic hazard of volcanic activity abstract seismic activity is a common feature of volcanic eruptions the majority of volcanic earthquakes are small their magnitudes do not exceed 2 or 3 at the same time significant moderate size and large volcanic earthquakes may also occur the study of 28 significant m w 4 5 earthquakes associated with volcanic eruptions of 20th century allowed us to formulate the following results about seismic hazard of volcanic activity 1 during the 20th century only three large m w 7 0 earthquakes directly associated with volcanic eruptions in the world were recorded 2 the maximum magnitude m w was estimated to be 5 4 for earthquakes related to central eruptions 7 0 for caldera collapse 5 9 for central eruptions accompanied by flank and or fissure eruptions 7 1 for flank and or fissure eruptions without central eruptions and 5 9 for submarine eruptions for seismicity just before the eruption the maximum magnitude of earthquakes was estimated to be m w 7 1 for seismicity at the initial stage of eruption m w 7 0 for paroxysmal stage of eruption m w 5 6 and for final stage of eruption m w 6 1 3 it was shown that the recurrence time of eruptions of the same type of volcano associated with significant m w 4 5 earthquakes was more than 100 years for 86 of events studied

calderas or gravity slide structures in the lesser antilles island arc abstract large arcuate depressions up to about 10 km in diameter on the back arc side of st lucia dominica and st vincent in the lesser antilles arc are discussed the qualibou depression on st lucia has been previously described as a caldera partly because it was believed to be the source of ignimbrites on the island remapping and stratigraphic studies of these ignimbrites show they were not erupted from the depression but from central vents in the highland rainforests and are much younger dominica is geologically similar and has two scarped depressions at the southern end of the island soufriere volcano st vincent has a prominent arcuate scarp opening to the west the southern half of which has been buried under the youngest volcanic products of the volcano we interpret these structures as the root zones of gravity slides perhaps eruption related and triggered by magmatic inflation post slide activity lava domes and fumaroles has occurred within them due to reduction in lithostatic load and pressure release on the flanks of these island volcanic complexes the presence of these structures only on the western coasts is correlated with the steeper 9 slopes into the grenada basin in contrast to the 1 submarine slopes of the atlantic side

geomorphological evolution of montserrat west indies importance of flank collapse and erosional processes analysis of topography and new swath bathymetry as well as geophysical data provides information about aerial and submarine morphological features and mass transfer processes on montserrat the island has a characteristic shallow c 4000 years ago or the boxing day event during the current eruption 26 december 1997 montserrat9s older volcanic centres the centre hills and silver hills illustrate the third stage of evolution extinction and erosion magma production long term erosion and total sedimentation rates on montserrat have been estimated as 0 17 km 3 ka 1 0 0125 km 3 ka 1 and 0 11 km 3 ka 1 i e 1 1 cm ka 1 respectively

structural changes of volcanic tremor at stromboli volcano abstract the occurrence of a tectonic event sufficiently close to a volcano and or sufficiently energetic can trigger a change in its eruptive activity examples include ambrym vanuatu teide spain tungurahua ecuador and villarrica chile of course the possibility that an earthquake can even trigger a new eruption has serious implications in terms of hazard however no serious attempt has been carried out so far to formalize the identification of these structural changes with a statistical approach in this work a statistical approach is applied to identify structural changes in volcanic tremor recorded at stromboli from april to july 2006 we considered different fluctuation type tests using the open source package strucchange written in r language zeileis a leisch f hornik k kleiber c 2002 strucchange an r package for testing for structural change in linear regression models j stat softw 7 2 1 38 stromboli is a particularly interesting case study whilst previous work falsaperla s alparone s spampinato s 2003 seismic features of the june 1999 tectonic swarms in the stromboli volcano region italy j volcanol geotherm res 125 1 2 121 136 had suggested that tectonic events have no influence on volcanic activity most recent results carniel r tarraga m 2006 can tectonic events change volcanic tremor at stromboli geophys res lett 33 l20321 doi 10 1029 2006gl027690 suggest otherwise the aim of this work is to confirm by use of a statistical method the presence of changes in the recorded tremor related to the occurrence of volcano tectonic events on stromboli as pointed out by carniel and tarraga carniel r tarraga m 2006 can tectonic events change volcanic tremor at stromboli geophys res lett 33 l20321 doi 10 1029 2006gl027690 we found that there was at least one variation in the time series associated to every earthquake even in the cases for which previous analyses could not recognize any variation carniel r tarraga m 2006 can tectonic events change volcanic tremor at stromboli geophys res lett 33 l20321 doi 10 1029 2006gl027690

differences of precursory seismic energy release for the 2007 effusive dome forming and 2014 plinian eruptions at kelud volcano indonesia abstract early warnings of the timing style and size of volcanic eruptions made on the basis of seismic monitoring are important for mitigation of the hazards associated with volcanic eruptions we calculated the rates of seismic energy release at kelud volcano indonesia preceding both the 2007 effusive lava dome eruption and the 2014 plinian eruption for the 2007 eruption there was first a step wise increase in the rate of release of seismic energy followed by a gradual decrease until the eruption for the 2014 eruption the rate of energy release was almost constant until 10 days before the eruption then gradually increased until there was a dramatic acceleration during the last day before the eruption the total seismic energy released by the 2007 and 2014 eruptions were 3 10 8 j and 2 2 10 9 j respectively the relative difference between the ejected volumes of the 2007 and 2014 eruptions is roughly equivalent to that of the total seismic energy released preceding the eruptions we conducted several trials of the material failure forecast method ffm applying it to the square root of the rate of seismic energy released to assess its usefulness for predicting the timing of eruptions the predicted onset of the 2007 eruption was one day earlier than the actual eruption and the seismic energy release preceding the actual eruption did not increase dramatically as suggested by the ffm model several trials of ffm for the 2014 eruption predicted the onset of the eruption to be three days to two weeks later than the actual eruption even as the end time of the ffm time window approaches several hours to 10 min before the actual eruption onset the predicted eruption onset is still 3 h later than the actual onset thus the results of our ffm modeling did not show the method to be useful for predicting eruption times for kelud volcano the differences of the ffm modeling results for the 2007 and 2014 eruptions likely reflect the differences in the rate of energy release immediately before the two eruptions a deceleration before the 2007 eruption and an acceleration before the 2014 eruption these differences may reflect differences in precursory processes for effusive lava dome and plinian eruptions

monochromatic infrasonic tremor driven by persistent degassing and convection at villarrica volcano chile 1 infrasonic data collected at villarrica volcano chile in march 2009 show a sustained continuous infrasonic oscillation tremor with a monochromatic low frequency content at 0 75 hz this tremor is extremely stable in time both at the summit and at a distal 4 km small aperture array infrasonic tremor is characterized by discrete high amplitude bursts with a cyclic recurrence time of 40 s and is well correlated 0 93 with seismic tremor these new data are compared with previous datasets collected in 2002 and 2004 during different levels of activity all data show the same persistent infrasonic tremor and have the same strong correlation with seismic tremor the stability and correlation of infrasonic and seismic tremor indicate the existence of a sustained and continuous process which we suggest is related to the gravity driven bubble column dynamics responsible for conduit convection

a late holocene explosive mafic eruption of villarrica volcano southern andes the chaimilla deposit abstract villarrica chile is one of the most active volcanoes in south america having erupted about 60 times in the last 460 years although its historical eruptive activity has been mainly effusive and weakly explosive it had strong explosive behaviour in postglacial times chaimilla

geochemical variations in andean basaltic and silicic lavas from the villarrica lanin volcanic chain 39 5 s an evaluation of source heterogeneity fractional crystallization and crustal assimilation at 39 5 s in the southern volcanic zone of the andes three pleistocene recent stratovolcanoes villarrica quetrupillan and lanin form a trend perpendicular to the strike of the andes 275 to 325 km from the peru chile trench basalts from villarrica and lanin are geochemically distinct the latter have higher incompatible element abundances and la sm but lower ba la and alkali metal la ratios these differences are consistent with our previously proposed models involving a a west to east decrease in an alkali metal rich high ba la slab derived component which causes an across strike decrease in degree of melting or b a west to east increase in the contamination of subduction related magma by enriched subcontinental lithospheric mantle silicic and mafic lavas from the stratovolcanoes have overlapping sr nd and o isotopic ratios silicic lavas also have geochemical differences that parallel those of their associated basalts e g rhyolite from villarrica has lower la sm and incompatible element contents than high sio2 andesite from lanin at each volcano the most silicic lavas can be modelled by closed system fractional crystallization while andesites are best explained by magma mixing apparently crustal contamination was not an important process in deriving the evolved lavas basaltic flows from small scoria cones 20 35 km from villarrica volcano have high incompatible element contents and low ba la like lanin basalts but trend to higher k rb 356 855 and lower 87sr 86sr 0 70361 0 70400 than basalts from either stratovolcano however all basalts have similar nd pb and o isotope ratios the best explanation for the unique features of the cones is that the sources of svz magmas e g slab derived fluids or melts of the subcontinental lithospheric mantle have varying alkali metal and radiogenic sr contents these heterogeneities are not manifested in stratovolcano basalts because of extensive subcrustal pooling and mixing this model is preferable to one involving crustal contamination because it can account for variable sr isotope ratios and uniform nd and pb isotope ratios among the basalts and the divergence of the cones from across strike geochemical trends defined by the stratovolcanoes

analysis of the unrest of active volcanoes using variations of the base level noise seismic spectrum we present an easy to use robust tool for monitoring the unrest of active volcanoes the base level noise seismic spectrum blnss the volcano s base level activity can easily be determined by continuous monitoring of the minimum amplitude of all spectral components and thus indicates the volcanic activity which is always present on fixed segment waveforms the selection of comparative time intervals also eliminates transitory signals related to weather environmental conditions thus avoiding the misinterpretations in terms of predominant frequencies found in short term analysis the application to data recorded at the soufriere hills llaima and villarrica volcanoes demonstrates the methodology s ability to clearly distinguish volcanic background activity from signs of re activation and provides information related to the behavior and dynamics of volcanic unrest

the fault nature of the ms 5 4 volcanic earthquake preceding the 1996 subglacial eruption of grimsvotn volcano iceland abstract the seismic activity preceding and accompanying the september 30 1996 subglacial eruption of the grimsvotn volcano iceland developed in three stages 1 the first stage first 19 h included the main shock of magnitude m s 5 4 and its aftershocks along the northern slope of the bardarbunga volcano situated about 20 km nw from grimsvotn 2 seismic foci during the next 17 h marked a line connecting two volcanoes bardarbunga and grimsvotn this stage culminated in the opening of a fissure and the beginning of eruption 3 the third stage was observed during the eruption midnight of september 30 october 7 and included continuous seismic activity along the northern slope of the bardarbunga volcano as well as more western distributed epicenters which together had clustered the ring fault epicentral zone a finite fault broadband teleseismic p waveform inversion was applied to the main shock of september 29 the inversion showed that the rupture had developed downdip from the hypocenter in about 3 s and the main asperity was ruptured at depths between 4 and 6 km a comparison with the deep distribution of aftershocks showed that their hypocenters were situated above the destroyed asperities at the depths between 0 and 4 km these space time seismic patterns and the results of the finite fault inversion may be interpreted in the following way there was a magma chamber under bardarbunga volcano covered by the strong rocks or asperities the main shock of september 29 broke the asperity and formed a path for magma transport then a fissure was formed connecting the opened magma chamber with the feeding structures of grimsvotn volcano and magma was injected laterally to the site of eruption the continuous seismic activity during the third period was related to the collapse of rocks around the released parts of the magma chamber the role of the m s 5 4 earthquake in this sequence was decisive

uth fractionation by fluids in k rich magma genesis the vico volcano central italy abstract the 230th 238u disequilibrium method has been applied to the potassic volcanic series of vico latium central italy the 3 main events of the recent volcanic activity have been dated using whole rock isochrons the lava flows of the main cone were erupted between 260 and 180 ky pyroclastic flows are dated around 90 ky and the final effusive activity mte venere around 60 ky these results are in good agreement with previous k ar ages the intense th u fractionation th u varying from 3 2 to 11 is apparently not related to processes of partial melting and crystal fractionation the th u fractionation is the most intense in basic terms of the first episode and is due to the percolation of a deep hydrothermal fluid which impoverishes u in different batches of primary magmas more limited th u fractionations in highly differentiated magma are due to u accompanied by sb and alkalies enrichments in the shallow magma chambers a time integrated model is proposed for the evolution of the 230th 232th ratio in the mantle source of vico it shows that th u and th ta fractionations are probably related to the bulk k u and th enrichment of the mantle of the roman province around 300 ky ago a metasomatic enrichment by a silicate melt is proposed to explain the anomalously high th u and th ta fractionations

volcanic tremors and shocks associated with eruptions at etna sicily september 1980 abstract three strong ash eruptions superimposed on an otherwise rather quiet state of volcanic activity took place from the northeast crater of etna during september 1980 the eruptions lasted only a few hours and were associated with an increase in the amplitudes of volcanic tremors by a factor of 10 compared with the mean value of the preceding months special emphasis in the tremor analysis was given to the eruption of september 26 1980 the time function of the amplitude envelope of the tremors follows a mathematical function which resembles the behaviour of a mechanical oscillator with a resonant period of about 300 s a detailed spectral analysis of the tremors before during and after the eruption reveals factors which seem to be associated with the ascent and descent of the tremor sources in the magma columns the turbulent eruptive magma flow apparently is concentrated in a few dykes and pipes their eigenvibrations during an eruption are observed as spectral peaks of small bandwidth superimposed on the smoother spectrum without a volcanic eruption an analysis of seismicity shows a maximum in august with epicenters clustering along a nw se direction

volcanic tremors at etna a model for hydraulic origin spectral analysis of volcanic tremors at etna reveals 2 characteristic features 1 the escaping vapor and gas streams drive the magma in random turbulent motion generating a seismic wave emission according toa f n exp m f k wherea amplitude f frequency n m k parameters 2 sudden transients in the boundary conditions of the piping system generate hydraulic pressure pulses which in the seismogram appear as wave packages their monochromatic frequency content suggests that their origin is associated with strong resonance phenomena it is conclusive that volcanic eruptions may be distinguished and classified according to different eigenfrequencies of the fissure and pipe network involved in the volcanic activity furthermore positions of active dykes may be traced following the amplitude distributions associated with pronounced spectral lines in the tremor spectra

seismic triggering by rectified diffusion in geothermal systems widespread seismicity was triggered by the june 28 1992 landers california earthquake at a rate which was maximum immediately after passage of the exciting seismic waves rectified diffusion of vapor from hydrothermal liquids and magma into bubbles oscillating in an earthquake can increase the local pore pressure to seismically significant levels within the duration of the earthquake in a hydrothermal system modeled as a two component h 2o co 2 fluid in porous rock the pressure initially increases linearly with time the rate of pressure buildup depends sensitively on the mean bubble radius and is large for small bubbles the diffusion induced pressure is relaxed by percolation and resorption of vapor into the liquid solution the induced seismicity itself also relieves stress values of parameters used in the present calculations give results consistent with observations of triggered seismicity at long valley caldera after the landers earthquake for one representative condition at 250 c and 5 6 km depth oscillating strain acting on 10 m diameter bubbles increases pore pressure at the rate of 151 pa s resulting in a pressure increase of 12 kpa in the 80 s duration of the landers earthquake the elevated pressure induced by a single 26 m diameter cloud of bubbles in saturated rock relaxes by percolation through soil of 0 2 mdarcy permeability in 53 6 hours observations of earthquake swarms at other locations suggest that self induced buildup of pore pressure by rectified diffusion can provide a positive feedback mechanism for amplifying seismicity

volcanology 2020 how will thermal remote sensing of volcanic surface activity evolve over the next decade abstract volcanological remote sensing spans numerous techniques wavelength regions data collection strategies targets and applications attempting to foresee and predict the growth vectors in this broad and rapidly developing field is therefore exceedingly difficult however we attempted to make such predictions at both the american geophysical union agu meeting session entitled volcanology 2010 how will the science and practice of volcanology change in the coming decade held in december 2000 and the follow up session 10 years later looking backward and forward volcanology in 2010 and 2020 in this summary paper we assess how well we did with our predictions for specific facets of volcano remote sensing in 2000 the advances made over the most recent decade and attempt a new look ahead to the next decade in completing this review we only consider the subset of the field focused on thermal infrared remote sensing of surface activity using ground based and space based technology and the subsequent research results this review keeps to the original scope of both agu presentations and therefore does not address the entire field of volcanological remote sensing which uses technologies in other wavelength regions e g ultraviolet radar etc or the study of volcanic processes other than the those associated with surface mostly effusive activity therefore we do not consider remote sensing of ash gas plumes for example in 2000 we had looked forward to a golden age in volcanological remote sensing with a variety of new orbital missions both planned and recently launched in addition exciting field based sensors such as hand held thermal cameras were also becoming available and being quickly adopted by volcanologists for both monitoring and research applications all of our predictions in 2000 came true but at a pace far quicker than we predicted relative to the 2000 2010 timeframe the coming decade will see far fewer new orbital instruments with direct applications to volcanology however ground based technologies and applications will continue to proliferate and unforeseen technology promises many exciting possibilities that will advance volcano thermal monitoring and science far beyond what we can currently envision

a model to describe precursory material failure phenomena applications to short term forecasting at colima volcano mexico some volcanoes exhibit at times accelerating strain and seismicity before eruptions different authors have used this behavior to predict eruptions and to develop materials science models here a linear kelvin voigt viscoelastic model is proposed to describe the observed behavior this model also has applications to other failure phenomena such as landslides the strain rate of a variety of materials under constant stress after an instantaneous elastic response is found to be well described by a general relaxation law dot varepsilon left t right b over 1 st where b and s are parameters depending on the material and its creep state whether the creep regime is primary or tertiary depends upon the sign of s s 0 corresponds to pseudoviscous flow the creep behavior of the viscoelastic body is analyzed for different load histories it is found that the body has an exponential distribution of retardation frequencies that may or may not converge depending on the sign of s according to the model tertiary creep implies material degradation and a critical weakening of the medium leading to a runaway growth of the strain and seismic energy release rates if tertiary creep is detected time of failure predictions may be done from field data through determination of two model parameters for varying loads the model response compare well with reported examples of pre eruptive volcano behavior and with reported results of landslide experiments the model is tested with the july 1994 in hindsight and november 1998 in foresight colima volcano eruptions although this method provides some guidance in estimating the time over which accelerating volcanic precursors may end in an eruption it is emphasized that eruptions may fail to occur at the estimated time or may not occur at all on the other hand eruptions may not be preceded by such a behavior

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

using a cross correlation technique to refine the accuracy of the failure forecast method application to soufriere hills volcano montserrat prior to many volcanic eruptions an acceleration in seismicity has been observed suggesting the potential for this as a forecasting tool the failure forecast method ffm relates an accelerating precursor to the timing of failure by an empirical power law with failure being defined in this context as the onset of an eruption previous applications of the ffm have used a wide variety of accelerating time series often generating questionable forecasts with large misfits between data and the forecast as well as the generation of a number of different forecasts from the same data series here we show an alternative approach applying the ffm in combination with a cross correlation technique which identifies seismicity from a single active source mechanism and location at depth isolating a single system at depth avoids additional uncertainties introduced by averaging data over a number of different accelerating phenomena and consequently reduces the misfit between the data and the forecast similar seismic waveforms were identified in the precursory accelerating seismicity to dome collapses at soufriere hills volcano montserrat in june 1997 july 2003 and february 2010 these events were specifically chosen since they represent a spectrum of collapse scenarios at this volcano the cross correlation technique generates a five fold increase in the number of seismic events which could be identified from continuous seismic data rather than using triggered data thus providing a more holistic understanding of the ongoing seismicity at the time the use of similar seismicity as a forecasting tool for collapses in 1997 and 2003 greatly improved the forecasted timing of the dome collapse as well as improving the confidence in the forecast thereby outperforming the classical application of the ffm we suggest that focusing on a single active seismic system at depth allows a more accurate forecast of some of the major dome collapses from the ongoing eruption at soufriere hills volcano and provides a simple addition to the well used methodology of the ffm

a sliding consolidation model for flow slides a model is proposed for the behaviour of flow slides in loose cohesionless materials in which the debris spreads out as a uniform sheet excess pore fluid pressures are assumed to be generated for example by undrained loading arising from the collapse of metastable structure in the source area of the flow slide under the influence of these the leading element of the debris moves downslope by basal sliding consolidating as it does so by single upward drainage as a result the pore pressure at the base of the element eventually decays to a value that brings the element to rest hence defining the run out of the flow slide the model is applicable in principle to subaqueous and subaerial flow slides and to pore fluids consisting of water gas or both of these the predictions of the model are tested against the observed behaviour and measured properties of the 1966 flow slide at aberfan south wales the results show that a sliding consolidation model provides a possible mechanism for that event

using volcanic tremor for eruption forecasting at white island volcano whakaari new zealand abstract eruption forecasting is a challenging task because of the inherent complexity of volcanic systems despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions the material failure forecast method ffm is one of the very few techniques that can provide a forecast time for an eruption however the method requires testing and automation before being used as a real time eruption forecasting tool at a volcano we developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by real time seismic amplitude measurement rsam at one station and optimised this algorithm for the period august 2011 january 2014 which comprises the recent unrest period at white island volcano whakaari new zealand a detailed residual analysis was paramount to select the most appropriate model explaining the rsam time evolutions in a hindsight simulation four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0 21 which is 37 times higher than the probability of having an eruption on any day during the same period 0 0057 moreover the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view whereas the rsam time evolutions preceding these four eruptions have a similar goodness of fit with the ffm their spectral characteristics are different the duration amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions we propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes this hindsight exercise can be useful for future real time implementation of the ffm at white island a similar methodology could also be tested at other volcanoes even if only a limited network is available

recurrence of major flank landslides during the last 2 ma history of reunion island new detailed swath bathymetry and backscatter data corroborate the existence of four large bulges on the submarine flanks of reunion island these fan shaped promontories are 20 25 km wide at the coastline and 70 150 km across the seafloor 40 50 km offshore their surfaces are characterized by a speckle sonar pattern indicating the presence of large blocks up to several hundred meters across each bulge results from the superposition of multiple landslide deposits whose older ones are dissected and delimited by erosive channels as much as 200 m deep and 20 km long the submarine flanks of reunion island are thus mostly built by accumulation of debris avalanche fans morphologic and geologic evidence define large subaerial source areas for these mass wasting events in particular inferred headwalls of most landslides having affected the piton des neiges massif generally coincide with the boundaries of its cirques mafate salazie and cilaos whereas recurrent landslides have resulted in the formation of large concentric amphitheatre structures through the piton de la fournaise massif thus about 15 slide events accompanied growth of the reunion island shield since 2 ma