most recent fall deposits of ksudach volcano kamchatka russia three of four plinian eruptions from ksudach volcano are among the four largest explosive eruptions in southern kamchatka during the past 2000 years the earliest of the eruptions was voluminous and was accompanied by an ignimbrite and the fifth and most recent caldera collapse event at ksudach the isopach pattern is consistent with a column height of 23 km the three more recent and smaller eruptions were from the shtyubel cone within the fifth caldera using isopach and grain size isopleth patterns column heights ranged from 10 to 22 km although the oldest eruption may have produced a large acidity peak in the greenland ice the three shtyubel events may not be related to major acid deposition thus it is possible that few if any of the uncorrelated acidity peaks of the past 2000 years in greenland ice cores result from eruptions in southern kamchatka

the caldera forming eruption of ksudach volcano about cal a d 240 the greatest explosive event of our era in kamchatka russia the largest plinian eruption of our era and the latest caldera forming eruption in the kuril kamchatka region occurred about cal a d 240 from the ksudach volcano this catastrophic explosive eruption was similar in type and characteristics to the 1883 krakatau event the volume of material ejected was 18 19 km3 8 km3 dre including 15 km3 of tephra fall and 3 4 km3 of pyroclastic flows the estimated height of eruptive column is 22 30 km a collapse caldera resulting from this eruption was 4 6 5 km in size with a cavity volume of 6 5 7 km3 tephra fall was deposited to the north of the volcano and reached more than 1000 km pyroclastic flows accompanied by ash cloud pyroclastic surges extended out to 20 km the eruption was initially phreatomagmatic and then became rhythmic with each pulse evolving from pumice falls to pyroclastic flows erupted products were dominantly rhyodacite throughout the eruption during the post caldera stage when the shtyubel cone started to form within the caldera basaltic andesite and andesite magma began to effuse the trigger for the eruption may have been an intrusion of mafic magma into the rhyodacite reservoir the eruption had substantial environmental impact and may have produced a large acidity peak in the greenland ice sheet

a proximal record of caldera forming eruptions the stratigraphy eruptive history and collapse of the palaeogene arran caldera western scotland caldera forming volcanic eruptions are among the most dangerous and can generate extensive pyroclastic deposits and deliver ash into global atmospheric circulation systems as calderas collapse the eruptions can deposit thick proximal ignimbrite sequences and thinner ignimbrites more distally however the proximal record of caldera collapse is often obscured by later intrusions volcanism faults alteration water and sediments which significantly limits our understanding of these eruptions a palaeogene caldera system in central arran western scotland preserves a rare proximal caldera fill succession the arran volcanic formation this caldera largely comprises highly heterogeneous ignimbrites and minor intra caldera sedimentary rocks the current level of erosion and the general absence of faults intrusions and sediments allows a complex stratigraphy and collapse history to be determined which can be linked to changing eruptive styles at a constantly evolving volcano the first recorded phase was eruption of a homogeneous rhyolitic lava like tuff deposited from high temperature high mass flux pyroclastic density currents generated from low fountaining columns that retained heat a succeeding phase of highly explosive plinian eruptions marked by a thick blanket of massive lapilli tuffs was then followed by piston like caldera collapse and erosion of steep caldera walls volcanism then became generally less explosive with predominantly lava like and eutaxitic tuffs and cognate spatter rich agglomerates interbedded with non homogenous lapilli tuffs high topographic relief between distinct units indicate long periods of volcanic quiescence during which erosive processes dominated these periods are in several places marked by sedimentary rocks and evidence for surface water which includes a localised basaltic andesitic phreatomagmatic tuff the caldera forming eruptions recorded by the arran volcanic formation provide an important insight into caldera collapse processes and proximal ignimbrite successions the lack of thick autobreccias and lithic rich lapilli and block layers indicates that subsidence was relatively gradual and incremental in this caldera and not accompanied by catastrophic wall collapse during eruption the relatively horizontal nature of the caldera fill units and paucity of intra caldera faulting indicate that piston subsidence was the dominant method of collapse with a relatively coherent caldera floor bounded by a steeply dipping ring fault possible resurgence may have caused later doming of the floor and radial distribution of subsequent ignimbrites and sedimentary rocks our work emphasises the continued need for field studies of caldera volcanoes

statistical data analysis of the ccdb collapse caldera database insights on the formation of caldera systems collapse calderas are one of the most important volcanic structures because of their hazard implications but also because of their high energy potential and their association with mineral deposits of high economic interest the worldwide collapse caldera database ccdb 22 http www gvb csic es ccdb htm currently formed by 473 calderas and 28 variables updates the current field based knowledge on calderas merging together the existing databases complementing them with new examples found in the bibliography and leaving it open for the incorporation of new data from future studies the area of the caldera is a relevant indicator of the dynamics of the caldera system as it is directly related to the size of the magma chamber and other variables of the volcanic systems such as crustal type magma composition and tectonic setting despite this being a generally assumed geological belief it has never been numerically studied in this paper we have conducted a statistical analysis using anova analysis of variance on a selected sample from the ccdb containing the relevant variables in order to determine if the area of the collapse caldera depends on a group of geological characteristics or is it due to random variability alone and if so what is the relationship the results identify three groups of collapse calderas in different geodynamic environments according to crustal type rock suite and plate tectonic setting which we name ge1 ge2 and ge3 these groups have significantly different caldera area suggesting how the dynamics of the volcanic system hosting the collapse caldera are intrinsically related to the geodynamic environment where it develops

tsunami generation by a rapid entrance of pyroclastic flow into the sea during the 1883 krakatau eruption indonesia 1 the 1883 eruption of krakatau volcano in indonesia was one of the most explosive volcanic events in history it was a marine caldera forming eruption that resulted in voluminous ignimbrite deposits and huge tsunamis we have used numerical simulations to investigate three major mechanisms for tsunami generation caldera collapse phreatomagmatic explosion and pyroclastic flow and have constrained the source parameters computed tsunami characteristics for each hypothesis are compared with observations at locations along the coasts of the sunda strait where tsunami data were obtained immediately after the eruption for the pyroclastic flow hypothesis two types of two layer shallow water models dense and light type models were used under different initial conditions pyroclastic flows are erupted from a circular source following a sine function that assumes waning and waxing phases caldera collapse was performed using a simple piston like plunger model in which collapse duration was assumed to be up to 1 h the phreatomagmatic explosion hypothesis was examined using simple empirical models for underwater explosions in shallow water with explosion energy between 1016 and 1017 j the results show that when a pyroclastic flow with a volume of 5 km3 and an average discharge rate of the order of 107 m3 s enters the sea the computed tsunami heights are broadly consistent with historical records in coastal areas including a tide gauge record at batavia now jakarta we conclude that a pyroclastic flow entering the sea is the most plausible mechanism of the 1883 krakatau tsunami

fresh pumice from the central indian basin a krakatau 1883 signature the occurrence of pumice in the central indian basin cib has been a controversy some are of the opinion that these pumices are erupted from a volcano along the ninetyeast ridge while others suggest the indonesian arc volcanism as their probable source recently it is also suggested that the pumice are the products of in situ silicic volcanism in the cib this study was initiated in order to resolve this controversy about the origin of the fresh pumice from the cib the fresh pumice pieces of different sizes and shapes were collected from the surficial sediments of the cib from an average depth of about 5000 m 12 s 76 e glass is the main phase comprising about 95 volume and resembles the matrix glass in krakatau 1883 dacitic pumice which is also very poor 5 in the modal mineral composition the mineral and glass analyses were carried out with the help of the electron microprobe the orthopyroxenes clinopyroxenes plagioclases and spinels are the mineral phases present in these pumices the pyroxenes have similar wo en and fs components to those previously reported from the 1883 krakatau eruption products geochemically these fresh pumices have a high sio2 content 71 and high total alkali content 8 similar to 1883 eruption products of krakatau thus based on the similarities in mineralogy and glass chemical composition it is inferred that these fresh pumices are the products of the fierce 1883 eruption of the krakatau volcano in the sunda strait of the indonesian arc

petrologic evolution of krakatau indonesia implications for a future activity abstract krakatau volcano is located along a n35e volcanic lineament running through the sunda straits indonesia its last activity has been characterized by successive phases each beginning with the construction of a cone and ending with its destruction and the formation of a caldera the two last pre and post 1883 cycles are well known but the more ancient ones are not so clearly defined lavas of krakatau belong to an andesitic series in which fractional crystallization plays the most important role the petrologic evolution is characterized by a cyclicity in good agreement with the structural evolution the succession is regular basalts basic andesites acid andesites dacites a gap between acid and basic andesites occurs in each cycle the destructive stages correspond to the occurrence of dacitic terms the anak cycle was characterized from 1927 to 1979 by basalts and basic andesites the 1981 eruption involved a more differentiated magma close to dacitic detailed study of the petrologic evolution since 1883 emphasizes the predominant role of fractional crystallization this process occurred during a very short period between 1979 and 1981 separation of labradorite augite olivine and magnetite from parental basic andesite may generate the dacitic descendant in a shallow reservoir p h 2 o estimated about 0 5 kbar implications for a future activity are considered

a geophysical interpretation of the 1883 krakatau eruption abstract from the present submarine topography in the vicinity of the krakatau islands it is concluded that the focus of the large explosions was situated to the northwest of the present rakata island the channel between krakatau and sebesi islands was completely blocked by banks of volcanic material immediately after the eruptions and it is suggested that this material was mainly lithic fragments the explosion sequences of krakatau are deduced from the records of sea waves and air waves observed at jakarta the large tsunami was caused by the most violent explosion simultaneously with the largest air waves it is inferred that the origin of the tsunami was a sudden upheaval of the seawater due to a violent explosion and that the height of the tsunami near its source was 30 40 m energy of the explosion is estimated from analyses of the air waves as one order of magnitude greater than that of the 1956 bezymianny eruption thus the 1883 krakatau eruption may have caused explosive removal of more than 10 km3 of material the subsurface structure of krakatau islands after the 1883 eruption is deduced from gravity anomalies it is concluded that at the bottom of the caldera there are deposits of low density in the shape of an inverted cone 8 km in diameter and 1 km in depth from the residual gravity anomaly observed over the caldera one can estimate the mass deficiency there this allows estimates to be made as to the amount of ejecta although large uncertainties remain these data indicate that explosive removal of material was the main process responsible for the disappearance of the northern half of the former rakata krakatau island in the 1883 eruption

stress fields controlling the formation of nested and overlapping calderas implications for the understanding of caldera unrest abstract commonly the formation of a collapse caldera does not necessarily imply the end of the volcanic activity in the area in many cases successive calderas may form close to the previous collapse depression or intersecting it leading to overlapping collapse structures occasionally subsequent caldera collapses may take place at the interior of the first caldera creating nested collapse structures during the last years several authors have investigated numerically how the stress field around magma chambers may favour the formation of collapse calderas assuming that the host rock surrounding the magmatic reservoir behaves as a linear elastic homogeneous medium the numerical models presented in this work study how a caldera collapse may modify the stress field of a volcanic area and hence the conditions for the formation of future collapse calderas our models take into account the effect of the collapse structure considering it as a mechanical discontinuity we also investigate the mechanical influence of the intra and extra caldera deposits on the formation of new calderas all the numerical models are two dimensional assuming plane strain and considering that the surrounding crust behaves as a linear homogeneous elastic material the computational domain corresponds to a cross section of the upper crust 50 25 km and magma chambers are modelled as sill like cavities located at a certain depth below the earth s surface the existing collapse caldera depression is 8 km wide and 2 75 km deep however we consider the caldera infill i e intra caldera material to be 1 25 or 1 75 km thick we assume as loading conditions an underpressure of 10 mpa imposed at the chamber walls that is negative excess pressure in the chamber in some numerical runs we have considered the existence of a previous ring fault by introducing a thin and elongate vertical weak zone at the caldera margins we find that the stress field around shallow level magma chambers favouring the formation of either nested or overlapping caldera structures depend on 1 the dimensions of the previous caldera collapse structure 2 the size of the new magma chamber susceptible to generate the subsequent caldera forming event and 3 the mechanical properties of the surrounding host rock and the syn and post collapse materials moreover results obtained in this paper may be relevant to the interpretation of unrest episodes in active caldera systems our numerical results confirm that the formation of multiple calderas nested overlapping or separate imply the development of new shallow magma chambers different from the one that lead to the first collapse caldera in consequence interpretation of magmatic unrest episodes in active collapse calderas should not be based on the assumption that the responsible for the current unrest is the same system that originated the caldera

model of a strong volcanic blast and a method of estimating the mass ejected summary a hydrodynamic model of a strong volcanic blast associated with large calderaforming ash gas flow eruptions is presented we show that the mass erupted from a vent influences considerably the damping of the shock wave if the ejected mass flux is constant the shock amplitude as a function of distance will decrease slower in accordance with the inverse 4 3 power law than that of an atomic explosion the inverse cube power law from the modelling we extract a relation connecting the evective energy of a blast with the mass ejected during the blast phase the mass released during the largest explosion of the 1883 eruption of krakatau and the lateral blast energy at mount st helens on 1980 may 18 are estimated on the basis of the equation obtained

tsunami deposits associated with the 7 3 ka caldera forming eruption of the kikai caldera insights for tsunami generation during submarine caldera forming eruptions abstract timing and mechanism of volcanic tsunamis will be a key to understand the dynamics of large scale submarine explosive volcanism tsunami deposits associated with the vei 7 eruption of the kikai caldera at 7 3 ka are found in the yakushima and kuchinoerabujima islands 40 km south southeast of the caldera rim the tsunami deposits distribute along the rivers in their northern coast up to 4 5 km from the river exit and up to 50 m above the present sea level the tsunami deposits in the yakushima area consist of pumice bearing gravels in the lower part of the section unit i and pumiceous conglomerate in the upper part unit ii the presence of rounded pebbles of sedimentary rocks which characterize the beach deposit indicates a run up current from the coastal area the rip up clasts of the underlying paleosol in unit i show strong erosion during the invasion of tsunami compositional similarity between the pumices in the tsunami deposit and the juvenile materials erupted in the early phase of the akahoya eruption indicates the formation of tsunami deposit during the early phase of the eruption which produced the initial plinian pumice fall and the lower half of the koya pyroclastic flow presence of the dense volcanic components obsidians and lava fragments besides pumices in the tsunami deposit supports that they were carried by the koya pyroclastic flow and not the pumices floating on the sea surface sequential relationship between the koya pyroclastic flow and the tsunami suggests that the emplacement of the pyroclastic flow into the sea surrounding the caldera is the most probable mechanism of the tsunami

generation mechanism of tsunamis from the 1883 krakatau eruption the 1883 eruption of krakatau generated a destructive tsunami which claimed about 34 000 lives we compute the generation and propagation of tsunamis from three models previously proposed they are 1 large scale caldera collapse of the northern part of krakatau island 2 emplacement of pyroclastic flow deposits 3 submarine explosion we numerically solve the non linear shallow water equations on actual bathymetry all three models displace the same volume 11 5 km 3 of water in different ways we compare the results of our computation with the observed tsunami waveforms at batavia and tsunami wave heights along the coasts of java and sumatra the comparison shows that the submarine explosion model of 1 to 5 min duration best explains the generation of the largest tsunami

syn eruptive chaotic breccia on kos greece associated with an energetic pyroclastic flow the climax of the kos plateau tuff kpt eruption eastern aegean greece generated a highly energetic coarse grained lithic rich pyroclastic flow in most places on kos the deposit from this event is an ignimbrite ignimbrite el that comprises a basal coarse grained lithic breccia and overlying pumiceous part above a planar strongly erosional lower contact however along the northern coast of central kos normal ignimbrite el overlies a hummocky 6 m thick layer of chaotic breccia comprising mingled to pervasively mixed ignimbrite el and unconsolidated sediment the surface morphology of the chaotic breccia and its internal texture resemble those of a debris avalanche deposit but the breccia is neither proximal nor downcurrent of steep topography the lower part of the chaotic breccia comprises distinct domains of unconsolidated sediment or lower kpt units that are deformed and or mingled with pumiceous ignimbrite the upper part is dominated by a matrix of mingled to pervasively mixed ignimbrite and sediment that contains sediment domains as large as 2 10 m in diameter such large intact allochthonous domains are best preserved at the top of the chaotic breccia and form the hummocks the chaotic breccia formed synchronously with the passage of a highly energetic pyroclastic flow where it traversed wet unconsolidated sediment shear induced liquification together with possible ground shaking associated with the eruption probably caused failure part of the unconsolidated substrate and basal part of ignimbrite el were dislodged and resedimented a short distance tens to hundreds of metres downcurrent the lower part records deformation and disintegration of the substrate induced by the overriding shearing flow mingling and deformation of the poorly consolidated material occurred as a result of within flow lateral shear attenuated worm burrows within the sediment domains and pinch and swell and flame structures within the mingled domains preserve evidence of shear in the lower part the upper part was transported downcurrent above a zone of shear failure internal heterogeneities in physical properties resulted in variable strain rates causing some domains to be pervasively mixed while others remained intact intact large unconsolidated domains at the top were transported mostly above the zone of shearing

two examples of subaqueously welded ash flow tuffs the visean of southern vosges france and the upper cretaceous of northern anatolia turkey abstract pyroclastic deposits interpreted as subaqueous ash flow tuff have been recognized within archean to recent marine and lacustrine sequences several authors proposed a high temperature emplacement for some of these tuffs however the subaqueous welding of pyroclastic deposits remains controversial the visean marine volcaniclastic formations of southern vosges france contain several layers of rhyolitic and rhyodacitic ash flow tuff these deposits include from proximal to distal settings breccia lapilli and fine ash tuff the breccia and lapilli tuff are partly welded as indicated by the presence of fiamme fluidal and axiolitic structures the lapilli tuff form idealized sections with a lower coarse and welded unit and an upper bedded and unwelded fine ash tuff sedimentary structures suggest that the fine ash tuff units were deposited by turbidity currents welded breccias interbedded in a thick submarine volcanic complex indicate the close proximity of the volcanic source the lapilli and fine ash tuff are interbedded in a thick marine sequence composed of alternating sandstones and shales presence of a marine stenohaline fauna and sedimentary structures attest to a marine depositional environment below storm wave base in northern anatolia thick massive sequences of rhyodacitic crystal tuff are interbedded with the upper cretaceous marine turbidites of the mudurnu basin some of these tuffs are welded as in southern vosges partial welding is attested by the presence of fiamme and fluidal structures the latter are frequent in the fresh vitric matrix these tuff units contain a high proportion of vitroclasis and were emplaced by ash flows welded tuff units are associated with non welded crystal tuff and contain abundant bioclasts which indicate mixing with water during flowage at the base basaltic breccia beds are associated with micritic beds containing a marine fauna the welded and non welded tuff sequences are interbedded in an alternation of limestones and marls these limestones are rich in pelagic microfossils the evidence above strongly suggest that in both examples tuff beds are partly welded and were emplaced at high temperature by subaqueous ash flows in a permanent marine environment the sources of the pyroclastic material are unknown in both cases we propose that the ash flows were produced during submarine fissure eruptions such eruptions could produce non turbulent flows which were insulated by a steam carapace before deposition and welding the welded ash flow tuff deposits of southern vosges and northern anatolia give strong evidence for existence of subaqueous welding

calderas and caldera structures a review abstract calderas are important features in all volcanic environments and are commonly the sites of geothermal activity and mineralisation yet it is only in the last 25 years that a thorough three dimensional study of calderas has been carried out utilising studies of eroded calderas geophysical analysis of their structures and analogue modelling of caldera formation as more data has become available on calderas their individuality has become apparent a distinction between caldera caldera complex cauldron and ring structure is necessary and new definitions are given in this paper descriptions of calderas based on dominant composition of eruptives basaltic peralkaline andesitic dacitic rhyolitic can be used and characteristics of each broad group are given styles of eruption may be effusive or explosive with the former dominant in basaltic calderas and the latter dominant in andesitic dacitic rhyolitic and peralkaline calderas four end member collapse styles occur plate or piston piecemeal trapdoor and downsag but many calderas have multiple styles features of so called funnel and chaotic calderas proposed in the literature can be explained by other collapse styles and the terms are considered unnecessary ground deformation comprises subsidence or collapse essential characteristics of a caldera and uplifting doming and fracturing due to tumescence and or resurgence frequent but not essential collapse may occur on pre existing structures such as regional faults or on faults created during the caldera formation and the shape of the collapse area will be influenced by depth size and shape of the magma chamber the final morphology of a caldera will depend on how the caldera floor breaks up whether collapse takes place in one event or multiple events whether vertical movement is spasmodic or continuous throughout the eruptive sequence and whether blocks subside uniformly or chaotically at one or more collapse centres a meaningful description of any caldera should therefore include number of collapse events presence or absence of resurgence caldera floor coherency caldera floor collapse geometry and dominant composition of eruptives

the new worldwide collapse caldera database ccdb a tool for studying and understanding caldera processes collapse calderas are one of the most important volcanic structures not only because of their hazard implications but also because of their high geothermal energy potential and their association with mineral deposits of economic interest the objective of this work is to describe a new general worldwide collapse caldera database ccdb in order to provide a useful and accessible tool for studying and understanding caldera collapse processes the principal aim of the ccdb is to update the current field based knowledge on calderas merging together the existing databases and complementing them with new examples found in the bibliography and leaving it open for the incorporation of new data from future studies this database does not include all the calderas of the world but it tries to be representative enough to promote further studies and analyses we have performed a comprehensive compilation of published field studies of collapse calderas including more than 200 references and their information has been summarized in a database linked to a geographical information system gis application thus it is possible to visualize the selected calderas on a world map and to filter them according to different features recorded in the database e g age structure the information recorded in the ccdb can be grouped in seven main information classes caldera features properties of the caldera forming deposits magmatic system geodynamic setting pre caldera volcanism caldera forming eruption sequence and post caldera activity additionally we have added two extra classes the first records the references consulted for each caldera the second allows users to introduce comments on the caldera sample such as possible controversies concerning the caldera origin a further purpose of this work is to construct the ccdb web page in this web page where registered users can acquire the current database version as well as to propose corrections or updates and to exchange information with other registered members also involved in the study of caldera collapse processes additionally the ccdb includes a formulary that will facilitate the incorporation of new calderas into the database

paleomagnetic evidence for high temperature emplacement of the 1883 subaqueous pyroclastic flows from krakatau volcano indonesia the paroxysmal 1883 eruption of krakatau volcano in indonesia discharged at least 6 5 km3 dense rock equivalent of pyroclastic material into the shallow waters of the sunda straits within a 15 km radius of the volcano progressive thermal demagnetization studies of individually oriented pumice clasts from a core sample of the submarine pyroclastic deposits show that 41 out of 47 clasts exhibit single component remanence with mean inclination of 2 4 the partial thermoremanent magnetization components of both pumice and lithic clasts are well grouped in orientation indicating that substantial cooling of clasts must have occurred following deposition estimated subaqueous emplacement temperature for such clasts is greater than 500 c rare two component lithic fragments exhibit inflection points on vector endpoint diagrams that mark the temperature below which the fragments acquired magnetization of similar orientation these inflection points range from 350 to 550 c indicating a minimum subaqueous emplacement temperature of 350 c paleomagnetic evidence for high emplacement temperature supports the hypothesis that proximal 1883 submarine pyroclastic deposits resulted from entrance of hot subaerially generated pyroclastic flows into the sea similar deposits have been interpreted from the geologic record but this is the first documented example of submarine pyroclastic flows from a historic eruption the krakatau deposits thus serve as an important modern analog for the study of pyroclastic flow seawater interactions

the tsunami phenomenon abstract with human activity increasingly concentrating on coasts tsunamis from japanese tsu harbour nami wave are a major natural hazard to today s society stimulated by disastrous tsunami impacts in recent years for instance in south east asia 2004 or in japan 2011 tsunami science has significantly flourished which has brought great advances in hazard assessment and mitigation plans based on tsunami research of the last decades this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view starting with the wave features tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss at the coast tsunamis typically show wave shoaling funnelling and resonance effects as well as a significant run up and backflow tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms such are earthquakes as the main trigger submarine and subaerial mass wastings volcanic activity atmospheric disturbances meteotsunamis and cosmic impacts as is demonstrated by giving corresponding examples from the past tsunamis are known to have a significant sedimentary and geomorphological off and onshore response so called tsunamites form allochthonous high energy deposits that are left at the coast during tsunami landfall tsunami deposits show typical sedimentary features as basal erosional unconformities fining upward and landward a high content of marine fossils rip up clasts from underlying units and mud caps all reflecting the hydrodynamic processes during inundation the on and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro and morphodynamic numerical models the paper provides an overview of the basic tsunami modelling techniques including discretisation guidelines for appropriate temporal and spatial resolution as well as the nesting method furthermore the boussinesq approximation a simplification of the three dimensional navier stokes equations is presented as a basic theory behind numerical tsunami models which adequately reflects the non linear dispersive wave behaviour of tsunamis the fully non linear boussinesq equations allow the simulation of tsunamis e g in the form of n waves based on the various subtopics presented recommendations for future multidisciplinary tsunami research are made it is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre history and physiogeographical setting of a specific region

ritter island volcano lateral collapse and the tsunami of 1888 summary in the early morning of 1888 march 13 roughly 5 km 3 of ritter island volcano fell violently into the sea northeast of new guinea this event the largest lateral collapse of an island volcano to be recorded in historical time flung devastating tsunami tens of metres high on to adjacent shores several hundred kilometres away observers on new guinea chronicled 3 min period waves up to 8 m high that lasted for as long as 3 h these accounts represent the best available first hand information on tsunami generated by a major volcano lateral collapse in this article we simulate the ritter island landslide as constrained by a 1985 sonar survey of its debris field and compare predicted tsunami with historical observations the best agreement occurs for landslides travelling at 40 m s 1 but velocities up to 80 m s 1 cannot be excluded the ritter island debris dropped little more than 800 m vertically and moved slowly compared with landslides that descend into deeper water basal friction block models predict that slides with shorter falls should attain lower peak velocities and that 40 ms 1 is perfectly compatible with the geometry and runout extent of the ritter island landslide the consensus between theory and observation for the ritter island waves increases our confidence in the existence of mega tsunami produced by oceanic volcano collapses two to three orders of magnitude larger in scale

crustal differentiation processes at krakatau volcano indonesia anak krakatau is a basaltic andesite cone that has grown following the famous caldera forming 1883 eruption of krakatau it breached sea level in 1927 and since the 1950s has been growing at an average rate of similar to 8 cm a week we present new major and trace element data combined with whole rock delta o 18 sr and nd isotope data for 1883 1993 and 2002 krakatau eruptive products and the surrounding crust bombs erupted from anak krakatau during 2002 contain frothy metasedimentary and plutonic xenoliths that show variable degrees of thermal metamorphism plastic deformation and partial melting contact metamorphic minerals such as cordierite and tridymite in metasedimentary xenoliths are consistent with high temperature metamorphism and incorporation at mid to upper crustal depth energy constrained assimilation and fractional crystallization modelling of whole rock data suggests that the anak krakatau magmas have a genetic relationship with the 1883 eruption products the geochemical impact of crustal contaminants on whole rock compositions is apparently small and we conclude that low levels of assimilation of a quartzo feldspathic sediment are recorded in anak krakatau magmas plagioclase phenocrysts from the 2002 eruption exhibit disequilibrium textures and complex compositional zoning however and are also isotopically variable with a total range in sr 87 sr 86 of 0 center dot 7043 0 center dot 7048 as determined by in situ laser ablation inductively coupled plasma mass spectrometry this suggests that although shallow crustal assimilation appears to have had a limited effect on whole rock chemistry a complex late stage differentiation history is recorded within the magma s cargo of crystals and xenoliths

reconstructing the anak krakatau flank collapse that caused the december 2018 indonesian tsunami volcanogenic tsunamis are one of the deadliest volcanic phenomena understanding their triggering processes and mitigating their effect remains a major challenge on 22 december 2018 flank failure of the anak krakatau volcano in indonesia generated a tsunami which killed more than 400 people this event was captured in unprecedented detail by high resolution satellite imagery and eyewitness accounts here we combine historic observations with these recent data to for the first time interpret the internal architecture of anak krakatau and reconstruct the failure tsunamigenesis and regrowth processes observed we calculate the volume of material initially lost from the volcano flank failure and find that it was relatively small 0 1 km3 compared to the overall changes observed during the entire eruption but was nonetheless able to generate rapid tsunami waves with devastating impacts the flank failure also changed the eruption style and upper volcanic plumbing system with these subsequent explosive eruptions destroying the summit and then partially rebuilding the lost flank the nature of the flank failure was controlled by the internal structure of the island and although regrowth rate will be a primary control on flank failure intervals the reconfiguring of the volcano s internal vent network is likely to have re stabilised it in the medium term the findings demonstrate that hazard assessments at ocean islands must consider that even small flank failures during unexceptional eruptions can have catastrophic consequences

phase of solar activity affects response of solar proxy be 10 the solar proxy be 10 measured in natural archives has previously been assumed to lag solar activity by 1 2 yr this reflects its residence time in the stratosphere where its main source lies this study based on a 30 yr global model simulation of the atmospheric transport of be 10 shows that the stratospheric fraction of production varies significantly with the phase of solar activity this leads to a lag between production change and deposition response of ca 1 yr during the decreasing phase of solar activity but nearly no lag when solar activity increases no lag is found for be 7 the fraction of 10be production in the stratosphere varies from ca 65 to 69 between solar minimum phi 400 mv and maximum phi 1200 mv being highest during low solar activity when production is highest when solar activity starts to decrease and production rate increase the change is largest in polar stratosphere where residence time is long this leads to a delayed response in be 10 deposition when production rate decreases the relative production change is larger in the troposphere leading to a quicker deposition response the difference between phases is larger in southern hemisphere the form of reconstructed 11 yr cycles based on high resolution be 10 records could therefore be biased if no correction is applied c 2013 elsevier b v all rights reserved less

large scale volcanic cone collapse the 1888 slope failure of ritter volcano and other examples from papua new guinea a largely submarine avalanche amphitheatre that formed catastrophically in 1888 on ritter volcano has been identified from a bathymetric survey collapse of the volcano in 1888 therefore is considered to have been caused by rapid large scale slope failure rather than by cauldron subsidence as previously supposed escarpments of pre historic slope failures are common on other papua new guinea volcanoes directions of avalanching on some volcanoes in the bismarck volcanic arc appear to be controlled by a regional stress pattern and those for some volcanoes in the fly highlands province on mainland papua new guinea point away from the regional centre of pliocene uplift large amphitheatres such as at doma peaks in the fly high lands province probably originated by multiple collapses

secondary hydroeruptions in pyroclastic flow deposits examples from mount st helens abstract secondary hydroeruptions occur in pyroclastic flow deposits when water or ice is trapped beneath hot pyroclastic debris and rapidly heated to steam these eruptions display various styles of activity including fumarolic degassing tephra fountaining and explosive cratering the deposits which occupy the layer 3 stratigraphic position on the top of pyroclastic flow units can be distinguished from ash cloud material by lateral thickness variation clast composition and other sedimentary features the ejecta of secondary hydroeruptions comprise a subset of hydrovolcanic pyroclastic deposits a small secondary hydroeruption observed on the mount st helens pumice plain in 1981 produced tephra that was emplaced ballistically by deposition from base surges and by fallout from an eruption column stratigraphic descriptions and grain size analysis of the ejecta from several secondary craters on the pumice plain demonstrate that the bedforms produced by a hydroeruption change with crater diameter in particular craters of small diameter are surrounded by interbedded ripple laminated ash horizons and nonstratified fines depleted units large craters have ejecta ramparts comprised of coarse dunes and antidunes these bedform changes are related to a progressive increase in eruptive energy which produces base surges of greater power and eruptive columns of greater height we suggest that the style of activity displayed during a secondary hydroeruption is controlled by both the total thermal energy of the system and the permeability of the pyroclastic overburden

tsunami generation by pyroclastic flow during the 3500 year b p caldera forming eruption of aniakchak volcano alaska a discontinuous pumiceous sand a few centimeters to tens of centimeters thick is located up to 15 m above mean high tide within holocene peat along the northern bristol bay coastline of alaska the bed consists of fine to coarse poorly to moderately well sorted pumice bearing sand near the top of a 2 m thick peat sequence the sand bed contains rip up clasts of peat and tephra and is unique in the peat sequence major element compositions of juvenile glass from the deposit and radiocarbon dating of enclosing peat support correlation of the pumiceous sand with the caldera forming eruption of aniakchak volcano the distribution of the sand and its sedimentary characteristics are consistent with emplacement by tsunami the pumiceous sand most likely represents redeposition by tsunami of climactic fallout tephra and beach sand during the approximately 3 5 ka aniakchak caldera forming eruption on the alaska peninsula we propose that a tsunami was generated by the sudden entrance of a rapidly moving voluminous pyroclastic flow from aniakchak into bristol bay a seismic trigger for the tsunami is unlikely because tectonic structures suitable for tsunami generation are present only south of the alaska peninsula the pumiceous sand in coastal peat of northern bristol bay is the first documented geologic evidence of a tsunami initiated by a volcanic eruption in alaska

the origin of the 1883 krakatau tsunamis abstract hypotheses for the origin of the krakatau tsunamis of 27 august 1883 are reviewed the 151 minute sea wave travel time between krakatau and batavia jakarta first proposed by verbeek cannot be substantiated thus hypotheses for the origin of the tsunamis which rest on very accurate timings of the origins of the air and sea waves such as that of latter 1981 also cannot be substantiated there was one exceptionally large sea wave tsunami on 27 august and many smaller ones most of the smaller waves appear to have been air sea coupled waves rather than true tsunamis of the few sea waves that were probably true tsunamis only one may have originated by emplacement of a pyroclastic flow at a point nearer batavia than krakatau the catastrophic event in the eruption of august 27th was preceded some 40 minutes earlier by a subordinate event which also propagated an air sea coupled wave and a tsunami the largest heard explosion produced an air sea coupled wave but was not associated with a tsunami although the precise time relations between the origins of the air and sea waves cannot be definitely established the most likely scenario for the catastrophic phase of the eruption is broadly similar to that originally proposed by verbeek in which collapse of part of the original volcanic edifice propagated a major volcanic explosion

source mechanisms of volcanic tsunamis volcanic tsunamis are generated by a variety of mechanisms including volcano tectonic earthquakes slope instabilities pyroclastic flows underwater explosions shock waves and caldera collapse in this review we focus on the lessons that can be learnt from past events and address the influence of parameters such as volume flux of mass flows explosion energy or duration of caldera collapse on tsunami generation the diversity of waves in terms of amplitude period form dispersion etc poses difficulties for integration and harmonization of sources to be used for numerical models and probabilistic tsunami hazard maps in many cases monitoring and warning of volcanic tsunamis remain challenging further technical and scientific developments being necessary and must be coupled with policies of population preparedness

mobility of a large volume pyroclastic flow emplacement of the campanian ignimbrite italy abstract the trachytic campanian ignimbrite originally exposed over a 30 000 km 2 area around naples italy is the product of a highly energetic gas rich eruption the deposit lies in valleys and isolated watersheds and in its medial and distal extent to the south north and east of naples the campanian pyroclastic current encountered mountains exceeding 1000 meters anisotropy of magnetic susceptibility ams measurements indicate that the campanian pyroclastic current the transport system traveled radially outward from the phlegrean fields area but the ignimbrite forming flow the deposition system that developed from the base of the transport system moved downslope from mountainsides to valleys including slopes facing the eruption source and flowed down drainage systems from intermontane basins the campanian pyroclastic current flowed 35 km over the water of the bay of naples to deposit 43 m of ignimbrite on the south shore and also overtopped a 685 1000 m high ridge of the sorrento peninsula to deposit more on the other side the distribution of the ignimbrite and the measured flow directions suggest that the campanian pyroclastic current moved across the landscape as an expanded and therefore turbulent decompressing flow rather than as a high density nonturbulent sheet like current moving over mountains by momentum acquired by eruption column collapse strong expansion is corroborated by shard morphology that indicates derivation from highly inflated pumice and suggests vesicles must have been at least 80 by volume of the original magma

abrupt transitions during sustained explosive eruptions examples from the 1912 eruption of novarupta alaska plinian ignimbrite activity stopped briefly and abruptly 16 and 45 h after commencement of the 1912 novarupta eruption defining three episodes of explosive volcanism before finally giving way after 60 h to effusion of lava domes we focus here on the processes leading to the termination of the second and third of these three episodes early erupted pumice from both episodes show a very similar range in bulk vesicularity but the modal values markedly decrease and the vesicularity range widens toward the end of episode iii clasts erupted at the end of each episode represent textural extremes at the end of episode ii clasts have very thin glass walls and a predominance of large bubbles whereas at the end of episode iii clasts have thick interstices and more small bubbles quantitatively all clasts have very similar vesicle size distributions which show a division in the bubble population at 30 m vesicle diameter and cumulative number densities ranging from 107 109 cm 3 patterns seen in histograms of volume fraction and the trends in the vesicle size data can be explained by coalescence signatures superimposed on an interval of prolonged nucleation and free growth of bubbles compared to experimental data for bubble growth in silicic melts the high 1912 number densities suggest homogeneous nucleation was a significant if not dominant mechanism of bubble nucleation in the dacitic magma the most distinct clast populations occurred toward the end of plinian activity preceding effusive dome growth distributions skewed toward small sizes thick walls and teardrop vesicle shapes are indicative of bubble wall collapse marking maturation of the melt and onset of processes of outgassing the data suggest that the superficially similar pauses in the 1912 eruption which marked the ends of episodes ii and iii had very different causes through episode iii the trend in vesicle size data reflects a progressive shift in the degassing process from rapid magma ascent and coupled gas exsolution to slower ascent with partial open system outgassing as a precursor to effusive dome growth no such trend is visible in the episode ii clast assemblages we suggest that external changes involving failure of the conduit vent walls are more likely to have effected the break in explosive activity at 45 h

structure and dynamics of a silicic magmatic system associated with caldera forming eruptions at batur volcanic field bali indonesia the batur volcanic field bvf in bali indonesia underwent two successive caldera forming eruptions that resulted in the deposition of silicic ignimbrites the magmas erupted during and between these eruptions show a broad range of compositions from low sio2 andesite to high sio2 dacite on the basis of their geochemistry and mineralogy these magmas may be assigned to six groups 1 homogeneous andesites with phenocryst compositions essentially in equilibrium with the whole rock composition 2 remobilized crystal rich low sio2 andesites with resorbed phenocrysts in equilibrium with the whole rock composition 3 mixed low sio2 dacite with a relatively large range of phenocryst compositions with most phenocrysts slightly too evolved to be in equilibrium with the wholerock 4 extensively mixed low sio2 dacites with a very large and discontinuous range of phenocryst compositions with most phenocrysts either more mg rich or more evolved than the equilibrium compositions 5 remobilized crystal rich low sio2 dacites with resorbed and euhedral phenocrysts 6 homogeneous high sio2 dacites lacking evidence for magma mixing and showing narrow ranges of phenocryst compositions in equilibrium with the whole rock composition this range of silicic magmas is interpreted to reflect a combination of closedand open system fractional crystallization magma mixing and remobilization of cumulate piles by heating the variety of magmas erupted simultaneously during the caldera forming eruptions suggests that the magmatic system consisted of several independent reservoirs of variable composition and degree of crystallization the magmatic evolution of individual reservoirs varied from closed system fractional crystallization to fully open system evolution thereby resulting in simultaneous production of magmas with contrasted compositions and mineralogy extensive emptying of the magmatic system during the caldera forming eruptions led to successive or simultaneous eruption of several reservoirs

subaqueous intermediate to silicic composition explosive volcanism a review abstract mass flow deposits of pyroclastic debris commonly consist of two parts a lower coarse grained basal section and an upper finer grained bedded section subaqueous pyroclastic flow deposits particularly those derived from a vertically directed eruption appear better sorted than their subaerial counterparts because of the efficient sorting characteristics of water compared to air subaqueous deposits frequently are depleted in bubble wall pumice that floats off and vitric ash that remains in suspension hence the deposits show a relative enrichment of crystals especially at the bases from 1 flotation and suspension of the vitric material and 2 ingestion of water at the head of the flow a subaqueous volcaniclastic flow deposit may contain evidence indicative of both turbulent and non turbulent movement the flow may have had a turbulent head and non turbulent body or flow transformations may have occurred from 1 collapse of the eruption column 2 changes in slope and in the velocity of the flow and or 3 the amount of water mixed into the flow retention of heat in the subaqueous environment may be enhanced by lateral eruptions high eruption rates large eruptive volumes and little or no mixing of pyroclastic debris with water the lack of welded subaqueous deposits in the geologic record may be a result of 1 effusive rather than explosive eruptions in a deep water environment 2 explosive phreatic disintegration of pyroclastic flows in a shallow subaqueous environment and or 3 the inability of subaerial pumiceous pyroclastic flows to penetrate the land water interface characteristics of explosive intermediate to silicic composition subaqueous volcanic eruptions also have been summarized in terms of 1 environment of the eruption 2 orientation of the eruption and 3 composition of the juvenile debris these three aspects of explosive subaqueous volcanism are ideal end members and gradations no doubt occur

modelling of tsunami generated by the giant late bronze age eruption of thera south aegean sea greece summary tsunami generated by the late bronze age lba eruption of thera were simulated using synthetic tide records produced for selected nearshore 20 m depths sites of northern crete the cyclades islands sw turkey and sicily inundation distances inland were also calculated along northern crete modelling was performed by incorporating fully non linear boussinesq wave theory with two tsunamigenic mechanisms the first involved the entry of pyroclastic flows into the sea assuming a thick 55 m 30 km3 flow entering the sea along the south coast of thera in three different directions all directed towards northern crete then a thin pyroclastic flow 1 m 1 2 km3 entering the sea along the north coast of thera directed towards the cyclades islands flows were modelled as a solid block that slowly decelerates along a horizontal surface the second mechanism assumed caldera collapse of 19 km3 and 34 km3 modelled as a dynamic landslide producing rapid vertical displacements calculated nearshore wave amplitudes varied from a few metres to 28 m along northern crete from pyroclastic flows and up to 19 m from caldera collapse 34 km3 volume inundation distances on crete were 250 450 m waves produced by pyroclastic flows were highly focused however as a function of sea entry direction smaller volume pyroclastic flows produced nearshore wave amplitudes up to 4 m in the cyclades islands north of thera wave amplitudes in the cyclades from smaller volume caldera collapse 19 km3 were up to 24 m whereas in sw turkey were as low as 2 1 and 0 8 m didim and fethye where lba tsunami deposits have been found wave amplitudes for the larger volume caldera collapse 34 km3 were generally 2 5 3 times larger than those generated by the smaller volume collapse 19 km3 these results provide estimates for understanding possible consequences of tsunami impact in lba coastal zones thus providing criteria at archaeological sites for detecting inundation damage as well as for contemporary hazard assessment they also provide additional criteria for deciphering homogenite layers in the abyssal stratigraphy of the ionian and eastern mediterranean seas

pyroclastic flows and surges over water an example from the 1883 krakatau eruption pyroclastic deposits from the 1883 eruption of krakatau are described from areas northeast of the volcano on the islands of sebesi sebuku and lagoendi and the southeast coast of sumatra massive and poorly stratified units formed predominantly from pyroclastic flows and surges that traveled over the sea for distances up to 80 km granulometric and lithologic characteristics of the deposits indicate that they represent the complement of proximal subaerial and submarine pyroclastic flow deposits laid down on and close to the krakatau islands the distal deposits exhibit a decrease in sorting coefficient median grain size and thickness with increasing distance from krakatau crystal fractionation is consistent with the distal facies being derived from the upper part of gravitationally segregated pyroclastic flows in which the relative amount of crystal enrichment and abundance of dense lithic clasts diminished upwards the deposits are correlated to a major pyroclastic flow phase that occurred on the morning of 27 august at approximately 10 a m energetic flows spread out away from the volcano at speeds in excess of 100 km h and traveled up to 80 km from source the flows retained temperatures high enough to burn victims on the sw coast of sumatra historical accounts from ships in the sunda straits constrain the area affected by the flows to a minimum of 4x103 km2 at the distal edge of this area the flows were relatively dilute and turbulent yet carried enough material to deposit several tens of centimeters of tephra the great mobility of the krakatau flows from the 10 a m activity may be the result of enhanced runout over the sea it is proposed that the generation of steam at the flow seawater interface may have led to a reduction in the sedimentation of particles and consequently a delay in the time before the flows ceased lateral motion and became buoyantly convective the buoyant distal edge of these ash and steam laden clouds lifted off into the atmosphere leading to cooling condensation and mud rain

the thermal history of a spatter fed lava flow the 8 ka pantellerite flow of mayor island new zealand the thermal history of the 8 ka spatter fed lava flow of mayor island new zealand has been investigated via relaxation geospeedometry cooling rates extant during the vitrification of the clastogenic pantellerite flow have been quantified cooling rates modelled for two obsidian layers at the top and the base of the flow vary over four orders of magnitude the flow base defined by a lower obsidian layer shows a gradual increase in cooling rates from 0 00072 k min adjacent to the crystalline core of the flow to 0 017 k min at the contact to a basal crumble breccia cooling rates of flow ridges formed by an upper obsidian layer vary between 0 001 and 6 k min based on field observation and thermal modelling cooling rates of kelvins to tens of kelvins per day for both upper and lower obsidians are difficult to interpret as simple cooling processes instead we propose a thermal history involving thermal annealing as an alternative explanation for these slow effective cooling rates such thermal annealing appears to have facilitated welding and rheomorphism of the spatter deposit leading to the development of a coherent lava sheet based on the results obtained here we present a quantitative scenario of the thermal history during the final stages of flow emplacement as a contribution to understanding the rheology of rheomorphic spatter deposits associated with explosive peralkaline rhyolitic volcanism and briefly address the hazard potential of such deposits

submarine volcaniclastic rocks in this chapter we are concerned with underwater volcaniclastic eruptions and products as well as pyroclastic flows and debris generated on land and transported by mass flowage into the sea submarine fallout deposits derived from land based eruptions are treated in chapter 7 clastic materials redistributed as mass flows or turbidity currents originating from the rapid build up of tephra and epiclastic volcanic debris along coastal parts of volcanoes are also discussed in various places throughout the text e g chap 13

the 1883 eruption of krakatau the 1883 eruption of krakatau was a modest ignimbrite forming event the deposits are primarily coarse grained dacitic non welded ignimbrite large explosions produced pyroclastic flows that entered the sea generating destructive tsunami grain size studies of the ignimbrite suggest that these explosions were not driven by magma seawater interaction the total bulk volume of pyroclastic deposits including co ignimbrite ash is estimated to be 18 21 km3

experimental study of caldera formation scaled experiments have been carried out on caldera collapse mechanisms using silicone as analogue magma and dry sand as analogue rock experiments were carried out in two and three dimensions using a range of roof aspect ratios thickness width 0 2 to 4 5 appropriate for caldera collapse they reveal a general mechanism of collapse only weakly dependent on the shape of the reservoir for low roof aspect ratios 1 subsidence starts by flexure of the roof and the formation of outward dipping reverse ring faults which in turn trigger formation of peripheral inward dipping normal ring faults the subsidence always occurs asymmetrically in cross section the reverse faults delimit a coherent piston bounded on each side by an annular zone of inwardly tilted strata located between the reverse and normal ring fault sets the surface depression consists of a nondeformed area piston surrounded by an annular extensional zone tilted strata for high aspect ratios 1 multiple reverse faults break up the roof into large pieces and subsidence occurred as a series of nested wedges 2 d or cones 3 d the extensional zone dominates the surface depression in the case where preexisting regional faults do not play a major role the collapse mechanics of calderas probably depends strongly on the roof aspect ratio calderas with low roof aspect ratios are predicted to collapse as coherent pistons along reverse faults the annular extensional zone might be the source of the large landslides that generate intracaldera megabreccias collapse into magma reservoirs with high roof aspect ratios may be the origin of some funnel calderas where explosive reaming is not dominant

evidence of clustering and nonstationarity in the time distribution of large worldwide earthquakes 1 the purpose of this paper is to characterize the statistical distribution of worldwide largest earthquakes we analyze the distribution of worldwide shallow events with ms 7 0 since 1900 by following the occam s razor philosophy we start from the simplest possible model stationary poisson process and we inspect more complicated models only if the data show significant departures from the simplest one the results show two important characteristics first worldwide ms 7 0 earthquakes tend to cluster in time and space with features similar to smaller events second for some seismic regions there is evidence in favor of long term fluctuations of the earthquake rate these results support the hypothesis of universality suggesting that an etas model with a background varying with time can be considered reliable to describe the seismicity distribution over a wide space time magnitude window from a practical point of view our findings suggest that the paradigm that seismic zones are stationary systems implicitly assumed in seismic hazard assessment should be regarded with caution

the denham caldera on raoul volcano dacitic volcanism in the tonga kermadec arc denham caldera on raoul volcano in the tonga kermadec arc is a simple collapse structure it is 6 5 4 km2 across 0 3 km deep represents an erupted magma volume of 8 16 km3 and is considerably larger than previously estimated caldera formation was contemporaneous with an eruption of homogeneous dacitic magma at 2 2 ka tephra from this event is preserved as a pumice fall and pyroclastic flow sequence up to 120 m thick on raoul island offshore this sequence forms a submarine deposit diminishing in thickness from 120 m near the northern caldera rim to 80 m at a distance of 3 5 km where it rests upon an erosional planation surface of 17 20 ka age incised into older volcaniclastic rocks both the caldera volume and ejecta distribution of the 2 2 ka eruption are comparable to the caldera volume and ejecta distribution of the 1883 krakatau eruption resurgent volcanism has built at least six submarine pyroclastic cones along a north northeast trending lineament crossing denham caldera redistribution of pumiceous dacite from these cones including ephemeral islands that emerged during the 1814 and 1870 eruptions has contributed to recent shoaling in denham bay a smaller eruption occurred in 1964 65 and hydrothermal activity persists at several sites along the lineament voluminous felsic volcanism at intra oceanic arcs is usually associated with crustal extension and was unexpected in the tonga kermadec arc however because the tectonic fabric within the active back arc havre trough is oblique to the kermadec arc rifts within the trough apparently propagate to the volcanic front and transfer extensional strain to the arc thereby promoting the ascent of felsic magma the orientation of denham caldera as well as that of macauley caldera 110 km further south thus reflect the stress field of the havre trough and not the predominant field of the arc

sedimentary and volcano tectonic processes in the british paleocene igneous province a review research on the british paleocene igneous province bpip has historically focused on the emplacement chemistry and chronology of its elaborate central intrusive complexes and lava fields however the bpip has also been dramatically shaped by numerous erosion sedimentation and volcano tectonic events the significance of which becomes ever clearer as localities in the bpip are re investigated and our understanding of volcano sedimentary processes advances the resultant deposits provide important palaeo environmental palaeo geographical and stratigraphical information and highlight the wide range of processes and events that occur in ancient volcanic settings such as the bpip in this paper we review the sedimentary and volcano tectonic processes that can be distinguished in the bpip and conceptualize them within a generalized framework model we identify and describe the sedimentary responses to four broadly chronological stages in the history of the bpip volcanoes 1 the development of the lava fields 2 early intrusion induced uplift 3 caldera collapse and 4 post volcano denudation and exhumation of central complexes we highlight and illustrate the range of sedimentary processes that were active in the bpip these operated on and helped shape a dynamic landscape of uplands and lowlands of alluvial fans braided rivers lakes and swamps and of volcanoes torn apart by catastrophic mass wasting events and or caldera collapse

coarse grained volcanic detritus in deep sea sediments of the northeastern equatorial pacific abstract coarse grained volcanic detritus in near surface sediments of the northeastern equatorial pacific consists mainly of feldspar plagioclase with an35 70or0 4 and magnetite with minor parts of pyroxene augite wo25 32en53 32 and volcanic quartz except for plagioclase 0 005 0 5 of total sediment all concentrations range between 0 and 30 grains m 1 of piston core where differences exist within the stratigraphic sequence and also from mineral to mineral the following relationships have been found plagioclase magnetite volcanic quartz pyroxene contents are low in plio quaternary sediments and in lower miocene pure radiolarian ooze they increase within the late eocene to early oligocene sediments and near the early oligocene hiatus the morphology distribution and alteration of the minerals are described and singlegrain analyses for plagioclase and pyroxene are given the origin of plagioclase pyroxene and magnetite is related to the formation of new oceanic crust at the east pacific ridge transport and distribution by slumping high density currents and reworking of older sediments are assumed the origin of volcanic quartz from potential source areas in northern central america and western mexico and transport and accumulation in deepsea sediments are discussed

volcanogenic mass flow deposits and seafloor diapirism following the largest insular quaternary eruption of the eastern mediterranean at nisyros island aegean volcanic arc abstract nisyros volcanic island at the eastern end of the aegean volcanic arc was mainly constructed after the ultra plinian kos plateau tuff kpt eruption at 161 ka the surrounding submarine area consists mostly of marginal mass transport deposits that commonly characterize insular stratovolcanoes this study aims at providing insights into the deposition and volume of such deposits by elucidating the products of a mega eruption and subsequent paroxysmal volcanicity typical of subduction zone island arc systems seismic reflection and multibeam bathymetry around nisyros identify pyroclastic and debris flow deposits covering areas several orders of magnitude greater than the island the entire seabed between the basins of east kos and tilos is underlain by a 7 km3 volcaniclastic unit that defines a ubiquitous basal unconformity at an average depth of 30 m below the seafloor southwest of nisyros two groups of avalanche deposits from the same unit are bathymetrically identified on the slopes of the northernmost karpathos basin apron seismic stratigraphic markers that trace the unit on the shelf of tilos suggest it is concomitant with the kpt eruption this formerly unknown submarine expansion of the kpt deposits into three neighboring basins when added to the volume of this massive unit to the rest of the nisyros surroundings gives it an explosivity index vei 6 as such it represents the largest quaternary subaqueous volcanogenic mass flow deposit of the eastern mediterranean from this dataset it can be inferred that the submarine advance of the erupted material occurred mainly through erosive gravity flows envisioned as the main dispersion mechanism of large scale subaqueous pyroclastic deposits of plinian eruptions east of nisyros unique small scale diapiric domes and seafloor mounds are attributed to loading by the kpt in combination with regional faulting subsequent nisyros effusive activity produced pyroclastic units around the northeast as well as debris avalanche and lava flows south of the island these have been correlated to known onshore formations the present study documents the intensity and impacts of a volcanic island mega eruption and paroxysmal epilogue over a cycle of 100 kyr

coupling eruption and tsunami records the krakatau 1883 case study indonesia the well documented 1883 eruption of krakatau volcano indonesia offers an opportunity to couple the eruption s history with the tsunami record the aim of this paper is not to re analyse the scenario for the 1883 eruption but to demonstrate that the study of tsunami deposits provides information for reconstructing past eruptions indeed though the characteristics of volcanogenic tsunami deposits are similar to those of other tsunami deposits they may include juvenile material e g fresh pumice or be interbedded with distal pyroclastic deposits ash fall surges due to their simultaneity with the eruption five kinds of sedimentary and volcanic facies related to the 1883 events were identified along the coasts of java and sumatra 1 bioclastic tsunami sands and 2 pumiceous tsunami sands deposited respectively before and during the plinian phase 26 27 august 3 rounded pumice lapilli reworked by tsunami 4 pumiceous ash fall deposits and 5 pyroclastic surge deposits only in sumatra the stratigraphic record on the coasts of java and sumatra which agrees particularly well with observations of the 1883 events is tentatively linked to the proximal stratigraphy of the eruption

volcano meteorological tsunamis thec ad 200 taupo eruption new zealand and the possibility of a global tsunami meteorological tsunamis are long period waves that result from meteorologically driven disturbances they are also generated by phase coupling with atmospheric gravity waves arising through powerful volcanic activity the ad 1883 krakatau eruption generated volcano meteorological tsunamis that were recorded globally because of its extreme violence and energy release 150 50 megatons explosive yield and by analogy with the krakatau event it is highly possible that the ignimbrite emplacement phase of the c ad 200 taupo eruption of north island new zealand generated a similar volcano meteorological tsunami that may have reached coastal areas worldwide tsunami deposits of identical age to the taupo eruption occur in central coastal new zealand and probably relate to that event definitive evidence elsewhere has not yet been found in theory volcano meteorological tsunamis are likely to be produced during comparable eruptive events at other explosive volcanoes and thus represent an additional volcan

subaqueous pyroclastic flows and ignimbrites an assessment an assessment of the literature on subaqueous pyroclastic flows and their deposits shows that the term pyroclastic flow is frequently used loosely to describe primary hot gas rich pyroclastic flows mass flows which resulted from the transformation of gassupported flows into water supported ones and secondary mass flows carrying redeposited pyroclastic debris based on subaerial pyroclastic flows the term pyroclastic flow should be restricted to demonstrably hot gas rich mass flows of pyroclastic debris using this definition very few examples of subaqueous pyroclastic deposits with evidence for hot emplacement and of having been wholly submerged have been described in the majority of these cases the evidence for a hot state of emplacement and for the subaqueous nature of the host depositional environment is inadequate the only unequivocal cases of hot pyroclastic flow deposits with adequate supporting evidence are the ordovician nearshore shallow marine ignimbrites of ireland and wales and miocene ignimbrites of southwest japan resulting from the passage of subaerially erupted pyroclastic flows into shallow water other possible examples are near vent dense clast deposits in the donzurobo formation of japan possible submarine intra caldera ponded ignimbrite successions in california and wales and near vent pumiceous deposits of ramsay island wales all other purported cases are either clearly the result of water supported mass flow transportation and deposition debris avalanches debris flows turbidity currents or lack adequate supporting evidence regarding the heat state or the palaeoenvironment only the shallow marine ignimbrites of ireland and wales show adequate evidence of welding but even these could have been nearly wholly exposed above sea level when welding occurred we conclude that when pyroclastic flows enter water they are generally disrupted explosively and or ingest water and transform into water supported mass flows and we suggest the various scenarios in which this occurs there is no evidence to suggest that welding in wholly subaqueous environments is common

volcanic deposits in antarctic snow and ice major volcanic eruptions are able to spread large amounts of sulfuric acid all over the world acid layers of volcanic origin were detected for the first time a few years ago by hammer in greenland ice the present paper deals with volcanic deposits in the antarctic the different methods that can be used to find volcanic acid deposits in snow and ice cores are compared electrical conductivity sulfate and acidity measurements numerous snow and ice samples collected at several antarctic locations were analyzed the results reveal that the two major volcanic events recorded by h2so4 fallout in antarctic ice over the last century are the eruptions of krakatoa 1883 and agung 1963 both located at equatorial latitudes in the southern hemisphere the volcanic signals are found to be particularly well defined at central antarctic locations apparently in relation to the low snow accumulation rates in these areas it is demonstrated that volcanic sulfuric acid in snow is not even partially neutralized by ammonia the possible influence of antarctic volcanic activity on snow chemistry is also discussed using the three recent eruptions of the deception island volcano as examples only one of them seems to have had a significant effect on the chemistry of snow at a location 200 km from this volcano it is concluded that antarctic volcanic ice records are less complicated than greenland records because of the limited number of volcanos in the southern hemisphere and the apparently higher signal to background ratio for acidity in antarctica than in greenland

marine emplacement of welded ignimbrite the ordovician pitts head tuff north wales the pitts head welded ignimbrite records a subaerial large volume eruption and associated pyroclastic current that flowed into the sea the current 15 km from source was steadily sustained with high mass flux and high particle concentration towards its base and it entered the sea without substantial mixing with water and thus without large scale hydroexplosivity and without general cooling it continued to aggrade ignimbrite at 580 c for at least 3 4 km from the original shoreline in water initially 50 m deep entirely subaqueous hot state progressive aggradation and welding of the ignimbrite occurred where the water could not be wholly displaced by the current although eventually the deposit displaced the shore 4 km seawards wet sea floor sediments buried by the ignimbrite were heated and locally fluidized by steam and several square kilometres of hot ignimbrite with variable thicknesses of sedimentary substrate detached and slid downslope directions of sliding and the order of piling up of slide sheets are shown by hot state rheomorphic deformation fabrics and the geometric relations of detachment surfaces extensional disruption of the ignimbrite is marked by breaks in the sheet via which fluidized sediments were mobilized locally to form rootless vents both the initial incursion of the pyroclastic current into the sea and the subsequent submarine sliding of the ignimbrite are likely to have caused tsunamis similar occurrences at modern coastlines presently susceptible to incursion of high mass flux pyroclastic currents e g taupo volcanic zone new zealand neapolitan region italy vicinity of manila taal philippines would according to tsunami propagation behaviour cause significant near and far field coastal hazard

from structure to erosion controlled subsiding calderas evidence thresholds and mechanics collapse calderas evolve by increasing their depth diameter ratio to properly characterize caldera evolution a structural s d ratio between structural subsidence and ring fault diameter ss ds and a topographic s d ratio between topographic caldera depth and topographic caldera width st dt are considered we review the evolution of the a d 2000 miyakejima caldera with two concentric ring faults at earlier collapsing stages and erosion of its wall accumulating debris on the floor at later collapsing stages while st dt and ss ds show a similar increase at initial stages when ss ds 0 33 the ss ds becomes significantly different from st dt while continuous caldera subsidence monotonically increases ss ds the erosion of the wall and the filling of the floor decrease st dt this evolution finds close similarities with recent caldera collapses of krakatau 1883 katmai 1912 fernandina 1968 tolbachik 1975 1976 pinatubo 1991 and dolomieu 2007 analog experiments mimic the observed variation evolving from a depression controlled by the activity of the double ring faults to that controlled by the erosion of the wall and sedimentation at the floor these natural and modeling results show that the control on the shape of mature calderas ss ds 0 07 and approaching ss ds 0 3 0 4 passes from a mainly structural to a mainly erosional control both st dt and ss ds are needed to describe the evolution of a collapse and the processes accompanying it evaluating st dt and ss ds allows proper description of the precise evolutionary stage of a caldera and of the relative importance of the structural and erosional processes and allows making semiquantitative comparisons between evolutionary stages

landscape evolution on the eastern part of lombok indonesia related to the 1257 ce eruption of the samalas volcano abstract one of the most powerful eruptions of the holocene known as the samalas eruption had a vei of 7 and took place on lombok eastern indonesia in 1257 ce thick tephra fall covered the entire island and pyroclastic density currents pdcs up to 50 m thick buried almost half of lombok until now there has been no detailed study of the geomorphological evolution of lombok related to this eruption especially for the eastern part of lombok the main goal of this paper is therefore to reconstruct the paleo topography on the eastern part of lombok before the eruption of the samalas volcano in 1257 ce and to analyse the subsequent landscape evolution following this eruption data were collected from more than 1300 points in order to gather geomorphological geological and geochemical information for the eastern part of lombok over the last millennium data were obtained from wells which are widespread in the studied area natural outcrops mainly cliffs along the shoreline and the rivers and human made outcrops in quarries as well as from the two dimensional resistivity profiling dipole dipole array carried out on eastern lombok in 2016 and 2017 we estimate that 4435 5 5 106 m3 of pumice rich pdc over a surface of 171 km2 buried the eastern part of lombok in the aftermath of the 1257 ce eruption and as a result of this rapid pumice rich pdc deposition there has been some aggradation of the shoreline at some points resulting in most of the pre 1257 coral reef being buried after several intense rainfall events the deposited volcanic material was probably eroded during the first decades following the 1257 ce eruption by mountain streams producing lahars we estimate that the remaining volume of pumice rich pdc deposits following this erosion is 625 5 5 106 m3 over a surface of 89 km2 which is equivalent to 14 of the initial volume

dimensions and dynamics of co ignimbrite eruption columns very powerful volcanic eruptions cannot always form classical plinian eruption columns1 4 instead collapsing fountains may develop above the vent and shed pyroclastic flows which spread laterally along the ground5 the upper part of these hot dense pyroclastic flows may become buoyant through the entrainment heating and expansion of ambient air coupled with the sedimentation of larger clasts suspended in the flow the buoyant material may rise in a co ignimbrite eruption column carrying massive quantities of fine dust and volatiles into the stratosphere6 7 here we present a model of this process and show that the co ignimbrite columns associated with the eruptions of toba8 9 75 000 years ago and tambora10 in 1815 may have ascended only about 32 and 23 km the latter is comparable with the less powerful 1982 plinian eruption column of el chichon11 this corroborates arguments that the mass of sulphuric acid aerosols injected into the stratosphere and not the eruptive power determines the climatic impact of an eruption12 13

convective fractionation a mechanism to provide cryptic zoning macrosegregation layering crescumulates banded tuffs and explosive volcanism in igneous processes a large array of igneous and volcanic features has characteristics that are recognized in other disciplines as conclusive and direct evidence of convection in stratified and or solidifying melts e g macroscopic segregation cryptic variation zoning in magma chambers mineral layering in mafic intrusives crescumulates fingering in the vertical and horizontal banding in pyroclastics rollover with attendant flashing of volatiles explosive volcanism etc some quantitative and qualitative aspects of convection in solidifying and or stratified melts e g mineral layer widths such as are observed in the skaergaards are examined to show consistency with field evidence convective fractionation does not possess the physical implausibilities of gravitational segregation crystal settling neither is the field evidence as ambiguous if interpreted in terms of convective fractionation which can explain amongst other things heavier material overlying lighter convective fractionation may operate on larger scales in the interior of planets

a laboratory study of ash flows hot ash flows propagate from volcanic vents during some explosive volcanic eruptions as a flow entrains and heats ambient air and simultaneously deposits pyroclasts part of the flow may become less dense than the air and ascend from the flow if entrainment of air is more important than sedimentation in controlling the flowbehaviour then a large buoyant ash cloud may form above the flow conversely if sedimentation of particles dominates then a much smaller fraction of the particles are able to ascend in the buoyant cloud we have carried out a series of analog laboratory experiments to simulate the motion and buoyancy generation in dilute ash flows propagating along the ground the first series of experiments investigated buoyancy generation through entrainment using mixtures of methanol ethylene glycol and water the second series examined the role of sedimentation upon the generation of buoyancy using particle laden fresh water currents propagating in a saline ambient fluid the experiments showed that the rate of entrainment increases while the sedimentation rate decreases as the downward slope of the terrain increases suggesting that massive ash laden clouds are more likely to rise from flows traveling on steeper slopes changes in slope angle also control the motion of ash flows the experiments suggest that flow separation and hydraulic jumps resulting from sudden changes in slope angle can enhance entrainment or sedimentation and increase buoyancy observations of the the interactions of ash flows with topography at redoubt volcano in april 1990 and at mount st helens on may 18 1980 are consistent with our laboratory observations

sedimentology of the krakatau 1883 submarine pyroclastic deposits the majority of tephra generated during the paroxysmal 1883 eruption of krakatau volcano indonesia was deposited in the sea within a 15 km radius of the caldera two syneruptive pyroclastic facies have been recovered in scuba cores which sampled the 1883 subaqueous pyroclastic deposit the most commonly recovered facies is a massive textured poorly sorted mixture of pumice and lithic lapilli to block sized fragments set in a silty to sandy ash matrix this facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the krakatau islands on the basis of grain size and component abundances a less common facies consists of well sorted planarlaminated to low angle cross bedded vitric enriched silty ash entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated deflated components of pyroclastic flows as they traveled over water the basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction high temperature of emplacement and lack of traction structures and no significant hydraulic sorting of components the laminated facies was most likely deposited from low concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater the krakatau deposits are the first well documented example of true submarine pyroclastic flow deposition from a modern eruption and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences

field survey and numerical modelling of the december 22 2018 anak krakatau tsunami on december 22 2018 the eruption and flank collapse of the anak krakatau volcano generated a tsunami in the sunda strait causing catastrophic damage to uninhabited coastlines proximal to the source along the heavily populated shores of banten and lampung provinces in java and sumatra tsunami waves caused severe damage extensive inundation and more than 430 deaths an international tsunami survey team itst deployed 6 weeks after the event documented the tsunami effects including runup heights flow depths and inundation distances as well as sediment deposition patterns and impacts on infrastructure and the natural environment the team also interviewed numerous eyewitnesses and educated residents about tsunami hazards this itst was the first to visit and document the extreme tsunami effects on the small islands in the sunda strait closest to anak krakatau rakata panjang sertung sebesi and panaitan along the steep slopes of rakata and sertung islands located less than 5 km from and facing directly towards the southwest flank of anak krakatau all of the dense coastal vegetation was stripped to bare earth up to elevations of more than 80 m while on the northeast tip of sertung island facing away from the source a single tree remained standing after flow depths of 11 m above ground struck there the runup distributions on the islands encircling anak krakatau highlight the directivity of the tsunami source suggesting that the collapse occurred towards the southwest this manifested as tsunami runup of 10 m that stripped away coastal forests to bare rock for up to 400 m inland in the ujung kulon national park located 50 km to the south southwest inundation and damage were mostly limited to within 400 m of the shoreline likely the result of the relatively short wavelengths caused by the landslide generated tsunami a significant variation in tsunami impact was observed along the shorelines of the sunda strait with runup heights rapidly decreasing with distance from the inferred tsunami source to model the event we applied a hot start initial condition that roughly reproduced the measured tsunami runup heights along rakata and sertung the waveforms were then propagated through the sunda straight using a boussinesq type wave model the results showed a good fit to the observed heights along the java and sumatra coastlines the northern coast of panaitan island and ujung kulon nation park the model also produced an acceptable fit to the observed amplitudes at tide gauges despite the regional volcanic and tsunamigenic history of the region and 6 months of eruptive activity prior to the event the tsunami largely caught the local population off guard this further highlights the need for community based education and awareness programs as essential to save lives in locales at risk from locally generated tsunamis

tsunamis generated by eruptions from mount st augustine volcano alaska during an eruption of the alaskan volcano mount st augustine in the spring of 1986 there was concern about the possibility that a tsunami might be generated by the collapse of a portion of the volcano into the shallow water of cook inlet a similar edifice collapse of the volcano and ensuing sea wave occurred during an eruption in 1883 other sea waves resulting in great loss of life and property have been generated by the eruption of coastal volcanos around the world although mount st augustine remained intact during this eruptive cycle a possible recurrence of the 1883 events spurred a numerical simulation of the 1883 sea wave this simulation which yielded a forecast of potential wave heights and travel times was based on a method that could be applied generally to other coastal volcanos

on the emplacement of ignimbrite in shallow marine environments abstract the emplacement of primary pyroclastic flow deposits on the sea floor can occur 1 by nonturbulent dense flows that conserve their heat under water or 2 because the flow either turbulent or nonturbulent temporarily pushes back the shoreline the feasibility of the second mechanism has been investigated theoretically and experimentally using a simple analogue system the experiments involved sustained turbulent saline currents of different densities flowing into a sectorial tank of ambient fluid that was either lighter or denser than the current the currents in all cases displaced the entire layer of ambient fluid up to a distance r irrespective of whether they were denser or lighter r is analogous to the shoreline displacement distance up to which hot ignimbrite can be emplaced by a pyroclastic flow entering the sea by varying flow rate density contrast and depth of the ambient fluid layer a simple equation for r is found that is in good agreement with the experimental data the effect of seawater boiling on shoreline displacement was also investigated by experiments using currents of carbonate solution that produced gas when flowing into a layer of ambient acid the distance r was not reduced in these experiments the equations show that pyroclastic flows of about 10 km 3 or more are capable of pushing back the sea at least a couple of kilometres and possibly more in areas of extensive shallow water enabling hot ignimbrite to be laid down on the seabed at depths corresponding to a few tens of metres shoreline displacement is thus a feasible mechanism for the emplacement of welded ignimbrite in shallow marine settings emplacement of subaerially erupted ignimbrite below storm wave base is not ruled out by the calculations but requires a combination of high discharge rate sustained eruption low density contrast between flow and water steep bathymetric gradient and small island volcano application of the model to the 1883 krakatau eruption suggests that seawater displacement may explain the occurrence of primary ignimbrite on the seabed 10 km northwest of the volcano

tsunami deposits from major explosive eruptions an example from the 1883 eruption of krakatau inundation of coastal areas by tsunamis during the 1883 eruption of krakatau volcano led to the deposition of unusual pumice enriched deposits fractal analysis of pumice shapes and lithologic characterization of the deposits suggest that the source of the abundant pumiceous material was widespread pumice rafts on the surface of the sunda straits that formed by fallout and pyroclastic flow activity the rafts contained pumices rounded by particle to particle abrasion and were strongly depleted in dense components such as lithics and crystals by differential settling stranding of the floating pumice is inferred to have occurred during the receding phase of tsunamis after they had inundated low lying coastal areas other pumice bearing tsunami deposits contain significant amounts of coral fragments and nonvolcanic beach sediment these units represent redeposition of beach and shallow water sediments that were mixed with varying proportions of primary pyroclastic material the krakatau example illustrates the great diversity of lithofacies that may occur in deposits formed from volcanogenic tsunamis recognition of such deposits in coastal areas near centers of active explosive volcanism may provide an additional criterion with which to assess volcanic hazards

constraints on the geomorphological evolution of the nested summit craters of lascar volcano from high spatio temporal resolution terrasar x interferometry small scale geomorphological changes that are associated with the formation development and activity of volcanic craters and eruptive vents are often challenging to characterize as they may occur slowly over time can be spatially localized and difficult or dangerous to access using high spatial and high temporal resolution synthetic aperture radar sar imagery collected by the german terrasar x tsx satellite in spotlight mode in combination with precise topographic data as derived from pleiades 1a satellite data we investigate the surface deformation within the nested summit crater system of lascar volcano chile the most active volcano of the central andes our aim is to better understand the structural evolution of the three craters that comprise this system to assess their physical state and dynamic behavior and to link this to eruptive activity and associated hazards using multi temporal sar interferometry mt insar from ascending and descending orbital geometries we retrieve the vertical and east west components of the displacement field this time series indicates constant rates of subsidence and asymmetric horizontal displacements of all summit craters between june 2012 and july 2014 as well as between january 2015 and march 2017 the vertical and horizontal movements that we observe in the central crater are particularly complex and cannot be explained by any single crater formation mechanism rather we suggest that short term activities superimposed on a combination of ongoing crater evolution processes including gravitational slumping cooling and compaction of eruption products as well as possible piston like subsidence are responsible for the small scale geomorphological changes apparent in our data our results demonstrate how high temporal resolution synthetic aperture radar interferometry insar time series can add constraints on the geomorphological evolution and structural dynamics of active crater and vent systems at volcanoes worldwide