recent dyke induced large scale block movement at mount etna and potential slope failure here we report the results of a geodetic survey undertaken on mount etna between 1981 and 1988 observed horizontal ground movements in the vicinity of the valle del bove caldera demonstrate that dyke emplacement during 1983 and 1985 resulted in the 2 8 m eastward displacement of a block of western caldera rim a history of past instability and collapse along the rim is indicated by the presence of large back rotated blocks of prehistoric volcanics1 furthermore the unusually linear form of the present western rim indicates past slope failure along north south aligned surfaces and therefore that dyke induced collapse may have been an important agent in caldera enlargement we suggest a self sustaining mechanism whereby the stress regime generated as a consequence of the caldera s existence results in the repeated injection of north south orientated dykes adjacent to the western rim2 3 dilation associated with magma intrusion leads in turn to periodic phases of slope instability and failure of the cliff wall causing a progressive westward migration of the western rim

cenozoic ice volume history development of a composite oxygen isotope record to view cenozoic ice volume and ocean temperature history a composite 18 o time series was constructed for tropical shallow dwelling planktonic foraminifers and for deep water benthic foraminifers we conclude that cenozoic benthic 18 o primarily reflect considerable deep ocean temperature variation and that tropical planktonic 18 o afford the best record of cenozoic ice volume the planktonic composite indicates the presence of a significant ice budget for the past 40 m y the difference between the benthic and planktonic 18 o composites suggests that low latitude production of warm saline bottom water dominated tertiary thermohaline circulation

remote determination of sif4 in volcanic plumes a new tool for volcano monitoring sif4 is probably a common trace component of fumarole gases on volcanoes arising from interactions between magmatic hf and wall rocks it is not distinguished from hf in conventional analyses a strong absorption band at 1032 cm 1 makes sif4 well suited to remote open path ftir spectroscopic techniques we report the first measurements of sif4 in volcanic gases at etna and vulcano sicily sif4 concentrations were low at etna but higher at vulcano where the so2 sif4 ratio was consistently around 1 7 10 2 1 thermodynamic considerations show that the hf sif4 ratio increases sharply with increasing temperature thus remote measurements of sif4 may offer a qualitative way of constraining fumarole temperatures we use our ftir measurements of hcl sif4 in combination with conventional measurements of hcl hf to infer an hf sif4 ratio for vulcano of 10 1 consistent with gas temperatures in the range 200 450 c

ground deformation and gravity changes accompanying the march 1981 eruption of mount etna abstract we present reults from simultaneous precise levelling and gravity surveys on mount etna covering the period august 1980 august 1981 the flank eruption of march 1981 erupted 18 35 10 5 m 3 of lava following it upward movements of more than 17 cm were observed close to the new fissure and a broad apparently independent uplift of 5 cm was observed 4 km to the west a zone of about 2 cm depression to the east of the fissure is insufficient to account for the volume of magma erupted gravity results show positive changes of up to 63 microgal and display good positive correlation with elevation changes both sets of measurements appear to be due to new intrusion of magma rather than subsurface magma drainage ground deformation close to the new fissure is well modelled by intrusion of a dyke in the zone 100 500 m below the surface striking along the fissure and of dip between 75 90 the gravity changes are modelled as due to a deeper intrusion of magma along the same line but some 1500 m below the surface the changes were not present immediately after the eruption but occurred during the ensuing 5 months it is proposed that this introduction of matter occurred by crack propagation along the fissure in the aftermath of the eruption towards the west of the fissure and some 4 km west of the summit ground deformation is modelled by intrusion of a dyke in the zone 300 1500 m below the surface and dipping at 80 85 again gravity changes appear to be due to magma intrusion at greater depth close to sea level in this case gravity changes are interpreted as due to magma density changes as a result of pressure increase in a larger scale fissure zone this same pressure increase may be forcing the new intrusion close to the surface and makes this part of the volcano a region of especially high risk

latest eocene early oligocene climate change and southern ocean fertility inferences from sediment accumulation and stable isotope data abstract the earliest oligocene 33 5 ma is marked by a major step in the long term transition from an ice free to glaciated world the transition characterized by both cooling and ice sheet growth triggered a transient but extreme glacial period designated oi 1 high resolution isotope records suggest that oi 1 lasted for roughly 400 000 yr the duration of magnetochron 13n before partially abating and that it was accompanied by an ocean wide carbon isotope anomaly of 0 75 one hypothesis relates the carbon isotope anomaly to enhanced export production brought about by climate induced intensification of wind stress and upwelling particularly in the southern ocean to understand how this climatic event affected export production in the southern ocean biogenic silica opal and carbonate accumulation rates were computed for the sub polar indian ocean using deep sea cores from odp site 744 kerguelen plateau our findings suggest that net productivity in this region increased by several fold in response to the oi 1 glaciation in addition calcareous primary producers dominant in the late eocene were partially replaced by opaline organisms suggesting a trend toward seasonally greater surface divergence and upwelling in this sector of the southern ocean we attribute these changes to intensification of atmospheric oceanic circulation brought about by high latitude cooling and the appearance of a full scale continental ice sheet on east antarctica higher terrigenous sediment accumulation rates support the idea that wind induced changes in regional productivity were augmented by an increased supply of glacial dust and debris that provided limiting micro nutrients e g iron rich dust particles we speculate that the rapid changes in biogenic sediment accumulation in the southern ocean and other upwelling dominated regions contributed to the ocean wide positive carbon isotope anomaly by temporarily increasing the burial rate of organic carbon relative to carbonate carbon the changes in burial rates in turn may have produced a positive feedback on climate by briefly drawing down atmospheric pco2

the volume and shape of the 1991 1993 lava flow field at mount etna sicily the 1991 1993 lava flow is the most voluminous flow erupted at mount etna sicily in over 300 years estimates of the volume obtained by various methods range from 205 106 m3 tanguy 1996 to over 500 106 m3 barberi et al 1993 this paper describes the results of an electronic distance measurement edm based field survey of the upper surface of the 1991 1993 flow field undertaken in 1995 the results were digitised interpolated and converted into a digital elevation model and then compared with a pre eruption digital elevation model constructed from a 1 25 000 contour map of the area based on 1989 aerial photographs our measurements are the most accurate to date and show that the 1991 1993 lava flow occupies a volume of 231 29 106 m3

gravity and tilt earth tides measured on an active volcano mt etna sicily abstract three kinemetrics tiltmeters and an askania tidal gravimeter were installed on mt etna sicily in order to test if previously reported anomalous tides are a permanent feature of the volcano s deformation two of the tiltmeters were installed near the summit of the volcano and the third on its flank the gravimeter recorded tides both on the volcano and 30 km away at catania comparison of the measured m2 tidal amplitudes and phases with values predicted theoretically shows that the gravity tides both on the volcano and at catania are within 4 of the theoretical values m2 tidal tilts are all less than 2 5 times those predicted theoretically these results imply that the anomalous tidal behaviour on mt etna reported previously is possibly a transient phenomenon associated with eruptions rather than a permanent modification of the solid earth tide by the volcanic structure

tertiary oxygen isotope synthesis sea level history and continental margin erosion tertiary benthic and planktonic foraminiferal oxygen isotope records are correlated to a standard geomagnetic polarity time scale making use of improved chronostratigraphic control and additional oligocene isotope data synchronous changes in both benthic and planktonic 18o values which occurred in the oligocene to miocene 36 5 2 ma are interpreted in part to represent ice growth and decay the inferred ice growth events correlate with erosion on passive continental margins as interpreted from seismic and chronostratigraphic records this association is consistent with a link between oligocene to miocene erosional events and rapid 15 m m y glacioeustatic lowerings of about 50 m high benthic foraminiferal 18o values suggest the presence of continental ice sheets during much of the oligocene to recent 36 0 ma substantially ice free conditions probably existed throughout the paleocene and eocene 66 36 ma the mechanisms and rates of sea level change apparently were different between the early and late tertiary with glacioeustatic changes restricted to the past 36 m y pre oligocene erosion on passive continental margins was caused by eustatic lowerings resulting from global spreading rate changes we apply a model which suggests that large areas of the continental shelves were subaerially exposed during such tectonoeustatic lowstands stimulating slope failure and submarine erosion the different mechanisms and rates of eustatic change may have caused contrasting erosional patterns between the early and late tertiary on passive continental margins this speculation needs to be confirmed by examination of data from several passive margins

diatom distribution and paleoceanographic reconstruction in the southern ocean present and last glacial maximum abstract diatom assemblage and preservational data are used to reconstruct paleoceanographic conditions at the last glacial maximum 18 000 yrs bp in the southern ocean from these data the following points can be made about the last glacial maximum in this region 1 contraction and slight northern shift of the belt of well preserved diatoms appears to be related to the northward shift of late spring early summer sea ice cover 2 presence of open ocean though poorly preserved diatom assemblages to the south of this belt strongly suggest that during many summers large areas of the southern ocean were ice free 3 the distribution of thenitzschia kerguelensis factor both in surface sediments and at the last glacial maximum indicates that the gyre systems particularly the weddell gyre were intensified during glacial times 4 although data are sparse in the higher latitude south atlantic there is an indication that the weddell polynya also existed during glacial times although it was shifted a few degrees northward

remote detection of hcl and so2 in volcanic gas from unzen volcano japan a telescope attached ft ir spectral radiometer was applied for remote measurement of chemical composition of the volcanic gas of unzen volcano japan which started erupting in november 1990 the observations were carried out at the site about 1 3 km away from the gas emitting region of the volcano in march and july 1992 absorption features of so2 vl and hcl were identified and column amounts of so2 and hcl of the volcanic gas plume were estimated using a nonlinear least squares method the so2 hcl ratio was in the range between 0 7 and 1 8 for both march and july observations this is the first remote ground based observation of hcl in volcanic gas

pattern of first and last appearance in diatoms oceanic circulation and the position of polar fronts during the cenozoic 1 first and last occurrences of 389 diatom species from the first global cenozoic record are used to reconstruct the position of major oceanographic boundaries first appearances and extinctions group in three latitudinal bands middle to high northern latitudes equatorial region and high southern latitudes sparse paleogene occurrences were limited to southern high latitudes along the equivalent of the modern antarctic polar front its late middle eocene to middle miocene position varied within 10 and within a 20 band from middle miocene to present suggesting an association with global cooling first and last occurrence events appear in the two remaining latitudinal regions during the eocene and increase in a stepwise fashion mimicking significant cooling events at about 16 ma first and last appearances shift from the north atlantic to the north pacific low latitude data suggest low surface water productivity prior to 40 ma while increased abundance from the middle miocene correlates with expansion of the east antarctic ice sheet

the 1989 1990 eruption of redoubt volcano alaska impacts on aircraft operations abstract the december 1989 june 1990 eruption of redoubt volcano affected commercial and military air operations in the vicinity of anchorage alaska these effects were due to the direct impact of volcanic ash on jet aircraft as well as to the rerouting and cancellations of flight operations owing to eruptive activity between december and february five commercial jetliners were damaged from ash encounters the most serious incident took place on december 15 1989 when a boeing 747 400 aircraft temporarily lost power of all four engines after encountering an ash cloud as the airplane descended for a landing in anchorage while there were no injuries to passengers the damage to engines avionics and aircraft structure from this encounter is estimated at 80 million four additional encounters between jet aircraft and redoubt ash clouds occurred in the anchorage area on december 15 and 16 1989 and february 21 1990 none resulted in engine failure two additional encounters took place on december 17 1989 when jet airliners encountered the redoubt cloud over west texas at the time of these encounters the cloud was up to 55 hours old and had traveled in excess of 2 900 nautical miles 5 300 km following the december 15 encounters anchorage international airport remained open however most airline companies canceled operations for up to several days as communications between federal agencies and airlines improved and as a better understanding of the nature and behavior of ash rich eruption clouds was achieved most airlines resumed normal service by early january 1990 the resulting loss of revenue at anchorage international airport during several months following the eruption is estimated to total 2 6 million the impact on general aviation and military operations consisted mostly of cancellation and rerouting of flights

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

the oscillation model of hydrothermal dynamics beneath aso volcano southwest japan after small eruption on may 2011 a new understanding model using repeated absolute and relative gravity measurement abstract at the end of 2010 the seismic activity in aso volcano intensely increased and water level in the nakadake crater decreased until early in 2011 then was followed by a small eruption in may 2011 after the eruption and heavy rain the volcanic activity subsided to calm period crater bottom was refilled with water and water level increased in the nakadake crater the next tremor reappeared in 2014 and tracked to eruption in november 2014 this eruptive pattern and water level variation in the crater repeatedly appeared on the surface and it should be related to the hydrothermal dynamics beneath aso volcano we initiated the gravity measurements in relation to hydrothermal dynamics in the subsurface of aso volcano using scintrex cg 5 549 and lacoste romberg type g 1016 relative gravimeter at 28 benchmarks in april 2011 one month before the eruption the repeated gravity measurements continue to monitor aso volcano with a series of the measurement after the eruption in every three months to a half year we analyze the gravity variation from 2011 to 2014 between the time of the phreatic and strombolian eruption the measurements covered the area more than 60 km 2 in the west side of aso caldera a new gravity network was also installed in may 2010 at seven benchmarks using a10 017 absolute gravimeter which re occupied in october 2010 june 2011 and two benchmarks in june 2014 as a result the gravity changes distinguish hydrothermal dynamic in the subsurface which has a direct correlation to water level fluctuation in the crater after the first eruption and before the second discharge the monitoring data notice large gravity changes between the surveys at benchmarks around nakadake crater and kusasenri area the simple 3d inversion models of the 4 d gravity data deduce the density contrast distribution beneath aso volcano the inversion and mass change result generate the oscillation typical as a new understanding model the variation of the mass shows a similar trend with the hydrothermal input rate to the crater of past research the third year monitoring from april 2013 displays a large gravity and mass variation while precipitation data in this period is smaller than the previous season the largest increased mass about 43 million tons by gaussian method occurred between may 2013 and september 2013 according to the three year gravity monitoring the calm period in aso volcano happens after may 2011 eruption until september 2013 which is followed by the active period before the november 2014 eruption this result will contribute to understand the process of eruption

thermal survey of mount etna volcano from space surveys of ground thermal anomalies and the monitoring of their evolution are of great importance in the study of volcanoes thermal monitoring techniques could be used in conjunction with classical monitoring tools i e seismological and deformation networks to give better predictions of the onset of a volcanic event in order to detect and emphasize small anomalies in the surface temperature of the ground we have developed a new method based on the joint use of two satellite radiometers the noaa advanced very high resolution radiometer avhrr for the quality of its thermal band calibration and the landsat thematic mapper tm for its high spatial resolution this method is applied to the mount etna volcano sicily and reveals several thermal anomalies one anomaly is already known and is associated with the permanently active craters of the summit zone the second is a larger area where an eruption occurred one week after the data acquisition 10 23 86 the general trend of the thermal anomalies leads to recognition of a large semi circular intrusive zone corresponding to the borders of the well known valle del bove

mechanisms of magma eruption and emplacement at mt etna between 1989 and 1992 the present eruption sequence of mt etna began during september 1989 with extensive fracturing and culminated in 1991 93 with the largest lava eruption this century1 here we present measurements of gravity and ground deformation which in conjunction with seismic data provide a detailed record of the processes occurring before and during eruption these reflect a complex interplay between magma injection into the paths of lowest compressive stress through the volcano flanks forcing elastic deformation and fracture growth in response to gravitational stresses we find that after the end of the eruptive activity in 1989 fractures in the south southeast flank of the volcano remained unfilled until some months before the 1991 93 eruption these results indicate the utility of microgravity monitoring as the precursory processes that we identify were largely undetected by seismic and ground deformation monitoring

magma movements in etna volcano associated with the major 1991 1993 lava eruption evidence from gravity and deformation the 1991 1993 eruption was probably the largest on mt etna for 300 years since then the volcano has entered an unusually quiescent period a comprehensive record of gravity and ground deformation changes presented here bracket this eruption and give valuable insight into magma movements before during and after the eruption the gravity and deformation changes observed before the eruption 1990 1991 record the intrusion of magma into the summit feeder and the sse trending fracture system which had recently been active in 1978 1979 1983 and 1989 creating the feeder dyke for the 1991 1993 eruption in the summit region gravity changes between 1992 and 1993 spanning the end of the eruption reflect the withdrawal of magma from the conduit followed more recently 1993 1994 by the re filling of magma in the conduit up to pre eruption levels in contrast in the vicinity of the fracture zone gravity has remained at the 1991 1992 level indicating that no withdrawal has occurred here rather magma has solidified in the fracture system and sealed it such that the 1993 1994 increase in magma level in the conduit was not accompanied by further intrusion into the flanks mass calculations suggest that a volume of at least 107 m3 of magma has solidified within the southeastern flank of the volcano

location and orientation of eruptive fissures and feederdykes at mount etna influence of gravitational and regional tectonic stress regimes abstract lava extrusion from fissures on the flanks of the etna volcano is a common feature of recent activity as evidenced by the eruptions of 1971 1981 1983 and 1985 and was of similar importance during prehistoric times we propose here a model within which the location and orientations of the large majority of historic eruptive fissures on etna s flanks together with their feeder dykes are explained within the framework of a gravitational stress regime stress orientations within this regime are controlled largely by the gross morphology of the volcano but are significantly modified by local topographic anomalies we propose that the gravitational stress regime largely supercedes an earlier developed regional tectonic stress regime which still operates in the sub volcanic basement and may remain the dominant control of eruptive fissure and feeder dyke disposition at lower altitudes on the flanks the proposed model is supported by 1 detailed examination of fissure locations and orientations and the relationship between fissure azimuths and topography 2 precise horizontal distance measurement and vertical ground deformation studies of a recent eruption and 3 qualitative physical modelling experiments in which coloured water is injected into solidified gelatine solutions representing variously shaped volcanic constructs a cautious approach is advocated when extrapolating trends of spatially limited fissure segments for the purpose of locating potential sites of magma ascent and implications of the model for hazard analysis are outlined

upper cretaceous and lower paleocene diatom and silicoflagellate biostratigraphy of seymour island eastern antarctic peninsula

application of modern analog technique to marine antarctic diatoms reconstruction of maximum sea ice extent at the last glacial maximum modern analog technique mat applied to antarctic diatoms is a new approach for quantitative sea ice paleoreconstructions in the southern ocean in a first step we show that mat is a better approach than the imbrie and kipp method to reconstruct the modern sea ice pattern we then use this approach to reconstruct sea ice presence in number of months per year during the last glacial maximum lgm at this time sea ice presence was greater than today leading to a shorter diatom growing season the maximum sea ice extent inferred from quantitative values of sea ice presence was located 5 8 north of its actual position leading to double the surface of modern winter sea ice this greater sea ice extent may have played a significant role on atmospheric and surface oceanic circulations and therefore on southern mid latitude and high latitude climates it may also have reduced the amount of heat moisture and co2 from the ocean to the atmosphere thus participating in the lowering of atmospheric co2 during the lgm

palaeoclimatology communication arising tropical temperatures in greenhouse episodes we agree with zachos and colleagues that much can be learned about transient climate events from well dated carbonate sediments from the deep ocean and that the problem of recrystallization of such sediments when tens of millions of years old means that constraining relative temperature changes from oxygen isotope data is more appropriate than attempting to measure absolute values

slope movement crisis on the east flank of mt etna volcano models for eruption triggering and forecasting abstract benchmarks installed on the upper eastern flank of mt etna in 1982 have subsided continually since then with the rate of subsidence twice accelerating prior to eruptions the first of these eruptions was in december 1985 and the second in september 1989 this pattern of accelerating downslope movement has also been observed prior to landslides and recent work applying knowledge of the failure of materials has shown that analysis of the inverse rate of these movements can be used to predict the time of failure post eruption analyses of geodetic or seismic data from volcanoes has shown that in several cases this approach could have been used to forecast eruptions weeks in advance applying the same principles to the accelerating subsidence on mt etna s eastern flank prior to the eruptions of 1985 and 1989 shows that rough estimates of eruption dates could have been obtained several months in advance these observations also suggest a speculative eruption triggering mechanism involving an interplay between slope creep deformation and extensional weakening over the zone of intrusion

vertical ground deformation on mount etna 1975 1980 we present the results of repeated precise leveling between the years 1975 and 1980 of an 11 km traverse over the summit of mount etna together with data from a network of dry tilt stations measured between 1976 and 1980 both methods demonstrate that little vertical movement occurs except on fresh lava flows which show a consistent pattern of downward movement interpreted as compaction and downhill sliding of lava after it has solidified other small vertical movements of a few centimetres recorded on the leveling traverse appear to be related to activity particularly the eruptions from a new vent area on the southeast side of the summit in 1978 and 1979 models of the recorded movement indicate that a small amount of magma was already stored in a dike below this eruption site as much as two years before it was erupted although the bulk of the magma for these eruptions was not stored in the upper few kilometres of the volcano the latter conclusion is supported by the dry tilt data which are dominated by local movements of 10 to 20 microradians with no consistent pattern of movement over the whole volcano

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty