volcanic shards from santorini upper minoan ash in the nile delta egypt one of the largest volcanic outbursts recorded in early human history is the cataclysmic eruption of santorini thera which occurred about 35 centuries ago in the southern aegean sea this explosive event termed upper minoan or upper thera produced a tephra fall believed by archaeologists and volcanologists to have been widespread in the eastern mediterranean1 4 upper minoan ash has been found on land in the aegean and hellenic arc regions including crete5 6 and rhodes7 to date however there has been no confirmed observation of this ash on land across the mediterranean in north africa we now report evidence for the presence of ash ejected from this explosion in sediment cores recovered in the eastern nile delta of egypt this discovery of upper minoan glass shards extends considerably the zone of confirmed ash fall to the southeast of santorini and serves as evidence of a major natural phenomenon affecting egypt during the reign of pharaohs in the eighteenth dynasty it is quite possible that this ash fall event may have given rise to texts pertaining to darkening of the sky and veiling of the sun in early historic records

petrological and geochemical characteristics of cenozoic high k calc alkaline volcanism in konya central anatolia turkey abstract late miocene to pliocene volcanic rocks outcrop west northwest and southwest of the konya area in central anatolia turkey volcanic products are lava domes nuee ardentes and ignimbrite deposits predominantly andesitic to dasitic in composition together with rare basalt basaltic andesite basaltic trachyandesite and trachyandesite 50 35 69 39 sio2 the serie exhibits high k calc alkaline affinities fractional crystallization of pyroxene plagioclase and fe ti oxides is the main process in the magmatic evolution of konya volcanic rocks volcanic units exhibit typical high k calc alkaline character their geochemical characteristics e g enrichments in lil elements such as k rb ba sr depletion in hfse such as ti nb and high ba nb and low nb y ratios are consistent with those of active continental margin regions high 87 sr 86 sr 0 704841 0 707340 and low 143 nd 144 nd 0 512390 0 512618 ratios suggest crustal involvement in their petrogenesis correlations between 86 sr 87 sr isotope with rb rb nb rb ba and rb sr also emphasize the effect of crustal contamination on the andesitic and dacitic magmas as a consequence konya volcanic rocks are products of assimilation and fractional crystallization afc processes of a magma which seems to be linked to the subduction of the african plate underneath the anatolian plate during miocene

the transition from calc alkaline to potassic orogenic magmatism in the aeolian islands southern italy the aeolian volcanic arc displays a wide range of magmatic products mafic lavas range from hypersthene normative calc alkaline basalts to silica undersaturated potassic absarokites although the former are spatially and temporally dominant consistent with the subduction zone tectonic setting in addition intermediate and acidic members of the various fractionation series may be recognised large variations in trace element and isotope ratios accompany the rapid calc alkaline to potassic transition and it is argued that these may be largely explained in terms of subduction zone mantle enrichment involving components derived from both basaltic ocean crust and subducted sediments in addition it seems that the mantle wedge itself was substantially heterogeneous prior to the onset of subduction zone processes not only are these subduction components similar to those proposed in a number of island arcs but they also resemble those recognised in the ultra potassic lavas of the roman province supporting recent subduction related petrogenetic models of the roman magmatism although subducted sediment plays an important role in the generation of some potassic magmatism it is not uniquely responsible for k2o rich lavas which are also produced without a large sediment contribution

mechanisms of hydrovolcanic pyroclast formation grain size scanning electron microscopy and experimental studies pyroclasts produced by explosive magma water interactions are of various sizes and shapes data from analysis of over 200 samples of hydrovolcanic ash are interpreted by comparison with experimentally produced ash grain size and scanning electron microscopy sem reveal information on the formation of hydrovolcanic pyroclasts strombolian explosions result from limited water interaction with magma and the pyroclasts produced are dominantly centimeter sized with increasing water interaction hydrovolcanism increases in explosivity to surtseyan and vulcanian activity these eruptions produce millimeter to micron sized pyroclasts the abundance of fine ash 63 m diameter increases from 5 to over 30 percent as water interaction reaches an explosive maximum this maximum occurs with interactions of virtually equal volumes of melt and water five dominant pyroclast shape types determined by sem result from hydrovolcanic fragmentation 1 blocky and equant 2 vesicular and irregular with smooth surfaces 3 moss like and convoluted 4 spherical or drop like and 5 plate like types 1 and 2 dominate pyroclasts greater than 100 m in diameter types 3 and 4 are typical of fine ash type 5 pyroclasts characterize ash less than 100 m in diameter resulting from hydrovolcanic fragmentation after strong vesiculation fragmentation mechanisms observed in experimental melt water interactions result from vapor film generation expansion and collapse fragments of congealed melt are products of several alternative mechanisms including stress wave cavitation detonation waves and fluid instability mixing all result in rapid heat transfer these mechanisms can explain the five observed pyroclast shapes stress wave fracturing cavitation of the melt results from high pressure and temperature gradients at the melt water interface simultaneous brittle fracture and quenching produces type 1 pyroclasts type 2 develops smooth fused surfaces due to turbulent mixing with water after fracture and before quenching fluid instabilities promote turbulent mixing of melt and water and produce fine ash this kind of fragmentation occurs during high energy explosions the increased melt surface area due to fine fragmentation promotes high efficiency heat exchange between the melt and water shapes of resulting pyroclasts are determined by maximum surface area type 3 and surface tension effects type 4 type 5 pyroclasts result from nearly simultaneous vesicle burst and melt water fragmentation

40ar 39ar dating of latest pleistocene 41 ka marine tephra in the mediterranean sea implications for global climate records abstract fifty one 40 ar 39 ar laser heating analyses of sanidine crystals in the c 13 tephra layer recovered out of a piston core raised from 3000 m depth in the tyrrhenian sea yielded apparent ages between 25 and 112 ka twenty four of these measurements define an age probability maximum and generate an isochron of 41 1 2 1 ka 2 with a 40 ar 36 ar intercept of 288 21 that is indistinguishable from the modern atmosphere however the entire population is skewed toward older apparent ages with smaller peaks at 48 ka 55 ka 67 ka and 110 ka the composition of glass shards in the c 13 tephra overlaps that of the sio 2 rich phase of the 150 km 3 campanian ignimbrite which erupted from the campi flegrei caldera 130 km northwest of the core site although the 41 1 2 1 ka isochron is 15 older than k ar and 14 c ages for the campanian ignimbrite it is indistinguishable from recent 40 ar 39 ar age determinations the campanian ignimbrite eruptions were also chemically similar to and correlated with the y 5 ash layer the most voluminous and widely dispersed late pleistocene tephra in the mediterranean region the age of the y 5 layer was constrained originally at 38 0 2 5 ka on the basis of astronomical dating of o isotope stages the 40 ar 39 ar ages astronomical dating plus chemical similarities permit correlation of the c 13 tephra layer with both the campanian ignimbrite and the y 5 tephra layer the older ages preserved in the c 13 tephra layer may reflect xenocrysts incorporated during the explosive eruption accompanying collapse of the campi flegrei caldera 41 ka the c 13 tephra layer is correlated with a 10 be peak in an adjacent marine core o isotope stage 3 12 and immediately preceded a cooling episode corresponding to heinrich event 4 thus the age of these features is constrained by radioisotope dating the 41 ka peak in 10 be deposition is a global phenomenon whose age matches that of the laschamp geomagnetic excursion thus our results provide a new tie point among several polar ice core and marine proxy records of paleoclimate during the past 50 kyr precise age information independent of radiocarbon dating can be recovered from latest pleistocene marine tephra using the 40 ar 39 ar laser heating method despite the presence of multiple components that may have been incorporated during or after its deposition

marine tephra from the cape riva eruption 22 ka of santorini in the sea of marmara abstract a discrete tephra layer has been discovered in three marine sediment cores from the sea of marmara eastern mediterranean the rhyodacitic glass chemistry and the stratigraphical position suggest a santorini provenance and in particular a correlation with the marine y 2 tephra that is known from the southern aegean sea and eastern levantine basin this tephra represents the distal facies of the cape riva eruption of santorini which has been dated by 14c on land at 21 950 cal yr bp hitherto the y 2 tephra has been detected only in marine sediment cores recovered south to southeast of its volcanic source the new occurrence in the sea of marmara approximately 530 km nne of the santorini eruptive centre suggests a more north easterly dispersal of fallout products of the cape riva eruption than previously supposed

computer simulation of transport and deposition of the campanian y 5 ash analyses of grain size and modal composition of the campanian tuff ash layer y 5 from 11 deep sea cores have been carried out this layer represents ash fall that has been correlated with the 38 000 y b p campanian ignimbrite thunell et al 1979 a deposit formed by the largest eruption documented in the mediterranean region during the late pleistocene barberi et al 1978 the bulk deposit is bimodal in grain size and dominated by glass shards the calculated mean grain size of the coarse mode of the individual size distributions decreases with distance from the source and progressively approaches a near constant fine mode of approximately 13 microns distal samples are unimodal in grain size these data combined with a set of vertical profiles of wind 10 year average have been used as input to a computer model that simulates fallout of tephra modelling indicates that the downwind variation of grain size of the coarse mode can be accurately reproduced with transport of ash between 5 and 35 km the observed fine mode of the deposit cannot however be generated by transport of ash as individual particles at these elevations such transport would result in deposition of virtually all of the fine ash beyond the studied area deposition of fine ash within the studied distance of 1600 km from source can only occur by fallout as particle aggregates from a high eruption plume or as individual particles from co ignimbrite ash clouds with a maximum elevation of 3 km the large volume of ash in the fine mode 70 wt and the irregularity in azimuth of low level winds argue against major low level transport of co ignimbrite ash rather the ash may have been derived from both a plinian eruption column and high altitude clouds of co ignimbrite ash with settling of fine ash as particle aggregates

towards a tephrochronology for the holocene of the north of ireland discrete layers of tephra have been found in both raised and blanket bogs in the north of ireland some of the layers have been identified to an icelandic source and in two cases specific eruptions of known radiocarbon age are suggested nine layers spanning the holocene are replicated in three lowland raised bogs one of the major layers has also been identified at a number of sites in two separate upland blanket peat systems and in a lake sediment

vent evolution and lag breccia formation during the cape riva eruption of santorini greece the 18 500 yr b p cape riva cr eruption of santorini vented several km3 or more of magma generating four eruption units a basal plinian fall deposit cr a and three pyroclastic flow deposits cr b to cr d upwards cr b and cr d are welded ignimbrites cr c consists predominantly of up to 25 m thick coarse lithic rich co ignimbrite lag breccias resulting from a climactic phase of the eruption the initial plinian phase occurred from a localized vent in n santorini and subsequent column collapse resulted in emplacement of cr b towards the end of cr b new conduits were activated and pyroclastic flows discharged from multiple vents to generate the lag breccias cr c cr d probably records a return to a localized vent as the eruption waned the eruption sampled a zoned magma chamber containing rhyodacite overlying andesite and leaks of these magmas were manifested as the skaros therasia lavas preceding the cr eruption plinian and initial ignimbrite stages occurred while the magma chamber was ove

deep sea tsunami deposits triggered by the explosion of santorini 3500 y bp eastern mediterranean abstract the collapse of the santorini caldera after the catastrophic eruption of the bronze age 3500 y bp caused a tsunami wave that had catastrophic effects in the ionian basin including its deepest parts pelagic turbidites of local origin were deposited on the bottom of small perched basins of the southern calabrian western and central mediterranean ridges type a homogenite whereas a megaturbidite of distal origin presumably triggered by the tsunami wave hitting the shoreline of the sirte gulf was deposited on the ionian and sirte abyssal plains extending eastwards as far as the western herodotous trough depositing a thick acoustically transparent layer type b homogenite three core transects crossing the deformation front of the mediterranean ridge are presented and discussed a fourth transect of giant piston cores was collected on the abyssal plains located to the south of the mediterranean ridge all those to the west of the collision zone contain the holocene homogenite with a thickness in excess of 20 m whereas the cores taken from the herodotous abyssal plain east of the collision zone are devoid of the homogenite sedimentological analyses were performed on the only giant core that penetrated the sandy base of the homogenite and the underlying pelagic sediments of late pleistocene last glacial age the african provenance of this typical type b homogenite is corroborated by shallow water fauna derived from the north african shelf no sedimentological characteristics peculiar to tsunamiites are observed in the deep sea homogenite of the eastern mediterranean

tephrostratigraphy and tephrochronology in the philippi peat basin macedonia northern hellas greece abstract three tephra layers have been identified in the upper 15 m of a 190 m section of peat beneath the philippi fen they provide significant lithological and chronological markers throughout the fen and the aegean region the upper tephra pht1 consists of shards of a transparent calcalkaline felsic glass and fragments of plagioclase augite hypersthene and rare hornblende magnetite apatite and quartz peat directly beneath pht1 gave a radiocarbon approximate age of 13 000 yr the middle tephra layer pht2 which resembles pht1 in chemistry and petrography but contains more crystals and lithic fragments rests on peat dated ca 18 000 14 c yr bp the lower tephra pht3 has colorless to brown glass shards with a trachytic chemistry and a mineral assemblage of sanidine sodic plagioclase biotite aegirine augite hornblende titanite and apatite bracketing radiocarbon ages imply that pht3 accumulated about 30 000 14 c yr bp the likely ages of pht1 and pht2 together with their mineralogical and chemical characteristics suggest that these tephras came from the volcanic field of thera in the hellenic arc pht2 particularly was derived from a major known explosive eruption ca 18 000 yr bp the cape riva eruption correlative to the y 2 tephra layer evidence for pht3 suggests derivation from the campanian province of italy and correlation with the campanian ignimbrite and the y 5 ash beneath the mediterranean sea

tephrostratigraphy and petrological study of chikurachki and fuss volcanoes western paramushir island northern kurile islands evaluation of holocene eruptive activity and temporal change of magma system a tephrostratigraphic and petrological study of the chikurachki 1816 m tatarinov lomonosov volcanic chain ctl volcanic chain and fuss 1772 m located at the southern part of paramushir island in the northern kurile islands was carried out to reveal the explosive eruption history during the holocene and the temporal change of the magma systems of these active volcanoes tephra successions were described at 54 sites and more than 20 major eruptive units were identified consisting of pumice fall scoria fall and ash fall deposits each of which are separated by paleosol or peat layers the source volcano of each recognized tephra layer was confirmed by correlation with proximal deposits of each eruption center with respect to petrography and whole rock and glass chemistry the age of each layer was determined by radiocarbon dating and the stratigraphic relationship with the dated widespread tephra from kamchatka according to the thickness of paleosols bracketed between tephra layers the holocene activity in this region was initiated by eruptions from the tatarinov and lomonosov volcanoes after the eruptions the fuss and chikurachki volcanoes started their explosive activities at ca 7 5 ka bp soon after the deposition of widespread tephra from the kurile lake caldera in southern kamchatka compared with fuss located on the back arc side chikurachki has frequent repeated explosive and voluminous eruptions whole rock compositions of the rocks of the ctl volcanic chain and fuss are classified into medium k and high k groups respectively these suggest that magma systems beneath the ctl volcanic chain and fuss differ from each other and have been independently constructed the rocks of the chikurachki volcano are basalt basaltic andesite and have gradually evolved their chemical compositions when graphed on a sio2 oxide diagram these form smooth trends from mafic to more felsic this suggests that the magma system evolved mainly by fractional crystallization in contrast matrix glass chemistries for fuss pumices are distinct for each eruption and show different k2o levels on a sio2 k2o diagram this implies that the magma system of fuss has been frequently replaced both volcanoes have been active under the same subduction system however the chikurachki volcano will continue eruptive activity under a stable magma system with a higher magma discharge rate whereas fuss may continue construction with an intermittent supply of distinct small magma batches

tephra from the minoan eruption of santorini in sediments of the black sea the explosive eruption of santorini volcano in the aegean sea about 3 300 years ago is of considerable archaeological and volcanological significance1 5 here we report the discovery of tephra from this minoan event in laminated sediments of the black sea this finding provides constraints on the distribution of debris from the eruption we estimate a minimum fallout area of 2 l06 km2 extending from the black sea in the north to the southeastern mediterranean sea the main dispersal axis trends through southern turkey in agreement with other studies of minoan tephra6 7 the tephra deposits should provide a useful reference horizon for assessing the chronology of black sea sediments which has been much debated8 15

distribution and chemical composition of tephra layers from eastern mediterranean abyssal sediments abstract most cores of late quaternary sediments from the eastern mediterranean sea contain many ash layers glass shards from discrete layers have been analysed chemically for major elements the layers from different cores have been correlated and unambiguously related to known volcanic events on the basis of the chemical data most of the layers are derived from explosive eruptions of the santorini volcanic complex other layers have their source in other volcanoes of the hellenic arc yali nisyros kos one layer originated from the campanian area italy

new geological insights and structural control on fluid circulation in la fossa cone vulcano aeolian islands italy accepted 1 june 2009 available online 21 june 2009 keywords electrical resistivity self potential soil co2 degassing temperature fluid circulation hydrothermal system structural boundary vulcano la fossa cone electric resistivity tomography ert self potential sp soil co2 ux and temperature are used to study the inner structure of la fossa cone vulcano aeolian islands nine profiles were performed across the cone with a measurement spacing of 20 m the crater rims of la fossa cone are underlined by sharp horizontal resistivity contrasts sp co2 flux and temperature anomalies underline these boundaries which we interpret as structural limits associated to preferential circulation of fluids the pietre cotte crater and gran cratere crater enclose the main hydrothermal system identified at the centre of the edifice on the base of low electrical resistivity values b20 m and strong co2 degassing sp and temperature anomalies in the periphery the hydrothermal activity is also visible along structural boundaries such as the punte nere forgia vecchia and palizzi crater rims and at the base of the cone on the southern side of the edifice along a fault attributed to the nwmain tectonic trend of the island inside the punte nere crater the ert sections show an electrical resistive body that we interpret as an intrusion or a dome this magmatic body is reconstructed in 3d using the available ert profiles its shape and position with respect to the pietre cotte crater fault allows replacing this structure in the chronology of the development of the volcano it corresponds to a late phase of activity of the punte nere edifice considering the position of the sp soil co2 flux and temperature maxima and the repartition of conductive zones related to hydrothermal circulation with respect to the main structural features la fossa cone could be considered as a relevant example of the strong influence of preexisting structures on hydrothermal fluid circulation at the scale of a volcanic edifice

correlation of a tephra layer in western greece with a late pleistocene eruption in the campanian province of italy abstract the kalodiki fen is a 2 km 2 mire in a small basin within a tectonic depression in epirus western greece since the last glaciation the basin has been occupied by a freshwater lake and has accumulated as much as 9 m of peat which continues to form today a 10 cm thick light brown to olive fine sandy layer appears in cores at depths ranging from 2 9 to 5 7 m the sand fraction of this layer consists mostly of pumice fragments and brown and colorless glass shards with similar major element compositions and it also contains crystal fragments of feldspars mainly sanidine ferromagnesian minerals and probably sphene and apatite the colorless glass has an index of refraction 1 519 0 002 a sample of the overlying peat layer gave a minimum radiocarbon age of about 31 800 1200 yr b p for the deposition of the tephra the likely age of the tephra its index of refraction and its mineralogical and chemical characteristics display strong similarities to tephra from the campanian province of italy mineralogically similar tephra layers have also been reported from a peat deposit at philippi in northeastern greece

the discovery of santorini minoan tephra in western turkey dispersal of volcanic ash from the violent bronze age minoan eruption of the santorini volcano in the southern aegean has been the subject of much research1 6 a sediment core taken from a small mountain lake in western turkey contains a layer of tephra from the minoan eruption the santorini origin is established by refractive index major glass chemistry and stratigraphic position the lake is located north of the recognized dispersal area for the tephra this deposit provides evidence for dispersal of the minoan tephra well to the northeast of santorini and implies that the west coast of asia minor must have experienced heavy tephra fallout from the bronze age eruption the minoan tephra has not previously been identified from sites in turkey

laacher see tephra a widespread isochronous late quaternary tephra layer in central and northern europe a late quaternary tephra layer widespread in central and northern europe resulted from explosive plinian and phreatomagmatic eruptions of the laacher see volcano 11 000 yr b p the tephra is distinguished from other late quaternary andesitic rhyolitic airfall tuff layers in northern europe and from basaltic or trachytic tuff deposits in southern europe by its phonolitic composition and abundance of sanidine plagioclase clinopyroxene amphibole and sphene the proximal tephia sequence at laacher see is divided into three main deposits the predominantly plinian deposits of lower and middle laacher see tephra llst and mlst and phreatomagmatic deposits of the upper laacher see tephra ulst the mlst member is further subdivided into beds a b and c1 c2 and c3 the chemical composition of the magma is highly differentiated phonolite in the llst to mlst b sections but mafic phonolite in the mlst c1 to ulst sections all deposits are considered to be isochronous the frequency maximum of 16 radiocarbon datings indicating an eruption about 11 000 50 yr b p distal ash was deposited in three main fans directed to the northeast lst traced up to 1 100 km distance south lst traced up to 600 km and southwest lst traced up to 100 km tephrostratigraphic correlation of the distal ash deposits is based on a the major element composition of glass shards b lithology and c heavy mineral analyses the northeastern fan consists of deposits from llst mlst b and mlst c1 eruptive phases the southern fan comprises mlst a mlst c2 and ulst deposits and the southwestern fan consists exclusively of ash from the ulst eruptive phase northeastern transport of ash during eruptive phases with high plinian eruption columns but southern and southwestern transport of ash along phases of relatively low eruption columns are interpreted in terms of prevailing southwesterly paleowinds at high altitudes tropopause level but northerly winds dominating in the lower atmosphere the laacher see eruption columns were emplaced into an atmosphere vertically zoned with respect to paleowind directions which also explains the near vent shifting of llst mlst b and mlst c1 iso pach axes from east southeast to northeast within the first 20 km of transport

large amplitude moho reflections sms from landers aftershocks southern california closely spaced aftershocks of the 28 june 1992 landers earthquake m w 7 3 were used to make event record sections that show the transverse components of s and sms arrivals at a distance of 70 to 170 km for the data recorded toward the north in the mojave desert large sms phases are observed with amplitudes 2 to 5 times greater than the direct s for similar distances to the south the sms arrival is comparable to or smaller than the s comparisons to synthetic seismograms indicate that the large amplitude sms phases are produced by the simple crustal structure of the mojave desert that allows a large moho reflection in contrast the more complex geologic structure to the south partitions the seismic energy into a more complicated set of seismic phases so that the moho reflection is diminished in amplitude the large sms phases observed in the mojave enhance the overall ground motions by a factor of 2 to 3 this suggests that when damaging earthquakes occur in other regions of simple crustal structures moho reflections will produce amplified strong motions at distance ranges around 100 km depending on the local structure

identification and dating of tephra layers from quaternary sedimentary sequences of inner anatolia turkey abstract results presented here are part of a research programme to investigate the environmental evolution in central anatolia during the pleistocene in this study tephra are used as chronostratigraphical markers between lacustrine sequences studied in cores or in sections surrounding eruptive centres of the central anatolian province at different locations in the konya plain and cappadocia tephra have been identified characterized and linked to eruptions of the nearby volcanoes seven different tephra have been clearly identified in lacustrine sequences of the konya plain 14 c dates on shells or organic matter as well as 230 th 234 u ages on gypsum give a chronological framework to the tephra layers in addition the study of the sediment fill of the eski acigol maar near nevsehir has allowed the recognition of several eruptions during late glacial and holocene in the vicinity of acigol the results show the first tephra to be identified in lacustrine sequences of anatolia they also show the cappadocian volcanism to be very young 35 ka this young volcanism is often of a basaltic type and does not include thick differenciated pyroclastic deposits

new radiocarbon dates for the vedde ash and the saksunarvatn ash from western norway abstract the vedde ash bed mid younger dryas and the saksunarvatn ash early holocene are important regional stratigraphic event markers in the north atlantic the norwegian sea and the adjacent land area it is thus essential to date them as precisely as possible the occurrence of the saksunarvatn ash is reported for the first time from western norway and both tephras are dated precisely by ams analyses of terrestrial plant material and lake sediment at krakenes the vedde ash has been previously dated at sites in western norway to about 10 600 yr b p it is obvious in the younger dryas sediments at krakenes and its identity is confirmed geochemically the mean of four ams dates of samples ofsalix herbacealeaves adjacent to the tephra is 10 310 50 yr b p the saksunarvatn ash is not visible in the early holocene lake sediment at krakenes after removal of organic material and diatoms the identity of the tephra particles was confirmed geochemically and their stratigraphic concentration was estimated from curve matching of a series of seven ams dates of terrestrial plant macrofossils and whole sediment the radiocarbon age of the ash is 8930 9060 yr b p corresponding to an age of 9930 10 010 cal yr b p 7980 8060 cal yr b c