Ralf Gertisser - Profile on Academia.edu (original) (raw)

Papers by Ralf Gertisser

Journal of Volcanology and Geothermal Research, Jun 1, 2012

The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commo... more The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commonly inferred to be a function of granular or inertial grain flow, similar to debris flows and cold rock avalanches. Existing geophysical mass flow models are either based on frictional (Mohr-Coulomb) behavior (the Titan2D model developed at the State University of New York at Buffalo, USA) or another rheological law (i.e., a constant retarding stress), eventually adding some viscous and turbulent components (the VolcFlow model developed at the Laboratoire Magmas et Volcans, Clermont-Ferrand, France). The 2006 BAFs of Merapi present a rare opportunity to test these two well-established models against a well-constrained field example. Integration of high-resolution field-based data into numerical simulations allows the validity of these models to be tested and rapid quantification of best-fit input parameters. We first show that with the incorporation of spatially varying bed friction angles, Titan2D is capable of reproducing the paths, runout distances, areas covered and deposited volumes of the 2006 Merapi flows over highly complex topography. However, some discrepancies with field data are noted and the velocity and travel time of the flows do not match entirely. Using a single free parameter (a constant retarding stress), simulations obtained with the VolcFlow model also reproduce the morphology and distribution of the natural deposits as well as the time of emplacement and velocities of the flows. The results suggest that the performance of these models in simulating actual events is critically dependent on: (1) the calibration of the model by using extensive field-based data such as deposit distribution, and processes of flow generation, transport and deposition; (2) the incorporation of a suitable numerical topographic dataset (i.e., high-resolution digital elevation model), and (3) the choice of input parameters, such as location and volume of the initial pile of material and source characteristics (single or multiple dome-collapse, dome-collapse duration and total volume of collapsed material). Sensitivity analyses and inundation maps based on the probability of impact were used to produce a suite of potentially inundated areas from future gravitational dome-collapse events affecting the Gendol valley and adjacent areas on the southern flank of the volcano. Our results provide the basis for defining hazard zonations of key areas at risk from BAFs which will be generated during future comparable eruptions at Merapi.

Evolution of Stromboli basaltic plumbing system via magma recharges and mush rejuvenation

Basaltic volcanoes can remain active for tens to thousands of years with the continual presence o... more Basaltic volcanoes can remain active for tens to thousands of years with the continual presence of magma, requiring storage and transport conditions that can sustain persistently eruptible melt. Magma storage conditions beneath these volcanoes may significantly change with time, leading to sudden and dramatic changes in explosivity. Determining the rates and causes of these changes and how they modulate eruptive style over societally relevant timescales is of paramount importance for evaluating potential hazards. In June-August 2019, one major explosion and two paroxysms occurred at Stromboli volcano (Southern Italy) within only 64 days offering a unique opportunity to study the short-term variations in a basaltic plumbing system that can lead to paroxysmal events.Stromboli is an active open conduit basaltic volcano well-known for its persistent mild (normal) Strombolian activity occasionally interrupted by sudden, short-lived events ranging in size and intensity from major (violent Strombolian) to paroxysmal explosions. Strombolian activity, effusive eruptions and major explosions, all involve a degassed, highly porphyritic (hp) magma from a shallow reservoir. Deep-seated more mafic and, volatile-rich low-porphyritic (lp) magma is erupted, alongside hp-magma, during paroxysms, and in smaller quantities during some of the major explosions. Both lp- and hp-magmas were erupted during the 3 July and 28 August 2019 paroxysms, whereas only hp-magma was erupted during the major explosion on 25 June 2019.Via a multifaceted approach using clinopyroxene from the summer 2019 paroxysms, we reveal a key role for batches of volatile-rich lp-magma recharge arriving in the shallow reservoir up to a few days before these events. Our data indicate a rejuvenated Stromboli plumbing system where the extant crystal mush is efficiently permeated by recharge lp-magma with minimum remobilisation promoting a direct linkage between the deeper (lp) and shallow (hp) reservoirs. This sustains the current variability of eruptive styles with near immediate eruptive response to mafic magma recharge. The remarkable agreement between our calculated recharge timescales and the observed variation in time of various monitoring signals strongly supports such a model.Our approach provides vital insights into magma dynamics and their effects on monitoring signals demonstrating that detailed petrological studies integrated with volcano monitoring signals are fundamental for a fast response during a volcanic unrest phase or crisis.This work has been published in Nature Communication: Petrone, C.M., Mollo, S., Gertisser, R. et al. Magma recharge and mush rejuvenation drive paroxysmal activity at Stromboli volcano. Nat Commun 13, 7717 (2022). https://doi.org/10.1038/s41467-022-35405-z.

Evaluation of Geophysical Mass Flow Models Using the 2006 Block-and-ash Flows of Merapi Volcano, Indonesia

AGUSM, May 1, 2009

The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commo... more The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commonly inferred to be a function of granular or inertial grain flow, similar to debris flows and cold rock avalanches. Existing geophysical mass flow models are either based on frictional (Mohr-Coulomb) behavior (the Titan2D model developed at the University of Buffalo, USA) or another rheological law (i.e., a

Quaternary Science Reviews, Nov 1, 2018

Field observations and surface characteristics of pristine block-and-ash flow deposits from the 2006 eruption of Merapi Volcano, Java, Indonesia

Journal of Volcanology and Geothermal Research, Nov 1, 2008

... 1 partly buried by overbank pyroclastic-flow deposits resulting from impact of the basal aval... more ... 1 partly buried by overbank pyroclastic-flow deposits resulting from impact of the basal avalanche; (g) pyroclastic surge deposits in the proximal part of Kali Gendol 1; (h) pyroclastic surge deposits decoupled from the basal avalanche below a 30-m-high cliff in Kali Gendol 1 ...

Journal of Petrology, Mar 1, 2003

Merapi volcano (Central Java), located within the Quaternary volcanic front of the Sunda arc, is ... more Merapi volcano (Central Java), located within the Quaternary volcanic front of the Sunda arc, is one of the most active volcanoes of the Indonesian archipelago. During the Holocene, Merapi erupted basalts and basaltic andesites of medium-K affinity during its earlier stages of activity and high-K compositions over the past $1900 years. Merapi lavas and pyroclastic rocks are characterized by enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE) and higher 87 Sr/ 86 Sr, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios and lower 143 Nd/ 144 Nd ratios compared with Indian Ocean mid-ocean ridge basalt (MORB). Merapi high-K series rocks are enriched in LILE and LREE and slightly depleted in heavy REE (HREE) and HFSE compared with rocks from the medium-K series. The increase in K 2 O is accompanied by a marked increase in 87 Sr/ 86 Sr and a general decrease in 143 Nd/ 144 Nd, but not by systematic variations in d 18 O values. The low d 18 O nature of the Merapi magmas, and the lack of any major shift in isotopic compositions along the evolutionary trend of the two individual series, precludes extensive crustal assimilation during magma ascent and differentiation, emphasizing the importance of subducted continental material in the genesis of Merapi magmas. The compositional contrast between medium-K and high-K series volcanics largely reflects variable contributions from subducted sediment to the mantle wedge, which was similar to a MORB-source mantle before any subduction-related modification. The temporal change in the K 2 O content of the magmas reflects compositional variation in the mantle wedge rather than intracrustal processes occurring within the shallow volcanic system.

Gone with the Wind: Dispersal of Ciomadul Tephra

Springer eBooks, 2022

Palaeogeography: Syn- and Post-eruptive Landscape Evolution Around Ciomadul

Springer eBooks, 2022

Geology Today, Mar 1, 2017

Violent explosive eruptions occurred between c. 51 and 29 thousand years ago-during the Last Glac... more Violent explosive eruptions occurred between c. 51 and 29 thousand years ago-during the Last Glacial Maximum in East-Central Europe-at the picturesque volcano of Ciomadul, located at the southernmost tip of the Inner Carpathian Volcanic Range in Romania. Field volcanology, glass geochemistry of tephra, radiocarbon and optically stimulated luminescene

Applied Clay Science, Sep 1, 2018

Sepiolite-based catalysts loaded with potassium hydroxide were prepared via the wet impregnation ... more Sepiolite-based catalysts loaded with potassium hydroxide were prepared via the wet impregnation and ion-exchange methods and evaluated as catalysts in base-assisted reactions, such as transesterification of renewable oils. The structural features of these catalysts were characterised in detail by variable-temperature in situ X-ray diffraction, N 2 adsorption-desorption, scanning electron microscopy with energy-dispersive X-ray analysis and in situ FTIR spectroscopy. Although a high yield of fatty acid methyl esters was achieved in transesterification reactions in the presence of Kcontaining sepiolite, this system showed significant deactivation due to its structural degradation and loss of the active component during the reaction and regeneration cycles. This work demonstrates for the first time how the thermal and structural stability of sepiolite based systems can affect their performance, which is an essential issue that has not been sufficiently addressed in recent research related to the catalytic applications of these materials.

Journal of Quaternary Science, Aug 1, 2016

We present major element glass data and correlations of the 'Roxolany Tephra'-a so far geochemica... more We present major element glass data and correlations of the 'Roxolany Tephra'-a so far geochemically unconstrained volcanic ash layer previously described in last glacial (MIS2) loess deposits of the Roxolany loess-palaeosol complex in the SW Ukraine. This exceptionally well preserved, 2-3 cm thick tephra layer is characterised by a rhyolitic glass composition that is comparable to that of proximal tephra units from Ciomadul volcano in the East Carpathians, central Romania. The chemistry particularly matches that of the final LSPA pyroclastic fall unit of St. Ana crater that is radiocarbon dated in the proximal Mohoş coring site (MOH-2) at 29.6±0.62 cal ka BP. The age of the tephra correlative is in agreement with the newest radiocarbon and IR-OSL age constraints from overlying palaeosols and tephraembedding loess of the Roxolany sequence, respectively, which place the tephra between ca. 33 and 24 cal ka BP, and thus confirm the long-debated chronostratigraphy of this important

Earth-Science Reviews, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Geology Today, May 1, 2010

GUEST, J., COLE, P., DUNCAN, A. & CHESTER, D. 2003. Volcanoes of Southern Italy. Earth in View Series. ix + 284 pp. London, Bath: Geological Society of London. Price £65.00 (paperback). ISBN 1 86239 138 6

Geological Magazine, Nov 1, 2004

The Jurassic of Denmark and Greenland is rightly claimed by the publishers as a milestone publica... more The Jurassic of Denmark and Greenland is rightly claimed by the publishers as a milestone publication from GEUS, the now combined Geological Surveys of Denmark and Greenland. It represents the first issue of the new serial pub-lication, the Geological Survey of Denmark and ...

WHITE, J. D. L., SMELLIE, J. L. & CLAGUE, D. A. (eds) 2005. Explosive Subaqueous Volcanism. Geophysical Monograph Series Vol. 140. x + 379 pp. Washington DC: American Geophysical Union. Price US 90.00(hardcovers);AGUmembers′priceUS90.00 (hard covers); AGU members' price US 90.00(hardcovers);AGUmembers′priceUS63.00. ISBN 0 87590 999 X

Geological Magazine, Nov 1, 2006

Bulletin of Volcanology, Mar 29, 2019

Located at the southern tip of the Intra-Carpathian Volcanic Range in Romania, and composed of a ... more Located at the southern tip of the Intra-Carpathian Volcanic Range in Romania, and composed of a dozen dacitic lava domes, the Ciomadul (Csomád) volcanic complex is the youngest eruptive centre of the Carpatho-Pannonian Region. Whereas, in the last decade, the explosive history of Ciomadul since 50 ka has been well constrained by numerous studies, the chronology of the dome sequence still lacks robust chronological constraints and an extended analysis of all available data. Here, we apply a detailed K-Ar dating approach to refine the chronology of the lava dome eruptions, using the unspiked K-Ar Cassignol-Gillot technique. Our dating focused on the most voluminous central part of the lava dome complex. New eruption ages were determined following a strict separation (of 10 g) of groundmass from about 3 kg of unaltered sample rocks, thereby isolating material whose Manuscript Click here to access/download;Manuscript;Lahitte_BUVO-D-18-00067_R3.doc Click here to view linked References cooling was contemporaneous with the eruption. The newly applied methodology, mainly consisting of a double full preparation, first at larger grain size (~ 0.4 mm) and then at < 100 µm, provides an appropriate procedure to separate suitable material to obtain the K-Ar age of the eruption, i.e. the sample's groundmass, in which there is no risk of the presence of older, inherited crystals. Our new geochronological data set gives an improved insight into the temporal construction of the Ciomadul volcanic complex, where (due to the method applied here) all ages are younger than those from previous studies that used whole-rock K-Ar ages. Our new results show that Ciomadul's volcanic activity began with the construction of the southeastern, peripheral domes from ca. 850 ka to 440 ka. After a ca. 250 ky long repose period, the activity resumed in the northern part at around 200 ka, with subsequent domes emplaced between 200 and 130 ka, aligned roughly north-south in the westerncentral part of the complex. Following a 30 ky long quiescence period, the eastern-central domes formed between 100 and 60 ka. In addition to the chronological history of lava dome volcanism, we also investigated the sequence of crystallisation of mineral phases present in the lavas with respect to the modification of eruption ages. Ages obtained on pure minerals (plagioclase, amphibole and biotite) are systematically older than those obtained on groundmass, showing that most of them formed up to 1.85 Myr before eruption in a longlived, pre-Ciomadul magmatic system. Crystal size distributions (CSD) data support the age contrasts between juvenile groundmass and older inherited minerals. After injection of new magma and convective mixing with crystal clots, ascent of the resulting led to eruptions of material representing contrasting ages.

Journal of Petrology, Oct 13, 2012

Earth and Planetary Science Letters, Feb 1, 2005

This paper shows how 226 Ra-230 Th disequilibria can be used to date Holocene volcanic rocks from... more This paper shows how 226 Ra-230 Th disequilibria can be used to date Holocene volcanic rocks from some well selected volcanoes. A systematic study of these disequilibria on historical or well-dated volcanic samples is indeed first required to test the applicability of this method. Two examples are described here to illustrate its potential. In the case of Mt. Etna, the good correlation observed between (226 Ra) 0 activities at the time of eruption and Th contents in lava flows from the last two millennia [M. Condomines, J.C. Tanguy, V. Michaud, Magma dynamics at Mt. Etna: constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas, Earth Planet. Sci. Lett. 132 (1995) 25-41] is used to infer the ages of several newly analysed lava flows. The calculated ages are in good agreement with those deduced from the archaeomagnetic curve describing the variation of the geomagnetic field direction in southern Italy [

Chapter 9 Eruptive history and magmatic evolution of the island of Salina (central Aeolian archipelago)

Geological Society, London, Memoirs, 2013

Stratigraphic, structural, volcanological and geochemical data allow a detailed reconstruction of... more Stratigraphic, structural, volcanological and geochemical data allow a detailed reconstruction of the geological history of the island of Salina (central Aeolian sector). Its subaerial volcanism (c. 244 ka to 15.6 ka) developed through six successive Eruptive Epochs interrupted by major quiescence periods, volcano-tectonic collapses and recurrent episodes of marine terrace formation during MIS 7 and MIS 5. Several stratovolcanoes were constructed by strombolian and effusive (Pizzo Capo, Monte Rivi, Monte Fossa delle Felci, Monte dei Porri) to hydromagmatic and subplinian (Monte dei Porri, Pollara) activity, with a general east–west shift of active vents, controlled primarily by the dominant NNW–SSE and minor NE–SW regional tectonic trends, and a progressive chemical differentiation of the erupted products from calc-alkaline basalts to rhyolites. The magma compositions and variations through time are the result of contamination of primary magmas derived from a subduction-modified mantle source with the Calabro–Peloritano lower crust and subsequent differentiation dominated by polybaric fractional crystallization. Magma mixing and mingling processes occurred during individual eruptions. The early basalts were fed from deep reservoirs located near the crust–mantle boundary, whereas the later andesitic to dacitic and, ultimately, rhyolitic magmas originated through combined assimilation and fractional crystallization processes in magma reservoirs at mid- to upper-crustal levels.DVD:The 10 000 scale geological map of Salina is included on the DVD in the printed book and can also be accessed online at http://www.geolsoc.org.uk/Memoir37-electronic. Also included is a full geochemical dataset for Salina.

Interplinian explosive activity of Santorini volcano (Greece) during the past 150,000 years

Journal of Volcanology and Geothermal Research, May 1, 2006

The eruptive history of Santorini was dominated by twelve major Plinian eruptions. Six of these (... more The eruptive history of Santorini was dominated by twelve major Plinian eruptions. Six of these (Middle Pumice, Vourvoulos, Upper Scoriae 1, Upper Scoriae 2, Cape Riva and Minoan) occurred during the past ∼150 ky. This study focuses on the stratigraphy and geochemistry of the interplinian pyroclastic deposits between 145 ka (Middle Pumice) and 3.6 ka (Minoan). Five interplinian eruptive intervals

Journal of Volcanology and Geothermal Research, Jun 1, 2012

The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commo... more The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commonly inferred to be a function of granular or inertial grain flow, similar to debris flows and cold rock avalanches. Existing geophysical mass flow models are either based on frictional (Mohr-Coulomb) behavior (the Titan2D model developed at the State University of New York at Buffalo, USA) or another rheological law (i.e., a constant retarding stress), eventually adding some viscous and turbulent components (the VolcFlow model developed at the Laboratoire Magmas et Volcans, Clermont-Ferrand, France). The 2006 BAFs of Merapi present a rare opportunity to test these two well-established models against a well-constrained field example. Integration of high-resolution field-based data into numerical simulations allows the validity of these models to be tested and rapid quantification of best-fit input parameters. We first show that with the incorporation of spatially varying bed friction angles, Titan2D is capable of reproducing the paths, runout distances, areas covered and deposited volumes of the 2006 Merapi flows over highly complex topography. However, some discrepancies with field data are noted and the velocity and travel time of the flows do not match entirely. Using a single free parameter (a constant retarding stress), simulations obtained with the VolcFlow model also reproduce the morphology and distribution of the natural deposits as well as the time of emplacement and velocities of the flows. The results suggest that the performance of these models in simulating actual events is critically dependent on: (1) the calibration of the model by using extensive field-based data such as deposit distribution, and processes of flow generation, transport and deposition; (2) the incorporation of a suitable numerical topographic dataset (i.e., high-resolution digital elevation model), and (3) the choice of input parameters, such as location and volume of the initial pile of material and source characteristics (single or multiple dome-collapse, dome-collapse duration and total volume of collapsed material). Sensitivity analyses and inundation maps based on the probability of impact were used to produce a suite of potentially inundated areas from future gravitational dome-collapse events affecting the Gendol valley and adjacent areas on the southern flank of the volcano. Our results provide the basis for defining hazard zonations of key areas at risk from BAFs which will be generated during future comparable eruptions at Merapi.

Evolution of Stromboli basaltic plumbing system via magma recharges and mush rejuvenation

Basaltic volcanoes can remain active for tens to thousands of years with the continual presence o... more Basaltic volcanoes can remain active for tens to thousands of years with the continual presence of magma, requiring storage and transport conditions that can sustain persistently eruptible melt. Magma storage conditions beneath these volcanoes may significantly change with time, leading to sudden and dramatic changes in explosivity. Determining the rates and causes of these changes and how they modulate eruptive style over societally relevant timescales is of paramount importance for evaluating potential hazards. In June-August 2019, one major explosion and two paroxysms occurred at Stromboli volcano (Southern Italy) within only 64 days offering a unique opportunity to study the short-term variations in a basaltic plumbing system that can lead to paroxysmal events.Stromboli is an active open conduit basaltic volcano well-known for its persistent mild (normal) Strombolian activity occasionally interrupted by sudden, short-lived events ranging in size and intensity from major (violent Strombolian) to paroxysmal explosions. Strombolian activity, effusive eruptions and major explosions, all involve a degassed, highly porphyritic (hp) magma from a shallow reservoir. Deep-seated more mafic and, volatile-rich low-porphyritic (lp) magma is erupted, alongside hp-magma, during paroxysms, and in smaller quantities during some of the major explosions. Both lp- and hp-magmas were erupted during the 3 July and 28 August 2019 paroxysms, whereas only hp-magma was erupted during the major explosion on 25 June 2019.Via a multifaceted approach using clinopyroxene from the summer 2019 paroxysms, we reveal a key role for batches of volatile-rich lp-magma recharge arriving in the shallow reservoir up to a few days before these events. Our data indicate a rejuvenated Stromboli plumbing system where the extant crystal mush is efficiently permeated by recharge lp-magma with minimum remobilisation promoting a direct linkage between the deeper (lp) and shallow (hp) reservoirs. This sustains the current variability of eruptive styles with near immediate eruptive response to mafic magma recharge. The remarkable agreement between our calculated recharge timescales and the observed variation in time of various monitoring signals strongly supports such a model.Our approach provides vital insights into magma dynamics and their effects on monitoring signals demonstrating that detailed petrological studies integrated with volcano monitoring signals are fundamental for a fast response during a volcanic unrest phase or crisis.This work has been published in Nature Communication: Petrone, C.M., Mollo, S., Gertisser, R. et al. Magma recharge and mush rejuvenation drive paroxysmal activity at Stromboli volcano. Nat Commun 13, 7717 (2022). https://doi.org/10.1038/s41467-022-35405-z.

Evaluation of Geophysical Mass Flow Models Using the 2006 Block-and-ash Flows of Merapi Volcano, Indonesia

AGUSM, May 1, 2009

The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commo... more The dynamics and depositional processes associated with block-and-ash flows (BAFs) are most commonly inferred to be a function of granular or inertial grain flow, similar to debris flows and cold rock avalanches. Existing geophysical mass flow models are either based on frictional (Mohr-Coulomb) behavior (the Titan2D model developed at the University of Buffalo, USA) or another rheological law (i.e., a

Quaternary Science Reviews, Nov 1, 2018

Field observations and surface characteristics of pristine block-and-ash flow deposits from the 2006 eruption of Merapi Volcano, Java, Indonesia

Journal of Volcanology and Geothermal Research, Nov 1, 2008

... 1 partly buried by overbank pyroclastic-flow deposits resulting from impact of the basal aval... more ... 1 partly buried by overbank pyroclastic-flow deposits resulting from impact of the basal avalanche; (g) pyroclastic surge deposits in the proximal part of Kali Gendol 1; (h) pyroclastic surge deposits decoupled from the basal avalanche below a 30-m-high cliff in Kali Gendol 1 ...

Journal of Petrology, Mar 1, 2003

Merapi volcano (Central Java), located within the Quaternary volcanic front of the Sunda arc, is ... more Merapi volcano (Central Java), located within the Quaternary volcanic front of the Sunda arc, is one of the most active volcanoes of the Indonesian archipelago. During the Holocene, Merapi erupted basalts and basaltic andesites of medium-K affinity during its earlier stages of activity and high-K compositions over the past $1900 years. Merapi lavas and pyroclastic rocks are characterized by enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE) and higher 87 Sr/ 86 Sr, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios and lower 143 Nd/ 144 Nd ratios compared with Indian Ocean mid-ocean ridge basalt (MORB). Merapi high-K series rocks are enriched in LILE and LREE and slightly depleted in heavy REE (HREE) and HFSE compared with rocks from the medium-K series. The increase in K 2 O is accompanied by a marked increase in 87 Sr/ 86 Sr and a general decrease in 143 Nd/ 144 Nd, but not by systematic variations in d 18 O values. The low d 18 O nature of the Merapi magmas, and the lack of any major shift in isotopic compositions along the evolutionary trend of the two individual series, precludes extensive crustal assimilation during magma ascent and differentiation, emphasizing the importance of subducted continental material in the genesis of Merapi magmas. The compositional contrast between medium-K and high-K series volcanics largely reflects variable contributions from subducted sediment to the mantle wedge, which was similar to a MORB-source mantle before any subduction-related modification. The temporal change in the K 2 O content of the magmas reflects compositional variation in the mantle wedge rather than intracrustal processes occurring within the shallow volcanic system.

Gone with the Wind: Dispersal of Ciomadul Tephra

Springer eBooks, 2022

Palaeogeography: Syn- and Post-eruptive Landscape Evolution Around Ciomadul

Springer eBooks, 2022

Geology Today, Mar 1, 2017

Violent explosive eruptions occurred between c. 51 and 29 thousand years ago-during the Last Glac... more Violent explosive eruptions occurred between c. 51 and 29 thousand years ago-during the Last Glacial Maximum in East-Central Europe-at the picturesque volcano of Ciomadul, located at the southernmost tip of the Inner Carpathian Volcanic Range in Romania. Field volcanology, glass geochemistry of tephra, radiocarbon and optically stimulated luminescene

Applied Clay Science, Sep 1, 2018

Sepiolite-based catalysts loaded with potassium hydroxide were prepared via the wet impregnation ... more Sepiolite-based catalysts loaded with potassium hydroxide were prepared via the wet impregnation and ion-exchange methods and evaluated as catalysts in base-assisted reactions, such as transesterification of renewable oils. The structural features of these catalysts were characterised in detail by variable-temperature in situ X-ray diffraction, N 2 adsorption-desorption, scanning electron microscopy with energy-dispersive X-ray analysis and in situ FTIR spectroscopy. Although a high yield of fatty acid methyl esters was achieved in transesterification reactions in the presence of Kcontaining sepiolite, this system showed significant deactivation due to its structural degradation and loss of the active component during the reaction and regeneration cycles. This work demonstrates for the first time how the thermal and structural stability of sepiolite based systems can affect their performance, which is an essential issue that has not been sufficiently addressed in recent research related to the catalytic applications of these materials.

Journal of Quaternary Science, Aug 1, 2016

We present major element glass data and correlations of the 'Roxolany Tephra'-a so far geochemica... more We present major element glass data and correlations of the 'Roxolany Tephra'-a so far geochemically unconstrained volcanic ash layer previously described in last glacial (MIS2) loess deposits of the Roxolany loess-palaeosol complex in the SW Ukraine. This exceptionally well preserved, 2-3 cm thick tephra layer is characterised by a rhyolitic glass composition that is comparable to that of proximal tephra units from Ciomadul volcano in the East Carpathians, central Romania. The chemistry particularly matches that of the final LSPA pyroclastic fall unit of St. Ana crater that is radiocarbon dated in the proximal Mohoş coring site (MOH-2) at 29.6±0.62 cal ka BP. The age of the tephra correlative is in agreement with the newest radiocarbon and IR-OSL age constraints from overlying palaeosols and tephraembedding loess of the Roxolany sequence, respectively, which place the tephra between ca. 33 and 24 cal ka BP, and thus confirm the long-debated chronostratigraphy of this important

Earth-Science Reviews, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Geology Today, May 1, 2010

GUEST, J., COLE, P., DUNCAN, A. & CHESTER, D. 2003. Volcanoes of Southern Italy. Earth in View Series. ix + 284 pp. London, Bath: Geological Society of London. Price £65.00 (paperback). ISBN 1 86239 138 6

Geological Magazine, Nov 1, 2004

The Jurassic of Denmark and Greenland is rightly claimed by the publishers as a milestone publica... more The Jurassic of Denmark and Greenland is rightly claimed by the publishers as a milestone publication from GEUS, the now combined Geological Surveys of Denmark and Greenland. It represents the first issue of the new serial pub-lication, the Geological Survey of Denmark and ...

WHITE, J. D. L., SMELLIE, J. L. & CLAGUE, D. A. (eds) 2005. Explosive Subaqueous Volcanism. Geophysical Monograph Series Vol. 140. x + 379 pp. Washington DC: American Geophysical Union. Price US 90.00(hardcovers);AGUmembers′priceUS90.00 (hard covers); AGU members' price US 90.00(hardcovers);AGUmembers′priceUS63.00. ISBN 0 87590 999 X

Geological Magazine, Nov 1, 2006

Bulletin of Volcanology, Mar 29, 2019

Located at the southern tip of the Intra-Carpathian Volcanic Range in Romania, and composed of a ... more Located at the southern tip of the Intra-Carpathian Volcanic Range in Romania, and composed of a dozen dacitic lava domes, the Ciomadul (Csomád) volcanic complex is the youngest eruptive centre of the Carpatho-Pannonian Region. Whereas, in the last decade, the explosive history of Ciomadul since 50 ka has been well constrained by numerous studies, the chronology of the dome sequence still lacks robust chronological constraints and an extended analysis of all available data. Here, we apply a detailed K-Ar dating approach to refine the chronology of the lava dome eruptions, using the unspiked K-Ar Cassignol-Gillot technique. Our dating focused on the most voluminous central part of the lava dome complex. New eruption ages were determined following a strict separation (of 10 g) of groundmass from about 3 kg of unaltered sample rocks, thereby isolating material whose Manuscript Click here to access/download;Manuscript;Lahitte_BUVO-D-18-00067_R3.doc Click here to view linked References cooling was contemporaneous with the eruption. The newly applied methodology, mainly consisting of a double full preparation, first at larger grain size (~ 0.4 mm) and then at < 100 µm, provides an appropriate procedure to separate suitable material to obtain the K-Ar age of the eruption, i.e. the sample's groundmass, in which there is no risk of the presence of older, inherited crystals. Our new geochronological data set gives an improved insight into the temporal construction of the Ciomadul volcanic complex, where (due to the method applied here) all ages are younger than those from previous studies that used whole-rock K-Ar ages. Our new results show that Ciomadul's volcanic activity began with the construction of the southeastern, peripheral domes from ca. 850 ka to 440 ka. After a ca. 250 ky long repose period, the activity resumed in the northern part at around 200 ka, with subsequent domes emplaced between 200 and 130 ka, aligned roughly north-south in the westerncentral part of the complex. Following a 30 ky long quiescence period, the eastern-central domes formed between 100 and 60 ka. In addition to the chronological history of lava dome volcanism, we also investigated the sequence of crystallisation of mineral phases present in the lavas with respect to the modification of eruption ages. Ages obtained on pure minerals (plagioclase, amphibole and biotite) are systematically older than those obtained on groundmass, showing that most of them formed up to 1.85 Myr before eruption in a longlived, pre-Ciomadul magmatic system. Crystal size distributions (CSD) data support the age contrasts between juvenile groundmass and older inherited minerals. After injection of new magma and convective mixing with crystal clots, ascent of the resulting led to eruptions of material representing contrasting ages.

Journal of Petrology, Oct 13, 2012

Earth and Planetary Science Letters, Feb 1, 2005

This paper shows how 226 Ra-230 Th disequilibria can be used to date Holocene volcanic rocks from... more This paper shows how 226 Ra-230 Th disequilibria can be used to date Holocene volcanic rocks from some well selected volcanoes. A systematic study of these disequilibria on historical or well-dated volcanic samples is indeed first required to test the applicability of this method. Two examples are described here to illustrate its potential. In the case of Mt. Etna, the good correlation observed between (226 Ra) 0 activities at the time of eruption and Th contents in lava flows from the last two millennia [M. Condomines, J.C. Tanguy, V. Michaud, Magma dynamics at Mt. Etna: constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas, Earth Planet. Sci. Lett. 132 (1995) 25-41] is used to infer the ages of several newly analysed lava flows. The calculated ages are in good agreement with those deduced from the archaeomagnetic curve describing the variation of the geomagnetic field direction in southern Italy [

Chapter 9 Eruptive history and magmatic evolution of the island of Salina (central Aeolian archipelago)

Geological Society, London, Memoirs, 2013

Stratigraphic, structural, volcanological and geochemical data allow a detailed reconstruction of... more Stratigraphic, structural, volcanological and geochemical data allow a detailed reconstruction of the geological history of the island of Salina (central Aeolian sector). Its subaerial volcanism (c. 244 ka to 15.6 ka) developed through six successive Eruptive Epochs interrupted by major quiescence periods, volcano-tectonic collapses and recurrent episodes of marine terrace formation during MIS 7 and MIS 5. Several stratovolcanoes were constructed by strombolian and effusive (Pizzo Capo, Monte Rivi, Monte Fossa delle Felci, Monte dei Porri) to hydromagmatic and subplinian (Monte dei Porri, Pollara) activity, with a general east–west shift of active vents, controlled primarily by the dominant NNW–SSE and minor NE–SW regional tectonic trends, and a progressive chemical differentiation of the erupted products from calc-alkaline basalts to rhyolites. The magma compositions and variations through time are the result of contamination of primary magmas derived from a subduction-modified mantle source with the Calabro–Peloritano lower crust and subsequent differentiation dominated by polybaric fractional crystallization. Magma mixing and mingling processes occurred during individual eruptions. The early basalts were fed from deep reservoirs located near the crust–mantle boundary, whereas the later andesitic to dacitic and, ultimately, rhyolitic magmas originated through combined assimilation and fractional crystallization processes in magma reservoirs at mid- to upper-crustal levels.DVD:The 10 000 scale geological map of Salina is included on the DVD in the printed book and can also be accessed online at http://www.geolsoc.org.uk/Memoir37-electronic. Also included is a full geochemical dataset for Salina.

Interplinian explosive activity of Santorini volcano (Greece) during the past 150,000 years

Journal of Volcanology and Geothermal Research, May 1, 2006

The eruptive history of Santorini was dominated by twelve major Plinian eruptions. Six of these (... more The eruptive history of Santorini was dominated by twelve major Plinian eruptions. Six of these (Middle Pumice, Vourvoulos, Upper Scoriae 1, Upper Scoriae 2, Cape Riva and Minoan) occurred during the past ∼150 ky. This study focuses on the stratigraphy and geochemistry of the interplinian pyroclastic deposits between 145 ka (Middle Pumice) and 3.6 ka (Minoan). Five interplinian eruptive intervals

The Middle Pumice eruption, Santorini, Greece: welding characteristics of a Plinian air-fall deposit. pdf

The Middle Pumice A eruption of Santorini, Greece (144.6 ka) is a fine example of a welded Plinia... more The Middle Pumice A eruption of Santorini, Greece (144.6 ka) is a fine example of a welded Plinian air-fall deposit. Welding characteristics and factors controlling welding were determined through field observations and laboratory analysis such as pumice clast characterisation, Rf/phi strain analysis and physical eruption parameter calculations. Welding intensity varies vertically and laterally, with welding decreasing away from source, and increasing centrally. Lateral welding zones are defined by the highest observed welding grade: A = densely-welded (< 0.25 km from source); B = slightly- welded (0.25-2.38 km); C = tack-welded (2.38-3.71 km), and D = non-welded (> 3.71 km). With welding, there is increased density and decreased porosity. A density of 2.36 gcm-3 and porosity of 4.9% is found in the most densely-welded section. Distal, non-welded pumices have densities of 0.37 gcm-3 and porosities of > 75%. Strain calculations show the deposit is moderately flattened but relatively undeformed. Accumulation rates and deposit thicknesses decrease away from source, with ~10.5 mh-1 and 25.8 m in proximal areas, and 0.77-1.26 mh-1 and ~3 m at distal locations. Threshold values of accumulation rate are > 7.5 mh-1 for dense welding, 3.0-7.5 mh-1 for slight welding and < 3 mh-1 for tack- to non-welding. An eruption column height of 23 km and mass discharge rate of 3.0 x 107 kg s-1 were calculated. The deposit is dacitic to andesitic, becoming increasingly mafic with stratigraphic height. First order factors controlling welding are deposit thickness and accumulation rate. High emplacement temperatures and magmatic temperatures are secondary factors.

Nature GeoScience, 2021

Supplementary Figure 1. (after Wulf et al., 2019) A) Map showing the location of Santorini (black... more Supplementary Figure 1. (after Wulf et al., 2019) A) Map showing the location of Santorini (black box) and of the marine cores (black dots) which contribute both the sea-level record (core LC21) and the tephrochronology dates for the Plinian eruptions which constrain Santorini's eruption history (KL49, KL51, LC21from 20). B) The islands of Santorini and the locations of stratigraphic sections contributing to Santorini's chronology and eruption count estimates 43, 44, this study. While the palaeostratigraphy is derived from locations in the caldera wall (Thera and Therasia islands), the central island of Nea Kameni is the location of historical eruptive activity (after the Late Bronze Age Eruption at 3.6 ka), Supplementary Figure 2: A) shows the COMSOL model geometry B) Graph shows the relationship (blue line) between the first principle (tensile) stress at the top of the magma storage region and the fall in sea level below the present day. Note the x-axis is exponential, creating a curved line. The relationship between the first principle stress and the drop in sea level is actually linear in an elastic model. The likely range of tensile strengths (tensile stress at which rocks start to fracture) is between 3 and 4 MPa 22,23 with an average of 3.5 MPa, this defines our modelled prediction that a 40 m drop in sea level being large enough to allow magmatic excess pressure pe (see equation in the main text) to fracture the roof of the magma reservoir and for dykes to begin to propagate.

Nature Geoscience, 2021

Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to inte... more Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (for example, magma recharge rates) remain poorly understood. Here we compare an approximately 360-kyr-long record of effusive and explosive eruptions from the flooded caldera volcano at Santorini (Greece) with a high-resolution sea-level record spanning the last four glacial-interglacial cycles. Numerical modelling shows that when the sea level falls by 40 m below the present-day level, the induced tensile stresses in the roof of the magma chamber of Santorini trigger dyke injections. As the sea level continues to fall to −70 or −80 m, the induced tensile stress spreads throughout the roof so that some dykes reach the surface to feed eruptions. Similarly, the volcanic activity gradually disappears after the sea level rises above −40 m. Synchronizing Santorini’s stratigraphy with the sea-level record using tephra layers in marine sediment cores shows that 208 out of 211 eruptions (both effusive and explosive) occurred during periods constrained by sea-level falls (below −40 m) and subsequent rises, suggesting a strong absolute sea-level control on the timing of eruptions on Santorini—a result that probably applies to many other volcanic islands around the world.