Karoly Nemeth - Academia.edu (original) (raw)

Papers by Karoly Nemeth

Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that fo... more Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that form clusters, alignments or distributed randomly over large territory. The geoheritage values of such volcanic fields are difficult to characterize due to the scale problem they pose within the commonly magnitudes larger regions than their footprints. Monogenetic volcanoes are defined by their simple geological architecture. Their geological and geomorphological diversity of them not detectable easily within the common spatial scale diversity estimates performed mostly with an aim to quickly identify geological and geomorphological diversity hotspots. Here we explore this paradox situation from three distinct, nearby large monogenetic volcanic fields – Harrat Rahat, Harrat Khaybar and Harrat Lunayyir - each considered to be an active volcanic system in the western Arabian Peninsula. Historic records documented 52 days eruption in 1256 CE nearby Madinah City at Harrat Rahat. Archaeological evidence (desert kites) and some direct radiometric dating indicate Holocene (< 5-ky) volcanism at Harat Khaybar. In contrast, Harrat Lunayyir experienced a failed eruption (e.g., magma has not reached the surface) in 2009. These young volcanic activities and proximity to large cities and infrastructure triggered an elevated effort to monitor volcanic hazards in the region. Geoheritage has recently been considered as an avenue toward developing resilient society against volcanic hazard. Geotourism has also been recently considered as a prime sector for investment for economic development especially in the volcanic fields of West Arabia. The rapid economic growth and the industrial need of raw materials put unprecedent pressure on the geoheritage of these volcanic fields threating the reduction of geodiversity of the region. Accurate method to estimate the geodiversity of these volcanic fields is in great need, however, to develop quantitative methods by using advanced GIS technologies is challenging. This is partially due to the nature of measuring geodiversity of volcanic fields and the quality and availability of accurate geological information capturing the volcanic geoheritage. Here we provide a qualitative approach first to define the volcanic geoheritage of these three volcanic fields applying the volcanic geology and associated facies mapping approach. Such method is promising as the arid climate and lack of vegetation-cover help to identify clearly the geoheritage of those regions fall beyond the volcanic edifices. This is particularly important in these fields where great variety of surface textures of pāhoehoe and ʻaʻā lavas as well as inter-edifice mixed arid terrestrial sedimentation occur. In addition, geological attributes of volcanic edifices such as geochemistry, petrological information and pyroclastic successions ordered in their volcanic hazard perspective been used to refine diversity elements. The utilization of remote sensing satellite data, high resolution terrain analysis methods and collating information on geoheritage elements such as archaeology, geocultural aspects and types of geotourism utilities are also considered. Combination of these data to the most up to date geological mapping information clearly showed the correlation of geodiversity with the maturity and longevity of volcanism of the studied volcanic field fields.

Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that fo... more Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that form clusters, alignments or distributed randomly over large territory. The geoheritage values of such volcanic fields are difficult to characterize due to the scale problem they pose within the commonly magnitudes larger regions than their footprints. Monogenetic volcanoes are defined by their simple geological architecture. Their geological and geomorphological diversity of them not detectable easily within the common spatial scale diversity estimates performed mostly with an aim to quickly identify geological and geomorphological diversity hotspots. Here we explore this paradox situation from three distinct, nearby large monogenetic volcanic fields – Harrat Rahat, Harrat Khaybar and Harrat Lunayyir - each considered to be an active volcanic system in the western Arabian Peninsula. Historic records documented 52 days eruption in 1256 CE nearby Madinah City at Harrat Rahat. Archaeological...

The Mio/Pliocene Bakony-Balaton Highland Volcanic Field includes more than 100 alkaline basaltic ... more The Mio/Pliocene Bakony-Balaton Highland Volcanic Field includes more than 100 alkaline basaltic volcanoes. The maar complex Fekete-hegy is volumetrically one of the largest volcanic complexes of the BBHVF. Fekete-hegy forms a lava-capped butte in the central part of the volcanic field with basaltic lava flows overlying pyroclastic units. At least 3 vents have been identified at Fekete-hegy. Every single vent started initially with phreatomagmatic activity, interpreted on the basis of the presence of chilled, angular, blocky, slightly to moderately vesicular sideromelane glass shards, accidental lithic clasts and bedding characteristics of the pyroclastic units. Fekete-hegy is considered to be a large nested phreatomagmatic volcanic vent system,

International journal of geoheritage and parks, Mar 1, 2022

International Journal of Earth Sciences, Nov 1, 2001

... Facies characteristics and distribution allow us to (a) substantiate small-sized calderas, th... more ... Facies characteristics and distribution allow us to (a) substantiate small-sized calderas, the erodedrims or proximal palaeoslopes of which have been preserved by volcaniclastic breccias (mostly debris-flow depos-its); (b) reconstruct a well-developed volcaniclastic apron ...

Scientific Reports

During Earth’s history, geosphere-biosphere interactions were often determined by momentary, cata... more During Earth’s history, geosphere-biosphere interactions were often determined by momentary, catastrophic changes such as large explosive volcanic eruptions. The Miocene ignimbrite flare-up in the Pannonian Basin, which is located along a complex convergent plate boundary between Europe and Africa, provides a superb example of this interaction. In North Hungary, the famous Ipolytarnóc Fossil Site, often referred to as “ancient Pompeii”, records a snapshot of rich Early Miocene life buried under thick ignimbrite cover. Here, we use a multi-technique approach to constrain the successive phases of a catastrophic silicic eruption (VEI ≥ 7) dated at 17.2 Ma. An event-scale reconstruction shows that the initial PDC phase was phreatomagmatic, affecting ≥ 1500 km2 and causing the destruction of an interfingering terrestrial–intertidal environment at Ipolytarnóc. This was followed by pumice fall, and finally the emplacement of up to 40 m-thick ignimbrite that completely buried the site. Howe...

Geologica Carpathica, 2021

Detailed investigation of a Lower Miocene Plinian pyroclastic sequence that crops out in the Bükk... more Detailed investigation of a Lower Miocene Plinian pyroclastic sequence that crops out in the Bükk Foreland Volcanic Area (BFVA) in Northern Hungary is presented here. The studied eruptive products are part of a ca. 50 metres thick pyroclastic succession comprising of a basal ignimbrite that is covered by stratified pyroclastic unit including a topmost ignimbrite (Mangó ignimbrite unit, part of the Lower Pyroclastic Complex). The investigated pyroclastic unit is part of the Mangó ignimbrite unit, and consists of a pyroclastic fallout deposit, a ground-surge deposit, and an ignimbrite, all indicating a complete Plinian eruption phase. This pyroclastic succession has been identified in three locations, which crops out along a ~20 km long, SW-NE transect in the BFVA (two in the western, and one in the eastern part). The pyroclastic rocks in these sites are correlated well on the basis of the lithologically and texturally similar layers and their identical field volcanological properties. The correlation is also supported by the paleomagnetic signature of the two ignimbrites (upper ignimbrite-declination: 275-302°, lower ignimbrite with overprint magnetization-declination: 320-334°). The paleomagnetic directions of the stratigraphically upper ignimbrite suggest that this sequence belongs to the oldest known pyroclastic rock assemblages of the BFVA (Lower Pyroclastic Complex, deposited between 18.5 and 21 Ma according to previously published K/Ar dating results in good agreement with paleomagnetic measurements). Based on proximal-to-distal variations in the grain size of the pyroclastic fallout deposit (with maximal thickness is 71 cm), a potential source region to the east (or northeast, or southeast) of the BFVA has been inferred in a relatively close distance (~5-15 km). The (north)eastward-located source region is also supported by comparison of the characteristics of the studied fallout deposit with the spatial distribution of selected Plinian fallout tephra from worldwide examples using their digitalized isopach maps.

Journal of Volcanology and Geothermal Research, 2020

A Middle Miocene,~8 m thick pyroclastic succession, reported from the Bükk Foreland Volcanic Area... more A Middle Miocene,~8 m thick pyroclastic succession, reported from the Bükk Foreland Volcanic Area (BFVA) in Northern Hungary (Central Europe) specified here as the Jató Member, was produced by silicic phreatomagmatism (Phreatoplinian sensu lato). Two well-preserved outcrops~8 km apart and inferred to be within~10-50 km from source represent the discontinuously exposed, layered, paleosol-bounded, phreatomagmatic Jató Member. They show an identical phenocrystal assemblage of feldspar, biotite and amphibole without weathered zones or signs of erosion, that suggest deposition in one eruption phase lasting hours to months. The succession contains three subunits: 1) subunit A, 1.8 m thick, a series of well-sorted fine to coarse ash or lapilli tuff layers with constant thickness; 2) subunit B, 2.1 m thick, a series of normal-graded layers with an upper fine-grained zone containing abundant ash aggregates with a coarser-grained core and distinctively finer-grained outer rim; 3) subunit C, 4.5 m thick, a massive, poorly to well-sorted coarse ash with gas escape structures and ash aggregates at its base. The upward change of these lithofacies implies an initially sustained dry fallout-dominated deposition of ash and pumice lapilli resulting in subunit A. Subsequently, multiple wet and dilute Pyroclastic Density Currents (PDCs) dispersed subunits B and C. The general abundance of PDC-related ash aggregates in the middle-upper part of the succession (particularly in subunit B), and the transformation of a fall-dominated to a collapsing depositional regime producing wet dilute PDCs, imply the increasing influence of water during the eruption (Phreatoplinian sensu lato). The presence of water is related to an epicontinental sea during Middle to Late Miocene in the Carpatho-Pannonian region. The transition from an initial dry magmatic phase generated fallout activity followed by the emplacement of wet PDCs' rich in ash aggregates, when external water infiltrated from a surrounding lake or sea water entered the vent.

Bulletin of Volcanology, 2017

Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the... more Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the South Atlantic. Volcanic activity since the eighteenth century, along with the latest volcanic unrest episodes in the twentieth and twenty first centuries, demonstrates that the volcanic system is still active and that future eruptions are likely. Despite its remote location, the South Shetland Islands are an important touristic destination during the austral summer. In addition, they host several research stations and three summer field camps. Deception Island is characterised by a Quaternary caldera system with a postcaldera succession and is considered to be part of an active, dispersed (monogenetic), volcanic field. Historical postcaldera volcanism on Deception Island involves monogenetic smallvolume (VEI 2-3) eruptions such forming cones and various types of hydrovolcanic edifices. The scientific stations on the island were destroyed, or severely damaged, during the eruptions in 1967, 1969, and 1970 mainly due to explosive activity triggered by the interaction of rising (or erupting) magma with surface water, shallow groundwater, and ice. We conducted a detailed revision (field petrology and geochemistry) of the historical hydrovolcanic postcaldera eruptions of Deception Island with the aim to understand the dynamics of magmawater interaction, as well as characterise the most likely eruptive scenarios from future eruptions. We specifically focused on the Crimson Hill (estimated age between 1825 and 1829), and Kroner Lake (estimated age between 1829 and 1912) eruptions and 1967, 1969, and 1970 events by describing the eruption mechanisms related to the island's hydrovolcanic activity. Data suggest that the main hazards posed by volcanism on the island are due to fallout, ballistic blocks and bombs, and subordinate, dilute PDCs. In addition, Deception Island can be divided into five areas of expected activity due to magmawater interaction, providing additional data for correct hazard assessment on the island.

European Journal of Mineralogy, 2021

Structural hydroxyl content of volcanic quartz phenocrysts was investigated with unpolarized Four... more Structural hydroxyl content of volcanic quartz phenocrysts was investigated with unpolarized Fouriertransform infrared spectroscopy. The phenocrysts originated from five pyroclastic fallout deposits from the Bükk Foreland Volcanic Area (BFVA), Hungary, and two from the AD 1314 Kaharoa eruption (KH eruption), Okataina Volcanic Complex (Taupo Volcanic Zone), New Zealand. All investigated quartz populations contain structural hydroxyl content in a narrow range with an average of 9.3 (±1.7) wt ppm. The earlier correlated horizons in the BFVA had the same average structural hydroxyl content (within uncertainty). Thus, it can be concluded that the structural hydroxyl content does not depend on the geographical distance of outcrops of the same units or the temperature or type of the covering deposit. The rare outlier values and similar structural hydroxyl contents show that the fallout horizons cooled fast enough to retain their original structural hydroxyl content. The similarity of the structural hydroxyl contents may be the result of similar P , T , and x (most importantly H 2 O and the availability of other monovalent cations) conditions in the magmatic plumbing system just before eruption. Therefore, we envisage common physical-chemical conditions, which set the structural hydroxyl content in the quartz phenocrysts and, consequently, the water content of the host magma (∼ 5.5 wt %-7 wt % H 2 O) in a relatively narrow range close to water saturation.

IECG 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

IECG 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

IECG 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Geographies

Hydrology is one of the most influential elements of geodiversity, where geology and geomorpholog... more Hydrology is one of the most influential elements of geodiversity, where geology and geomorphology stand as the main values of abiotic nature. Hydrological erosion created by river systems destructing rock formations (eluvial process) from streams’ sources and then transporting and redepositing (alluvial process) the rock debris into the main river channels, make it an ongoing transformation element of the abiotic environment along channel networks. Hence, this manuscript demonstrates the influence of hydrological elements on geosite recognition, specifically for qualitative–quantitative assessment of geodiversity, which is based on a combination of geological and geomorphological values. In this concept, a stream system will be treated as an additional element. The basement area of the Manawatu Region has been utilized as the territory for the research of hydrological assessment. The region is in the southern part of the North Island of New Zealand and has relatively low geological...

Geoheritage, Geoparks and Geotourism

Geotourism is a relatively recent concept and a novel kind of tourism, which has acquired a signi... more Geotourism is a relatively recent concept and a novel kind of tourism, which has acquired a significant boom in the last decades, associated with the creation and consolidation of the UNESCO global geoparks network. There are two approaches to geotourism, one geological and the other geographical, much more global and inclusive of the elements of the natural and cultural heritage. In this chapter, we have chosen to use the geographical approach of geotourism, to apply it to the El Hierro global geopark and diversify the island's tourism, traditionally focused on diving and hiking, through geoforms (volcanic and non-volcanic), and its link with cultural heritage. For this, the most representative, preserved and accessible geomorphosites in the geopark have been identified, inventoried and selected, which can be visited through volcano tourism georoutes. To do this, a route is proposed in the El Faro-Orchilla geozone (GZH-07) of the geopark, since it is one of the best examples of...

Geoheritage, 2017

Harrat Khaybar is one of the most extensive of about 15 volcanic fields located in the western ma... more Harrat Khaybar is one of the most extensive of about 15 volcanic fields located in the western margin of the Arabian Peninsula. Most of these fields are located in the Kingdom of Saudi Arabia about 100-150 km inland from the Red Sea. The volcanic area is located near the culturally and religiously important city of Al Madinah. The field hosts monogenetic volcanoes such as scoria cones, tuff rings, spatter cones and extensive lava flow fields. It also contains several silicic lava domes and associated block-and-ash fans whose deposits fill intercone regions. Some of the field's volcanoes are inferred to have been erupted as recently as about 1000 AD, based on historic documents and geomorphologic evidence. There are no data available to directly support or better constrain the timing of the latest eruptions of the field. The area is also one of the highest regions of Saudi Arabia with a plateau at about 1500 m above sea level, topped by Jabal Abyad (2093 m) and Jabal Quidr (2022 m) volcanoes. Due to the elevation, Harrat Khaybar has a cold arid climate with a unique ecosystem and landscape. The region's high aesthetic value is derived from the bright white colour of several of its volcanoes which are dominantly rhyolitic ash. These edifices are strikingly different from the dark-coloured lava fields (harrats) of Arabia. Based on appearance, Harrat Khaybar has geoheritage value and could be a major geoconservation and geoeducation region of Arabia. Geological research in the region started only recently and is restricted to geological mapping and geochemical studies. Interest has recently increased because of the recognition of the field's potential volcanic hazards. There is a push to establish a geoheritage inventory of Harrat Khaybar with the aim of assessing the geoheritage framework of the region and developing more geotourism, geoeducational programmes and a geopark. Key volcanic geotopes and their geosites provide unique opportunities for a stand-alone geopark offering geoeducation and geotourism programmes in the region. The concept has been proposed to the geoheritage resource management of Harrat Rahat just south of Harrat Khaybar and Al Madinah City and could serve as a link between the two historically active volcanic fields located near Al Madinah.

Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that fo... more Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that form clusters, alignments or distributed randomly over large territory. The geoheritage values of such volcanic fields are difficult to characterize due to the scale problem they pose within the commonly magnitudes larger regions than their footprints. Monogenetic volcanoes are defined by their simple geological architecture. Their geological and geomorphological diversity of them not detectable easily within the common spatial scale diversity estimates performed mostly with an aim to quickly identify geological and geomorphological diversity hotspots. Here we explore this paradox situation from three distinct, nearby large monogenetic volcanic fields – Harrat Rahat, Harrat Khaybar and Harrat Lunayyir - each considered to be an active volcanic system in the western Arabian Peninsula. Historic records documented 52 days eruption in 1256 CE nearby Madinah City at Harrat Rahat. Archaeological evidence (desert kites) and some direct radiometric dating indicate Holocene (< 5-ky) volcanism at Harat Khaybar. In contrast, Harrat Lunayyir experienced a failed eruption (e.g., magma has not reached the surface) in 2009. These young volcanic activities and proximity to large cities and infrastructure triggered an elevated effort to monitor volcanic hazards in the region. Geoheritage has recently been considered as an avenue toward developing resilient society against volcanic hazard. Geotourism has also been recently considered as a prime sector for investment for economic development especially in the volcanic fields of West Arabia. The rapid economic growth and the industrial need of raw materials put unprecedent pressure on the geoheritage of these volcanic fields threating the reduction of geodiversity of the region. Accurate method to estimate the geodiversity of these volcanic fields is in great need, however, to develop quantitative methods by using advanced GIS technologies is challenging. This is partially due to the nature of measuring geodiversity of volcanic fields and the quality and availability of accurate geological information capturing the volcanic geoheritage. Here we provide a qualitative approach first to define the volcanic geoheritage of these three volcanic fields applying the volcanic geology and associated facies mapping approach. Such method is promising as the arid climate and lack of vegetation-cover help to identify clearly the geoheritage of those regions fall beyond the volcanic edifices. This is particularly important in these fields where great variety of surface textures of pāhoehoe and ʻaʻā lavas as well as inter-edifice mixed arid terrestrial sedimentation occur. In addition, geological attributes of volcanic edifices such as geochemistry, petrological information and pyroclastic successions ordered in their volcanic hazard perspective been used to refine diversity elements. The utilization of remote sensing satellite data, high resolution terrain analysis methods and collating information on geoheritage elements such as archaeology, geocultural aspects and types of geotourism utilities are also considered. Combination of these data to the most up to date geological mapping information clearly showed the correlation of geodiversity with the maturity and longevity of volcanism of the studied volcanic field fields.

Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that fo... more Monogenetic volcanic fields are group of short lived and small, typically mafic volcanoes that form clusters, alignments or distributed randomly over large territory. The geoheritage values of such volcanic fields are difficult to characterize due to the scale problem they pose within the commonly magnitudes larger regions than their footprints. Monogenetic volcanoes are defined by their simple geological architecture. Their geological and geomorphological diversity of them not detectable easily within the common spatial scale diversity estimates performed mostly with an aim to quickly identify geological and geomorphological diversity hotspots. Here we explore this paradox situation from three distinct, nearby large monogenetic volcanic fields – Harrat Rahat, Harrat Khaybar and Harrat Lunayyir - each considered to be an active volcanic system in the western Arabian Peninsula. Historic records documented 52 days eruption in 1256 CE nearby Madinah City at Harrat Rahat. Archaeological...

The Mio/Pliocene Bakony-Balaton Highland Volcanic Field includes more than 100 alkaline basaltic ... more The Mio/Pliocene Bakony-Balaton Highland Volcanic Field includes more than 100 alkaline basaltic volcanoes. The maar complex Fekete-hegy is volumetrically one of the largest volcanic complexes of the BBHVF. Fekete-hegy forms a lava-capped butte in the central part of the volcanic field with basaltic lava flows overlying pyroclastic units. At least 3 vents have been identified at Fekete-hegy. Every single vent started initially with phreatomagmatic activity, interpreted on the basis of the presence of chilled, angular, blocky, slightly to moderately vesicular sideromelane glass shards, accidental lithic clasts and bedding characteristics of the pyroclastic units. Fekete-hegy is considered to be a large nested phreatomagmatic volcanic vent system,

International journal of geoheritage and parks, Mar 1, 2022

International Journal of Earth Sciences, Nov 1, 2001

... Facies characteristics and distribution allow us to (a) substantiate small-sized calderas, th... more ... Facies characteristics and distribution allow us to (a) substantiate small-sized calderas, the erodedrims or proximal palaeoslopes of which have been preserved by volcaniclastic breccias (mostly debris-flow depos-its); (b) reconstruct a well-developed volcaniclastic apron ...

Scientific Reports

During Earth’s history, geosphere-biosphere interactions were often determined by momentary, cata... more During Earth’s history, geosphere-biosphere interactions were often determined by momentary, catastrophic changes such as large explosive volcanic eruptions. The Miocene ignimbrite flare-up in the Pannonian Basin, which is located along a complex convergent plate boundary between Europe and Africa, provides a superb example of this interaction. In North Hungary, the famous Ipolytarnóc Fossil Site, often referred to as “ancient Pompeii”, records a snapshot of rich Early Miocene life buried under thick ignimbrite cover. Here, we use a multi-technique approach to constrain the successive phases of a catastrophic silicic eruption (VEI ≥ 7) dated at 17.2 Ma. An event-scale reconstruction shows that the initial PDC phase was phreatomagmatic, affecting ≥ 1500 km2 and causing the destruction of an interfingering terrestrial–intertidal environment at Ipolytarnóc. This was followed by pumice fall, and finally the emplacement of up to 40 m-thick ignimbrite that completely buried the site. Howe...

Geologica Carpathica, 2021

Detailed investigation of a Lower Miocene Plinian pyroclastic sequence that crops out in the Bükk... more Detailed investigation of a Lower Miocene Plinian pyroclastic sequence that crops out in the Bükk Foreland Volcanic Area (BFVA) in Northern Hungary is presented here. The studied eruptive products are part of a ca. 50 metres thick pyroclastic succession comprising of a basal ignimbrite that is covered by stratified pyroclastic unit including a topmost ignimbrite (Mangó ignimbrite unit, part of the Lower Pyroclastic Complex). The investigated pyroclastic unit is part of the Mangó ignimbrite unit, and consists of a pyroclastic fallout deposit, a ground-surge deposit, and an ignimbrite, all indicating a complete Plinian eruption phase. This pyroclastic succession has been identified in three locations, which crops out along a ~20 km long, SW-NE transect in the BFVA (two in the western, and one in the eastern part). The pyroclastic rocks in these sites are correlated well on the basis of the lithologically and texturally similar layers and their identical field volcanological properties. The correlation is also supported by the paleomagnetic signature of the two ignimbrites (upper ignimbrite-declination: 275-302°, lower ignimbrite with overprint magnetization-declination: 320-334°). The paleomagnetic directions of the stratigraphically upper ignimbrite suggest that this sequence belongs to the oldest known pyroclastic rock assemblages of the BFVA (Lower Pyroclastic Complex, deposited between 18.5 and 21 Ma according to previously published K/Ar dating results in good agreement with paleomagnetic measurements). Based on proximal-to-distal variations in the grain size of the pyroclastic fallout deposit (with maximal thickness is 71 cm), a potential source region to the east (or northeast, or southeast) of the BFVA has been inferred in a relatively close distance (~5-15 km). The (north)eastward-located source region is also supported by comparison of the characteristics of the studied fallout deposit with the spatial distribution of selected Plinian fallout tephra from worldwide examples using their digitalized isopach maps.

Journal of Volcanology and Geothermal Research, 2020

A Middle Miocene,~8 m thick pyroclastic succession, reported from the Bükk Foreland Volcanic Area... more A Middle Miocene,~8 m thick pyroclastic succession, reported from the Bükk Foreland Volcanic Area (BFVA) in Northern Hungary (Central Europe) specified here as the Jató Member, was produced by silicic phreatomagmatism (Phreatoplinian sensu lato). Two well-preserved outcrops~8 km apart and inferred to be within~10-50 km from source represent the discontinuously exposed, layered, paleosol-bounded, phreatomagmatic Jató Member. They show an identical phenocrystal assemblage of feldspar, biotite and amphibole without weathered zones or signs of erosion, that suggest deposition in one eruption phase lasting hours to months. The succession contains three subunits: 1) subunit A, 1.8 m thick, a series of well-sorted fine to coarse ash or lapilli tuff layers with constant thickness; 2) subunit B, 2.1 m thick, a series of normal-graded layers with an upper fine-grained zone containing abundant ash aggregates with a coarser-grained core and distinctively finer-grained outer rim; 3) subunit C, 4.5 m thick, a massive, poorly to well-sorted coarse ash with gas escape structures and ash aggregates at its base. The upward change of these lithofacies implies an initially sustained dry fallout-dominated deposition of ash and pumice lapilli resulting in subunit A. Subsequently, multiple wet and dilute Pyroclastic Density Currents (PDCs) dispersed subunits B and C. The general abundance of PDC-related ash aggregates in the middle-upper part of the succession (particularly in subunit B), and the transformation of a fall-dominated to a collapsing depositional regime producing wet dilute PDCs, imply the increasing influence of water during the eruption (Phreatoplinian sensu lato). The presence of water is related to an epicontinental sea during Middle to Late Miocene in the Carpatho-Pannonian region. The transition from an initial dry magmatic phase generated fallout activity followed by the emplacement of wet PDCs' rich in ash aggregates, when external water infiltrated from a surrounding lake or sea water entered the vent.

Bulletin of Volcanology, 2017

Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the... more Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the South Atlantic. Volcanic activity since the eighteenth century, along with the latest volcanic unrest episodes in the twentieth and twenty first centuries, demonstrates that the volcanic system is still active and that future eruptions are likely. Despite its remote location, the South Shetland Islands are an important touristic destination during the austral summer. In addition, they host several research stations and three summer field camps. Deception Island is characterised by a Quaternary caldera system with a postcaldera succession and is considered to be part of an active, dispersed (monogenetic), volcanic field. Historical postcaldera volcanism on Deception Island involves monogenetic smallvolume (VEI 2-3) eruptions such forming cones and various types of hydrovolcanic edifices. The scientific stations on the island were destroyed, or severely damaged, during the eruptions in 1967, 1969, and 1970 mainly due to explosive activity triggered by the interaction of rising (or erupting) magma with surface water, shallow groundwater, and ice. We conducted a detailed revision (field petrology and geochemistry) of the historical hydrovolcanic postcaldera eruptions of Deception Island with the aim to understand the dynamics of magmawater interaction, as well as characterise the most likely eruptive scenarios from future eruptions. We specifically focused on the Crimson Hill (estimated age between 1825 and 1829), and Kroner Lake (estimated age between 1829 and 1912) eruptions and 1967, 1969, and 1970 events by describing the eruption mechanisms related to the island's hydrovolcanic activity. Data suggest that the main hazards posed by volcanism on the island are due to fallout, ballistic blocks and bombs, and subordinate, dilute PDCs. In addition, Deception Island can be divided into five areas of expected activity due to magmawater interaction, providing additional data for correct hazard assessment on the island.

European Journal of Mineralogy, 2021

Structural hydroxyl content of volcanic quartz phenocrysts was investigated with unpolarized Four... more Structural hydroxyl content of volcanic quartz phenocrysts was investigated with unpolarized Fouriertransform infrared spectroscopy. The phenocrysts originated from five pyroclastic fallout deposits from the Bükk Foreland Volcanic Area (BFVA), Hungary, and two from the AD 1314 Kaharoa eruption (KH eruption), Okataina Volcanic Complex (Taupo Volcanic Zone), New Zealand. All investigated quartz populations contain structural hydroxyl content in a narrow range with an average of 9.3 (±1.7) wt ppm. The earlier correlated horizons in the BFVA had the same average structural hydroxyl content (within uncertainty). Thus, it can be concluded that the structural hydroxyl content does not depend on the geographical distance of outcrops of the same units or the temperature or type of the covering deposit. The rare outlier values and similar structural hydroxyl contents show that the fallout horizons cooled fast enough to retain their original structural hydroxyl content. The similarity of the structural hydroxyl contents may be the result of similar P , T , and x (most importantly H 2 O and the availability of other monovalent cations) conditions in the magmatic plumbing system just before eruption. Therefore, we envisage common physical-chemical conditions, which set the structural hydroxyl content in the quartz phenocrysts and, consequently, the water content of the host magma (∼ 5.5 wt %-7 wt % H 2 O) in a relatively narrow range close to water saturation.

IECG 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

IECG 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

IECG 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Geographies

Hydrology is one of the most influential elements of geodiversity, where geology and geomorpholog... more Hydrology is one of the most influential elements of geodiversity, where geology and geomorphology stand as the main values of abiotic nature. Hydrological erosion created by river systems destructing rock formations (eluvial process) from streams’ sources and then transporting and redepositing (alluvial process) the rock debris into the main river channels, make it an ongoing transformation element of the abiotic environment along channel networks. Hence, this manuscript demonstrates the influence of hydrological elements on geosite recognition, specifically for qualitative–quantitative assessment of geodiversity, which is based on a combination of geological and geomorphological values. In this concept, a stream system will be treated as an additional element. The basement area of the Manawatu Region has been utilized as the territory for the research of hydrological assessment. The region is in the southern part of the North Island of New Zealand and has relatively low geological...

Geoheritage, Geoparks and Geotourism

Geotourism is a relatively recent concept and a novel kind of tourism, which has acquired a signi... more Geotourism is a relatively recent concept and a novel kind of tourism, which has acquired a significant boom in the last decades, associated with the creation and consolidation of the UNESCO global geoparks network. There are two approaches to geotourism, one geological and the other geographical, much more global and inclusive of the elements of the natural and cultural heritage. In this chapter, we have chosen to use the geographical approach of geotourism, to apply it to the El Hierro global geopark and diversify the island's tourism, traditionally focused on diving and hiking, through geoforms (volcanic and non-volcanic), and its link with cultural heritage. For this, the most representative, preserved and accessible geomorphosites in the geopark have been identified, inventoried and selected, which can be visited through volcano tourism georoutes. To do this, a route is proposed in the El Faro-Orchilla geozone (GZH-07) of the geopark, since it is one of the best examples of...

Geoheritage, 2017

Harrat Khaybar is one of the most extensive of about 15 volcanic fields located in the western ma... more Harrat Khaybar is one of the most extensive of about 15 volcanic fields located in the western margin of the Arabian Peninsula. Most of these fields are located in the Kingdom of Saudi Arabia about 100-150 km inland from the Red Sea. The volcanic area is located near the culturally and religiously important city of Al Madinah. The field hosts monogenetic volcanoes such as scoria cones, tuff rings, spatter cones and extensive lava flow fields. It also contains several silicic lava domes and associated block-and-ash fans whose deposits fill intercone regions. Some of the field's volcanoes are inferred to have been erupted as recently as about 1000 AD, based on historic documents and geomorphologic evidence. There are no data available to directly support or better constrain the timing of the latest eruptions of the field. The area is also one of the highest regions of Saudi Arabia with a plateau at about 1500 m above sea level, topped by Jabal Abyad (2093 m) and Jabal Quidr (2022 m) volcanoes. Due to the elevation, Harrat Khaybar has a cold arid climate with a unique ecosystem and landscape. The region's high aesthetic value is derived from the bright white colour of several of its volcanoes which are dominantly rhyolitic ash. These edifices are strikingly different from the dark-coloured lava fields (harrats) of Arabia. Based on appearance, Harrat Khaybar has geoheritage value and could be a major geoconservation and geoeducation region of Arabia. Geological research in the region started only recently and is restricted to geological mapping and geochemical studies. Interest has recently increased because of the recognition of the field's potential volcanic hazards. There is a push to establish a geoheritage inventory of Harrat Khaybar with the aim of assessing the geoheritage framework of the region and developing more geotourism, geoeducational programmes and a geopark. Key volcanic geotopes and their geosites provide unique opportunities for a stand-alone geopark offering geoeducation and geotourism programmes in the region. The concept has been proposed to the geoheritage resource management of Harrat Rahat just south of Harrat Khaybar and Al Madinah City and could serve as a link between the two historically active volcanic fields located near Al Madinah.