Károly Németh

By Károly Németh

Part of the book: Updates in Volcanology

By Gábor Kereszturi and Károly Németh

Part of the book: Updates in Volcanology

By Boris Chako Tchamabé, Gabor Kereszturi, Karoly Németh and Gerardo Carrasco‐Núñez

The increasing number of field investigations and various controlled benchtop and large‐scale experiments have permitted the evaluation of a large number of processes involved in the formation of maar‐diatreme volcanoes, the second most common type of small‐volume subaerial volcanoes on Earth. A maar‐diatreme volcano is recognized by a volcanic crater that is cut into country rocks and surrounded by a low‐height ejecta rim composed of pyroclastic deposits of few meters to up to 200 m thick above the syn‐eruptive surface level. The craters vary from 0.1 km to up to 5 km wide and vary in depth from a few dozen meters to up to 300 m deep. Their irregular morphology reflects the simple or complex volcanic and cratering processes involved in their formation. The simplicity or complexity of the crater or the entire maar itself is usually observed in the stratigraphy of the surrounding ejecta rings. The latter are composed of sequences of successive alternating and contrastingly bedded phreatomagmatic‐derived dilute pyroclastic density currents (PDC) and fallout depositions, with occasional interbedded Strombolian‐derived spatter materials or scoria fall units, exemplifying the changes in the eruptive styles during the formation of the volcano. The entire stratigraphic sequence might be preserved as a single eruptive package (small or very thick) in which there is no stratigraphic gap or significant discordance indicative of a potential break during the eruption. A maar with a single eruptive deposit is quantified as monogenetic maar, meaning that it was formed by a single eruptive vent from which only a small and ephemeral magma erupted over a short period of time. The stratigraphy may also display several packages of deposits separated either by contrasting discordance surfaces or paleosoils, which reflect multiple phases or episodes of eruptions within the same maar. Such maars are characterized as complex polycyclic maars if the length of time between the eruptive events is relatively short (days to years). For greater length of time (thousands to millions of years), the complex maar will be quantified as polygenetic. These common depositional breaks interpreted as signs of temporal interruption of the eruptions for various timescales also indicate deep magma system processes; hence magmas of different types might erupt during the formation of both simple and complex maars. The feeding dikes can interact with groundwater and form closely distributed small craters. The latter can coalesce to form a final crater with various shapes depending on the distance between them. This observation indicates the significant role of the magmatic plumbing system on the formation and growth of complex and polygenetic maar‐diatreme volcanoes.

Part of the book: Updates in Volcanology

By Károly Németh

Part of the book: Updates in Volcanology

By Boxin Li, Károly Németh, Julie Palmer, Alan Palmer, Jing Wu, Jonathan Procter and Jiaqi Liu

The Arxan-Chaihe Volcanic Field, Inner Mongolia, NE China is a Pleistocene to Recent volcanic field still considered to be active. In this chapter we provide an update of current volcanological research conducted in the last four years to describe the volcanic architecture of the identified vents, their eruptive history and potential volcanic hazards. Here we provide an evidence-based summary of the most common volcanic eruption styles and types the field experienced in its evolution. The volcanic field is strongly controlled by older structural elements of the region. Hence most of the volcanoes of the field are fissure-controlled, fissure-aligned and erupted in Hawaiian to Strombolian-style creating lava spatter and scoria cone cone chains. One of the largest and most complex volcano of the field (Tongxin) experienced a violent phreatomagmatic explosive phase creating a maar in an intra-mountain basin, while the youngest known eruptions formed a triple vent set (Yanshan) that reached violent Strombolian phases and created an extensive ash and lapilli plains in the surrounding areas. This complex vent system also emitted voluminous lava flows that change the landscape by damming fluival networks, providing a volcanological paradise for the recently established Arxan UNESCO GLobal Geopark.

Part of the book: Updates in Volcanology

By Hugo Murcia and Károly Németh

The study of monogenetic volcanism around Earth is rapidly growing due to the increasing recognition of monogenetic volcanic edifices in different tectonic settings. Far from the idea that this type of volcanism is both typically mafic and characteristic from intraplate environments, it occurs in a wide spectrum of composition and geological settings. This volcanism is widely known by the distinctive pyroclastic cones that represent both magmatic and phreatomagmatic explosive activity; they are known as scoria or spatter cones, tuff cones, tuff rings, maars and maar-diatremes. These cones are commonly associated with lava domes and usually accompanied by lava flows as part of their effusive eruptive phases. In spite of this, isolated effusive monogenetic emissions also appear around Earth’s surface. However, these isolated emissions are not habitually considered within the classification scheme of monogenetic volcanoes. Along with this, many of these effusive volcanoes also contrast with the belief that this volcanism is indicative of rapidly magma ascent from the asthenosphere, as many of the products are strongly evolved reflecting differentiation linked to stagnation during ascent. This has led to the understanding that the asthenosphere is not always the place that directly gives rise to the magma batches and rather, they detach from a crustal melt storage. This chapter introduces four singular effusive monogenetic volcanoes as part of the volcanic geoforms, highlights the fact that monogenetic volcanic fields can also be associated with crustal reservoirs, and outlines the processes that should occur to differentiate the magma before it is released as intermediate and acidic in composition. This chapter also provides an overview of this particular volcanism worldwide and contributes to the monogenetic comprehension for future studies.

Part of the book: Updates in Volcanology

By Gabriel Ureta, Károly Németh, Felipe Aguilera, Matias Vilches, Mauricio Aguilera, Ivana Torres, José Pablo Sepúlveda, Alexander Scheinost and Rodrigo González

Monogenetic volcanism produces small eruptive volumes with short eruption history, different chemical compositions, and relatively simple conduit. The Central Volcanic Zone of the Andes is internationally known as a natural laboratory to study volcanism, where mafic and felsic products are present. In this contribution, the spectrum of architectures, range of eruptive styles, lithological features, and different magmatic processes of the mafic and felsic monogenetic Neogene to Quaternary volcanoes from the Central Volcanic Zone of the Andes in northern Chile (18°S-28°S) are described. The major volcanic activity occurred during the Pleistocene, where the most abundant activity corresponds to effusive and Strombolian eruptions. This volcanism is characterized by external (e.g., magma reservoirs or groundwater availability) and internal (e.g., magma ascent rate or interaction en-route to the surface) conditions, which determine the changes in eruptive style, lithofacies, and magmatic processes involved in the formation of monogenetic volcanoes.

Part of the book: Updates in Volcanology

By Károly Németh

Part of the book: Updates in Volcanology

By Bo’xin Li, Károly Németh, Julie Palmer, Alan Palmer, Vladyslav Zakharovskyi and Ilmars Gravis

Fissure eruption is the most prominent type of Pleistocene to Holocene volcanism in Arxan-Chaihe Volcanic Field recording vent migration along fissures. This research is examined Sentinel Satellite Images to outline the youngest lava flows in the region in conjunction with field observations. Also, GIS-based analyses were performed with the aim to calculate the volumes of lava flows to determine the length of the lava flow emissions. Topographic cross sections and various geomorphological parameters (e.g., geomorphon and topographic position index) were used to reconstruct the pre-eruptive geomorphology of the region to simulate lava flow inundation using Q-LAVHA plug in the QGIS package. Pre-eruptive topography was created, and various simulations were used to obtain the best-fit lava inundation. This process yielded to estimate an average of 5 m lava flow thickness. The same parameters of the lava flow simulations were used to run on the post-eruptive topography to simulate future lava flow inundation. Results showed that the lava flows best simulate if they emitted along a NE–SE trending fissure between two young vent zones or in an extensive elongated area following the NW–SE trending valley axis initiated from the Yanshan vents.

Part of the book: Updates in Volcanology

By Károly Németh

Part of the book: Updates in Volcanology