K-Ar ages of dacitic lava domes of Rishiri volcano, northern Hokkaido.

The Triades-Galana Pb-Zn-Ag-Au mineralization is a shallow-submarine epithermal mineralization located along NE-trending faults, NW Milos Island, Greece. It is hosted in 2.5–1.4 Ma pyroclastic rocks and is genetically related to andesitic/dacitic lava domes. Mineralization occurs as breccias, quartz-barite galena veins and stockworks within sericite-adularia or kaolinitic altered rocks. The mineralization is enriched in Mo, W and base- and precious metals (e.g. Pb, Zn, Ag) similarly to the neighbouring mineralization at Kondaros-Katsimouti and Vani, indicating common source of metals from a deep buried granitoid feeding western Milos with metals and volatiles. Paragenetic relations suggest early deposition of pyrite, followed by famatinite, polybasite and Ag-rich tetrahedrite, and then by enargite, suggesting fluctuating sulfidation states during ore formation. The evolution from Sb- towards As-rich enrichment indicate a renewed magmatic pulse (probably in the form of magmatic gases) in the hydrothermal system. Silver is present in the structure of sulfosalts (up to 66.2 wt.% in polybasite-pearceite, 15.1 wt.% in tetrahedrite and 60 wt. % in pyrargyrite). Boiling processes (as evidenced by the presence of adularia accompanying intermediate-sulfidation ore) and mixing with seawater (presence of hypogene lead chlorides) and contemporaneous uplift, contributed to ore formation.

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The stability and collapse of lava domes: insight from UAS-derived 4D structure and slope stability models

10.1002/essoar.10501992.1 ◽

2020 ◽

Author(s):

Brett Carr ◽

Einat Lev ◽

Loÿc Vanderkluysen ◽

Danielle Moyer ◽

Gayatri Marliyani ◽

...

Keyword(s):

Slope Stability ◽

Lava Domes ◽

The Stability

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The hydrothermal alteration of cooling lava domes

Bulletin of Volcanology ◽

10.1007/s00445-015-0986-z ◽

2015 ◽

Vol 77 (12) ◽

Cited By ~ 26

Author(s):

Jessica L. Ball ◽

Philip H. Stauffer ◽

Eliza S. Calder ◽

Greg A. Valentine

Keyword(s):

Hydrothermal Alteration ◽

Lava Domes

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Effusive Monogenetic Volcanism

10.5772/intechopen.94387 ◽

2020 ◽

Author(s):

Hugo Murcia ◽

Károly Németh

Keyword(s):

Classification Scheme ◽

Wide Spectrum ◽

Lava Flows ◽

Magma Ascent ◽

Explosive Activity ◽

Monogenetic Volcanism ◽

Future Studies ◽

Lava Domes ◽

Tectonic Settings ◽

Monogenetic Volcanoes

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.

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Influence of conduit flow mechanics on magma rheology and the growth style of lava domes

Geophysical Journal International ◽

10.1093/gji/ggy073 ◽

2018 ◽

Vol 213 (3) ◽

pp. 1768-1784 ◽

Cited By ~ 7

Author(s):

Taha Husain ◽

Derek Elsworth ◽

Barry Voight ◽

Glen Mattioli ◽

Pamela Jansma

Keyword(s):

Conduit Flow ◽

Lava Domes ◽

Magma Rheology

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Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption

Natural Hazards and Earth System Science ◽

10.5194/nhess-18-3267-2018 ◽

2018 ◽

Vol 18 (12) ◽

pp. 3267-3281 ◽

Cited By ~ 4

Author(s):

Herlan Darmawan ◽

Thomas R. Walter ◽

Valentin R. Troll ◽

Agus Budi-Santoso

Keyword(s):

Gravitational Collapse ◽

Hydrothermal Alteration ◽

Factor Of Safety ◽

Lava Dome ◽

Pyroclastic Flows ◽

Infrared Images ◽

Merapi Volcano ◽

Rainfall Events ◽

Thermal Infrared Images ◽

Lava Domes

Abstract. Lava domes are subjected to structural weakening that can lead to gravitational collapse and produce pyroclastic flows that may travel up to several kilometers from a volcano's summit. At Merapi volcano, Indonesia, pyroclastic flows are a major hazard, frequently causing high numbers of casualties. After the Volcanic Explosivity Index 4 eruption in 2010, a new lava dome developed on Merapi volcano and was structurally destabilized by six steam-driven explosions between 2012 and 2014. Previous studies revealed that the explosions produced elongated open fissures and a delineated block in the southern dome sector. Here, we investigated the geomorphology, structures, thermal fingerprint, alteration mapping and hazard potential of the Merapi lava dome by using drone-based geomorphologic data and forward-looking thermal infrared images. The block on the southern dome of Merapi is delineated by a horseshoe-shaped structure with a maximum depth of 8 m and it is located on the unbuttressed southern steep flank. We identify intense thermal, fumarole and hydrothermal alteration activities along this horseshoe-shaped structure. We conjecture that hydrothermal alteration may weaken the horseshoe-shaped structure, which then may develop into a failure plane that can lead to gravitational collapse. To test this instability hypothesis, we calculated the factor of safety and ran a numerical model of block-and-ash flow using Titan2D. Results of the factor of safety analysis confirm that intense rainfall events may reduce the internal friction and thus gradually destabilize the dome. The titan2D model suggests that a hypothetical gravitational collapse of the delineated unstable dome sector may travel southward for up to 4 km. This study highlights the relevance of gradual structural weakening of lava domes, which can influence the development fumaroles and hydrothermal alteration activities of cooling lava domes for years after initial emplacement.

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Dome instability at Merapi volcano identified by drone photogrammetry and numerical modeling

10.5194/nhess-2018-120 ◽

2018 ◽

Cited By ~ 1

Author(s):

Herlan Darmawan ◽

Thomas R. Walter ◽

Valentin R. Troll ◽

Agus Budi-Santoso

Keyword(s):

Gravitational Collapse ◽

Gravitational Instability ◽

Pyroclastic Flows ◽

Fumarolic Activity ◽

Structural Development ◽

Merapi Volcano ◽

Rainfall Events ◽

Lava Domes ◽

Eventual Collapse ◽

Southern Flank

Abstract. The growth of lava domes may cause gradual oversteepening and can lead to gravitational instability and eventual collapse to produce pyroclastic flows that may travel up to several kilometers from a volcano’s summit. At Merapi volcano, Indonesia, pyroclastic flows are a major hazard, frequently involving high numbers of casualties. After the VEI 4 eruption in 2010, a new lava dome developed on Merapi volcano and was structurally destabilized by six steam-driven explosions between 2012 and 2014. Previous studies revealed that the explosions produced elongated open fissures and a structurally delineated sector at the southern part of the dome complex. Here, we investigate the geometry, thermal fingerprint, and hazard potential of the delineated unstable dome sector by integrating drone-based geomorphologic data and forward-looking thermal infrared images. The sector located on the un-buttressed southern flank of the steep dome that is delineated by a horseshoe-shaped structure and we identify intense thermal and fumarolic activity along this structure, hosting the high temperatures of the current dome. From the morphology, structures, and thermal mapping, we conjecture that the horseshoe shaped structure may develop into a failure plane that could lead to gravitational collapse of the unstable dome sector. To further elaborate on this instability hypothesis, we calculate the factor of safety, and run a numerical model of the resulting block and ash flows depositional area using Titan2D. Results of factor of the safety analysis confirm dome instability, especially during typical rainfall events. The titan2D model suggests that a hypothetical gravitational collapse of the delineated unstable dome sector would travel southward for up to 4 km distance. This study highlights the relevance of structural development of lava domes, which can affect hazards even years after dome emplacement, and influences the development of thermal and fumarolic activity of cooling lava domes.

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The rebirth and evolution of Bezymianny volcano, Kamchatka after the 1956 sector collapse

Communications Earth & Environment ◽

10.1038/s43247-020-00014-5 ◽

2020 ◽

Vol 1 (1) ◽

Author(s):

Alina V. Shevchenko ◽

Viktor N. Dvigalo ◽

Thomas R. Walter ◽

Rene Mania ◽

Francesco Maccaferri ◽

...

Keyword(s):

Growth Rate ◽

Numerical Modeling ◽

Volcanic Activity ◽

Summit Crater ◽

Sector Collapse ◽

Average Growth Rate ◽

Average Growth ◽

Bezymianny Volcano ◽

Lava Domes

Abstract Continued post-collapse volcanic activity can cause the rise of a new edifice. However, details of such edifice rebirth have not been documented yet. Here, we present 7-decade-long photogrammetric data for Bezymianny volcano, Kamchatka, showing its evolution after the 1956 sector collapse. Edifice rebirth started with two lava domes originating at distinct vents ~400 m apart. After 2 decades, activity became more effusive with vents migrating within ~200 m distance. After 5 decades, the activity focused on a single vent to develop a stratocone with a summit crater. We determine a long-term average growth rate of 26,400 m3/day, allowing us to estimate the regain of the pre-collapse size within the next 15 years. Numerical modeling explains the gradual vents focusing to be associated with loading changes, affecting magma pathways at depth. This work thus sheds light on the complex regrowth process following a sector collapse, with implications for regrowing volcanoes elsewhere.

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The mechanics of harmonic gas pressurization and failure of lava domes

Geophysical Journal International ◽

10.1111/j.1365-246x.2001.00370.x ◽

2001 ◽

Vol 145 (1) ◽

pp. 187-198 ◽

Cited By ~ 23

Author(s):

Derek Elsworth ◽

Barry Voight

Keyword(s):

Lava Domes

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