Pyroclastic Ash Research Articles

Solfataric Alteration at the South Sulfur Bank, Kilauea, Hawaii, as a Mechanism for Formation of Sulfates, Phyllosilicates, and Silica on Mars

Abstract Solfataric alteration at the South Sulfur Bank of the former Kilauea caldera produced opal, Mg- and Fe-rich smectites, gypsum, and jarosite through silica replacement of pyroclastic Keanakako’i ash and leaching of basaltic lavas. This site on the island of Hawaii serves as an analog for formation of several minerals found in altered deposits on Mars. Two distinct alteration environments were characterized in this study including a light-toned, high-silica, friable outcrop adjacent to the vents, and a bedded outcrop containing alternating orange/tan layers composed of smectite, gypsum, jarosite, hydrated silica, and poorly crystalline ferric oxide phases. This banded unit likely represents deposition of pyroclastic material with variations in chemistry over time that was subsequently altered via moderate hydrothermal and pedogenic processes and leaching of basaltic caprock to enhance the Si, Al, Mg, Fe, and Ca in the altered layers. In the light-toned, friable materials closest to the vents along the base of the outcrop glassy fragments were extensively altered to opal-A plus anatase. Lab measurements of samples returned from the field were conducted to replicate recent instruments at Mars and provide further characterization of the samples. These include elemental analyses, sample texture, XRD, SEM, VNIR/mid-IR reflectance spectroscopy, TIR emittance spectroscopy, and Mössbauer spectroscopy. Variations in the chemistry and mineralogy of these samples are consistent with alteration through hydrothermal processes as well as brines that may have formed through rain interacting with sulfuric fumes. Silica is present in all altered samples and the friable pyroclastic ash material with the strongest alteration contains up to 80 wt.% SiO2. Sulfate mineralization occurred at the South Sulfur Bank through fumarolic action from vents and likely included solfataric alteration from sulfuric gases and steam, as well as oxidation of sulfides in the basaltic caprock. Gypsum and jarosite are typically present in different layers of the altered wall, likely because they require different cations and pH regimes. The presence of both jarosite and gypsum in some samples implies high sulfate concentrations and the availability of both Ca2+ and Fe3+ cations in a brine percolating through the altered ash. Pedogenic conditions are more consistent with the observed Mg-smectites and gypsum in the tan layers, while jarosite and nontronite likely formed under more acidic conditions in the darker orange layers. Assemblages of smectite, Ca-sulfates, and jarosite similar to the banded orange/tan unit in our study are observed on Mars at Gale crater, Noctis Labyrinthus, and Mawrth Vallis, while high-silica outcrops have been identified in parts of Gusev crater, Gale crater, and Nili Patera on Mars.

Estimating Water Depths of Upper Cretaceous Pilot Knob Volcanic-Related Strata: The McKown and Pflugerville Formations and Pyroclastic Ash at the Lower Falls Section, McKinney Falls State Park, Austin, Texas

The McKown and Pflugerville formations and pyroclastic ash beds at McKinney Falls State Park in Austin, Texas, are closely associated with the Lower Campanian Pilot Knob volcano. This volcano is one of over 400 known Late Cretaceous volcanoes in the Balcones Igneous Province. The center of the Pilot Knob volcano is 1.5 mi (2.4 km) southeast of the McKinney Falls State Park. The McKown strata at the Lower McKinney Falls within the park have been interpreted as a beach complex deposited on the shallow-water north flank of the Pilot Knob volcano. Previous researchers based this interpretation on the presence of a shallow-water macrobiota and the coarse-grain texture of the limestones. However, a new investigation of the Lower McKinney Falls outcrops has developed evidence that the McKown limestones were deposited in deeper water (150 to 300 ft [50 to 100 m]) on the flank of the Pilot Knob volcano by gravity-flow processes that formed carbonate debrites and hyperconcentrated-density-flow deposits. The new evidence comes from micropetrography data that demonstrates the matrix of the packstones is dominated by coccolith hash and that there are calcispheres and planktic foraminifers in both the packstones and grainstones. The composition of the McKown limestone is a mixture of shallow- and deep-water biotas, indicating the shallow-water biota were resedimented into a deeper-water setting. Also, McKown bedding relationships with the pyroclastic ash beds below indicates deposition in a low-energy setting. The pyroclastic volcanic beds contain coccoliths and are interpreted as being deposited in a deeper-water, lower-energy setting. Also, the Pflugerville limestone section is very similar to the McKown limestone section and evidence indicates Pflugerville limestones were not deposited in a shallow-water setting. The evidence produced by the present investigation substantiates that the carbonate strata at the Lower McKinney Falls were not deposited in a beach or shoaling complex but were deposited on the deeper flank of the Pilot Knob volcano. The concepts developed by this investigation of these deeper-water carbonates can be applied to interpreting the depositional setting of other carbonates associated with the Balcones Igneous Province volcanic mounds.

PALYNOFACIES AND ORGANIC GEOCHEMISTRY OF LACUSTRINE SOURCE ROCKS: THE POTRERILLOS – CACHEUTA SOURCE ROCK SYSTEM IN THE TRIASSIC CUYO BASIN, WEST‐CENTRAL ARGENTINA

This study presents an integrated investigation of the Upper Triassic Potrerillos – Cacheuta lacustrine source rock in the Cuyo Basin of western Argentina. Data came from palynofacies analyses, organic petrography, Rock‐Eval pyrolysis and mineralogical studies based on X‐ray diffraction analyses. An 80 m thick outcrop section was studied and is interpreted to represent the transition from shallow‐lacustrine sediments influenced by fluvial discharges (uppermost Potrerillos Formation) to the deposits of a deep, permanent lake (Cacheuta Formation). Three palynofacies were defined. Palynofacies I is characterized by shallowing‐upward cycles with abundant woody material, and was deposited under an oxic, disturbed water column. Palynofacies II and III occur in laminated shales rich in amorphous organic matter (AOM) and freshwater algal material (Botryococcus) respectively, which were deposited under oxygen‐depleted conditions. In general, the detrital material present suggests an input derived from fluvial discharges; however, interbedded tuffs altered to analcime and smectite suggest the transformation of vitric material in pyroclastic ash under saline to alkaline water conditions. Kerogen Types II/III and III with high total organic carbon values indicate a moderate oil‐ and gas‐prone source rock whose thermal maturity varies from immature to the early oil window (Tmax: 430‐438 °C; vitrinite reflectance: 0.59‐0.67 % VRo; and thermal alteration index: 2‐2+).This study demonstrates the importance of palynofacies analyses for the interpretation of depositional changes and associated controls in lacustrine shale successions. When integrated with data from organic geochemistry, palynofacies analysis is an important tool in the evaluation of a source rock's thermal maturity and hydrocarbon generation potential.

Micronutrient Mineral and Nutrient Content of Volcanic Soils and Creeks from the Montserrat Soufriere Hills Volcano. Nature’s Fertilizer: Mineral Nutrient Content of Volcanic Soils

Agricultural soils and potable water supplies provide a major source of minerals known to be essential for plant and animal health. After several hundred years of relative quiescence, the Soufriere Hills Volcano of Montserrat roared back to life in 1995 through 1997, wreaking severe havoc and severe damage to the geography and ecosystems and serious immediate and chronic health risks to the remaining inhabitants of the Island. The pyroclastic ash flow reached temperatures of 1500 °F and progressed down the hillsides at speeds of 80 mph, causing incineration and virtual destruction of everything in its path, while the gaseous and particulate laden plume reached altitudes of 7 miles (10.7 km), impacting air quality and aircraft navigation in the region. A total of 19 individuals became entrapped in the lava flow, and perished quickly as a direct result of the volcanic eruption. Volcanic soils derive from deeper layers of the earths surfaces and are notoriously rich in mineral nutrients representative of those deep mineral deposits. While virtually all combustible objects in the path of the raging ash flow become incinerated within minutes, the aftermath of the eruptions delivers the mineral rich constituents over a wide swath of the surrounding geography often reaching miles from the volcanic origin. Soils and consumable water sources are well known to provide a reliable community source of essential minerals in human nutrition, and in their chronic absence, numerous pathologic sequela may develop. To determine the mineral content of surrounding surface soils, samples of surface ash layers and nearby creeks were obtained from 7 regions and 3 free-flowing creeks and subjected mineral analysis. The surface ash specimens contained abundant amounts of the nutrients Iron, Calcium, Sodium, Magnesium, Sulfur, and non-nutrient Aluminum, intermediate amounts of potassium, Phosphorous, and Manganese, and small amounts of Boron, Copper and Zinc. Creek water runoff originating from higher elevations was consistently acidic with a healthy mean pH of 5.1, and contained smaller proportions of the same minerals, reflective of their relative effective solubility in the acidic water. Thus, the volcanic ash flow while devastating to the environment and public health in the immediate aftermath, provided numerous minerals important to plant and animal nutrition and to human health and health water sources which contributed to the longer-term reinstitution of edible plants and to the recovery of the vibrant lush greenery of the Emerald Isle of the Caribbean.

GEOCHEMISTRY AND MINERAL CONTENT OF ASH FLOW FROM THE MONTSERRAT SOUFRIERE HILLS VOLCANO

The Soufriere Hills Volcano of Montserrat has ancient origins and roared back to life in 1995 wreaking severe havoc and damage to the inhabitants, geography, and ecosystems of the Island. The pyroclastic ash flow reached temperatures of 1500 °F and progressed down the hillsides at speeds of 80 mph, causing incineration and virtual destruction of everything in its path, while the gaseous and particulate laden plume reached altitudes of 35,000 feet, impacting air quality and aircraft navigation. The local health authorities recommended masking and physical protection from any potentially harmful effects from the ash to all residents who remained on Island following the 1995 eruption. Volcanic ash can be an irritant to exposed skin and respiratory surfaces upon contact due in part to the sharp and jagged nature of the microcrystalline particulate matter. In addition, the minute size of the smallest particulate matter can impact deep into the unprotected respiratory tree in humans and animals, potentially causing severe respiratory injury. The composition and physicochemical nature of the ash was largely unknown in 1995 and subsequent years. The current study was designed to determine the geochemical composition of the ash. Samples of ash were collected from 7 locations and water samples from three free flowing creeks in Montserrat and indicated that the creek water was acidic in nature. The mean pH of water was 5.2, while the ash showed abundant levels of Iron, Phosphorus, Calcium, Magnesium, Sodium, Aluminum, and sulfur, in addition to lower concentrations of potassium, boron, copper and zinc and intermediate concentrations of Manganese and was devoid of toxic minerals including lead and mercury. The emergence of acute respiratory issues was not found to exceed similar events in other healthy populations including individuals relocated to the UK. In conclusion, direct human and animal exposure to Montserrat volcanic ash was deemed non-harmful to humans when adequate protective measures including masking and exposure precautions were undertaken, while the rich mineral content of the ash can provide a rich source of micronutrient mineralization to soils and surrounding seawaters and support vigorous revegetation and recovery of affected land and sea zones throughout the island community.

Workflows for Construction of Spatio-Temporal Probabilistic Maps for Volcanic Hazard Assessment

Probabilistic hazard assessments for studying overland pyroclastic flows or atmospheric ash clouds under short timelines of an evolving crisis, require using the best science available unhampered by complicated and slow manual workflows. Although deterministic mathematical models are available, in most cases, parameters and initial conditions for the equations are usually only known within a prescribed range of uncertainty. For the construction of probabilistic hazard assessments, accurate outputs and propagation of the inherent input uncertainty to quantities of interest are needed to estimate necessary probabilities based on numerous runs of the underlying deterministic model. Characterizing the uncertainty in system states due to parametric and input uncertainty, simultaneously, requires using ensemble based methods to explore the full parameter and input spaces. Complex tasks, such as running thousands of instances of a deterministic model with parameter and input uncertainty require a High Performance Computing infrastructure and skilled personnel that may not be readily available to the policy makers responsible for making informed risk mitigation decisions. For efficiency, programming tasks required for executing ensemble simulations need to run in parallel, leading to twin computational challenges of managing large amounts of data and performing CPU intensive processing. The resulting flow of work requires complex sequences of tasks, interactions, and exchanges of data, hence the automatic management of these workflows are essential. Here we discuss a computer infrastructure, methodology and tools which enable scientists and other members of the volcanology research community to develop workflows for construction of probabilistic hazard maps using remotely accessed computing through a web portal.

Dielectric Properties of the Medusae Fossae Formation and Implications for Ice Content

AbstractThe extensive Medusae Fossae Formation (MFF) along the dichotomy boundary on Mars has geologic features indicative of wind erosion of low‐density material. There is evidence suggesting a water ice component, but with considerable uncertainty linked to the unknown MFF porosity and compaction behavior. We use SHARAD radar sounder data to estimate the real permittivity and loss tangent of MFF deposits, and compare these to a model for sediment compaction and to the properties of ice in mid‐latitude glaciers. In areas along the margins of Eumenides Dorsum, between Gordii Dorsum and Amazonis Mensa, and in northwest Zephyria Planum, the loss tangent is about 0.001 at 170 m and plateaus at about 0.003 for 310–550 m thickness. The real dielectric constant across the study areas ranges from 2 to 3. We propose that the MFF is a two‐layer deposit, with 300–600 m of fine‐grained, self‐compacting material above up to 2 km of minimally compacting, low‐loss material. The lower unit could be ice‐free and very coarse‐grained, but we see no evidence of extensive sand exposed by erosion. The lower layer might instead be ice‐rich and protected from sublimation by the dry cover. The volume of cover relative to a high ice content in the lower layer implies hybrid MFF formation as glacial or polar layered deposits capped by a dry, perhaps pyroclastic ash, component.

Stratigraphy and facies architecture of the Neoproterozoic syn- and inter-eruptive succession: An example from Gabal El Urf, Northeastern Desert, Egypt

A new integrated stratigraphic, sedimentological and geochemical study was carried out on the Gabal El Urf deposits to clarify their facies architecture, sequence stratigraphic framework, and evolutionary stages. The Gabal El Urf in the Northeastern Desert of Egypt is a well-preserved example of the Neoproterozoic volcano-sedimentary deposits. It comprises inter- and syn-eruptive facies that were generated by diverse depositional processes including debris flows, sheet floods, lacustrine flood flows, and pyroclastic ash falls/density currents. These facies correspond to alluvial fan, aeolian -fluvial, lacustrine, and pyroclastic facies associations that are arranged in four depositional cycles. They reveal variations in accommodation to sediment supply (A/S) ratio. Unconformities and lithofacies assemblages define six stages of volcanism and sedimentation and three unconformity-bounded tectonic sequences that should be allied to tectonic subsidence and basin uplift. These sequences may be subdivided in Low-Accommodation Systems Tracts (LAST) having negative A/S (A/S ratio close to zero) and High-Accommodation Systems Tracts (HAST) with fluctuation in A/S ratio between zero and +1. Sequences 1 and 3 are characterized by clast-supported conglomerates and pyroclastics, overlain by fluvial sand bodies and debris flow deposits, respectively denoting a LAST (positive A/S ratio close to zero). Sequence 2 is marked by pyroclastic ash fall facies at the base, passing to lacustrine deposits that are interlayered with fan-delta conglomerates at the top, defining a HAST (A/S ratio >1). The defined sequences are superimposed by thick fissure-fed ignimbrites which are capped by a co-ignimbritic breccia lag deposits with concentrated pyroclastic fountains. Clastic petrofacies of the El Urf succession indicate an adjacent miscellaneous rock sources involving volcanic, plutonic, and metamorphic terrains during the chief sedimentation processes in rift-related paleotectonic regime. The low to moderate magnitude of the CIA and PIA together with low SiO2/Al2O3 ratio indicate sediment recycling and moderate weathering of the protolith near uplifted basin flank(s) under dominant semi-arid to arid conditions. The development of the El Urf basin is akin to the post-amalgamation Ediacaran volcano-sedimentary basins that are widely distributed in the northern part of the Arabo-Nubian Shield, and is a key tectono-stratigraphic marker for the Cryogenian-Ediacaran shift along a major unconformity surface.

An Empirical Approach for Modeling Hysteresis Behavior of Pyroclastic Soils

For modeling physical and mechanical phenomena that occur in unsaturated soils, it is very important to identify the correct relationship between suction and water content. This relationship defines the soil water retention curve (SWRC). Its shape depends on numerous factors, including grain size composition, particles’ thickening state and, above all, the hydraulic and stress soil history. In particular, the SWRC in wetting phase differs from SWRC in drying phase, showing a hysteretic behavior. Hysteresis domain is defined by the main drying and wetting curves; when moving from one phase to another, relationship between suction and water content defines secondary curves within them. In this paper, a laboratory experiment was carried out to determine main wetting and drying curves of a pyroclastic ash sample from southern Italy. In same site of the sample collection, a monitoring station was installed that measured the suction and water content values. The experimental curves were compared with the data recorded on the site. In this paper, moreover, an empirical procedure is proposed to model secondary curves (or scanning curves) within the hysteresis domain. The scanning curves obtained with this method were compared with data collected by the in-situ monitoring network, revealing the ability to describe a situation realistically with a good adaptation. With this procedure, it is therefore possible to minimize errors since it covers a hysteretic behavior.

Evolution of the Jurassic Comallo volcanic sedimentary complex in the western North Patagonian Massif, Rio Negro province, Argentina

ABSTRACT Here we define the Comallo volcanic sedimentary complex of the western North Patagonian Massif. It is composed by two members that include 9 lithofacies and 7 facies associations. The lower member is represented by massive and stratified lapilli tuffs, lithic and tuffaceous breccias, coherent andesite-dacite lava-flows, andesitic breccias, and massive crystalline limestones. The upper member consists of red conglomerates, parallel and cross-stratification sandstones, and mudstones. The lower member is interpreted as having been deposited by dilute and dense pyroclastic currents, block and ash deposits and lava-flow, and hypersaline lacustrine environments. The upper member is considered to have been deposited in fluviatile environments. A new U-Pb age of 192.0 ± 3.0 Ma (Sinemurian) was obtained for this complex. It is coeval with several volcanic sedimentary units that crop out along the western North Patagonian Massif, the Neuquén basin and the Extraandean Chubut in pull-apart or rift depocentres. The movements of the NW-SE strike-slip faults that border the northern and southern limits of the Comallo depocentre made possible the development of a pull-apart basin as well as the volcanism and the fluvial system. This and other coeval units were deposited in similar environmental conditions along the North Patagonian Massif, the Neuquén basin and the extraandean Chubut, indicating a similar tectonomagmatic setting, in a tensional rear-arc during Lower Jurassic times.

Utilization of Microalgae (Nannochloropsis oculata) as Support Materi-al to Supply of Oxygen in Advanced Function of Respirator Mask in Preventing Society from URI Disease

Indonesia is the most country who has a lot of volcanic mounts of Ring of Fire can erupt everytime it can be. When volcanoes eruptions, some of material be exploded such as bomb, lapilli, pyroclastic ash etc. Piroclastic ash can influence respiration disease and it call ISPA (Infeksi Saluran Pernapasan Atas). ISPA is kind of disease which attacks lung by damaging alveolar under process of loading pyroclastic ash movement. The government gives supporting non standard mask 3 ply be used to protect people from pyroclastic ash. However, this mask can’t filter pyroclastic ash properly. So that, it makes society get suffer ISPA’s disease after have inhaled pyroclastic ash. Current research about support material for respirator mask is less than other country. In addition, the utilization of the supporting material for the mask, not many do. This research will find out solution to integrate support material e.g. microalgae (Nannochloropsis oculata) as a supplier of oxygen to enhance the advanced functionality of the mask in preventing the proliferation of ISPA’s disease.

Linking tephrochronology and soil characteristics in the Sila and Nebrodi mountains, Italy

Recent studies have demonstrated that soils formed on pyroclastic ash deposits are much more common in the Mediterranean area than previously assumed. These soils are an important key to understanding past volcanic events and landscape evolution. Chronological information in soils of Quaternary volcanic events, however, remains still poorly understood in southern Italy. Using a multi-method forensic approach, we explore the origin and age of volcanic deposits (soils) in Sicily and Calabria. The geochemical signature of the soil was compared to the chemical fingerprint of the magmas of potential source areas of southern Italian volcanoes. The results indicate that the investigated soils on the Nebrodi (Sicily) and Sila (Calabria) mountains were both impacted by materials having a high-K calc-alkaline series volcanism. The Aeolian Islands (in particular Lipari and Vulcano) are the most likely source of origin, but contributions also from the Etna (particularly the Biancavilla ignimbrites and Plinian eruptions) occurred. Weathering and leaching processes, along with a potential contribution from the underlying non-volcanic bedrock, has altered the main chemical composition of soils, often precluding direct relation to potential source areas. Immobile elements and their ratios (e.g. the Nb/Y vs Zr/Ti plot) or trace elements (Co, Th) and rare earth elements (laser ablation ICP-MS analyses of glass particles, volcanic clasts and pumice-like materials) gave precious hints of the origin of the volcanic deposits. Radiocarbon dating of the H2O2 resistant soil organic fraction indicates a minimum age of 8–10ka of the soils. The weathering index WIP (weathering index according to Parker) and the chemical composition of volcanic glasses and clasts were tested as proxies for the age of the volcanic deposits and time for soil formation. The soils and landscape are characterised by multiple volcanic depositional phases for the last about 50ka in the Sila mountains and about 70ka or more in the Nebrodi mountains. Chemical-mineralogical analyses enabled the detection of deposition phases during the Pleistocene and also Holocene. The multi-method approach enabled the identification of potential source areas, provided a tentative age estimate of the start (and in part duration) of ash deposits and therefore improved our understanding of volcanic landscape evolution.

Walking along the oldest human fossil pathway (Roccamonfina volcano, Central Italy)?

Here we report the remarkable superposition of a pre-historic trackway (349–350±3ka) with one used in more recent historical times, potentially forming one of the oldest path or trackways currently known. A Plinian eruption of the Roccamonfina Volcano resulted in a succession of pyroclastic flows. A combination of syn-sedimentary erosion and depositional morphology resulted in a bench, contouring the depositional slope. Prior to rapid lithification of the flow, early human ancestors used the bench as a route-way. At least two individuals diverted from this route-way to make the famous Trackways A and B of the Devil's Trails which have been described previously. The bench and associated animal tracks were covered by subsequent pyroclastic ash falls before being exhumed in historical times by a combination of natural erosion and quarrying. The bench was re-used as a route-way at this time and some of the tracks modified by human action to improve surface conditions and perhaps drainage. The P1-Trackway is the result and its detailed morphology is described here. Not only does it provide remarkable evidence of the convergence of route-ways through time along key geomorphological features in the landscape but the palimpsest of tracks provides a useful case study for archaeologists and ichnologists interpreting complex and superimposed surface traces.

Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount

AbstractAxial Seamount is the best monitored submarine volcano in the world, providing an exceptional window into the dynamic interactions between magma storage, transport, and eruption processes in a mid‐ocean ridge setting. An eruption in April 2015 produced the largest volume of erupted lava since monitoring and mapping began in the mid‐1980s after the shortest repose time, due to a recent increase in magma supply. The higher rate of magma replenishment since 2011 resulted in the eruption of the most mafic lava in the last 500–600 years. Eruptive fissures at the volcano summit produced pyroclastic ash that was deposited over an area of at least 8 km2. A systematic spatial distribution of compositions is consistent with a single dike tapping different parts of a thermally and chemically zoned magma reservoir that can be directly related to previous multichannel seismic‐imaging results.

Revisiting the field geology of Taurus–Littrow

Integration of Apollo 17 field observations and photographs, sample investigations, Lunar Reconnaissance Orbiter Camera images, Chandrayaan-1 Moon Mineralogy Mapper (M3) spectra, and Miniature Radio Frequency (Mini-RF) S-band radar images provides new insights into the geology of the valley of Taurus–Littrow on the Moon. Connecting the various remote observations to sample data enables a set of new conclusions to be drawn regarding the geological evolution of the valley. Structural considerations and published and recalculated 40Ar/39Ar analyses of samples from the North Massif and the Sculptured Hills indicate that the Crisium basin formed about 3.93 Ga; the Serenitatis basin about 3.82 Ga; and the Imbrium basin no earlier than 3.82 Ga and no later than the average of 3.72 Ga for 33 age dates from samples of the valley's mare basalts. Strong evidence continues to support the conclusion of others (Lucchitta, 1972; Spudis et al., 2011; Fassett et al., 2012) that the Sculptured Hills physiographic unit consists of Imbrium ejecta. Interpretation of M3 spectral data and Apollo 17 samples indicate that rock units of the Sculptured Hills consist of a largely coherent, Mg-suite pluton. LROC NAC stereo images and Mini-RF data indicate the presence of several exposed pyroclastic fissures across the Sculptured Hills. Rim boulders at Camelot Crater constitute nearly in situ wall rocks of that crater rather than ejecta and provide an opportunity for investigations of remanent magnetic field orientation at the time of the eruption of late mare basalt lavas in the valley. Paleomagnetic field orientation information also may be obtained relative to melt-breccia contacts in North Massif boulders that suggest original horizontal orientations. LROC images indicate the existence of two temporally separate light mantle avalanche deposits. The origin, potential flow mechanisms, and geology of the youngest avalanche from the South Massif have been clarified. The existence of two distinct light mantle avalanches raises doubt about the association of either light mantle avalanche with secondary impacts related to the Tycho impact event. Alternatively, the Lee-Lincoln thrust fault appears to have triggered the second light mantle avalanche between 70 and 110 Ma. A simple structural analysis shows that this thrust fault dips 20–25° to the southwest where it crosses the North Massif and to the west where it crosses the valley floor. Mini-RF data reveal a line of reduced reflections roughly perpendicular to contours on the North Massif about 3 km to the east of the Lee-Lincoln fault. Although this line is possibly an older ancillary fault, LROC NAC stereo images indicate that it may be best explained as a pyroclastic fissure. A debris flow of dark, apparent pyroclastic ash lies below the southeast end of the potential fissure. Finally, young lunar impact glass sample 70019 has been precisely located within LROC NAC images and oriented for the first time using 60 mm (f.l.) sample documentation photographs. Sample 70019 can now be employed in lunar paleomagnetic field orientation studies.

The effect of dynamic loading on the shear strength of pyroclastic Ash Deposits and implications for landslide hazard: The case of Pudahuel Ignimbrite, Chile

The co-seismic and post-seismic behaviour of pyroclastic ash deposits and its influence on slope stability remains as a challenging subject in engineering geology. Case studies in volcanic areas of the world suggest that soil structural changes caused by seismic shaking results in landslide activity. It is critical to constrain how this kind of soil behaves during coseismic ground shaking, as well as the effects of dynamic loading on shear strength parameters after shaking. Direct shear tests carried out on cineritic volcanic materials from the Pudahuel Ignimbrite formation in central Chile show a direct effect of cyclic loading on the shear strength and in a minor extent on the rheology. A high apparent cohesion found in monotonic shear tests, likely attributed to suction and cementation, is destroyed by dynamic loading. At the same time, the internal friction angle rises. This defines a differential post-dynamic behaviour depending on normal effective stress conditions, which favour the occurrence of shallow landslides. These results show how the use of shear strength parameters obtained from standard monotonic direct shear tests may produce misleading results when analysing seismic slope stability in this type of soils.

“Knobby Terrain” a Sign of Mars's Explosive Past

Newly identified knobby terrain related to ancient volcanoes on Mars hint that pyroclastic ash and rock flowed down slopes early in the red planet's history.

Compton–Belkovich Volcanic Complex (CBVC): An ash flow caldera on the Moon

Volcanic calderas are found on Earth, Mars, Venus and Io, and are rare, but unique volcanic structures in the Solar System. Compton–Belkovich Volcanic Complex (CBVC) (60.5°N–99.5°E) on the far side of the Moon is a unique non-mare feature due to its evolved lithology, regional tectonic setting, its location being near the north pole, far from the Procellarum KREEP Terrane (PKT) and its recent association with endogenic water. High-resolution remote sensing observations of several structural features at CBVC such as ring faults, radial faults, fractures manifested by various morphological features such as domes of varied sizes and shapes and pyroclastic ash flows characterize it to be a volcanic caldera. The loading of Humboldtianum basin with basalts and subsequent development of extensional structures outside it along with high-thorium anomaly and resulting silicic volcanism at CBVC producing central collapsed caldera could be considered as an analogy to silicic calderas on Earth formed in extensional tectonic regime even though the tectonic processes involved in these two cases are entirely different, the former being impact-related, whereas the latter involves rifting or hotspot-related activities associated with extensional plate tectonics. Presence of high-reflectance feature and its extension to the east–southeast of the topographic expression and its relation with pyroclastic dispersal have been supported by radar-based Mini-RF observations and high-resolution LROC-NAC imagery. It suggests the presence of a late-stage fine pyroclastic layer within the CBVC region. The diverse volcanic features that exist at the studied site indicate a series of deformation and eruption events associated with silicic magmatism and thus, CBVC could be considered as an ash flow caldera on the Moon. Here, we present a detailed appraisal of various volcanic and structural features detected at CBVC through high-resolution optical as well as radar observations. Based on the previous and present studies, an evolutionary model of the area has been proposed and the petrological implications of silicic magmatic activity, its manifestation, evolution and association with endogenic water have been discussed.

Change of landscape structure of Matua Island after the Sarichev Volcano Peak Eruption June 12–15, 2009

Due to the Sarichev volcano peak eruption June 12–15, 2009, the landscape of Matua Island was modified greatly. On the basis of field data, the spatial structure of the island landscape before and after eruption was analyzed. Scale maps 1: 200 000 reflecting the landscape structure of the island before June 12 and on June 30 are presented. It was established that the landscape on the slope of the volcano cone was essentially restructured by the influence of pyroclastic flows and volcanic ash fall-out. Complication of the island structure was noted after the volcanic eruption.

Column Elution Experiments on Volcanic Ash: Geochemical Implications for the Main Ethiopian Rift Waters

Column laboratory experiments were employed to assess the leaching behaviour of pyroclastic glassy ash deposits collected in the central Main Ethiopian Rift, where surface and groundwater resources are affected by fluoride (F−) pollution, which is the cause of an endemic disease (fluorosis) in the local community. To elucidate the source of F− and simulate the water–rock interaction processes, as well as quantify its distribution within different grain sizes, the pyroclastic ash was analysed by XRF, XRD and SEM and separated into coarse and fine fractions. Three columns were filled with raw (unsieved), coarse (63 μm–2 mm) and fine (<63 μm) fraction, respectively, and flushed with synthetic rain water in saturated conditions. Very fast F− leaching was observed in the fine fraction column at the start of the experiment, while in the other two columns, F− was slowly released; in addition, a strong accumulation of F− was found in the fine fraction. The effect was more pronounced in the fine fraction column due to the available effective adsorbing surface area. Subsequent to elution experiments, the columns were characterised via moment analysis of tracer test. Finally, flow and transport modelling (MODFLOW-2000 and MT3DMS) was employed to compute the amount of F− adsorbed onto the solid phase, comparing the calculated conservative transport of F− and the observed concentrations. The results of this study suggest that fluoride is a fundamental constituent of the glass phase (about 0.3 wt.%) and that it is released during the incongruent dissolution of glassy particles. Dissolution of coatings on glass particles could provide an additional contribution to the geochemistry of the interacting fluids. These processes are more effective in the fine fraction due to a much higher reactive (specific) surface area.