Slopes Of Volcano Research Articles

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Abstract Sete Cidades is an active central volcano on the western part of São Miguel. The geological record reveals that subaerial activity started more than 250 ka ago. Stratigraphic units defined for Sete Cidades deposits reflect major events in the history of the volcano and are organized into two main groups: the Inferior Group and the Superior Group. Caldera formation resulted from three major paroxysmal events that occurred at about 36, 29 and 16 ka ago. Analysis of the eruptive history of Sete Cidades shows that effusive or moderately explosive eruptions, of Hawaiian and/or Strombolian styles, were located on the slopes of the central volcano. Conversely, trachytic explosive activity is mostly centred inside the caldera involving, in a first stage, predominantly Plinian and sub-Plinian phenomena, changing about 5 ka ago to a dominant hydromagmatic style. Trachytic effusive eruptions are represented by domes and associated lava flows that crop out in the inner caldera walls and on the western slopes of the volcano. Offshore submarine activity is represented by the historic Surtseyan eruptions of 1638 and 1811. In the last 5 ka Sete Cidades was the most active central volcano in the Azores with 17 explosive eruptions predominantly with hydromagmatic character.

Elements and ectomycorrhizal symbiosis affecting the growth of Japanese larch seedlings regenerated on slopes of an active volcano in northern Japan

The growth of Japanese larch seedlings is regulated by the presence of nutrients as well as ectomycorrhizal symbiosis. The mountain slope of an active volcano is a severe environment for the regeneration of larch (Larix kaempferi Sarg. hereafter larch) seedlings. To determine parameters affecting the growth of larch seedlings, we analyzed stoichiometry of elements in the soils and plant organs, ectomycorrhizal (ECM) colonization, and photosynthetic abilities. These parameters were compared with two different elevations. From nutrient analysis of plant organs from larch seedlings grown on the slope of a volcano, potassium (K) was insufficient compared with the seedlings grown in other habitats. Symbiosis with ECM fungi enabled the uptake of nutrients, especially phosphorous (P) and nitrogen (N). The main factor affecting the differences in relative height growth rate (RHGr) of larch was attributed to ECM colonization. There was a positive relationship between ECM colonization and concentrations of P or N in needles. Larch seedlings with high rates of ECM colonization showed high concentrations of P and N, and had high photosynthetic rates. At lower elevation sites, concentrations of N and K in needles were low with high density of individuals. Moreover, larch showed a high accumulation of aluminum (Al) and iron (Fe) even though the amount of these elements in the soil was small. These seedlings exhibited a suppressed photosynthetic rate and RHGr. Symbiosis with ECM fungi could suppress the excessive uptake of Al and Fe.

Volcanic-glacial interactions: GIS applications to the assessment of lahar hazards (case study of Kamchatka)

On the Kamchatka peninsula, lahars or volcanogenic mudflows arise as a result of intensive snow melting caused by incandescent material ejected by volcanoes onto the surface. Such flows carrying volcanic ash and cinders together with lava fragments and blocks move with a speed up to 70 km/h that can result in significant destructions and even human victims. Formation of such water flows is possible during the whole year. Large-scale GIS «Hazards of lahars (volcanogenic mudflows)» has been developed for some volcano group as well as for individual volcanoes on the peninsula in framework of the GIS «Volcanic hazard of the Kuril-Kamchatka island arc». Main components of this database are the following: physic-geographical information on region of active volcanism and adjacent areas, on human settlements; data on the mudflow activity; data on distribution of the snow and ice reserves. This database is aimed at mapping of surrounding territories and estimating a hazard of lahars. For illustration the paper presents a map of the lahar hazards, results of calculations of the distances of ejects and maximal area of ejected material spreading in dependence on a character and power of an eruption. In future we plan to perform operational calculations of maximal possible volumes of such flows and areas of their spreading. The calculations will be made on the basis of the GIS «Volcanic hazard of the Kuril-Kamchatka island arc». A volume of hard material carried by lahars onto slopes and down to foot of the Kluchevskaya volcanic massif is estimated on the basis of data on the snow and ice reserves on volcano slopes. On the average for many years, the snow accumulation in zones of the mudflow formations their volume often reaches 15–17 millions of cubic meters. Depending on the snowfall activity in different years this value may vary within 50% relative to the norm. Further on, calculations of maximal possible volume of such flows will be performed in a real time regime with regard for a character of power of a volcano eruption and reserves of snow and ice in the mudflow-forming basins. The main objective of this work is an effort to reduce a risk of a mudflow formation and to prevent possible damages.

Landscape and relief evolution of the Central Mexican plateau in the final stage of Late Pleistocene and Holocene

The paper describes the reconstructed history of landscapes and relief of the Central Mexican plateau in the final stage of Late Pleistocene and Holocene. The new stage of erosion has started in LGM with the formation of small lakes and further initiation of barrancos –gullies along the slopes of small and large volcanoes. This stage was not unidirectional, but had several alternating stages with the filling of depressions (small lakes, heads of barrancos, paleocuts) and their stabilization with the formation of heterochronous soils. The highest rates of gullies formation took place at the end of Pleistocene – beginning of Holocene, and at the present time when the badlands are forming. The stages of linear erosion (formation of barrancos) alternated with the increased sheet erosion (accumulation of colluviums in the depressions with further soil or tepetate formation). Soils were associated with the warm and wet enough climatic conditions about 13 350, 8 100, and 6 200 years ВР. Tepetates were formed under cool and wet environment. The role of small lakes was revealed. Small lakes at various levels being periodically broken through gave rise to the barrancos formation or dried out. The anthropogenic erosion had several stages: formation of the eroded sites (heads), barrancos formation inside the filled paleocuts, badlands formation. The “scalped” areas were formed in the sites of the contact of several exposed tepetates of various gullies. Such areas (badlands) may reach considerable size and are practically unsuitable for agricultural use.

Frequency of occurrence of debris flow at the caldera wall slopes of Aso volcano, Central Kyushu

Frequency of occurrence of debris flow at the caldera wall slopes of Aso volcano, Central Kyushu

Ancient oral tradition describes volcano–earthquake interaction at merapi volcano, indonesia

erapi volcano is among the most hazardous volcanoes on the planet. Ancient avanese folklore describes erapi's activity as the interaction between the pirit Kings that inhabit the volcano and the ueen of the South ea, who resides at arangtritis beach, 50 km of erapi. The royal palace in ogyakarta is located half‐way along the hypothetical line between erapi and arangtritis (the erapi–raton–outh ea axis) to bring balance between these mystical forces.In 2006 and 2010, erapi erupted explosively and on both occasions, earthquakes shook the region and the eruptions grew more violent in response. These earthquakes appear to influence the sub‐volcanic magma supply of erapi and a positive feedback loop has recently been postulated between the volcano and local earthquake patterns. The 2006 earthquakes clustered along the pak iver fault to the south of the volcano, which trends –, and reaches the southern sea at arangtritis beach, the fabled residence of the ueen of the South ea.Our interpretation of the erapi–raton–outh ea axis is that local folklore was used by ancient people to describe and rationalize the complex interplay between geological processes. We suggest that erapi displayed volcano–earthquake interaction many times in the past, and not only during its most recent eruptive cycle. Although now shrouded in mystery, these oral traditions can be thought of as an ancient hazard mitigation tool, which makes them likely useful in helping to foster effective dialogues with a variety of target parties and interest groups around the volcano's slopes.

“Bottomsets” of the lava−fed delta of James Ross Island Volcanic Group, Ulu Peninsula, James Ross Island, Antarctica

Abstract Sedimentological study of the three geographically separated outcrops of bottom− sets of a single lava−fed delta (Pliocene) in the James Ross Island (Antarctica) allows recognition of six lithofacies.Deposits of traction currents, deposits of volcaniclastic debris flows and products of such flows transformations (both low− and high−density turbidity currents) and glacigenic deposits (subaqueous debris flows and traction/turbidity currents) were all recognised. Existence of submarine proglacial environment formed prior to formation of volcani− clastic deposits partly covering the subaqueous slopes of volcano is supposed. The principal role of mass flow processes was recognised and explained by relative steep slopes of the lava−fed delta. The distribution of lithofacies significantly differs in the individual outcrops. These variations in sedimentary succession and also in thickness of volcaniclastic deposits of “bottomsets” of the single lava fed delta suggest principal role of local conditions and paleogeography for development and preservation of this part of delta depositional system. Moreover proximal and distal setting can be followed and direct vs. more distant relation to over−riding lava−fed delta supposed. The sedimentary succession terminated by foresets of hyaloclastite breccia.

Experimental works on rapid reforestation by aerial seeding in the devastated slope of Unzen volcano

Experimental works on rapid reforestation by aerial seeding in the devastated slope of Unzen volcano

Southward Migration of Magmatic Activity in the Colima Volcanic Complex, Mexico: An Ongoing Process

The Colima Volcanic Complex trends in a nearly N-S direction in western Mexico, and one of its structures, Colima volcano, is the most historically active volcano in the country. Immediately to the N, there is another volcanic center called El Cántaro volcano, whose activity started around 1.7 Ma in its N portion and migrated to the S in various episodes. Volcanic activity migrated further south, from El Cántaro to the Colima Volcanic Complex where the southernmost manifestation, Hijos del Volcán domes, is located on the south slope of Fuego volcano. The above date appears to mark initiation of the rather continuous volcanic activity in the area. It has been noted that these volcanic manifestations lie on, or near the Rivera-Cocos inland plate boundary. Colima’s Fuego volcano is also the closest to the Middle America Trench, among the polygenetic volcanoes in Mexico. We submit that the anomalous location of volcanism in this area originates in an anomalous subduction process of the Rivera and Cocos plates and evoke a tectonic model, proposed elsewhere, to support the idea. Modeling gravimetric and aeromagnetic data we locate the magma chambers of the Fuego (active) and Nevado (extinct) volcanoes within a 65 mGals negative Bouguer anomaly elongated in a nearly N-S direction. The corresponding aeromagnetic map displays a magnetic high over the southern portion of the Fuego volcano edifice. We found two additional, associated structures whose anomalies have not been previously reported, which appear to follow the southward magmatic migration pattern. One of them is a collapse structure with a circular topographic expression, and the southernmost is a low-density intrusion ~1 km below sea level, associated with a moderate topographic bulge at the surface that we interpret as a magma body. Five lines cross the anomalies; gravimetric and magnetic fields are concurrently modeled along them to locate the magmatic bodies. In addition to the 2-D models we perform 3-D gravimetric and magnetic inversions. For each field a 3-D mesh is built under the area occupied by the Colima Volcanic Complex, the volume elements are then assigned density or magnetic susceptibility values and their surface contributions in various points are evaluated. The process is iterated until the difference between the measured and the calculated fields is less than a predetermined value. The results of each inversion adequately and independently define the location of the magmatic chambers although they cannot distinguish between the individual chambers of the Nevado and Fuego volcanoes. 2-D and 3-D results complement each other and consistently show the locations of potential magmatic regions. Our models support a multiple, complex magmatic system that appears to continue to spread southwardly, which can pose additional volcanic risks to an already threatened local population.

Geological factors governing ichthyofauna formation in rivers of Semlyachikskii volcanic region (Eastern Kamchatka)

The role of environmental factors is considered for the lower reaches of rivers and creeks originating from the slopes of volcanoes of the Semlyachikskaya group (East Kamchatka volcanic region). The hydrological and environmental conditions of rivers and creeks flowing into the Semlyachikskii Liman are described for the first time. The specific hydrological and geomorphological characteristics of the lower reaches of those streams and the relationship between abiotic characteristics and the specific features of the structure and abundance of fish communities are studied. The spawning intensity (density) of salmon Salmonidae and the complexity (balance) of the structure of young fish and resident fish communities depend on the stream size. The habitation density and the uniformity of young fish distribution are determined by channel slope and the morphology of channel relief forms. The temperature regime determines fish growth rate, and water chemistry determines the phonetic features of resident fish population.

Revealing the hidden faults in the SE flank of Mt. Etna using radon in-soil gas measurement.

Although there are many methods for investigating tectonic structures, many faults remain hidden, and they can endanger the life and property of people living along them. The slopes of volcanoes are covered with such hidden faults, near which strong earthquakes and gas releases can appear. Revealing hidden faults can therefore contribute significantly to the protection of people living in volcanic areas. In the study, seven different techniques were used for making measurements of in-soil radon concentrations in order to search for hidden faults on the SE flank of the Mt. Etna volcano. These reported methods had previously been proved to be useful tools for investigating fault structures. The main aim of the experiment presented here was to evaluate the usability of these methods in the geological conditions of the Mt. Etna region, and to find the best place for continual radon monitoring using a permanent station in the near future.

フィリピン共和国，イロシン火砕流噴火の推移と特徴

フィリピン共和国，ルソン島南東端のソルソゴン地域での41 cal kBPの大規模火砕流噴火の結果，11 × 11 kmのイロシン（Irosin）カルデラが形成された。このときの噴火は，カルデラを形成する大規模噴火とその先駆的な噴火の2つに区分される。 先駆的噴火は，現在のカルデラ縁の南東斜面の小規模溶岩ドームであるマロバゴ（Malobago）溶岩ドームの形成と細粒火山灰の噴出からなる。ほかにも類似した溶岩の流出がカルデラ内にあったかもしれない。 地質学的短期間（およそ10年以内）の休止後，3つの噴火フェーズからなるカルデラ形成噴火がはじまった。最初の噴火フェーズは，現在のカルデラ内でおこったプリニー式噴火であり，バルク体積約 20 km3の軽石質テフラが北方に拡散した。プリニー式噴火の早い段階で噴煙柱の崩壊が繰り返し発生し，intra-plinian火砕流が薄い細粒火山灰と降下軽石層に挟在している。プリニー式フェーズの終わりごろにソルソゴン地域に強い地盤振動があり，プリニー式噴火による堆積物の上下面に撹乱構造を形成した。 イロシン火砕流の噴火は，グランドレーヤーを基底部に伴う下部ユニット火砕流の噴出ではじまった。そして，それに続く破局的な噴火によって上部ユニット火砕流が噴出し，現在のカルデラ地形を形成した。上部ユニットは，厚く粗粒な火砕流堆積物であり，基底部に粗粒な岩片濃集層（地点Dで厚さ約 2 m）が認められる。イロシン火砕流のバルク体積は，およそ 25 km3と見積もられる。 マヨン（Mayon）火山西麓のイナスカン（Inascan）スコリア丘の山頂部で，イロシン火砕流に伴う降下火山灰（co-ignimbrite ash-falls）が発見されている。ここでの火山灰層は，層厚約1mで細粒火山ガラスと少量の斑晶鉱物からなる。比較的粗粒の最下部層は，プリニー式降下軽石層の遠方相に対比される。これらの降下テフラも含めたイロシンカルデラから噴出した火砕物全体のバルク体積は，ほぼ 70 km3に達する。

Proximal record of the 273 ka Poris caldera-forming eruption, Las Cañadas, Tenerife

Lithofacies architecture analysis is applied to the most proximal exposures of the 273 ka Poris Formation, in the Diego Hernandez caldera wall of Las Canadas. Here, the succession records an opening Plinian phase followed by generation of a pyroclastic density current (PDC) that was partly blocked by near-vent topography. The upper part of the current surmounted the barrier and deposited an ignimbrite veneer. During a hiatus in energetic flow, ash and various ash aggregates were deposited from a hybrid cloud comprising parts of both the Plinian and the co-ignimbrite plumes. Phreatomagmatic explosions then generated currents rich in fine-grained lithics; current waxing with local erosion was followed by pulsing-unsteady waning, recorded in repeated sets of graded tuff. Reversion to magmatic activity was marked by hybrid deposition, as coarse pumice fallout and juvenile ballistics entered pyroclastic currents to form stratified pumice-block tuff. Increasingly energetic flow is recorded in 9 m of mainly massive lapilli tuff that includes evidence of widespread scour and bypass; lithic-rich layers record incremental onset of edifice disruption due to magma withdrawal. Laterally variable stratification and load structures show that the PDC was unsteady and highly non-uniform at times, with locally rapid aggradation of gas-rich ignimbrite. Climactic edifice disruption is marked by a lithic-block layer in erosional contact with the underlying ignimbrite, recording intense pyroclastic current activity and widespread bypass of material to distal volcano slopes. Pumice-block breccia, 10 m thick and with blocks up to 1.2 m in diameter, forms the top of the succession and registers modification of the magmatic plumbing. The timing of collapse to form a major summit depression is uncertain. However, the abrupt termination of the proximal aggradation of coarse breccia, with no record there of any waning-stage pyroclastic currents, suggests subsidence at that time, conceivably with formation of a caldera that contained late-erupted material.

Spatio-temporal reconstruction of lahars on the southern slopes of Colima volcano, Mexico – A dendrogeomorphic approach

Historical records of lahar occurrence and distribution are typically scarce in volcanic environments, even more so if they occur outside of human settlements. In the context of hazard assessment and process understanding, documenting their temporal frequency and drivers of activity might be crucial. On forested volcanoes, lahars may significantly damage trees along their flow paths, and sometimes even eliminate entire forest stands. This study is based on growth disturbances in trees affected by lahars (i) to assess the potential of dendrogeomorphic techniques in lahar research and (ii) to analyze the temporal frequency and spatial patterns of lahars at Montegrande and Arena, two of the most active of the ephemeral streams on the southern sector of Colima volcano. A total of 78 Pinus leiophylla live trees were sampled along the ravines, yielding evidence for 20 lahar events after the AD 1913 eruption, adding seven events to the historic records. Although the number of lahars reconstructed with tree-ring records can only be considered as a minimum frequency, the method clearly improves the local lahar chronology. Despite the scarcity of meteorological records at the study sites, the timing of reconstructed lahars points to heavy rainfalls after explosive activity as the main driver of events.

The volcanic debris avalanche on the SE submarine slope of Nisyros volcano, Greece: geophysical exploration and implications for subaerial eruption history

A spectacular hummocky topography was discovered offshore of the south-eastern slope of the Nisyros island volcano in the eastern sector of the Aegean volcanic arc in 2000–2001, using multibeam bathymetric mapping and seismic profiling, and interpreted as part of a volcanic debris avalanche originating onland. During E/V Nautilus cruise NA011 in 2010, a detailed side-scan sonar and ROV exploration aimed at evaluating the surface morphology of this avalanche field. Combining the new data with selected older datasets reveals that the debris avalanche is characterized by numerous (at least 78) variously sized and shaped hummocks. Some of these are distinctly round, either scattered or aligned in groups, whereas others are elongated in the form of ridges. This is consistent with existing models accounting for variations in the longitudinal and lateral velocity ratio of landslides. Maximum dimensions reach 60 m in height above the sea bottom, 220 m in length and 230 m in width. The structures outline a large tongue-shaped, submarine hummock field of about 22.2 km2, approx. 4.8 km wide and 4.6 km long and with an estimated volume of 0.277 km3. Due to its characteristic shape, the collapsed volcanic flank is interpreted to represent a singular failing event, involving a rapid and virtually instantaneous downslope movement of the slide mass into the sea. Indeed, the H/L (height of 280 m vs. run-out of 7 km) ratio for the Nisyros slide is 0.04; plotted against volume, this falls within the theoretical bounds as well as measured values typical of submarine landslides. The timing of the event is probably related to the extrusion of Nikia lavas and their subsequent failure and formation of a main scarp observed at about 120 m depth on an 8-km-long seismic profile and a map of slope angle distribution, at the depth where the palaeo-coastline was located 40 ka ago. An inferred age of ca. 40 ka for the avalanche awaits confirmation based on dating of core material.

Gender differences and regionalization of the cultural significance of wild mushrooms around La Malinche volcano, Tlaxcala, Mexico

The purpose of this study was to determine the cultural significance of wild mushrooms in 10 communities on the slopes of La Malinche volcano, Tlaxcala. The frequency and order of mention of each mushroom species in interviews of 200 individuals were used as indicators of the relative cultural significance of each species. A X2 analysis was used to compare the frequency of mention of each species between males and females, and a Mann-Whitney U test was used to compare the difference in the total number of fungi mentioned by either gender. Traditional names for mushroom species were documented and frequency of mention assessed through multivariate statistics. The fungi with highest frequency of mention were Amanita basii, Lyophyllum decastes, Boletus pinophilus, Gomphus floccosus and Cantharellus cibarius complex. We found significant differences in the frequency of mention of different fungi by males and females but no significant difference was found for the total number of fungi mentioned by either gender. Principal component analysis suggested a cultural regionalization of La Malinche volcano communities based on preferences for consumption and use of traditional names. We observed two groups: one formed by communities on the eastern part of the volcano (with mixed cultures) and the other including communities on the western slope (ethnic Nahua towns). San Isidro Buensuceso is the most distinct community, according to the criteria in this study.

Early MIS 3 occupation of Mochena Borago Rockshelter, Southwest Ethiopian Highlands: Implications for Late Pleistocene archaeology, paleoenvironments and modern human dispersals

Between 70 and 50 ka BP, anatomically modern humans dispersed across and out of Africa to eventually populate all inhabitable continents. Knowledge of paleoenvironments and human behavioral patterns in Africa prior to and during these dispersals is crucial for understanding how and why hunter-gatherers were able to adapt rapidly to the new environments they encountered. However, few well-dated sites from this time period are known from the Horn of Africa, one of the purported staging areas for population movements into southern Arabia and Asia. Excavations at Mochena Borago Rockshelter, situated on the western slopes of a dormant volcano where the SW Ethiopian Highlands meet the Ethiopian Rift, have yielded the first securely dated archaeological sequence for later periods of the dispersal. Three major lithostratigraphic groups incorporating occupational episodes have yielded charcoal radiocarbon ages ∼53–38 ka calBP; deeper deposits have been tested but remain undated. Archaeological assemblages consist mainly of obsidian flaked stone artifacts manufactured from small, minimally prepared, single- to multi-platform flake cores; radially prepared cores are rare and blade cores are absent. Small unifacial to bifacial points from non-radial cores dominate the earliest shaped tool assemblages, and backed pieces first appear by ∼45 ka calBP. By ∼43 ka calBP, scrapers and backed pieces are predominant, rather than points. However, there is little evidence for technological change other than the appearance of bipolar technology. Mochena Borago's archaeological sequence thus cannot be neatly classified as Middle Stone Age, Later Stone Age or “transitional” and calls into question some of the principles by which archaeologists have attempted to classify African toolmaking traditions.

Observing volcanic ash plumes and ballistics using Doppler radar

When volcanoes erupt, they often emit coarse rocks with ballistic trajectories that fall onto the slopes of the volcano, as well as a plume of fine ash that drifts into the atmosphere. It can be challenging to monitor both simultaneously and discriminate between the two to collect quantitative data, but Valade and Donnadieu have done that with a ground‐based Doppler radar, which they used to make measurements of smallscale eruptions at Arenal volcano in Costa Rica. They were able to estimate the mass of the ballistic rocks and the mass of ash particles ejected into the atmosphere. Such studies could be useful for understanding and mitigating the hazards associated with volcanic eruptions. (Geophysical Research Letters, doi:10.1029/2011GL049415, 2011)

Effects of volcano profile on dilute pyroclastic density currents: Numerical simulations

Explosive activity and lava dome collapse at stratovolcanoes can lead to pyroclastic density currents (PDCs; mixtures of volcanic gas, air, and volcanic particles) that produce complex deposits and pose a hazard to surrounding populations. Two-dimensional computer simulations of dilute PDCs (characterized by a turbulent suspended load and deposition through a bed load) show that PDC transport, deposition, and hazard potential are sensitive to the shape of the volcano slope (profile) down which they flow. We focus on three generic volcano profiles: straight, concave-upward, and convex-upward. Dilute PDCs that flow down a constant slope gradually decelerate over the simulated run-out distance (5 km in the horizontal direction) due to a combination of sedimentation, which reduces the density of the PDC, and mixing with the atmosphere. However, dilute PDCs down a concave-upward slope accelerate high on the volcano flanks and have less sedimentation until they begin to decelerate over the shallow lower slopes. A convex-upward slope causes dilute PDCs to lose relatively more of their pyroclast load on the upper slopes of a volcano, and although they accelerate as they reach the lower, steeper slopes, the acceleration is reduced because of the upstream loss of pyroclasts (lower density contrast with the atmosphere). Dynamic pressure, a measure of the damage that can be caused by PDCs, reflects these complex relations.

Kliuchevskoi volcano diary

Numerous ash layers deposited at the slopes of Kliuchevskoi volcano provide a detailed and continuous record of its explosive activity during the last ca. 10,000 years