Major Eruptions Research Articles

Extended North Atlantic Oscillation and Greenland Blocking Indices 1800–2020 from New Meteorological Reanalysis

Based on newly-available meteorological reanalysis, we compile and present extended seasonal series of the North Atlantic Oscillation (NAO) and Greenland Blocking indices spanning 1800–2020, which we analyse for evidence of significant trends. This represents a major backward extension of the previously available instrumental-/reanalysis-based Azores–Iceland and principal component-based NAO indices, and allows us to evaluate the potential effect of natural climate perturbations, especially the 1809 and 1815 major volcanic eruptions and ~1790s–1830 Dalton solar minimum, on North Atlantic atmospheric circulation. We find that winters 1809/10 and 1816/17 mark positive NAO peaks, relative to several years before and afterwards, which is in accordance with the theory of volcanic forcing of climate. However, there is little evidence of a summer NAO volcanic signature. Overall, based on the significantly longer new reanalysis time series, the new series presented here corroborate and extend our previous results of: (1) a significantly more variable year-to-year NAO with a recent exceptional clustering of extreme events since 2000 for winter; (2) a significant increasing trend in blocking over Greenland in summer. These trends have major repercussions for the probability of the occurrence of extreme weather events over northwest Europe and for the sensitivity and response of the Greenland Ice Sheet to global warming, especially if they continue as an integral part of anthropogenic climate change.

A New Way to Explore Volcanic Areas: QR-Code-Based Virtual Geotrail at Mt. Etna Volcano, Italy

In this body of work, we showcase a historic virtual geotrail on the eastern flank of the iconic Mt. Etna volcano (Italy), along a series of outstanding geological sites and features subsequent to an important eruption that took place in 1928. A geohistoric account of such a major eruption, is of great interest, since it is the only event since 1669 to have caused the destruction of a town (Mascali) in the Etna region. Volcanologists, educators, the lay public, tourists and volcano explorers can now access a series of “virtual geostops” belonging to this virtual geotrail, such that “visitors” can virtually fly above these sites by scanning a QR code on the printed or electronic version of the present manuscript, as well as on the poster provided as additional material for this manuscript. The virtual geostops that comprise the virtual geotrail were developed using the structure-from-motion (SfM) photogrammetry technique from images captured by using unmanned aerial vehicles (UAVs). The main result of our work is the virtual geotrail, subdivided in two parts and composed of eight geostops, each showing outstanding examples of geological features resulting from volcanic phenomena that took place also during 1979. Our approach is designed to support classical field trips, and it can undoubtedly become complementary to traditional field teaching in earth sciences, both now and in the future.

Structural evolution of a magnetic flux rope associated with a major flare in the solar active region 12205

Solar eruptions are often generated as a result of the complex magnetic environment in solar active regions (ARs). Unravelling the relevant structure and evolution is vital to disclosing the underlying mechanisms that initiate such eruptions. In this work, we conduct a comprehensive study of the magnetic field structure and evolution responsible for a major flare eruption in a complex AR: NOAA 12205. The study is based on a detailed analysis of observations from the SDO and a time sequence of coronal magnetic field extrapolations. The AR is characterized by a long sequence of sunspots, harboring two groups of δ type that evolved dynamically via continual rotation, shearing, colliding, and flux cancellation. Our study suggests that the joint effect of the sunspot motions along a large-scale magnetic flux rope (MFR) supporting a filament was gradually built up along the main polarity inversion line. A quantitative analysis of the coronal magnetic evolution strongly indicates that an ideal instability of the MFR finally led to the major eruption of the X1.6 flare, although it was preceded by episodes of localized reconnections. These localized reconnections should play a key role in building up the unstable MFR by, for example, tether-cutting reconnection low near the photosphere, as driven by the shearing and flux cancellation. Through these reconnections, the MFR gains a significant amount of twisted flux and is lifted up to a height above the torus unstable threshold, at which the background restraining force decreases fast enough with the height.

Numerical simulations of the great eruption of η Carinae from the 1840s

In this work, we present new 2D hydrodynamical simulations of the major eruption of η Car in the 1840s, which resulted in the formation of a bipolar nebula that is commonly known as the large Homunculus. In our numerical models, we have included the high-speed component of 10 000 km s−1, which was detected in recent observations, providing direct evidence of an explosive event. Here, we investigate whether such a violent explosion is able to explain both the shape and the dynamical evolution of η Car’s nebula. As in our previous work, we have assumed a two-stage scenario for η Car’s eruption: a slow outflow phase for a few decades before the eruption, followed by the explosive event. From the collision of these outflow phases, the large Homunculus is produced. Our numerical simulations show that such a scenario does not resemble some of the observed physical features and the expansion of the nebula. Notwithstanding, we also explore other injection parameters (mass-loss rate and ejection velocity) for these outflow phases. In particular, we find that an explosion with an intermediate speed of 1000 km s−1 is able to reproduce the morphology and the kinematical age of the large Homunculus.

Minor impacts of major volcanic eruptions on hurricanes in dynamically-downscaled last millennium simulations

The effects of volcanic eruptions on hurricane statistics are examined using two long simulations from the Community Earth System Model (CESM) Last Millennium Ensemble (LME). The first is an unforced control simulation, wherein all boundary conditions were held constant at their 850 CE values (LMEcontrol). The second is a “fully forced” simulation with time evolving radiative changes from volcanic, solar, and land use changes from 850 CE through present (LMEforced). Large tropical volcanic eruptions produce the greatest change in radiative forcing during this time period, which comprise the focus of this study. The Weather Research and Forecasting (WRF) model is used to dynamically downscale 150 control years of LMEcontrol and an additional 84 years of LMEforced for all mid-latitude volcanic eruptions between 1100 and 1850 CE. This time period was selected based on computational considerations. For each eruption, 2 years are dynamically downscaled. 23 of these volcanic eruptions are in the Northern Hemisphere and 19 are in the Southern Hemisphere. The effectiveness of the downscaling methodology is examined by applying the same downscaling approach to historical ERA-I reanalysis data and comparing the downscaled storm tracks and intensities to the International Best Track Archive for Climate Stewardship (IBTrACS) database. Hurricane statistics are then computed from both the downscaled control and downscaled forced LME simulations. Results suggest moderate effects on hurricanes from the average of all northern hemisphere eruptions, with the largest effects being from the volcanoes with the most aerosol forcing. More specifically, reductions in hurricane frequency, intensity, and lifetime following northern hemisphere eruptions are apparent. Strong evidence is also shown for correlation between eruption strength and changes in these diagnostics. The aggregate effect from both northern and southern hemisphere eruptions is minor. While reductions in frequency, intensity, and lifetime from northern hemisphere eruptions occur, the opposite effect is observed from southern hemisphere eruptions.

Integration of DInSAR Time Series and GNSS Data for Continuous Volcanic Deformation Monitoring and Eruption Early Warning Applications

With approximately 800 million people globally living within 100 km of a volcano, it is essential that we build a reliable observation system capable of delivering early warnings to potentially impacted nearby populations. Global Navigation Satellite System (GNSS) and satellite Synthetic Aperture Radar (SAR) document comprehensive ground motions or ruptures near, and at, the Earth’s surface and may be used to detect and analyze natural hazard phenomena. These datasets may also be combined to improve the accuracy of deformation results. Here, we prepare a differential interferometric SAR (DInSAR) time series and integrate it with GNSS data to create a fused dataset with enhanced accuracy of 3D ground motions over Hawaii island from November 2015 to April 2021. We present a comparison of the raw datasets against the fused time series and give a detailed account of observed ground deformation leading to the May 2018 and December 2020 volcanic eruptions. Our results provide important new estimates of the spatial and temporal dynamics of the 2018 Kilauea volcanic eruption. The methodology presented here can be easily repeated over any region of interest where an SAR scene overlaps with GNSS data. The results will contribute to diverse geophysical studies, including but not limited to the classification of precursory movements leading to major eruptions and the advancement of early warning systems.

Clear and Present Dangers: The Multiple Health Hazards of Volcanic Eruptions.

Clear and Present Dangers: The Multiple Health Hazards of Volcanic Eruptions.

Evolution of the magma plumbing system of Miyakejima volcano with periodic recharge of basaltic magmas

Defining the variations in petrological characteristics of erupted magmas within a high-resolution chronostratigraphy provides a necessary framework for monitoring the long-term activity and eruption potential of an active volcano. Here, we investigate the evolution of the magmatic system of Miyakejima volcano, Japan, between the last two caldera-forming eruptions, at ~ 2.3 ka and AD 2000, based on new stratigraphic constraints, radiocarbon ages, and whole-rock geochemical data. The activity of Miyakejima during this interval can be divided into three magmatic periods based on cyclic whole-rock compositional trends. Period 1 spans the interval between ~ 2.3 ka and the 7th century, from the Hatchodaira eruption with caldera collapse to immediately before the Suoana–Kazahaya eruption. Period 2 spans the time period between the seventh century and the fourteenth century, from the Suoana–Kazahaya to the Sonei–bokujyo eruptions. Period 3 covers the period from the two major flank eruptions that occurred in the sixteenth century to the end of the twentieth century until the last caldera-collapse event in AD 2000. The eruption rate decreased from 0.5 km3 per 1000 years in Period 1 to ~ 0.2 km3 per 1000 years in Period 2 and 3. Recharge of primitive basaltic magmas into shallower crustal systems triggered extensive basaltic fissure eruptions at the beginning of each period. Progressively increasing whole-rock SiO2 contents of the hybrid magmas in subsequent eruptions indicates continuous fractional crystallization in small shallow magma chambers which formed at the start of each magmatic period. Intermittent injections of basaltic magma into shallow magma chambers induced magma mixing that caused eruption of hybrid basaltic andesite in each period. We suggest that some basaltic magmas formed isolated magma reservoirs at shallow depth, in which rapid fractionation was able to occur. Rupturing of these isolated magma storage regions filled with gas-rich evolved magma can lead to violent ejection of andesitic magmas, such as for the Suoana–Kazahaya eruption in the seventh century. Our results suggest two main scenarios of eruption for the basaltic magma system at Miyakejima and similar mafic volcanoes in the northern Izu–Bonin arc; (1) eruption of voluminous basaltic lavas after the recharge of primitive basaltic magmas into the shallow magmatic system, and (2) explosive fissure eruption by rupturing of isolated magma bodies filled with gas-rich evolved magmas.Graphical

Spatial - Temporal variability of Land Use Land Cover at Mount Merapi, Indonesia

One of the most active volcanoes in the island of Java is Merapi mount which was experienced the last major eruption peak on October 26th, 2010. This volcanic eruption was effusive eruption type where magmatic gas pressure in the crater was not too strong and magma eruption was just flown out past the slopes of the Merapi mount area. However, magmatic gas pressure and magma volume still result in deformation changes that have a direct impact on residential areas throughout the Merapi mount area. Residential areas were obtained through supervised classification process from Landsat 7 and 8-satellite imagery in the 2009, 2011 and 2019 acquisition year. The reason of observation year selection was based on pre and post eruption concept to get pattern of Merapi’s mountain body change through deformation analysis. The work focuses on spatial-temporal variability of land use land cover analysis at Mount Merapi pre and post 2010 eruption event considered here. The technique is based on NDVI (Normalized Difference Vegetation Index), Maximum Likelihood Classification (MLC) and False Colour Composite methodology. Based on change in number of pixels it was analysed. Actually, some portion of land was covered with clouds and its shadows. From the results it was observed that, water body, barren and built up features were miss classified. So finally False Colour Composite (FCC) images are used to identify the misclassified classes.

Age of the oldest known Homo sapiens from eastern Africa

Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish1–3 and Herto4,5 in Ethiopia, have drawn on a variety of chronometric evidence, including 40Ar/39Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I3,6,7, and around 160–155 kyr for the Herto hominins5,8. However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged6,8. Here we report geochemical analyses that link the Kamoya’s Hominid Site (KHS) Tuff9, which conclusively overlies the member of the Omo-Kibish Formation that contains Omo I, with a major explosive eruption of Shala volcano in the Main Ethiopian Rift. By dating the proximal deposits of this eruption, we obtain a new minimum age for the Omo fossils of 233 ± 22 kyr. Contrary to previous arguments6,8, we also show that the KHS Tuff does not correlate with another widespread tephra layer, the Waidedo Vitric Tuff, and therefore cannot anchor a minimum age for the Herto fossils. Shifting the age of the oldest known Homo sapiens fossils in eastern Africa to before around 200 thousand years ago is consistent with independent evidence for greater antiquity of the modern human lineage10.

Decadal Temperature Variations Over the Northwestern Tibetan Plateau Deduced From a 489‐Year Ice Core Stable Isotopic Record

AbstractInformation on decadal temperature variations over the northwestern Tibetan Plateau (TP) is still very limited due to a lack of long‐term instrumental data. In this paper, we present a 489‐year (1524–2012 A.D.) reconstruction of annual mean temperature for the northwestern TP using the δ18O record of a 58.82 meter‐long shallow ice core retrieved on the Chongce ice cap in the western Kunlun Mountains. The reconstructed temperature exhibits significant decadal variations, which were mainly driven by the Atlantic Multidecadal Variability. Decadal temperature variation during the Little Ice Age (LIA) is significantly larger than that during the post‐industrial warming period, possibly due to such external forcing as large fluctuations of solar activity and frequent major volcanic eruptions during the LIA. In addition, our reconstruction shows that the recent warming since the 1980s is moderate, comparable to an earlier warm interval in the mid‐20th century, which may partly explain the relatively stable status of glaciers in this region since 1970s.

Sanbe volcano: Long‐term evolution of an arc magmatic system

AbstractA suite of samples was studied that represents the major explosive eruptions of Sanbe volcano, SW Japan. We demonstrate how rate of magma flux into the Trans‐Crustal Magmatic System (TCMS) presents a major control on the type and style of the subsequently forthcoming eruptions. Erupted products can be separated into two distinct groups. An older group is characterized by highly evolved, high‐K, LILE‐rich rhyolitic magmas, showing a supressed adakitic trace element signature (otherwise characteristic for the young stratovolcanoes in the SW Japan arc) with low Ca, Sr concentrations and a negative Eu anomaly. In contrast, the younger group (dominantly of andesitic—dacitic composition) displays a strong adakitic trace element signature with characteristic steep REE profiles and high Sr concentrations. An Eu anomaly is generally lacking here. The two groups are also distinct in their petrographic features, with the early group being almost aphyric showing simple log linear crystal size distributions and homogeneous, uniform mineral chemistries. In contrast, products of the younger group show complex crystal size distributions with diverse mineral compositions and abundant disequilibrium features. Our study shows that an initial high melt‐production rate allowed dehydration melting of lower crustal rocks leading to the formation of highly evolved K‐rich magmas. These magmas intruded into the shallow crust and produced two large Plinian rhyolitic, caldera forming eruptions. Subsequently the primary magma production rate decreased and the lower crust became too refractory for additional dehydration melting by these lower volume magma batches, causing the conventional adakitic magmatism to produced several additional eruptions of smaller magnitude, mainly of Sub‐Plinian or Pelean styles.

The 1815 Tambora eruption: Its significance to the understanding of large-explosion caldera formations

Volcanic calderas, plentiful on the Earth and the moon, have been of much interest to volcanologists because of their large dimensions and extensive volumes of ejecta. Here, we consider the dynamics of caldera-forming by major explosive eruptions, examining how the breakdown of the earth's surface is caused by violent igneous activity. This leads to the definition of “typical explosion caldera”, which is a prototype of several newly-formed calderas in the historical timescale. There are three examples of such calderas: Tambora (Sumbawa), Krakatau (Sunda Straits), and Novarupta (Alaska). Tam- bora Caldera is the best example of a well-documented, recently formed typical explosion caldera, with no significant subsequent eruptions occurring after its formation. The subsurface structure of Tambora Caldera is discussed and compared to the 1883 eruption of Krakatau, the second largest eruption in historical times. Then, contrasting with the typically basaltic “collapse-type” calderas, a “Tambora-caldera type” is defined as a large “explosion-type” caldera, that may reach up to 10 km in diameter. The Tambora- type caldera concept is useful to qualify and understand the structure and components of other major calderas in the world. Fully developed larger explosion calderas such as Aso and Aira Calderas in Kyushu, Japan are discussed and explained as composite calderas based on geophysical data. Those calderas have repeatedly ejected massive pyroclastic products causing their original structures to grow wider than 10 km.

The explosive, basaltic Katla eruption in 1918, south Iceland, II: Isopach map, ice cap deposition of tephra and layer volume

Due to poor preservation and lack of proximal tephra thickness data, no comprehensive isopach map has existed for the tephra layer from the major eruption of the Katla volcano in 1918. We present such a map obtained by combining existing data on the thickness of the 1918 tephra in soil profiles with newly acquired data from the 590 km² Mýrdalsjökull ice cap which covers the Katla caldera and its outer slopes. A tephra thickness of 20–30 m on the ice surface proximal to the vents is inferred from photos taken in 1919. The greatest thicknesses presently observed, 30–35 cm, occur where the layer outcrops in the lowermost parts of the ablation areas of the Kötlujökull and Sólheimajökull outlet glaciers. A fallout location within the Katla caldera is inferred for the presently exposed tephra in both outlet glaciers, as estimates of balance velocities imply lateral transport since 1918 of ∼15 km for Kötlujökull, ∼11 km for Sólheimajökull and about 2 km for Sléttjökull. Calculations of thinning of the tephra layer during this lateral transport indicate that the presently exposed tephra layers in Kötlujökull and Sólheimajökull were respectively over 2 m and about 1.2 m thick where they fell while insignificant thinning is inferred for the broad northern lobe of Sléttjökull. The K1918 layer has an estimated volume of 0.95±0.25 km³ (corresponding to 1.15±0.30×1012 kg) whereof about 50\% fell on Mýrdalsjökull. About 90\% of the tephra fell on land and 10\% in the sea to the south and southeast of the volcano. The volume estimate obtained contains only a part of the total volume erupted as it excludes water-transported pyroclasts and any material that may have been left on the glacier bed at the vents. While three main dispersal axes can be defined (N, NE and SE), the distribution map is complex in shape reflecting tephra dispersal over a period of variable wind directions and eruption intensity. In terms of airborne tephra, Katla 1918 is the largest explosive eruption in Iceland since the silicic eruption of Askja in 1875.

Climate Response to Latitudinal and Altitudinal Distribution of Stratospheric Sulfate Aerosols

AbstractStratospheric aerosol injection is one of the most widely studied solar radiation modification methods to reduce some effects of anthropogenic warming. We perform idealized simulations to analyze climate response to different latitudinal and altitudinal distributions of additional stratospheric sulphate aerosols. We analyze climate response to both large volcanic‐size aerosols that are representative of sulphate aerosols which form when SO2 is injected into the stratosphere by major volcanic eruptions or by proposed stratospheric sulphate aerosol geoengineering option, and small background‐size aerosols which are present in the stratosphere during quiescent periods with no major volcanic eruptions. Our simulations show that under the climate state with doubled atmospheric CO2, for the same total mass, independent of size‐distributions, aerosols concentrated at higher latitudes produce less negative effective radiative forcing but larger surface cooling as a result of larger forcing efficacy. For the same latitudinal distribution, small background‐size aerosols added at lower altitudes cause larger surface cooling as a result of hygroscopic growth that increases scattering of sunlight. In contrast, large volcanic‐size aerosols added at lower altitudes cause smaller surface cooling than at higher altitudes as a result of enhanced stratospheric heating and associated water vapor feedback that enhance absorption of solar and terrestrial radiation. For both background‐size and volcanic‐size aerosols, asymmetric distributions about the equator induce substantial cross‐equatorial energy transport, causing the Intertropical Convergence Zone to move to the warmer hemisphere with less aerosol loading. Our study helps to understand the climate consequences of different spatial patterns and size distributions of stratospheric aerosol perturbation.

Rapid Evolution of Bald Patches in a Major Solar Eruption

Abstract A bald patch (BP) is a magnetic topological feature where U-shaped field lines turn tangent to the photosphere. Field lines threading the BP trace a separatrix surface where reconnection preferentially occurs. Here we study the evolution of multiple, strong-field BPs in AR 12673 during the most intense, X9.3 flare of solar cycle 24. The central BP, located between the initial flare ribbons, largely “disintegrated” within 35 minutes. The more remote, southern BP survived. The disintegration manifested as a 9° rotation of the median shear angle; the perpendicular component of the horizontal field (with respect to the polarity inversion line) changed sign. The parallel component exhibited a step-wise, permanent increase of 1 kG, consistent with previous observations of the flare-related “magnetic imprint.” The observations suggest that magnetic reconnection during a major eruption may involve entire BP separatrices, leading to a change of magnetic topology from BPs to sheared arcades.

Geomorphological hazard at some area of the Outer Dieng Volcanic Complex post explosive eruption era

Dieng area as an important and productive area needs the support of various aspects in encouraging regional growth and development. This region also has been experiences many disasters year by year. Disasters due to volcanism are events that cause many losses, especially casualties in the past. Discussions about potential disasters in the Dieng area should not only be limited to volcanism and earthquakes as hazards caused by endogenous processes. The Dieng area is an old landscape. As an old landscape that is heavily influenced by exogenous factors from a wet tropical climate, other potential hazards in the form of geomorphological hazards also need attention. In fact, there are some geomorphological hazards that occur due to the complexity of the landforms of this area, there are various processes that often occur such as mass movement and erosion and these processes usually have a negative impact on social and economic life. This paper aims to analyze the various types and levels of geomorphological hazards that exist outside of the Dieng Volcanic Complex. This region has experienced major eruptions in the past. At present, in the post-explosive era, it is necessary to know whether geomorphological hazards are limited to eruptions or if other hazards are a bigger threat. The terrain survey method or geomorphological survey is a field observation method used to achieve research objectives. The interpretation of remote sensing images, literature research, and documentation provides support in the form of additional data to complement the primary data from the observation. The results obtained show that the area of the Dieng Volcanic Complex after the explosive eruption era, which is largely composed of volcanic landforms, which physically dominates the denudation process. The denudation process is what causes mass movement and erosion to emphasize that there is a very high potential geomorphological hazard in this research location. This research area is also a productive agricultural production area. Although it cannot be separated from criticism because of its negative impact on the environment, because in the use and management of land carried out by the community it affects mass movement and erosion. Therefore, information on geomorphological hazards is very important to be provided and updated continuously in the interest of ensuring effective and sustainable disaster management.

Southern Hemisphere continental temperature responses to major volcanic eruptions since 1883 in CMIP5 models

Southern Hemisphere continental temperature responses to major volcanic eruptions since 1883 in CMIP5 models

Spring arctic oscillation as a trigger of summer drought in Siberian subarctic over the past 1494\xa0years

Rapid changes in the hydrological and temperature regimes over the past decades at the northern latitudes enhance significantly permafrost degradation accelerating carbon release, increase the frequency of drought events and extensive wildfires. However, the mechanisms and dynamics driving drought events and their influence on Siberian forests are currently the subject of numerous research activities. Newly developed and annually resolved stable carbon and oxygen isotope chronologies of larch tree-ring cellulose (δ13Ccell and δ18Ocell) for the period 516–2009 CE allowed the reconstruction of July precipitation and Arctic Oscillation (AO) in May, respectively. Unprecedented drought events occurred towards twentieth–twenty-first centuries as indicated by the July precipitation reconstruction. Positive AO phases in May were most pronounced during the second part of the first millennium, but also increased in frequency in the modern period of the twentieth–twenty-first centuries. Negative AO phases are associated with cold anomalies and show a remarkable decrease in the nineteenth century caused by a series of major volcanic eruptions. Our findings help explaining the increased frequency of Siberian forest fires over the past decades in Central Siberia consistent with a reduction of summer precipitation, triggered by a positive phase of the Arctic Oscillation in May.

Mantle xenolith-bearing phonolites and basanites feed the active volcanic ridge of Mayotte (Comoros archipelago, SW Indian Ocean)

Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the site of a major eruption located at 3.5 km depth bsl on a WNW-ESE volcanic ridge. Samples brought by oceanographic cruises carried out to monitor this seismo-volcanic crisis indicate that this volcanic ridge is built by a bimodal sodic alkaline magmatic series that includes basanites and phonolites. A petrological study of dredged samples allowed us to image the magmatic system feeding the volcanic ridge and to determine the link between basanitic and phonolitic magmas. The magmatic system feeding the volcanic ridge comprises multiple levels of magma storage. Basanitic magmas generated at 80–100 km mantle depth are stored in two or more deep reservoirs (≥ 37 km) and then in shallower basanitic and phonolitic lenses located close to the Moho interface before rising the surface. This study identifies three possible scenarios: (1) the deep basanitic magma rises directly and quickly to the surface from the deep mantle reservoir (as is currently happening 60 km offshore), (2) the basanitic magma stalls in a shallower reservoir near the Moho before resuming its ascent toward the surface and erupting as porphyritic basanite, (3) the basanitic magma stops and evolves to phonolite in these sub-crustal reservoirs. The phonolitic lavas are produced by approximately 80% fractional crystallization (34% clinopyroxene, 30% anorthoclase feldspar, 15.5% magnetite, 12.5% olivine, 5% apatite and 4% ilmenite) of a hydrous basanitic magma at mantle depths (P > 0.6 GPa) under reduced oxygen fugacity (~ FMQ-1). In this third scenario, the phonolitic magma might be reactivated by the arrival of a new batch of deeper basanitic magma.