Km In Radius Research Articles

Small planetesimals in a massive disk formed Mars

Mars is likely to be a planetary embryo formed through collisions with planetesimals, which can explain its small mass and rapid formation timescale obtained from 182Hf–182W chronometry. In the classical theory of planet formation, the final embryo mass is determined only by the solid surface density. However, embryos can stir surrounding planetesimals, leading to fragmentation through erosive (cratering) collisions. We find that radial drift of small fragments can drastically reduce the solid surface density. On the other hand, embryo growth is accelerated by fragment accretion. Since collisional fragmentation efficiency depends on the initial size of planetesimals, the final embryo mass and its growth time are determined by the initial planetesimal size and disk surface density. We have investigated the effect of these two parameters on the mass of Mars and the predicted radiogenic excess of 182W in the martian mantle. Two scenarios can explain the rapid formation of small Mars: (i) it formed by accretion of small planetesimals in a massive disk or (ii) it formed from large planetesimals but its growth was arrested by the inward then outward migration of Jupiter. Taking into account all constraints, we conclude that Mars is likely to have formed in a massive disk of about ∼0.1 solar mass from planetesimals smaller than ∼10km in radius. Such small planetesimal size cannot explain core accretion of Jupiter, suggesting that there may have been a heliocentric gradient in planetesimal size in the solar nebula.

Mn–Cr ages of dolomites in CI chondrites and the Tagish Lake ungrouped carbonaceous chondrite

53Mn–53Cr ages have been measured for dolomites in three CI chondrites and an ungrouped C2 chondrite Tagish Lake. For an accurate age determination, we utilized, in contrast to previous works, a matrix-matched carbonate standard to appropriately correct the observed Mn/Cr ratios. The Mn–Cr data of the dolomites most likely represent isochrons with chronological significances and the obtained ages are concentrated in 4563.8–4562.5 million years ago (4.4–5.7 million years after the birth of the solar system). The ages of the CI and Tagish Lake dolomites are very similar to those of carbonates in CM chondrites, although CI and CM chondrites are likely to have different alteration histories. The similar carbonate ages in various carbonaceous chondrites suggest that the aqueous activities in hydrous asteroids initiated almost concurrently. If this is the case, the most plausible heat source for the aqueous alteration is the decay energy of short-lived radionuclides, especially 26Al. We carried out a model calculation for the thermal history of the CI chondrite parent body assuming that 26Al is the dominant heat source. By two different approaches to estimate the accretion time of the CI chondrite parent body, we conclude that it accreted 3.0–3.9 million years after the birth of the solar system. This is also likely to be the case for the CM chondrite and Tagish Lake parent bodies, because the result of the calculation is not sensitive to the ice abundance. Therefore, we stress that near the condensation front of water ice, meteorite parent bodies with abundant ice accreted almost simultaneously at 3–4 million years after CAI formation. Combining our Mn–Cr ages of the dolomites with those of breunnerites reported previously (the youngest one is 4554.6 million years ago), we found that the aqueous alteration in the CI chondrite parent body lasted for at least 9 million years. Therefore, the parent body should be large enough (>50km in radius) so that the internal heat had been kept for 9 million years.

219 広域処理を考慮した食品系廃棄物の有効利用システムのLCA(環境マネジメント・手法(2))

Effective use of food waste is needed from a viewpoint of recycling and energy utilization system. But, it is in the situation which is hard to say that sufficient measure is progressing, because of not to have evaluated objectively superiority such as recycling and energy utilization system, to differ in the conditions of a systems configuration with the local characteristic and so on. Therefore, in order to examine the effective use of food waste generated in regional areas, the recycling and energy utilization system was evaluated by LCA. First, We carried out the case study based on the knowledge of reducing the environmental impacts of a processing system with selection of recovery area and cooperation with an existing infrastructure like a garbage processing plant. As a result, It turned out that it is most excellent that we perform a methane fermentation institution on the basis of less than 20 km in radius.

Luminous Shapes with Unusual Motions as Potential Predictors of Earthquakes: A Historical Summary of the Validity and Application of the Tectonic Strain Theory

For centuries and on every continent discrete shapes of lights with unusual motions have preceded earthquakes. The numbers of these lights per interval within a region have been strongly correlated with the amount of seismic energy subsequently released within that region. These temporal intervals range between 3 months and 6 months for areas more than 500 kmin radius and less than a month for smaller radii. Other analyses have shown that the same tectonic strain associated with earthquakes is also associated with the display of luminous events before those earthquakes. This strain can be precipitated by injections of fluids into the crust, natural changes in hydrological loads on rivers, or, purposeful displacement of water into reservoirs. The strengths of the associations are sufficient to allow modest forecasting of earthquakes within the boundaries of the region and the temporal interval of analysis. More accurate utilization of these phenomena as prognosticators of specific earthquakes will require a re-evaluation of the manner by which these data are systematically recorded and interpreted.

Expanding-contracting Earth

The Earth was born from a giant impact at 4.56 Ga. It is generally thought that the Earth subsequently cooled, and hence shrunk, over geologic time. However, if the Earth's convection was double-layered, there must have been a peak of expansion during uni-directional cooling. We computed the expansion-contraction effect using first principles mineral physics data. The result shows a radius about 120 km larger than that of the present Earth immediately after the consolidation of the magma-ocean on the surface, and subsequent shrinkage of about 110 km in radius within about 10 m.y., followed by gradual expansion of 11 km in radius due to radiogenic heating in the lower mantle in spite of cooling in the upper mantle in the Archean. This was due to double-layered convection in the Archean with final collapse of overturn with contraction of about 8 km in radius, presumably by the end of the Archean. Since then, the Earth has gradually cooled down to reduce its radius by around 12 km. Geologic evidence supports the late Archean mantle overturn ca. 2.6 Ga, such as the global distribution of super-liquidus flood basalts on nearly all cratonic fragments (>35 examples). If our inference is correct, the surface environment of the Earth must have undergone extensive volcanism and emergence of local landmasses, because of the thin ocean cover (3–5 km thickness). Global unconformity appeared in cratonic fragments with stromatolite back to 2.9 Ga with a peak at 2.6 Ga. The global magmatism brought extensive crustal melting to yield explosive felsic volcanism to transport volcanic ash into the stratosphere during the catastrophic mantle overturn. This event seems to be recorded by sulfur mass-independent fractionation (SMIF) at 2.6 Ga. During the mantle overturn, a number of mantle plumes penetrated into the upper mantle and caused local upward doming of by ca. 2–3 km which raised local landmasses above sea-level. The consequent increase of atmospheric oxygen enabled life evolution from prokaryotes to eukaryotes by 2.1 Ga, or even earlier in the Earth history.

Comet P/2010 TO20 LINEAR-Grauer as a Mini-29P/SW1

Discovered in October 2010 by the LINEAR survey, P/2010 TO20 LINEAR-Grauer (LG) was initially classified as an inert Jupiter Trojan. Subsequent observations obtained in October 2011 revealed LG to be a Jupiter-family comet. LG has one of the largest perihelia (q=5.1 AU) and lowest eccentricities (e=0.09) of the known JFCs. We report on observations of LG taken on 29 October 2011 and numerical simulations of its orbital evolution. Analysis of our data reveals that LG has a small nucleus (<3 km in radius) with broadband colours (B-R=0.99+/-0.06 mag, V-R=0.47+/-0.06 mag) typical of JFCs. We find a model dependent mass-loss rate close to 100 kg/s, most likely powered by water-ice sublimation. Our numerical simulation indicate that the orbit of LG is unstable on very short (10 to 100 yr) timescales and suggest this object has recently evolved into its current location from a more distant, Centaur-type orbit. The orbit, dynamics and activity of LG share similarities with the well known case of comet 29P/Schwassmann-Wachmann 1.

Lightning Distribution and Eyewall Outbreaks in Tropical Cyclones during Landfall

Abstract Cloud-to-ground lightning data and storm intensity data (winds and central pressure) for 33 northwest Pacific tropical cyclones were used to analyze lightning distributions during the period of landfall in China. Lightning activities varied enormously from storm to storm with an average flash rate over 500 km of radius from 3 to 3201 flashes per hour, and no obvious relationship between average intensity and average flash rate occurred. The maximum flash density shifted from the eyewall region (0–60 km) to outer rainbands (180–500 km) as the intensity level increased. The average ratio of flash density in the eyewall to outer rainband was highest (1:0.5) for storms with the level of a tropical storm (17.2–24.4 m s−1) and lowest (1:8.6) for severe typhoons (41.5–50.9 m s−1). After storm landfall, flash density in the rainband decreased more rapidly in severe typhoons than in severe tropical storms (24.5–32.6 m s−1) and typhoons, but increased in tropical depressions (10.8–17.1 m s−1) and tropical storms. With the strength of intensity level, lightning in the outer rainband gradually weakened after the storm landfall. Lightning outbreaks were identified in a consistent manner for all tropical cyclones to inspect the relationship of eyewall flashes to the changes of structure and intensity. Eyewall flash outbreaks were found during the period of intensity change (15% of outbreaks in intensification and 43% in weaken), and the period of maximum intensity (15% of outbreaks) of storms. A new result of this analysis found that 10% of the outbreaks occurred prior to and during periods of storm turning, which is potentially important for the trajectory change forecasting of tropical cyclones.

Environmental analysis of breeding sites of Lanner, Falco biarmicus, in Lazio

We examined 7 breeding sites of Lanner, Falco biarmicus, situated between 150 and 1200 m a.s.l. in Lazio, we analyzed the land cover use (types of Corine land cover) for each site in a buffer of 2 km of radius (1,250 ha) from the nest and we calculated the area of the single classes of land cover use present in each buffer. We found that the “Broad-leaved forest” covers 48% (33-76%), “Non-irrigated arable land” 22% (3-47%), “Moors and heathland” 6% (1-15%), the “Sparsely vegetated areas” 5% (1-20%), the remaining area covered is represented by classes with less than 5% of the area. Locally other classes such as “Natural grassland” (13% in one site) can become relevant. The classes related to “Artificial surfaces” are scarce (max 2% on one site).

Angrites, a small but diverse suite of ancient, silica-undersaturated volcanic-plutonic mafic meteorites, and the history of their parent asteroid

Angrites are medium- to coarse-grained (up to 2–3mm), unbrecciated and substantially unshocked igneous rocks of roughly basaltic composition. They are the most alkali-depleted basalts in the Solar System, but are not very depleted in moderately volatile elements such as Br, Se, S, Zn, In and Cd, and are relatively enriched in refractory elements such as Ca and Ti. They have uniform oxygen isotopic compositions and form a mass fractionation line on a Δ17O vs. δ18O diagram of Δ17O=−0.072±0.007 that sets them apart from other extraterrestrial basalts such as the HEDs. They consist of major Al-Ti-bearing diopside-hedenbergite (formerly called fassaite), calcic olivine, and anorthite. Minor and accessory phases include kirschsteinite, spinel, ulvöspinel, metallic Fe,Ni, troilite, titanomagnetite, whitlockite, ilmenite, and very rare carbonates, celsian, rhönite, and baddeleyite. On the basis of texture and mineralogical composition, they are divided into plutonic (5 members, +8 paired specimens) and volcanic (quenched) (6 members) angrites. Plutonic angrites have hypidiomorphic to granular and cumulate textures and contain nearly equilibrated, homogeneous minerals, whereas volcanic angrites have quench textures and consist of highly zoned minerals. These differences are the result of their different cooling rates: plutonic angrites cooled at model dependent rates of ∼303–323K/a or ∼274.6–275.4K/a (burial depths 14–17 or 68–75m, respectively), whereas volcanic angrites cooled at ∼280–286K/h in the temperature range of 1573–1273K, implying a burial depth of <0.5m. The angrites are amongst the oldest basaltic rocks in the Solar System, and Pb-Pb ages show that the slowly cooled plutonic angrites have younger ages ranging from ∼4558.86±0.30 to 4557.65±0.13Ma, and the more quickly cooled volcanic angrites have older ages ranging from 4564.18±0.14 to 4563.8±0.4Ma. While it has been suggested that the planet Mercury may be the source of the angrites, overwhelming evidence has been accumulated that they are fragments of a differentiated asteroid, probably >100km in radius and with a metal core which, based on 182Hf-182W systematics, formed within ∼2Ma of CAI formation. The origin and source lithologies of these fascinating rocks have been the topics of intense debates, and no consensus has yet been reached. However, the angrites are clearly igneous rocks and not impact melt-rocks or nebular condensates.

The Impact of Dry Midlevel Air on Hurricane Intensity in Idealized Simulations with No Mean Flow

Abstract This study examines the potential negative influences of dry midlevel air on the development of tropical cyclones (specifically, its role in enhancing cold downdraft activity and suppressing storm development). The Weather Research and Forecasting model is used to construct two sets of idealized simulations of hurricane development in environments with different configurations of dry air. The first set of simulations begins with dry air located north of the vortex center by distances ranging from 0 to 270 km, whereas the second set of simulations begins with dry air completely surrounding the vortex, but with moist envelopes in the vortex core ranging in size from 0 to 150 km in radius. No impact of the dry air is seen for dry layers located more than 270 km north of the initial vortex center (~3 times the initial radius of maximum wind). When the dry air is initially closer to the vortex center, it suppresses convective development where it entrains into the storm circulation, leading to increasingly asymmetric convection and slower storm development. The presence of dry air throughout the domain, including the vortex center, substantially slows storm development. However, the presence of a moist envelope around the vortex center eliminates the deleterious impact on storm intensity. Instead, storm size is significantly reduced. The simulations suggest that dry air slows intensification only when it is located very close to the vortex core at early times. When it does slow storm development, it does so primarily by inducing outward-moving convective asymmetries that temporarily shift latent heating radially outward away from the high-vorticity inner core.

A perfect focus of the internal tide from the Mariana Arc

[1] The Mariana Arc of ridges and islands forms an ∼1300-km-long arc of a circle, ∼630 km in radius centered at 17°N, 139.6°E. The hypothesis that the westward-propagating internal tides originating from the arc converge in a focal region is tested by examining the dominant M2 internal tides observed with air-launched expendable bathythermographs (AXBTs) and altimetric data from multiple satellites. The altimetric and AXBT observations agree well, though they measure different aspects of the internal tidal motion. M2 internal tides radiate both westward and eastward from the Mariana Arc, with isophase lines parallel to the arc and sharing the same center. The westward-propagating M2 internal tides converge in a focal region, and diverge beyond the focus. The focusing leads to energetic M2 internal tides in the focal region. The spatially smoothed energy flux is about 6.5 kW/m, about four times the mean value at the arc; the spatially un-smoothed energy flux may reach up to 17 kW/m. The size of the focus is close to the Rayleigh estimate; it is thus a perfect focus.

Size of the group IVA iron meteorite core: Constraints from the age and composition of Muonionalusta

The group IVA fractionally crystallized iron meteorites display a diverse range of metallographic cooling rates. These have been attributed to their formation in a metallic core, approximately 150 km in radius, that cooled to crystallization in the absence of any appreciable insulating mantle. Here we build upon this formation model by incorporating several new constraints. These include (i) a recent U–Pb radiometric closure age of < 2.5 Myr after solar system formation for the group IVA iron Muonionalusta, (ii) new measurements and modeling of highly siderophile element compositions for a suite of IVAs, and (iii) consideration of the thermal effects of heating by the decay of the short-lived radionuclide 60Fe. Our model for the thermal evolution of the IVA core suggests that it was approximately 50–110 km in radius after being collisionally exposed. This range is due to uncertainties in the initial abundance of live 60Fe incorporated into the IVA core. Our models define a relationship between cooling rate and closure age, which is used to make several predictions that can be tested with future measurements. In general, our results show that diverse cooling rates and early U–Pb closure ages can only coexist on mantle-free bodies and that energy released by the decay of 60Fe reduces the core size necessary to produce diverse metallographic cooling rates. The influence of 60Fe on cooling rates has largely been neglected in previous core formation models; accounting for this heat source can affect size estimates for other iron meteorite cores that cooled to crystallization in the presence of live 60Fe. Candidates for such a scenario of early, mantle-free formation include the iron IIAB, IIIAB and IVB groups.

Chondrites as samples of differentiated planetesimals

Chondritic meteorites are unmelted and variably metamorphosed aggregates of the earliest solids of the solar system. The variety of metamorphic textures in chondrites motivated the “onion shell” model in which chondrites originated at varying depths within a parent body heated primarily by the short-lived radioisotope 26Al, with the highest metamorphic grade originating nearest the center. Allende and a few other chondrites possess a unidirectional magnetization that can be best explained by a core dynamo on their parent body, indicating internal melting and differentiation. Here we show that a parent body that accreted to >~200 km in radius by ~ 1.5 Ma after the formation of calcium–aluminum-rich inclusions (CAIs) would have a differentiated interior, and ongoing accretion would add a solid undifferentiated crust overlying a differentiated interior, consistent with formational and evolutionary constraints inferred for the CV parent body. This body could have produced a magnetic field lasting more than 10 Ma. This hypothesis represents a new model for the origin of some chondrites, presenting them as the unprocessed crusts of internally differentiated early planetesimals. Such bodies may exist in the asteroid belt today; the shapes and masses of the two largest asteroids, 1 Ceres and 2 Pallas, can be consistent with differentiated interiors, conceivably with small iron cores with hydrated silicate or ice–silicate mantles, covered with undifferentiated crusts.

CONSTRAINTS ON CHARON'S ORBITAL ELEMENTS FROM THE DOUBLE STELLAR OCCULTATION OF 2008 JUNE 22

Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia and La Reunion Island, providing the east and north Charon Plutocentric offset in the sky plane (J2000): X= + 12,070.5 ± 4 km (+ 546.2 ± 0.2 mas), Y= + 4,576.3 ± 24 km (+ 207.1 ± 1.1 mas) at 19:20:33.82 UT on Earth, corresponding to JD 2454640.129964 at Pluto. This yields Charon's true longitude L= 153.483 ± 0fdg071 in the satellite orbital plane (counted from the ascending node on J2000 mean equator) and orbital radius r= 19,564 ± 14 km at that time. We compare this position to that predicted by (1) the orbital solution of Tholen & Buie (the solution), (2) the PLU017 Charon ephemeris, and (3) the solution of Tholen et al. (the solution). We conclude that (1) our result rules out solution TB97, (2) our position agrees with PLU017, with differences of ΔL= + 0.073 ± 0fdg071 in longitude, and Δr= + 0.6 ± 14 km in radius, and (3) while the difference with the T08 ephemeris amounts to only ΔL= 0.033 ± 0fdg071 in longitude, it exhibits a significant radial discrepancy of Δr= 61.3 ± 14 km. We discuss this difference in terms of a possible image scale relative error of 3.35 × 10-3in the 2002-2003 Hubble Space Telescope images upon which the T08 solution is mostly based. Rescaling the T08 Charon semi-major axis, a = 19, 570.45 km, to the TB97 value, a = 19636 km, all other orbital elements remaining the same (T08/TB97 solution), we reconcile our position with the re-scaled solution by better than 12 km (or 0.55 mas) for Charon's position in its orbital plane, thus making T08/TB97 our preferred solution.

Lightning risk warnings based on atmospheric electric field measurements in Brazil

This paper presents a methodology that employs the electrostatic field variations caused by thundercloud formation or displacement to generate lightning warnings over a region of interest in Southeastern Brazil. These warnings can be used to prevent accidents during hazardous operations, such as the manufacturing, loading, and test of motor-rockets. In these cases, certain equipment may be moved into covered facilities and personnel are required to take shelter. It is also possible to avoid the threat of natural and triggered lightning to launches. The atmospheric electric field database, including the summer seasons of 2007/2008 and 2008/2009 (from November to February), and, for the same period and region, the cloud-to-ground lightning data provided by the Brazilian lightning detection network - BrasilDAT - were used in order to perform a comparative analysis between the lightning warnings and the cloud-to- ground lightning strikes that effectively occurred inside the area of concern. The analysis was done for three areas surrounding the sensor installation defined as circles with 5, 10 and 15 km of radius to determine the most effective detection range. For each area it was done using several critical electric field thresholds: +/- 0.5; +/- 0.8; +/- 0.9; +/- 1.0; +/- 1.2; and +/- 1.5 kV/m. As a result of the reduction of atmospheric electric field data provided by the sensor installed in area of concern and lightning provided by BrasilDAT, it was possible, for each of the areas of alert proposals, to obtain the following parameters: the number of effective alarms; the number of false alarms; and the number of failure to warning. From the analysis of these parameters, it was possible to conclude that, apparently, the most interesting critical electric field threshold to be used is the level of 0.9 kV/m in association with a distance range of 10 km around the point where the sensor is installed.

VSB-30 sounding rocket: History of flight performance

The VSB-30 vehicle is a two-stage, unguided, rail launched sounding rocket, consisting of two solid propellant motors, payload, with recovery and service system. By the end of 2010, ten vehicles had already been launched, three from Brazil (Alcântara) and seven from Sweden (Esrange). The objective of this paper is to give an overview of the main characteristics of the first ten flights of the VSB-30, with emphasis on performance and trajectory data. The circular 3σ dispersion area for payload impact point has around 50 km of radius. In most launchings of such vehicle, the impact of the payload fell within 2 sigma. This provides the possibility for further studies to decrease the area of dispersion from the impact point.

OUTBURST OF COMET 217P/LINEAR

We present optical images of 217P/LINEAR taken with the Kiso 105 cm Schmidt Telescope. The images revealed a day-by-day variation of the 217P/LINEAR shape, indicating an outburst occurred. Since our observation started before the outburst event, we examined the morphological evolution of the expanding dust cloud produced by the outburst. It was found that the dust cloud expanded at a velocity of 120-140 m s–1 and that the comet became brighter by 1.7-2.3 mag. Using the observational result, we estimated that the onset time was 2009 October 13.4 and that the total mass released by the outburst was in the range of 106-109 kg. No fragments or split nuclei brighter than 18.5 mag (1.1 km in radius) were confirmed in our observations. Compared with other outbursts, we concluded that it was a relatively small event for an outburst.

THE SIZE DISTRIBUTION OF THE NEPTUNE TROJANS AND THE MISSING INTERMEDIATE-SIZED PLANETESIMALS

We present an ultra-deep survey for Neptune Trojans using the Subaru 8.2-m and Magellan 6.5-m telescopes. The survey reached a 50% detection efficiency in the R-band at 25.7 magnitudes and covered 49 square degrees of sky. This depth corresponds to Neptune Trojans that are about 16 km in radius (assuming an albedo of 0.05). A paucity of smaller Neptune Trojans (radii < 45 km) compared to larger ones was found. The brightest Neptune Trojans appear to follow a steep power-law slope (q = 5+-1) similar to the brightest objects in the other known stable reservoirs such as the Kuiper Belt, Jupiter Trojans and main belt asteroids. We find a roll-over for the Neptune Trojans that occurs around a radii of r=45+-10 km (23.5+-0.3 mags), which is also very similar to the other stable reservoirs. All the observed stable regions in the the solar system show evidence for Missing Intermediate Sized Planetesimals (MISPs). This indicates a primordial and not collisional origin, which suggests planetesimal formation proceeded directly from small to large objects. The scarcity of intermediate and smaller sized Neptune Trojans may limit them as being a strong source for the short period comets.

Evolution of Titan's rocky core constrained by Cassini observations

We model the thermal evolution of Titan's core and search for solutions that are consistent with the mean moment of inertia yielded by the Cassini‐Huygens Mission. Like previous studies we assume that Titan's core is enriched in hydrated silicates. However, our modeling accounts for the possible dehydration of these minerals. The resulting models are consistent with Titan's moment of inertia if the inner dry silicate core remains smaller than ∼1300 km in radius. This constraint is met if at least 30% of potassium was leached from the silicate during the hydration event, i.e., the core is depleted in one of its major heat source. In this scenario, the core is currently undergoing dehydration.

Volcanic evolution of São Vicente, Cape Verde Islands: The Praia Grande landslide

The island of São Vicente has undergone continuous volcanic activity from Pliocene to Pleistocene times. The earliest evidence of activity corresponds to some 9 million years ago when a submarine edifice of alkaline basaltic affinity had already started to develop. The island resulted from the growth of a single major edifice (the São Vicente Edifice) built up in several distinguishable growth stages. The early main stage occurred at 6.5 to 4.5 Ma giving rise to an edifice of about 10–12 km in radius and more than 2500 m in height whose centre was located south of the present city of Mindelo. Although the edifice in its earlier phase showed typical characteristics of a shield volcano (the Mindelo Formation) it adopted later on those of an ordinary composite volcano (the Madeiral–Monte Cara Formation). A giant landslide event, the Praia Grande landslide, destroyed the NE sector of the edifice and left a 10 × 12 km large depression that was successively refilled by nephelinitic lava flows and some associated carbonatites (the Monte Verde Formation, 4.5–3.1 Ma). The volcanic activity ceased about 3–2 Ma ago when the edifice started to be deeply eroded until disappearing about 90% of its total volume. Only in recent times (0.3 Ma) very scarce and local strombolian activity has been developed aside the São Vicente Edifice, in the eastern sector of the island.