The Impact of Volcanic Eruption on Decadal-Scale Climate Prediction Skill of Pacic Sea Surface Temperatures in the IAP Near-Term Climate Prediction System(IAP DecPreS)

Explosive volcanic eruptions are known to be a leading cause of natural climate change. There has been a growing recognition that there is a measurable climate system response even to moderate-sized volcanic eruptions. In this study, we investigated the hindcast skills of the Pacific Sea Surface Temperatures (SSTs) using the hindcast experiments based on the near-term climate prediction system DecPreS developed by the Institute of Atmospheric Physics (IAP)(hereafter DP-EnOI-IAU experiments). The DP-EnOI-IAU experiments were run for initial years from 1960 to 2005. These hindcasts took into account observed stratospheric aerosol concentrations that included the four large tropical volcanic eruptions during that period. The time evolution over the entire hindcast period for skill in predicting the patterns of the 3~7 year prediction averages for Pacific SSTs showed that there was statistically significant skill for most years except for a dramatic drop in skill during the 1980s and 1990s. Decadal hindcast skill is reduced if the post-eruption model response deviates the internal El Niño variability in the observations. The simulations showed a post-eruption SST of a La Niña-like pattern in the third northern winter after the 1982 El Chichon eruption and a El Niño-like pattern after the 1991 Pinatubo eruption, which were opposite in sign to what was in the observations. This lead to the loss of hindcast skill for years in the 1980s and 1990s affected by the eruptions. Agung (1963) happened to have post-eruption Pacific SSTs more similar to the observations and thus did not degrade prediction skill in the hindcasts.     

Pyroclastic Flow Hazard at Volcán Citlaltépetl

Volcán Citlaltépetl (Pico de Orizaba) with an elevation of 5,675 m is the highest volcano in North America. Its most recent catastrophic events involved the production of pyroclastic flows that erupted approximately 4,000, 8,500, and 13,000 years ago. The distribution of mapped deposits from these eruptions gives an approximate guide to the extent of products from potential future eruptions. Because the topography of this volcano is constantly changing computer simulations were made on the present topography using three computer algorithms: energy cone, FLOW2D, and FLOW3D. The Heim Coefficient (), used as a code parameter for frictional sliding in all our algorithms, is the ratio of the assumed drop in elevation (H) divided by the lateral extent of the mapped deposits (L). The viscosity parameter for the FLOW2D and FLOW3D codes was adjusted so that the paths of the flows mimicked those inferred from the mapped deposits. We modeled two categories of pyroclastic flows modeled for the level I and level II events. Level I pyroclastic flows correspond to small but more frequent block-and-ash flows that remain on the main cone. Level II flows correspond to more widespread flows from catastrophic eruptions with an approximate 4,000-year repose period. We developed hazard maps from simulations based on a National Imagery and Mapping Agency (NIMA) DTED-1 DEM with a 90 m grid and a vertical accuracy of ±30 m. Because realistic visualization is an important aid to understanding the risks related to volcanic hazards we present the DEM as modeled by FLOW3D. The model shows that the pyroclastic flows extend for much greater distances to the east of the volcano summit where the topographic relief is nearly 4,300 m. This study was used to plot hazard zones for pyroclastic flows in the official hazard map that was published recently.     

Basaltic subglacial sheet-like sequences: Evidence for two types with different implications for the inferred thickness of associated ice

Subglacially-erupted volcanic sequences provide proxies for a unique range of palaeo-ice parameters and they are potentially highly useful archives of palaeoenvironmental information, particularly for pre-Quaternary periods. They can thus be incorporated by climate and ice sheet modellers in the same way as other environmental proxies, yet they remain largely under-utilised. Basaltic volcanic sequences erupted subglacially consist empirically of two major types, corresponding to eruptions under “thick” and “thin” ice, respectively. The latter are called subglacial sheet-like sequences and only one generic type of sequence has been described so far. However, there is now evidence that there are at least two generic types, with significantly different implications for interpretations of associated palaeo-ice sheet thicknesses. One type, which is relatively well described, is believed to be a diagnostic product of eruptions associated with a relatively thin glacial cover (< c. 150–200 m), probably corresponding most commonly to mountain glaciers but also conceivably thin ice caps or sheets, of any thermal regime (temperate, sub-polar, polar). It is here called the Mount Pinafore type. By contrast, a second subglacial sheet-like sequence, described in this paper for the first time and called the Dalsheidi-type, represents products of eruptions under much thicker ice (probably > 1000 m). Eruptions that form the Dalsheidi-type of sequence commence with the injection and inflation of a sill along the ice:bedrock interface. Such “interface sills” were predicted theoretically but had no known geological example, until now. Subsequent evolution commonly involves floating of the ice cover, catastrophic meltwater drainage and emplacement of widespread sheets of hyaloclastite, as cohesionless mass flows and hyperconcentrated flows. The water-saturated hyaloclastite is characteristically intruded by apophyses sourced in the underlying “interface sill”. Eruptions are commonly not explosive until their later stages. Dalsheidi-type deposits are outflow sequences probably linked to subglacial pillow volcanoes, which in Iceland were erupted along fissures. They only provide an indication of minimum thicknesses of the associated overlying ice, although theoretical considerations suggest substantial ice thicknesses in excess of 1000 m. However, they are likely to be characteristic products of eruptions under the thick West Antarctic Ice Sheet, but are currently inaccessible. Such eruptions may be capable of destabilising that ice sheet.     

Physical Modelling and Human Survival in Pyroclastic Flows

Volcanic eruptions increasingly present catastrophic natural risks with hundreds of millions of people now living in areas of active volcanism and major conurbations around active eruptive centres. Interdisciplinary studies in disaster reduction have an important role in volcanic emergency management through advancing our understanding of the physical impacts of eruptive phenomena and the causes of death and injury in explosive eruptions. Numerical modelling of pyroclastic flows, amongst the most destructive of eruptive phenomena, provides new opportunities to improve the evaluation of the potential destructiveness of volcanic events and their human impacts in densely populated areas. In this work, the results of numerical modelling of pyroclastic flow propagation at Vesuvius have been analysed in terms of the physical parameters (temperature, ash in air concentration, and dynamic pressure) that are most critical for human survival. Our numerical simulations of eruptions of Vesuvius indicate that a large area exists where total destruction may not be inevitable in small to medium scale events, a finding that has prompted us to explore further the implications for human survival as part of an interdisciplinary approach to disaster reduction. The lessons of modelling at Vesuvius should be integrated into civil protection plans for other urban centres threatened by volcanoes.     

Two Scenarios for the Eruption of Magnetic Flux Ropes in the Solar Atmosphere

Eruptions of material from lower to upper layers of the solar atmosphere can be divided into two classes. The first class of eruptions maintain their (usually loop-like) shapes as they increase in size (eruptive prominences), or display a sudden expansion of fairly shapeless clumps of plasma in all directions (flare sprays). The second class refers to narrow, collimated flows of plasma on various scales (spicules, surges, jets). It is obvious that the magnetic configurations in which these phenomena develop differ: for the first class they form closed structures that confine the plasma, and in the second class open structures directing flows of plasma in a particular direction, as a rule, upward. At the same time, the mechanisms initiating eruptions of both classes could be similar, or even practically identical. This mechanism could be instability of twisted magnetic tubes (flux ropes), leading to different consequences under different conditions. It is shown that the results of eruptive instability are determined by the ratio of the scales of the magnetic flux rope and the confining coronal field, and also by the configuration of the ambient magnetic field in the corona. Observations of both types of eruptions are analyzed, the conditions for their develoment are examined, and phenomenological models are proposed.     

火山喷发形式与挥发分含量

火山喷发是由地球深部物质发生部分熔融产生的岩浆上涌至地表所形成的一种地质现象,是地球内部能量释放的主要途径之一。有些火山喷发极为猛烈,产生的大量火山灰能够在长达几个月的时间内影响当地气候环境,甚至可以在一瞬间掩埋整座城市;而有些火山喷发时只有大量的熔岩从火山口中静静地溢出,人们甚至可以在不远处进行观赏。火山喷发具有何种程度的破坏力取决于其喷发形式,而挥发分含量是影响喷发形式的重要因素之一。本文简述了几种常见的喷发形式及其相互之间可能存在的转化关系,着重论述了挥发分含量在其中所起到的作用,同时介绍了几种可能的去气模型及常见的测量岩浆挥发分含量的方法。其中使用单斜辉石斑晶来反演大陆玄武岩原始岩浆水含量的方法预计会在未来的研究中得到普及。     

Unusual eruption of the Main Pugachevo gas-water-lithoclastic (Mud) volcano in Sakhalin during the Winter of 2005

The examination of the Main Pugachevo gas-water-lithoclastic volcano during the summer of 2005 and GPS-controlled large-scale (1: 1000) mapping revealed its regular but rather peculiar eruption. It was the largest among the eruptions investigated since 1911 and produced a very unusual lithoclastic field with an area of about 100 000 m² and a volume of about 100 000 m³. The eruption occurred from three distinct active centers and began with a vigorous explosion-like gas burst from one center followed by the noncontemporaneous discharge of a gas-and water-saturated liquid lithoclastic mass from the three centers, which produced a number of flows of different directions and sizes. The flows almost completely covered the smoothed flat open area of the volcano and even invaded the larch forest surrounding the volcano, where they bent, overturned, broke, and occasionally uprooted and dragged over some distance some large trees. The analysis and comparison with all the previously documented eruptions of the Main Pugachevo gas-water-lithoclastic volcano revealed their fairly diverse, sometimes strongly variable character with respect to many parameters: the amount of ejected lithoclastic material; the number of eruption centers; and the proportions of the erupted gaseous, liquid, and solid components. In general, the eruptions show a distinctly multirank periodic character: relatively minor or small low-rank eruptions take place once every 1–2 yr, and large eruptions of a higher rank are much less frequent (supposedly, once in 70 years).     

Tephra Discovered in High Resolution Peat Sediment and Its Indication to Climatic Event

Floating tephra was deposited together with ice core,snow layer,abyssal sediment,lake sediments,and other geological records.It is of great significance to interpret the impact on the climate change of volcanic eruptions from these geological records.It is the first time that volcanic glass was discovered from the peat of Jinchuan(金川)Maar,Jilin(吉林)Province,China.And it is in situ sediments from a near-source explosive eruption according to particle size analysis and identification results.The tephra were neither from Tianchi(天池)volcano eruptions,Changbai(长白)Mountain,nor from Jinlongdingzi(金龙顶子)volcano about 1 600 aBP eruption,but maybe from an unknown eruption of Longgang(龙岗)volcano group according to their geochemistry and distribution.Geochemical characters of the tephra are similar to those of Jingiongdingzi,which are poor in s.Jica,deficient in alkali,Na20 content is more than K20 content,and are similar to distribution patterns of REE and incompatible elements,which helps to speculate that they originated from the same mantle magma with rare condemnation,and from basaltic explosive eruption of Longgang volcano group.The tephra,from peat with age proved that the eruption possibly happened in 15 BC-26 AD,is one of Longgang volcano group eruption that was not recorded and is earlier than that of Jinglongdingzi about 1 600 aBP eruption.And the sedimentary time of tephra is during the period of low temperature alteration.which may be the influence of eruption toward the local climate according to the correlativity of eruption to local temperature curve of peat cellulose oxygen isotope.     

On Selection of Analog Volcanoes

Estimating the occurrence probability of volcanic eruptions with VEI ??3 is challenging in several aspects, including data scarcity. A?suggested approach has been to use a simple model, where eruptions are assumed to follow a Poisson process, augmenting the data used to estimate the eruption onset rate with that from several analog volcanoes. In this model the eruption onset rate is a random variable that follows a gamma distribution, the parameters of which are estimated by an empirical Bayes analysis. The selection of analog volcanoes is an important step that needs to be explicitly considered in this model, as we show that the analysis is not always feasible due to the required over-dispersion in the resulting negative binomial distribution for the numbers of eruptions. We propose a modification to the method which allows for both over-dispersed and under-dispersed data, and permits analog volcanoes to be chosen on other grounds than mathematical tractability.     

STUDY OF ERUPTIONS AND EARTHQUAKES ORIGINATING FROM VOLCANOES (PART 1 OF 3)

Reports of volcanic eruptions and earthquakes originating from volcanoes indicate that seismic activity preceding the eruption is related not only to eruption magnitude and structure of the volcano, but also to viscosity of the lava at the time of eruption. This follows, since lava of higher viscosity meets greater resistance as it ascends from the magma chamber to the earth's surface and, consequently, greater stress will be produced within and beneath the volcano. The writer gives a condensed statistical breakdown of earthquakes and explosive eruptions of Asama Volcano. The Asama earthquakes treated in the report are mainly those of rather low magnitude (T = 1. 0 sec, V = 350) at the Asama Volcano Observatory, situated 4. 2 km east of the center of the summit crater. This investigation showed that most of the explosive eruptions were preceded by an increase in micro-earthquakes. In addition, an experimental formula for predicting volcanic eruptions, based on the statistical relation between frequency of earthquakes originating from Asama and its explosive eruptions. The forthcoming report (Part II) will discuss the same problem based on seismic observations by more sensitive instruments set nearer the summit crater. — A. Eustus     

Tall clouds from small eruptions: the sensitivity of eruption height and fine ash content to tropospheric instability

A critical factor in successfully monitoring and forecasting volcanic ash dispersion for aviation safety is the height reached by eruption clouds, which is affected by environmental factors, such as wind shear and atmospheric instability. Following earlier work using the Active Tracer High Resolution Atmospheric Model for strong Plinian eruptions, this study considered a range of eruption strengths in different atmospheres. The results suggest that relatively weak volcanic eruptions in the moist tropics can trigger deep convection that transports volcanic material to 15–20 km. For the same volcanic strength there can be ~9 km difference between eruption heights in moist tropical and dry subpolar environments (a larger height difference than previously suggested), which appears consistent with observations. These results suggest that eruption intensity should not be estimated from eruption height alone for tropospheric eruptions and also that the average height of volcanic eruptions may increase if the tropical atmospheric belt widens in a changing climate. Ash aggregation is promoted by hydrometeors (particularly liquid water), so the smaller modelled eruptions in moist atmospheres, which have a relatively small ash content for their height and water content, result in a relatively small proportion of fine ash in the dispersing cloud when compared to a dry atmosphere. This in turn makes the ash clouds much more difficult to detect using remote sensing than those in dry atmospheres. Overall, a weak eruption in the tropics is more likely to produce a plume above cruising levels for civil aviation, harder to detect and track, but with a lower concentration of fine ash than a mid-latitude or polar equivalent. There is currently no defined ‘acceptable’ concentration of ash for aircraft, but as these results suggest low-grade encounters in the tropics from undetected clouds are likely, it would be desirable to explore that issue.     

中国东北地区新生代火山活动的构造背景

中国东北地区新生代以玄武岩为主的喷发经历了60~29 Ma、25~15 Ma、＜2 Ma三期及不同喷发期之间的过渡阶段,而每一期又可以分为若干旋回。火山作用形成于不同的构造部位,沿断裂和非断裂分布的玄武岩均有存在,且与不同时期的大陆边缘构造演化相匹配。不同的构造背景下火山活动的分布也不同,且具明显的迁移性。构造环境体现为非造山大陆边缘张裂隙、上地幔上隆的陆内拉张环境、陆内非造山环境等特征。上新世晚期—更新世以来的火山活动与中国西南部地区的大陆板块间的碰撞作用没有关系。     

Probabilistic Assessment of Vent Locations for the Next Auckland Volcanic Field Event

Auckland, New Zealand’s most populous Region is centred on the Auckland volcanic field (AVF), which contains an estimated 49 small-volume basaltic volcanoes. Although these volcanoes are considered monogenetic, a number of centres may have been active either simultaneously or within a short period of time. After reviewing the characteristics of the field, known vent locations and a provisional eruption sequence were used to estimate likely eruption locations for the next event. The term event is used here to describe a short period of activity comprising one or more eruptions. Point pattern analysis and temporal consideration allow vents related by location and age to be grouped, suggesting that as few as 18 separate events may have produced the AVF. Probability distributions describing previous event attributes were used to generate Monte Carlo simulations, each defining likely vent locations for the next AVF event. Simulations were based on the assumption that distance from Rangitoto, the youngest volcano in the field, to the next event is best approximated using distances between the centroids of previous consecutive events. The maximum extent of the field is constrained only by faulting on its eastern side. The simulations show that 69% of events involved at least one eruption centred either on land or within 1 km of the coast. These events would result in substantial damage to buildings and infrastructure, significant business interruption and, potentially, loss of life. A simple risk assessment is presented considering only spatial eruption probability contingent upon a future event and building density within a 2 km grid. Work in progress aims to develop a more realistic assessment of risk for the region.     

The Hianana Volcanics: Remnants of a Late Permian tuff ring and lava flow,Coombadjha Volcanic Complex,northeastern New South Wales

The Hianana Volcanics consist of bedded tuff and dacitic lava that form a locally mappable unit within the extensive, Late Permian silicic volcanic sequence of northeastern New South Wales. Principal components of the bedded tuff are crystal and volcanic lithic fragments ranging from coarse ash to lapilli, accompanied by variable amounts of fine ash matrix. Well denned plane parallel thin bedding is characteristic. Sandwave bed forms, including low‐angle cross‐beds and wavy beds, are confined to an area of 2–3 km² coinciding with the thickest sections (70 m) of bedded tuff. A high‐aspect ratio flow of porphyritic dacitic lava overlies the bedded tuff in the same area. The setting, lithofacies, extent and geometry of the bedded tuffs of the Hianana Volcanics are comparable with modern tuff rings which are composed of the deposits from base surges generated by explosive phreatomagmatic eruptions at primary volcanic vents. Many of these have also discharged lava late in their activity. Proximal parts of the Hianana tuff ring were buried by the porphyritic lava after the phreatomagmatic eruptions had ceased. In more distal sections, the bedded tuff is less than 10 m thick and dominantly comprises fine grained, plane parallel, very thin beds and laminae; these features suggest an origin by fallout from ash clouds that accompanied the phreatomagmatic eruptions. The distal ash was covered and preserved from erosion by a layer of welded ignimbrite, the source of which is unknown.     

大兴安岭哈拉哈河—淖尔河地区第四纪火山活动初步研究

大兴安岭中部哈拉哈河-淖尔河地区受基底断裂控制,发育28座第四纪火山,这些火山总体呈北东向带状分布。研究区第四纪火山岩分布面积约1000km^2,岩性主要为碱性玄武岩。根据喷发时代和火山地质特征,这里的火山大体可分为更新世和全新世两期。按照火山作用方式不同,区内火山可分为岩浆成因和射汽岩浆成因两类：前者活动产物主要包括火山碎屑锥、碎屑席、熔岩流,其中发育结壳熔岩、渣状熔岩、块状熔岩,以及喷气锥、熔岩冢等火山地质现象;后者产物主要是射汽岩浆喷发形成的基浪堆积物,其中发育大型平行层理及交错层理。不同的火山作用形成了火山口湖、低平火山口湖、火山堰塞湖和塌陷熔岩湖四种不同规模与形态特征的湖泊,这种水火相容的火山地质现象为阿尔山火山温泉国家地质公园增添了景观。     

The Risk of Large Volcanic Eruptions and the Impact of this Risk on Future Ozone Depletion

Ozone depletion at mid-latitudes is caused by reactivehalogens from man-made halocarbons. The stratosphericsulphate aerosol which follows large volcaniceruptions enhances (multiplies) this ozone depletion(it has no effect on ozone without halocarbons). Mid-latitude depletion almost doubled for the twoyears after Mt. Pinatubo. Although the MontrealProtocol is expected to reduce atmospheric amounts ofhalocarbons in the 21st century, stratospheric ozonewill be at risk of depletion enhancement by largeeruptions for the next 50 years. Mechanisms ofvolcanoes suggest that large eruptions are random andthat their global rate is constant for severalcenturies. Measurements of large eruptions during thelast 1000 years in ice cores have a remarkable fit toa Poisson distribution, reinforcing the conclusionthat the global incidence is random and at a constantrate for this period. From this rate, the probabilityof one or more eruptions with at least the ozone-lossenhancement of Pinatubo is 58 % in 50 years. Thisprobability is large enough to be of serious concernfor future mid-latitude ozone loss.     

Effusive Activity at Mount Etna Volcano (Italy) During the 20th Century: A Contribution to Volcanic Hazard Assessment

Mount Etna is an open conduit volcano, characterised by persistent activity, consisting of degassing and explosive phenomena at summit craters, frequent flank eruptions, and more rarely, eccentric eruptions. All eruption typologies can give rise to lava flows, which represent the greatest hazard by the volcano to the inhabited areas. Historical documents and scientific papers related to the 20th century effusive activity have been examined in detail, and volcanological parameters have been compiled in a database. The cumulative curve of emitted lava volume highlights the presence of two main eruptive periods: (a) the 1900–1971 interval, characterised by a moderate slope of the curve, amounting to 436 × 10⁶ m³ of lava with average effusion rate of 0.2 m³/s and (b) the 1971–1999 period, in which a significant increase in eruption frequency is associated with a large issued lava volume (767 × 10⁶ m³) and a higher effusion rate (0.8 m³/s). The collected data have been plotted to highlight different eruptive behaviour as a function of eruptive periods and summit vs. flank eruptions. The latter have been further subdivided into two categories: eruptions characterised by high effusion rates and short duration, and eruptions dominated by low effusion rate, long duration and larger volume of erupted lava. Circular zones around the summit area have been drawn for summit eruptions based on the maximum lava flow length; flank eruptions have been considered by taking into account the eruptive fracture elevation and combining them with lava flow lengths of 4 and 6 km. This work highlights that the greatest lava flow hazard at Etna is on the south and east sectors of the volcano. This should be properly considered in future land-use planning by local authorities.     

Fingerprinting the Late Pleistocene tephras of Ciomadul volcano,eastern–central Europe

Late Pleistocene tephras derived by large explosive volcanic eruptions are widespread in the Mediterranean and surrounding areas. They are important isochronous markers in stratigraphic sections and therefore it is important to constrain their sources. We report here tephrochronology results using multiple criteria to characterize the volcanic products of the Late Pleistocene Ciomadul volcano in eastern–central Europe. This dacitic volcano had an explosive eruption stage between 57 and 30 ka. The specific petrological character (ash texture, occurrence of plagioclase and amphibole phenocrysts and their compositions), the high-K calc-alkaline major element composition and particularly the distinct trace element characteristics provide a strong fingerprint of the Ciomadul volcano. This can be used for correlating tephra and cryptotephra occurrences within this timeframe. Remarkably, during this period several volcanic eruptions produced tephras with similar glass major element composition. However, they differ from Ciomadul tephras by glass trace element abundances, ratios of strongly incompatible trace elements and their mineral cargo that serve as discrimination tools. We used (U-Th)/He zircon dates combined with U-Th in situ rim dates along with luminescence and radiocarbon dating to constrain the age of the explosive eruptions of Ciomadul that yielded distal tephra layers but lack of identified proximal deposits.     

Potential cauchy-poisson waves generated by submarine eruptions of kick 'em Jenny volcano

Kick 'em Jenny is the only known currently active submarine volcano in the Lesser Antilles. The volcano has erupted at least 10 times since first being discovered in 1939 and the summit has shoaled from a depth of 232 m in 1962 to its present-day depth of 150 m. Kick 'em Jenny is located in a province of explosive volcanism, has a known history of explosive eruptions and erupts magma of an explosive type. Future eruptions are likely to become increasingly more violent as the effect of the overlying water pressure becomes less. A preliminary study (Smith and Shepherd, 1993) suggests that Kick 'em Jenny is a prime candidate for tsunamigenic eruptions on a potentially hazardous scale, possibly affecting the whole of the eastern Caribbean region.The classic approach to problems of water waves generated by sudden disturbances of the free surface makes use of the Cauchy-Poisson-Lamb theory. A large number of theoretical developments to this theory have been made for specific forms of surface disturbance. A development by Unoki and Nakano (1953a, b) considers both two- and three-dimensional Cauchy-Poisson waves generated by finite initial elevations and impulses applied to a free surface of infinitely deep water. Unoki and Nakano's results compared well to the wave systems recorded following submarine eruptions of the Myojinsho Reef volcano in 1952–53.Given the similarity of the two situations, Unoki and Nakano's theory is applied to Kick 'em Jenny to provide estimates of potential Cauchy-Poisson wave heights throughout the eastern Caribbean for a range of eruption magnitudes. The results show that, although the waves generated are unlikely to pose much of a threat to the eastern Caribbean as a whole, they should be considered a hazard to the islands immediately adjacent to the volcano including Grenada, the Grenadines, and St Vincent.     

Stratigraphical framework of basaltic lavas in Torres Syncline main valley,southern Parana-Etendeka Volcanic Province

The Paraná-Etendeka Volcanic Province records the volcanism of the Early Cretaceous that precedes the fragmentation of the South-Gondwana supercontinent. Traditionally, investigations of these rocks prioritized the acquisition of geochemical and isotopic data, considering the volcanic stack as a monotonous succession of tabular flows. Torres Syncline is a tectonic structure located in southern Brazil and where the Parana-Etendeka basalts are well preserved. This work provides a detailed analysis of lithofacies and facies architecture, integrated to petrographic and geochemical data. We identified seven distinct lithofacies grouped into four facies associations related to different flow morphologies. The basaltic lava flows in the area can be divided into two contrasting units: Unit I - pahoehoe flow fields; and Unit II - simple rubbly flows. The first unit is build up by innumerous pahoehoe lava flows that cover the sandstones of Botucatu Formation. These flows occur as sheet pahoehoe, compound pahoehoe, and ponded lavas morphologies. Compound lavas are olivine-phyric basalts with intergranular pyroxenes. In ponded lavas and cores of sheet flows coarse plagioclase-phyric basalts are common. The first pahoehoe lavas are more primitive with higher contents of MgO. The emplacement of compound pahoehoe flows is related to low volume eruptions, while sheet lavas were emplaced during sustained eruptions. In contrast, Unit II is formed by thick simple rubbly lavas, characterized by a massive core and a brecciated/rubbly top. Petrographically these flows are characterized by plagioclase-phyric to aphyric basalts with high density of plagioclase crystals in the matrix. Chemically they are more differentiated lavas, and the emplacement is related to sustained high effusion rate eruptions. Both units are low TiO₂ and have geochemical characteristics of Gramado magma type. The Torres Syncline main valley has a similar evolution when compared to other Large Igneous Provinces, with compound flows at the base and simple flows in the upper portions. The detailed field work allied with petrography and geochemical data are extremely important to identify heterogeneities inside the volcanic pile and allows the construction of a detailed lithostratigraphical framework.