The central Alentejo plateaus: a review of the regional relief units

Since the 1990s, detailed studies on the relief units of the central and upper Alentejo region have been lacking. Previously, tectonics were used to explain most of the relief units, even those in which lithological differentiation is remarkable, such as the dolomitic plateaus of Elvas and Estremoz. The morphotectonic reliefs like Serra d’Ossa and Serra de S. Mamede were previously explained by vertical tectonics, in a horst-graben system, difficult to understand under the Cenozoic compressive tectonic regime affecting the Western Iberian margin. The superposition of geological maps with digital terrain models suggests a more complex genesis in the formation of the morphotectonic regional reliefs. The Serra d’Ossa (652 m) develops in a WNW-ESE general trend (N80ºW), slightly asymmetrical with a 200 m high north-facing escarpment, much steeper than the south-facing slope. The north-facing escarpment (Ossa Fault – OF) is transversal to the NW-SE variscan structures (N40ºW). Thus, this escarpment cannot be explained by differential erosion. Indeed, Feio (1983) already hypothesized a tectonic origin to the Serra d'Ossa, although without presenting a tectonic model. The western termination of the Serra d‘Ossa small scarps, with NE-SW orientation, coincide with the horse tail terminations of the NNE-SSW left strike-slip Graça do Divor fault (GDF). If both GDF and OF are connected, the Serra d’Ossa can be interpreted as a push up deformation of the South Portuguese Planation Surface (SPPS). In this work, a greater relevance of differential erosion is highlighted in the individualisation of Elvas and Estremoz plateaus, as well as the Serra de Monfurado. Towards the north of the town of Évora, the landscape is formed by broad-bottomed valleys at 240 m, with gentle slope and flat uplands at ca. 320-340 m. Looked in Davisian terms, the valleys looks like a mid-cycle maturity landscape. The flat upland level corresponds to the SPPS, well developed in the upper Alentejo (Nisa and Alpalhão), while the bottom of the valleys correspond to a younger level, embedded ca. 80–100 m in the SPPS. The valley bottoms widens to downstream forming a flattening surface (named N1 fluvial surface) related with the beginning of the incision of the drainage network in the SPPS and with the first (older) terraces of the Tejo and Guadiana rivers. The prominence in the landscape of the Serra de Monfurado should be understood as a resistant ridge, whose summits were not completely flattened due to the lithological diversity and to the geographic location in the watershed limit of the Tejo, Guadiana and Sado rivers, where the flattening of the SPPS was difficult to achieve. Differential erosion during the formation of the N1 fluvial surface is thought to be the main responsible for the prominence of this ridge in the central Alentejo landscape, as well as other resistant reliefs as the Monsaraz inselberg

The central Alentejo plateaus: a review of the regional relief units

Since the 1990s, detailed studies on the relief units of the central and upper Alentejo region have been lacking. Previously, tectonics were used to explain most of the relief units, even those in which lithological differentiation is remarkable, such as the dolomitic plateaus of Elvas and Estremoz. The morphotectonic reliefs like Serra d’Ossa and Serra de S. Mamede were previously explained by vertical tectonics, in a horst-graben system, difficult to understand under the Cenozoic compressive tectonic regime affecting the Western Iberian margin. The superposition of geological maps with digital terrain models suggests a more complex genesis in the formation of the morphotectonic regional reliefs. The Serra d’Ossa (652 m) develops in a WNWESE general trend (N80ºW), slightly asymmetrical with a 200 m high north-facing escarpment, much steeper than the south-facing slope. The north-facing escarpment (Ossa Fault – OF) is transversal to the NW-SE variscan structures (N40ºW). Thus, this escarpment cannot be explained by differential erosion. Indeed, Feio (1983) already hypothesized a tectonic origin to the Serra d'Ossa, although without presenting a tectonic model. The western termination of the Serra d‘Ossa small scarps, with NE-SW orientation, coincide with the horse tail terminations of the NNE-SSW left strike-slip Graça do Divor fault (GDF). If both GDF and OF are connected, the Serra d’Ossa can be interpreted as a push up deformation of the South Portuguese Planation Surface (SPPS). In this work, a greater relevance of differential erosion is highlighted in the individualisation of Elvas and Estremoz plateaus, as well as the Serra de Monfurado. Towards the north of the town of Évora, the landscape is formed by broad-bottomed valleys at 240 m, with gentle slope and flat uplands at ca. 320-340 m. Looked in Davisian terms, the valleys looks like a mid-cycle maturity landscape. The flat upland level corresponds to the SPPS, well developed in the upper Alentejo (Nisa and Alpalhão), while the bottom of the valleys correspond to a younger level, embedded ca. 80–100 m in the SPPS. The valley bottoms widens to downstream forming a flattening surface (named N1 fluvial surface) related with the beginning of the incision of the drainage network in the SPPS and with the first (older) terraces of the Tejo and Guadiana rivers. The prominence in the landscape of the Serra de Monfurado should be understood as a resistant ridge, whose summits were not completely flattened due to the lithological diversity and to the geographic location in the watershed limit of the Tejo, Guadiana and Sado rivers, where the flattening of the SPPS was difficult to achieve. Differential erosion during the formation of the N1 fluvial surface is thought to be the main responsible for the prominence of this ridge in the central Alentejo landscape, as well as other resistant reliefs as the Monsaraz inselberg. Acknowledgments: The authors acknowledge the funding provided by the Institute of Earth Sciences (ICT), under contract with Science and Technology Foundation (UID/GEO/04683/2019). References: Feio, M., 1983. O Relevo da Serra de Ossa: uma interpretação tectónica. Finisterra, XVIII, 35, 5-26

Prefiguring houses in a traditional city: a case for Benin house types and characteristics

House mean different things to different people. House could be a dwelling, home, hut, place for; entertainment, rest, sleeping, receiving guest, and a palace. The interpretation of house as shelter makes it a basic necessities of life. Thus the focus of the paper is to identify and document house types in Benin by observing the physical characteristics and type’s classification from the organization and pattern of architectural plan documented. The study explored qualitative and quantitative approach using observations, descriptive frequency, architectural sketches, photographs and interview guide. The findings revealed a cross sectional characterising and classifying houses in Benin City, Nigeria which reflect the typical cross section structure of a traditional city. The result of study would however, influence professional in built environment and policy maker decision positively. First published online 28 December 201

Macrossismicidade associada ao sismo de Arraiolos do dia 15 de Janeiro de 2018 com M = 4.9 e eventuais implicações na geometria da ruptura

É bem conhecida a existência de uma actividade sísmica fraca, difusa e persistente na região a Norte de Évora, particularmente concentrada entre Arraiolos, Pavia e Vimieiro. No dia 15 de Janeiro de 2018, pelas 11 horas e 51 minutos ocorreu um sismo de magnitude consideravelmente superior ao habitual, de 4.9 segundo os dados do Instituto Português do Mar e da Atmosfera (IPMA). Este evento ocorreu a uma profundidade de 11 km e o seu epicentro localizou-se entre as povoações de Aldeia da Serra e São Gregório. O seu efeito foi sentido numa região bastante vasta, inclusivamente até na cidade do Porto, de acordo com o que foi noticiado nos órgãos de comunicação social. Tendo em conta a magnitude deste evento, realizámos um estudo de macrossismicidade a nível regional, com vista à construção de um mapa de intensidades sísmicas. Os trabalhos de campo decorreram entre os dias 17 e 24 do mesmo mês, tendo-se usado o inquérito que o IPMA tem disponível em https://www.ipma.pt/pt/geofisica/informe/. A recolha de dados no campo procurou cobrir a região situada aproximadamente entre as latitudes 37.9o N e 39.5o N e entre as longitudes 7.3o W e 9o W. Em simultâneo o mesmo inquérito foi disponibilizado e divulgado na Internet, tendo-se recolhido respostas vindas de muitos pontos do país entre os dias 18 e 26 de Janeiro

Geomorphological sites in the northern domains of the Ossa Morena zone in Portugal: characterize aiming the promotion

This work characterizes eight geomorphological sites of the northern domains of the Ossa Morena Zone, aiming to expose their scientific, educational, scenic and touristic value, as well as to support the enhancement of the territory and its geoconservation. Six panoramic sites allow to approach and interpret the features of the Estremoz and Évora plateaus and the landforms that stand out from them, due to the joint action between lithology and climate, but also tectonics. One site illustrates a case of antecedent drainage and the last one highlight the tectonic constraints of the Guadiana River and its geomorphological evolution

Using in-situ airborne measurements to evaluate three cloud phase products derived from CALIPSO

International audienceWe compare the cloud detection and cloud phase determination of three independent climatologies based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) to airborne in situ measurements. Our analysis of the cloud detection shows that the differences between the satellite and in situ measurements mainly arise from three factors. First, averaging CALIPSO Level l data along track before cloud detection increases the estimate of high-and low-level cloud fractions. Second, the vertical averaging of Level 1 data before cloud detection tends to artificially increase the cloud vertical extent. Third, the differences in classification of fully attenuated pixels among the CALIPSO climatologies lead to differences in the low-level Arctic cloud fractions. In another section, we compare the cloudy pixels detected by colocated in situ and satellite observations to study the cloud phase determination. At midlatitudes, retrievals of homogeneous high ice clouds by CALIPSO data sets are very robust (more than 94.6% of agreement with in situ). In the Arctic, where the cloud phase vertical variability is larger within a 480 m pixel, all climatologies show disagreements with the in situ measurements and CALIPSO-General Circulation Models-Oriented Cloud Product (GOCCP) report significant undefined-phase clouds, which likely correspond to mixed-phase clouds. In all CALIPSO products, the phase determination is dominated by the cloud top phase. Finally, we use global statistics to demonstrate that main differences between the CALIPSO cloud phase products stem from the cloud detection (horizontal averaging, fully attenuated pixels) rather than the cloud phase determination procedures