Geochemical study of the rehabilitation of a shallow anoxic reservoir, in volcanic terrains, under semi-arid climate, in Cape Verde Archipelago

Poilão dam reservoir (Cape Verde Archipelago) is in critical conditions, owing the excessive silting up, the high concentration of nitrates and the pronounced anoxia all over the lake. Considering that the most suitable remediation strategy is the removal of the bottom sediments where nutrients are preferentially concentrated, we have done a geochemical study, in order of evaluating their suitability to agricultural use. Analyses indicate that sediments are rich in a few key nutrients, when compared with parent soils. Thus, adding suitable sediments to nearby degraded soils can improve food crops for smallholder farmers living in close proximity to this system.

The 1998-2001 submarine lava balloon eruption at the Serreta Ridge (Azores archipelago): constraints from volcanic facies architecture, isotope geochemistry and magnetic data

The most recent submarine eruption observed offshore the Azores archipelago occurred between 1998-2001 along the submarine Serreta ridge (SSR), ~4-5 nautical miles WNW of Terceira Island. This submarine eruption delivered abundant basaltic lava balloons floating at the sea surface and significantly changed the bathymetry around the eruption area. Our work combines bathymetry, volcanic facies cartography, petrography, rock magnetism and geochemistry in order to (1) track the possible vent source at seabed, (2) better constrain the Azores magma source(s) sampled through the Serreta submarine volcanic event, and (3) interpret the data within the small-scale mantle source heterogeneity framework that has been demonstrated for the Azores archipelago. Lava balloons sampled at sea surface display a radiogenic signature, which is also correlated with relatively primitive (low) 4He/3He isotopic ratios. Conversely, SSR lavas are characterized by significantly lower radiogenic 87Sr/86Sr, 206Pb/204Pb and 208Pb/204Pb ratios than the lava balloons and the onshore lavas from the Terceira Island. SSR lavas are primitive, but incompatible trace-enriched. Apparent decoupling between the enriched incompatible trace element abundances and depleted radiogenic isotope ratios is best explained by binary mixing of a depleted MORB source and a HIMU­type component into magma batches that evolved by similar shallower processes in their travel to the surface. The collected data suggest that the freshest samples collected in the SSR may correspond to volcanic products of an unnoticed and more recent eruption than the 1998-2001 episode.

Desenvolvimento do turismo em Cabo Verde a partir da abertura política (1990) à actualidade

O turismo é um fenómeno que ganhou terreno nas últimas décadas. A sua transversalidade fez com que se alastrasse a diversas áreas, contribuindo para o desenvolvimento de muitos países. Depois da Europa e América exploradas, voltou-se para Ásia e África, à descoberta do diferente. No início dos anos 90 deu-se uma viragem na política, muitos países em África abriram-se às eleições partidárias, pondo o fim ao partido único. Cabo Verde, a partir de 1990, conjuntamente com a abertura política abriu-se às cooperações, às privatizações e aos investimentos estrangeiros, e oportunamente, o sector turístico. Foi ganhando importância, ao ponto de os governos assumirem o fenómeno como um dos motores do desenvolvimento e de combate à pobreza. A presente dissertação pretende descrever o desenvolvimento do sector a partir de 1990 à actualidade, verificar a adequação das estratégias à realidade do país. Percebe-se a necessidade de planear o turismo, envolver mais a comunidade, desenvolver um turismo competitivo e sustentável, apostando na formação dos profissionais e na segurança. Fica explícito que a articulação dos sectores públicos e privados constitui a chave para o sucesso do turismo no arquipélago. ABSTRACT; Tourism is a phenomenon that won the ground in the last century. Its transversally makes it spread in several areas, helping to the development of many countries. After explorations of Europe and America, it returns to Asia and Africa to discover the different. In the beginning of years 90 gave a political change, many countries in Africa opened supporter elections, putting stop to unique party from 1990, Cape Verde, together with opening party opened to cooperation, privatizations and foreign investments and later on touristic sector. It won the importance that mode the government assume the phenomenon as one of the motor of development and fight against poverty. The present dissertation pretends to describe the sector development from 1990 till now, check suitable strategies to the reality of the country. We can see the need to plan tourism, develop our community, and develop a competitive and sustainable tourism by investing in staff training and safety. It is explicit that the articulation of public and private sectors is the key to the success of tourism in the archipelago.

Azores seismogenic zones

One condition to perform seismic hazard analysis is knowledge about seismogenic zones that is an invaluable source of information and play an important role because it is fundamental know the processes and properties that control the seismogenic zone. The aim of this work is distinguishing seismogenic zones in the Azores region applying different parameters such as the earthquake density, b-values, focal mechanism, historical seismicity and all of these conjugated within the geodynamic framework of the Azores. We identified 10 seismogenic zones plus the well known Mid Atlantic Ridge. The 10 zones we identified are over the major tectonic structures of the Archipelago, namely Terceira Rift and Linear Volcanic Ridges.