Deep drilling in an active geothermal area in the Azores

Muecke, G. K.; Ade-Hall, J. M.; Aumento, F.; MacDonald, A.C.; Reynolds, P. H.; Hyndman, R. D.; Quintino, J.; Opdyke, Neil D.; Lowrie, William

doi:10.1038/252281a0

Cited by 56 publications

(26 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The oldest age for the materials that form the basement of the Fogo volcano was obtained in submarine lava flows sampled at a 878 m depth during a research borehole drilling operation made on the northern flank of the volcano, and whose age is 280,000 ± 140,000 years (Muecke et al 1974). This survey allowed the identification of the Environ Earth Sci transition from submarine to subaerial volcanism at a depth of 786 m, showing also the subsidence that has occurred in the so-called Ribeira Grande graben.…”

Section: Geologymentioning

confidence: 99%

Groundwater composition in perched-water bodies in the north flank of Fogo volcano (São Miguel, Azores): main causes and comparison with river water chemistry

et al. 2014

View full text Add to dashboard Cite

A set of 46 springs located in the north flank of Fogo volcano (São Miguel, Azores) were sampled to characterize groundwater chemistry. The majority of the discharge from volcanic rocks with acidic character (95 %), at an elevation range of 200-400 m a.s.l., and the average discharge are usually not higher than 2 L/s. Nevertheless, the discharge in a few springs from trachytic lava flows can be higher (21.3 L/s). A group of 12 surface water samples were also collected twice along the Ribeira Grande River. Groundwater average temperature ranges between 19.6 and 20.7°C, and it is possible to depict two groups of discharges: thermal waters (16.7 %), with a temperature range from 27.8 to 71.2°C, and cold waters, with temperature under 20°C. In this latter group, temperature is inversely proportional to elevation. The average pH and conductivity range, respectively, between 5.7 and 7.8 and 291-425 lS/cm. Nevertheless, higher conductivity values were measured in boiling pools. Groundwater mainly belongs to the Na-HCO 3 to Na-Cl types. The major-ion relative composition of the cold springs shows a decreasing order for cations as Na [ Ca [ K [ Mg and for anions HCO 3 [ Cl [ SO 4 . In thermal discharges the relative composition is, respectively, Na [ Ca [ K [ Mg and SO 4 [ HCO 3 [ Cl. The average nitrate content ranges from 2.09 to 2.57 mg/L comparing all the sampling periods, and the cumulative probability plot shows that about 75 % of the samples present values lower than 1.98 mg/L. Results show clearly that the higher nitrate measurements are observed in river waters and springs sampled in areas where pasture lands are dominant.

show abstract

Section: Geologymentioning

confidence: 99%

Groundwater composition in perched-water bodies in the north flank of Fogo volcano (São Miguel, Azores): main causes and comparison with river water chemistry

et al. 2014

View full text Add to dashboard Cite

show abstract

“…(1) the age of 210 + 8 ka BP obtained for the oldest rocks cropping out (Moore 1983); and (2) the occurrence of subsidence phenomena related to the NW -SE regional tectonic system, as observed in the case of Fogo Volcano (Muecke et al 1974;Wallenstein et al 2015).…”

Section: Construction Of the Central Volcanomentioning

confidence: 99%

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Queiroz

Gaspar

Guest

et al. 2015

Memoirs

View full text Add to dashboard Cite

Sete Cidades is an active central volcano on the western part of São Miguel. The geological record reveals that subaerial activity started more than 250 ka ago. Stratigraphic units defined for Sete Cidades deposits reflect major events in the history of the volcano and are organized into two main groups: the Inferior Group and the Superior Group. Caldera formation resulted from three major paroxysmal events that occurred at about 36, 29 and 16 ka ago. Analysis of the eruptive history of Sete Cidades shows that effusive or moderately explosive eruptions, of Hawaiian and/or Strombolian styles, were located on the slopes of the central volcano. Conversely, trachytic explosive activity is mostly centred inside the caldera involving, in a first stage, predominantly Plinian and sub-Plinian phenomena, changing about 5 ka ago to a dominant hydromagmatic style. Trachytic effusive eruptions are represented by domes and associated lava flows that crop out in the inner caldera walls and on the western slopes of the volcano. Offshore submarine activity is represented by the historic Surtseyan eruptions of 1638 and 1811. In the last 5 ka Sete Cidades was the most active central volcano in the Azores with 17 explosive eruptions predominantly with hydromagmatic character. Scoria conesThese are the most common volcanic edifices on Sete Cidades massif and were formed as a result of the accumulation of basaltic † Deceased 19 May 2012.

show abstract

“…Fogo Volcano (Wallenstein 1999;Wallenstein et al 2015) dominates the central part of the island (Fig. 6.2) and its formation began around 200 ka bp (Muecke et al 1974). It has a basal diameter of about 13 km at sea-level, an area of 133 km 2 and a volume of 43.5 km 3 above sea-level.…”

Section: Fogo Volcanomentioning

confidence: 99%

Chapter 6 Volcano-tectonic structures of São Miguel Island, Azores

Carmo

Madeira

Ferreira

et al. 2015

Memoirs

View full text Add to dashboard Cite

The Azores archipelago is located at the triple junction between the Eurasia, Nubia and North America lithospheric plates. São Miguel Island, situated at the southeastern part of the western segment of the Azores-Gibraltar Fracture Zone, presents an east-west elongated shape, comprising three quiescent central volcanoes with summit calderas linked by zones of fissure volcanism. The eastern part of the island is older and inactive. Active faulting is represented by prominent fault scarps that constitute important extensional structures, or by linear volcanic structures in fissural volcanic zones, with a dominant NW-SE to WNW-ESE trend. Although less frequent, there are also NNW-SSE to north-south, NE-SW and east-west faults, reflected by some volcanic alignments and linear segments of the drainage system and sea cliffs. The geometric and kinematic data are in agreement with that observed in the rest of the archipelago. However, at eastern São Miguel Island data indicate two distinct groups of conjugated faults characterized by three-dimensional strain: NW-SE to WNW-ESE normal dextral structures are conjugated with NNW-SSE normal left-lateral faults and NW-SE to WNW-ESE normal left-lateral faults are conjugated with NE-SW normal dextral structures, showing the presence of two different stress fields separated in time.

show abstract

Deep drilling in an active geothermal area in the Azores

Cited by 56 publications

References 19 publications

Groundwater composition in perched-water bodies in the north flank of Fogo volcano (São Miguel, Azores): main causes and comparison with river water chemistry

Groundwater composition in perched-water bodies in the north flank of Fogo volcano (São Miguel, Azores): main causes and comparison with river water chemistry

Chapter 7 Eruptive history and evolution of Sete Cidades Volcano, São Miguel Island, Azores

Chapter 6 Volcano-tectonic structures of São Miguel Island, Azores

Contact Info

Product

Resources

About