Special issue: Volcanic geology of the Azores Islands

Journal of Volcanology and Geothermal Research
Edited by: João Carlos NunesRobert I. Tilling, and Gudmundur E. Sigvaldason



The volcanic islands making up the Azores Archipelago rise above sea from a prominent submarine topographic high (the “Azores Plateau”), marked by the 2000-m bathymetric contour. Specifically, the Azores Islands lie at the so-called “Azores Triple Junction” (ATJ), where the Eurasian, North American, and African (or Nubian) tectonic plates meet. In general terms, the ATJ is defined by the Mid-Atlantic Ridge (MAR) separating the North American plate from the other two, and the Azores–Gibraltar fault zone separating the Eurasian and African plates. In addition, the existence of a mantle plume (“hotspot) beneath Azores Plateau has been inferred in many previous investigations. Not surprisingly, because of its distinctive plate-tectonics setting and attributes, the Azores Archipelago has been the site of intense research, serving as an ideal natural laboratory for scientific studies involving diverse disciplines, including geology, seismotectonics, climatology, ecology, and oceanography. Of course, a special field of interest and research is volcanology, with particular emphasis not only on the eruptive processes and products of the individual island volcanoes, but also of the volcanic and structural evolution of the ATJ and the “Azores Plateau” as a whole.

There has been, and remains, considerable scientific debate about the dynamics of the ATJ, including the characterization of the nature and location of the involved plate boundaries, the determination of the sense and amount of plate motions, and the influence of the Azores hotspot on the involved three plates. At present, the basic nature of the ATJ is still not fully understood and the main unresolved issues are: where is the westernmost extent of Azores–Gibraltar fault zone? What is the nature of that extent? Is this fault zone a single, narrowly constricted linear boundary, or does it behave as a much larger, complex tectonic block (i.e., a “miniplate“ or “microplate”)? What is the size and location of the “Azores hot spot”? Is it fixed or moving?

By way of background, with the aim of addressing at least the volcanological aspects of these unresolved scientific questions, a “Pico Island International Volcanological Meeting” has been convened three times in recent years (2001, 2002, and 2004). We originally were invited by Elsevier to produce a Special Issue of JVGR focusing on the main conclusions of the papers to be presented at 2002 Pico meeting. However, at the time, we believed that it would be more appropriate to have a Special Issue that would be broader in scope than the meeting itself and involve a greater number of potential contributors, by inviting all researchers in Portugal and abroad who have conducted geoscience studies in the Azores. Thus, this Special Issue contains contributions of those researchers who accepted our invitation to share with the global volcanologic community the findings and insights from their investigations of the Azores Islands and surrounding seafloor. The collection of papers in this Special Issue constitutes a representative sampling of the wide-ranging research conducted on the Azores Archipelago, on land and offshore. This sampling encompasses a variety of geological, geophysical, tomographical, petrologic–geochemical, geothermal studies, as well as assessments of natural hazards.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Special issue: Volcanic geology of the Azores Islands
Series title Journal of Volcanology and Geothermal Research
Volume 156
Issue 1-2
Year Published 2006
Language English
Publisher Elsevier Science
Contributing office(s) Volcano Hazards Program
Description 186 p.