Abstract Studies of the water chemistry of Taal crater lake and echo-sounding surveys have provided new insights into its chemical and physical dynamics. During the volcano-seismic unrest of April 2010–June 2011, the waters of Taal crater lake showed changes in chemical composition and increases in CO 2 emissions associated with the seismic unrest. The chemical and isotopic data show that the lake water has contributions from both seawater and meteoric water and receives injections of deep hydrothermal water and gases during periods of intense volcano-seismic unrest. These inflationary periods may lead to faulting of the impermeable cap rock that usually seals the deeper Taal hydrothermal reservoir in response to degassing and convective movements in the underlying Taal magma chamber.

Abstract Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 15 explosive eruptive events registered over the past two centuries. Recent eruptions (1967, 1969 and 1970) and volcanic unrest episodes in 1992, 1999 and 2014–15 demonstrate that the occurrence of future volcanic activity is a valid and pressing concern for scientists, logistic personnel and tourists that are visiting or are working on or near the island. Over the last few decades, intense research activity has been carried out on Deception Island to decipher the origin and evolution of this very complex volcano. To that end, a solid integration of related scientific disciplines, such as tectonics, petrology, geochemistry, geophysics, geomorphology, remote sensing, glaciology, is required. A proper understanding of the island's evolution in the past, and its present state, is essential for improving the efficiency in interpreting monitoring data recorded during volcanic unrest periods and, hence, for future eruption forecasting. In this chapter, we briefly present Deception Island's most relevant tectonic, geomorphological, volcanological and magmatic features, as well as the results obtained from decades of monitoring the island's seismic activity and ground deformation.

Abstract We use a Global Positioning System (GPS) to unravel the complex geodynamics of the Azores Triple Junction where tectonic and volcanic activities coexist. The temporal analysis of densely distributed continuous GPS data on São Miguel for the period 2008–13 provides an improved understanding of interactions between present-day plate boundary kinematics and volcanic deformation. We find a high-strain-rate (0.28 ppm a –1 ) zone between Congro and Furnas, which accommodates about 50% of the Eurasian–Nubian plate spreading as predicted by the MORVEL plate angular velocity model. The seismic unrest of Fogo–Congro (2011–12) shows a strong similarity with the Matsushiro (Japan) earthquake swarm (1965–66) and the Campi Flegrei (Italy) volcanic unrest (1969–72 and 1982–85), in that an edifice-scale inflation associated with intense high-frequency earthquakes and inflation–deflation reversals coincided with a sharp drop in seismicity. We propose the following hypothesis for the Fogo unrest: (1) the primary inflation source beneath Fogo promotes lateral diffusion of fluids that is selectively guided by existing cracks/fissures formed from regional extension; (2) an influx of fluids increases pressure in cracks/fissures and generates lower-frequency earthquakes; and (3) discharge of fluids causes pressure decrease and dilatancy recovery (i.e. seismic quiescence).

Abstract São Miguel, the largest island of the Azores, corresponds to one of the most seismically active areas within the archipelago. During historical times it was affected at least six times by destructive earthquakes, which were responsible for thousands of deaths. Several seismic crises are related both to volcanic eruptions and unrest episodes, being the cause of significant damage over more restricted areas. The central region of the island has been the most active in recent years and is characterized by the occurrence of seismic swarms, generally with low-magnitude events (M D ≤2), that are clustered both spatially and temporally. A significant relevant seismic swarm occurred between May and September 2005 and was associated with an episode of volcanic unrest. Another part of the seismicity recorded on São Miguel is associated with submarine volcano-tectonic structures that are located near the island, some of which are the source of the strongest earthquakes. The spatial distribution of b -values shows that high values (i.e. b >1) are mainly associated with the Fogo–Congro region, whereas low b -values (i.e. <1) are more common offshore. The spatial distribution of b -values in the Fogo–Congro region is suggestive of the existence of material and/or stress heterogeneities, and this is supported by a mixture of fault plane solutions.

China is home to more than a dozen volcanoes that have erupted during the Holocene. Recent activity, such as the eruption of Ashikule in 1951 and unrest of Changbaishan during 2002–05, highlights the potential for future volcanic unrest and eruptions in the country. In 1999, a National Volcano Monitoring Network was established, inaugurating a programme of research and surveillance to understand the history and activity of China's volcanoes. Much progress has been made since, advancing understanding in the areas of geology, geochemistry and geophysics, and supporting hazard mitigation planning. This Special Publication reports the wide-ranging outcomes of this work for the first time to the international community.