After 200 yr of repose, Pacaya Volcano resumed Strombolian activity in 1961 and has remained active until the time of this writing (2013). A three-dimensional map of 50 yr of nearly continuous activity of Pacaya depicts an accumulation of homogeneous, crystal-rich high-Al basalt on the west side of a preexisting cone. The material erupted is loose and welded spatter, volcanic ash, and 249 pahoehoe and a‘a lava flows, most of which were extruded in a few days, and most have extended less than 2 km in length from vents near the 2500-m-high summit down slopes of 20°–33°. The configuration of lava flows makes up a rigid, web-like network that welds the asymmetrical, steep western slope of an expanded Pacaya cone. The vents have fed the lava flows, forming a sieve-like pattern where lava leaks out. The cone contains a complex network of intrusive feeders, which fill and empty with lava, degas, and drain back. The volcano has shown explosive lava fountaining and effusive periods of activity and often exhibits both, as summit eruptions occur while lava drains from the cone. Lava flows and pyroclastic units from collapse-related avalanches and tephra fall tend to alternate. The overall length of lavas is limited, so that inhabited areas below the cone on most flanks are unlikely to be reached by flows, although topographic barriers, which blocked the flow of lava to the closest villages north of Pacaya, are now filled, so that lavas of moderate length (~2 km) could reach towns to the north under some conditions. The volcano is known to have experienced catastrophic explosive collapse in the last few thousand years. The current cone itself may be unstable because the new material has mostly asymmetrically loaded the west side of an old cone, and collapse to the west may be more likely because of mass imbalance and because of persistent activity that opens paths and accumulates on that side. Collapse to the west would threaten significant populations. Pacaya's past eruptions lasted centuries, with repose intervals of similar length, so the current activity may continue for another century or more. Overall, Pacaya is a complex of overlapping basaltic cones, and its pattern of activity provides insight into the early stages of composite cones such as nearby Agua, Fuego, Atitlán, and Santa María, all larger and older cones on the volcanic front of Guatemala with Pacaya.

Geological mapping of the island of Lipari at 1:10,000 scale was performed by adopting a stratigraphic approach based on the integrated use of lithostratigraphic units, lithosomes, and unconformity-bounded units. This approach allows the geological peculiarity of this volcanic area to be reproduced through documention and interpretation of the different rock types (using lithostratigraphic units), and definition of the geometry of rock bodies (using lithosomes), with emphasis on unconformities in the volcano-sedimentary architecture (using unconformity-bounded units). In particular, by concentrating on accurate tephrostratigraphy and deposits formed during periods of prolonged volcanic quiescence (e.g., marine deposits and epiclastic products), unconformity-bounded units provide the main stratigraphic constraints at a regional level. Two first-order unconformities (U I and U II ), represented by surfaces of erosion bounding marine deposits emplaced during marine oxygen isotope stage (MIS) 5, can be correlated across most of the Aeolian archipelago. Furthermore, four second-order and seven third-order unconformities represented by erosion and non-deposition surfaces formed during main periods of dormancy or minor sea-level fluctuations of MIS 5 are introduced. The reconstructed unconformity-bounded stratigraphy, together with other rock-stratigraphic units, provides an effective reconstruction of the geological evolution of Lipari, ranging between ca. 220 ka and the present time, as the result of the interplay among volcanic activity of local and external provenance, sea-level fluctuations, and regional fault systems. In this framework, Lipari's eruptive history encompasses five successive eruptive epochs characterized by distinctive centers of eruption (eastwards shifting), eruption type (from mainly strombolian to hydromagmatic), and chemical composition (from calc-alkaline basalt-andesite to high-K calc-alkaline rhyolite).

Abstract The northwest rift zone (NWRZ) eruption took place at Newberry Volcano ~7000 years ago after the volcano was mantled by tephra from the catastrophic eruption that destroyed Mount Mazama and produced the Crater Lake caldera. The NWRZ eruption produced multiple lava flows from a variety of vents including cinder cones, spatter vents, and fissures, possibly in more than one episode. Eruptive behaviors ranged from energetic Strombolian, which produced significant tephra plumes, to low-energy Hawaiian-style. This paper summarizes and in part reinterprets what is known about the eruption and presents information from new and ongoing studies. Total distance spanned by the eruption is 32 km north-south. The northernmost flow of the NWRZ blocked the Deschutes River upstream from the city of Bend, Oregon, and changed the course of the river. Renewed mafic activity in the region, particularly eruptions such as the NWRZ with tephra plumes and multiple lava flows from many vents, would have significant impacts for the residents of Bend and other central Oregon communities.