Dacite is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz.
Andesite is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.
The Sunda Arc is a volcanic arc that produced the volcanoes that form the topographic spine of the islands of Sumatra, Nusa Tenggara, and Java, the Sunda Strait and the Lesser Sunda Islands. The Sunda Arc begins at Sumatra and ends at Flores, and is adjacent to the Banda Arc. The Sunda Arc is formed via the subduction of the Indo-Australian Plate beneath the Sunda and Burma plates at a velocity of 63–70 mm/year.
The Manila Trench is an oceanic trench in the Pacific Ocean, located west of the islands of Luzon and Mindoro in the Philippines. The trench reaches a depth of about 5,400 metres (17,700 ft), in contrast with the average depth of the South China Sea of about 1,500 metres (4,900 ft). It is created by subduction, in which the Sunda Plate is subducting under the Philippine Mobile Belt, producing this almost N-S trending trench. The convergent boundary is terminated to the north by the Taiwan collision zone, and to the south by the Mindoro terrane. It is an area pervaded by negative gravity anomalies.
The Central American Volcanic Arc is a chain of volcanoes which extends parallel to the Pacific coastline of the Central American Isthmus, from Mexico to Panama. This volcanic arc, which has a length of 1,100 kilometers is formed by an active subduction zone, with the Cocos Plate subducting underneath the Caribbean Plate. The region has been volcanically and geologically active for at least the past several million years. Numerous volcanoes are spread throughout various Central American countries; many have been active in the geologic past, some more so than others.
Bazman is a dormant stratovolcano in a remote desert region of Sistan and Baluchestan Province in south-eastern Iran. A 500-m-wide crater caps the summit of the dominantly andesitic-dacitic volcano, the flanks of which are covered by monogenetic centres especially to the northwest. Bazman is a geologically young volcano which formed mainly in the Quaternary, with the oldest dated rocks being 11.7 million years old and the youngest 0.6 million years. Although no historic eruptions have been reported from Bazman, it does contain fumaroles. Thus Bazman may be regarded as dormant, rather than extinct. Its satellite cones have been the source of basaltic lava flows.
Boninite is an extrusive rock high in both magnesium and silica, thought to be usually formed in fore-arc environments, typically during the early stages of subduction. The rock is named for its occurrence in the Izu-Bonin arc south of Japan. It is characterized by extreme depletion in incompatible trace elements that are not fluid mobile but variable enrichment in the fluid mobile elements. They are found almost exclusively in the fore-arc of primitive island arcs and in ophiolite complexes thought to represent former fore-arc settings or at least formed above a subduction zone.
Adakites are volcanic rocks of intermediate to felsic composition that have geochemical characteristics of magma originally thought to have formed by partial melting of altered basalt that is subducted below volcanic arcs. Most magmas derived in subduction zones come from the mantle above the subducting plate when hydrous fluids are released from minerals that break down in the metamorphosed basalt, rise into the mantle, and initiate partial melting. However, Defant and Drummond recognized that when young oceanic crust is subducted, adakites are typically produced in the arc. They postulated that when young oceanic crust is subducted it is "warmer" than crust that is typically subducted. The warmer crust enables melting of the metamorphosed subducted basalt rather than the mantle above. Experimental work by several researchers has verified the geochemical characteristics of "slab melts" and the contention that melts can form from young and therefore warmer crust in subduction zones.
The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones which are separated by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. While some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences within volcanic zones and even between neighboring volcanoes. Despite being a type location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a broad range of volcano-tectonic settings, as it has rift systems and extensional zones, transpressional faults, subduction of mid-ocean ridges and seamount chains as well as a large range of crustal thicknesses and magma ascent paths and different amounts of crustal assimilations.
In the geology of the Philippines, the Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines. It includes two subduction zones, the Manila Trench to the west and the Philippine Trench to the east, as well as the Philippine Fault System. Within the Belt, a number of crustal blocks or microplates which have been shorn off the adjoining major plates are undergoing massive deformation.
Ocean island basalt (OIB) is a volcanic rock, usually basaltic in composition, erupted in oceans away from tectonic plate boundaries. Although ocean island basaltic magma is mainly erupted as basalt lava, the basaltic magma is sometimes modified by igneous differentiation to produce a range of other volcanic rock types, for example, rhyolite in Iceland, and phonolite and trachyte at the intraplate volcano Fernando de Noronha. Unlike mid-ocean ridge basalts (MORBs), which erupt at spreading centers (divergent plate boundaries), and volcanic arc lavas, which erupt at subduction zones (convergent plate boundaries), ocean island basalts are the result of intraplate volcanism. However, some ocean island basalt locations coincide with plate boundaries like Iceland, which sits on top of a mid-ocean ridge, and Samoa, which is located near a subduction zone.
Terry Ann Plank is an American geochemist, volcanologist and professor of earth science at Columbia College, Columbia University, and the Lamont Doherty Earth Observatory. She is a 2012 MacArthur Fellow and member of the National Academy of Sciences. Her most prominent work involves the crystal chemistry of lava minerals in order to determine magma ages and movement, giving clues to how quickly magma can surface as lava in volcanoes. Most notably, Plank is known for her work establishing a stronger link between the subduction of ocean sediments and volcanism at ocean arcs. Her current work can be seen at her website.
Plank states that her interest in volcanoes began when her Dartmouth professor took her and other students to Arenal volcano in Costa Rica. He had them sit and have lunch while on top of a slow-moving lava flow and while watching bright red goops of lava crack out from their black casings. "It was totally cool, how could you not like that?" Plank recalled the event to State of the Planet, an Earth Institute News source at Columbia University.
The Troodos Ophiolite on the island of Cyprus represents a Late Cretaceous spreading axis that has since been uplifted due to its positioning on the overriding Anatolian plate at the Cyprus arc and ongoing subduction to the south of the Eratosthenes Seamount.
A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin. The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops. The magmatism and petrogenesis of continental crust are complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.
Tonalite–trondhjemite–granodiorite (TTG) rocks are intrusive rocks with typical granitic composition but containing only a small portion of potassium feldspar. Tonalite, trondhjemite, and granodiorite often occur together in geological records, indicating similar petrogenetic processes. Post Archean TTG rocks are present in arc-related batholiths, as well as in ophiolites, while Archean TTG rocks are major components of Archean cratons.
The geology of Panama includes the complex tectonic interplay between the Pacific, Cocos and Nazca plates, the Caribbean Plate and the Panama Microplate.
The geology of Costa Rica is part of the Panama Microplate, which is slowly moving north relative to the stable Caribbean Plate.
The subduction tectonics of the Philippines is the control of geology over the Philippine archipelago. The Philippine region is seismically active and has been progressively constructed by plates converging towards each other in multiple directions. The region is also known as the Philippine Mobile Belt due to its complex tectonic setting.
Catherine Chauvel is a geochemist at the Institut de Physique du Globe de Paris known for her research on the impact of volcanic activity on the chemistry of the mantle, continental crust, and island arc geochemistry.
Keiko Hattori is a geochemist and mineralogist. She is Distinguished University Professor of Geochemistry and Mineral Deposits in the Department of Earth and Environmental Sciences at the University of Ottawa.
