Glossary

0-9

Caldera: A volcanic structure, generally large, which is principally the result of collapse or subsidence into the top of a magma chamber during or immediately following eruptive activity (Cole et al., 2004). Collapse or subsidence is essential to form a caldera and analogue models help constrain the sub-surface features formed beneath them, caldera collapse has previously been considered as occurring on steeply inward-dipping faults (Fridrich et al., 1991).

Cinder cone: The cinder cone are formed due to the strombolian eruption. The cone-building process is mainly one of ballistic deposition and slumping with some of the fine-grained airfall carried away by wind (McGetchin et al., 1974). The cinder cones are primarily constructed by moderately explosive eruptions, pristine cone morphometry depending principally upon explosive eruptions that are based on pyroclastic size, distribution, ejection velocity, and ejection angle (Settle, 1979).

Debris Flow (Lahar): Lahar, or volcanic debris flow, appear similarly to debris flows in other environments but may differ significantly in size and origin. Through the work Schmidt (1934) and van Bemmelen (1949), the Indonesian word “lahar,” which refers to highly concentrated streaming combinations of rock debris, mud, and water emanating from volcanoes, was brought into the literature on volcanology. Events classified as lahars can involve mechanisms that are not typically included in the words lahar and debris flow, such as debris avalanches, flood flows, and pyroclastic flows. Here, an avalanche of debris is a flowing mixture of rock, debris, and moisture that slides downslope due to gravity. Debris avalanches are distinct from debris flows in that their weight is solely maintained by interactions between individual particles and they are not saturated with water (Vallance J., 2005).

Deformation: A change in the position or movement of a point on a body in absolute terms when assessed from the observed motion behaviour of the point and in relative terms when the motion is assessed from another point.

Flood Basalt: Flood basalt represent a very special type of intraplate volcanism. Flood basalt provinces comprise hundreds of thousands of km^3 of magma, covering tens of thousands ofsquare kilometers. Flood basalt are generated when a large plume head impinges at the base of the lithosphere. These mantle plumes are probably hotter than the mantle that rises beneath mid-ocean ridges and thus partially melt more strongly during drifting of the lithosphere. In many flood basalt fields, in which magmas have been erupted during very short times, they probably represent melts from a rapidly rising plume (Hans U., 2004).

Landslide: Volcanic landslide volumes depend partly on the volcano size, as larger edifices have greater volumes, larger flanks, and can deform more. The landslide volume depends also on the local setting. At the smallest scale, landslides of a few thousand cubic meters (Cecchi et al., 2005). At larger scales, landslides of several million cubic meter involve large valley flanks, and cut deeper into the volcanic edifice to involve hydrothermal systems. Most volcanoes have landslides, and collapse to form a debris avalanche at least once during their lifetime, sometimes several times, and such events occur on all types of volcano, be they oceanic, continental, monogenetic, or polygenetic. Landslides occur from volcanoes in all geodynamic contexts, including mid-ocean rifts, hot spots, arcs, and intraplate settings (Vries et al., 2015).

Lava Dome: Lava dome form when highly viscous lava is extruded from a volcanic vent and cannot flow far away so piles up, often in pre-existing calderas. Dome-building eruptions account for approximately 6% of volcanic eruptions around the world (Calder et al., 2015) and are often linked with highly explosive activity (Ogburn et al., 2015). Lava domes can collapse, forming pyroclastic flows and debris avalanches; these products can be very hazardous to populations surround.

Lava Flow: Lava flow is outpourings of molten rock, or magma. On Earth, the overwhelming majority have silicate compositions, for which common melting temperatures are in the range 800-1200°C; lavas of sulphur and of carbonate compositions also occur at lower temperatures (about 150°C for sulphur and 600°C for carbonatite), but these are extremely rare and are not important as far as general hazard studies are concerned. First applied at Vesuvius, the word “lava” is derived from the italian lavare (to wash), ironic since the washing normally meant cleaning away the fruits of human labour (Kilburn, 2000).

Pyroclastic Fall: Sedimentation of pyroclasts through the atmosphere from an eruption jet or plume during an explosive eruption.

Pyroclastic Flow: Pyroclastic flows are hot, dry flows of volcanic rock debris. The reasons behind the mobility of pyroclastic flow can be attributed to several elements such as the explosive force of the eruption, gas-emitting particles, trapped and heated air within the mass, or a combination of these. Pumice fragments, thick rock pieces, or combinations of the two could make up the next deposits. Pyroclastic flows can vary in size from less mobile avalanches of lithic blocks and ash to gas-rich, highly mobile flows of pumice. The rapid eruption of massive amounts of pumice is the usual source of pumiceous pyroclastic flows, pyroclastic flows primarily composed of lithic material are typically caused by the partial collapse of a volcanic dome or spine or by the sliding of hot rock debris accumulations down the side of the volcano (Hyde, 1975).

Shield Volcano: A shield volcano is a low-angle volcano formed principally by accumulation of low viscosity lava flows (mostly basaltic lavas). The name “shield” derives from “Skjalbreidhur” (broad shield) volcano in Iceland, which displays a warrior’s shield-like profile. Nevertheless, this latter volcano is a small-scale monogenetic edifice, and the “shield volcano” mostly refers to larger polygenetic edifices. While some shield volcanoes form at divergent borders, either on land or on the sea floor, the majority are linked to mantle plumes. Their non-viscous mafic magma causes their slopes to be generally mild (2 to 10 degrees), with the biggest ones reaching diameters of over 100 km (Paris, R., 2013).

Strato Volcano: Stratovolcano are often called composite volcanoes, the type that most people recognise as volcanoes. With peaks reaching several hundred metres in height from their surroundings, they dominate the visual landscape of the area. is composed of a mixture of pyroclastic deposits and lava flows. Indirectly, a stratovolcano is formed from multiple layers of viscous lava flows and other eruptive materials. Most stratovolcanoes have a complex structural form caused by repeated eruptions. Some of these types of volcanoes form over several thousand years, but may become active again tens or even hundreds of years later and rest again during the same time frame. This is due to the eruption of andesite rocks. The slope of the stratovolcano type is usually between 30-50 degrees and the eruption comes from continuous activity in the stomach which is then pushed out to the earth’s surface (ESDM, 2022).

Super Volcano: Supervolcano is a volcano that has produced at least one explosivesupereruption. Their eruptions are bigger, and hence their destructive capacity is greater. The size distinction, however, is arbitrary-1000 m3 of fragmental material is a convenient dividing line. As supervolcanoes rapidly emit material during eruption, whatever surfacestructure existed before the eruption collapses into the evacuating chamber to form the characteristic caldera (Smith, 1979). Supereruptions require a very large volume of magma withstrong explosive potential. Explosive potential results fromahigh content of volatile constituents (mostly H20) thatcan form gas bubbles, combined with high viscosity toinhibit escape of the bubbles from the magma; it is thebursting of these trapped bubbles that drives an explosion (Zhang et al., 2008).

Tephra: Tephra is unconsolidated falling pyroclastic material produced by volcanic eruptions. Tephra consists of a variety of materials that are generally volcanic glass (glass) formed by the cooling of magma ‘droplets’, vesicular, solid or flake-like in nature, and various proportions of crystalline and mineral components derived from volcanoes and magma kitchen walls. As the particles fall to the surface by wind and gravitational forces, tephra forms a layer of unconsolidated and generally layered material (ESDM, 2021).

Volcanic Ash: Volcanic ash is a non-genetic term and refers to fine fragments of magmatic glass shards, magmatic crystals, and other rocks (lithic material) with a diameter below 2 mm (White and Houghton, 2006). Fundamentally, volcanic ash is an inevitable product of the fragmentation of magmas and volcanic rocks. volcaninc ash erupted explosively from a volcano is generally composed of a mixture of pumice/glass shards (essentially quenched magma), fragments of older rocks from the volcano, and variable proportions of crystals or crystal fragments of various silicates and other less abundant mineral types (Plumlee et al, 2014).

Volcanic Gasses: The term “volcanic gas” identifies the fluid gas phase released by active volcanoes, both during eruption and quiescence. Compositionally, volcanic gases are molecular combinations of four major elements (H, C, O, and S) but also include a variety of minor (CI, F, N, He, Ne, and Ar) to trace components. Being generally water-dominated, volcanic gases show a spread of compositions, reflecting a combination of source processes (magma and its geodynamic context) and interactions with local hydrothermal or hydrologic systems (Aiuppa et al, 2016).

Volcano Type A: Volcanoes that have experienced magmatic eruptions at least once after 1600. The number of volcanoes in this classification is 79 spread across Sumatra, Java, Bali, Lombok, Sumbawa, Flores, Banda Sea, Sulawesi, Sangihe Islands, and Halmahera.

Volcano Type B: Volcanoes that after 1600 have no longer held magmatic eruptions, but still show symptoms of activity such as solfatara activity. The number of volcanoes in this classification is 29, spread across Sumatra, Java, Flores, Banda Sea, Sulawesi, and Halmahera.

Volcano Type C: Volcanoes whose eruptions are unknown in human history, but there are still signs of past activity in the form of solfatara/fumarola fields on weak whims. The number of volcanoes in this classification is 21, spread across Sumatra, Java, Flores, and Sulawesi.

Glossary

GLOSSARY

Support By

InaVHA

Contact