![]() ![]() In many eruptions, lavas erupt from newly formed vents, hence, the potential spatial distribution of new vents must be estimated as part of the analysis. Site-specific lava flow hazard assessments require that the hazard of lava inundation be estimated long before lava begins to erupt from any specific vent. An example based on a nuclear power plant site in Armenia demonstrates the strengths of this type of analysis (Figure 1).įull size image Spatial density estimation Given these input data, Monte Carlo simulations generate many possible vent locations and many possible lava flows, from which the conditional probability of site inundation by lava flow, given the opening of a new vent, is estimated. Thus, the model depends on mappable features found in the site area. Input data that are needed to develop a probability model include the spatial distribution of past eruptive vents, the distribution of past lava flows within an area surrounding the site, and measurable lava flow features including thickness, length, volume, and area, for previously erupted lava flows. The simulated lava flows follow the topography, represented by a digital elevation model (DEM). Second, the model simulates the effusion of lava from this vent based on field measurements of thicknesses and volumes of previously erupted lava flows within an area encompassing the site of interest. First, the location of the lava flow source is sampled from a spatial density model of new, potentially eruptive vents. There are two essential features of the analysis. This paper describes a computer model used to estimate the conditional probability that a lava flow will inundate a designated site area, given that an effusive eruption originates from a vent within the volcanic system of interest. Lava flows are considered to be beyond the design basis of nuclear facilities, meaning that the potential for the occurrence of lava flows above some level of acceptable likelihood would exclude the site from development of nuclear facilities because safe control or shutdown of the facility under circumstances of lava flow inundation cannot be assured ( IAEA 2011). Here, we develop a methodology for site-specific hazard assessment for lava flows. Although site hazards could be considered in terms of the cumulative effects of these various volcanic phenomena, a better approach is to assess the hazard and risk of each phenomenon separately, as they have varying characteristics and impacts. These hazard assessments consider the hazard and risk posed by specific volcanic phenomena, such as lava flows, tephra fallout, or pyroclastic density currents ( IAEA 2011 Hill et al 2009). Mudflows ( lahars) have buried entire communities located near erupting volcanoes.Volcanic hazard assessments are often conducted for specific sites, such as nuclear facilities, dams, ports and similar critical facilities that must be located in areas of very low geologic risk ( Volentik et al 2009 >Connor et al 2009). When hot volcanic materials mix with water from streams or melted snow and ice, mudflows form. ![]() If thick enough, blankets of ash can suffocate plants, animals, and humans. Ash erupted into the sky falls back to Earth like powdery snow. ![]() These fiery clouds race down mountainsides destroying almost everything in their path. Tephra can range in size from tiny particles of ash to house-size boulders.Įxplosive volcanic eruptions can be dangerous and deadly. They can blast out clouds of hot tephra from the side or top of a volcano. In this type of eruption, the magma blasts into the air and breaks apart into pieces called tephra. A good example is the eruption of Washington’s Mount St. Pressure builds up until the gases escape violently and explode. If magma is thick and sticky, gases cannot escape easily. Lava flows rarely kill people because they move slowly enough for people to get out of their way. A good example is the eruptions at Hawaii’s volcanoes. When this type of magma erupts, it flows out of the volcano. If magma is thin and runny, gases can escape easily from it. Some volcanic eruptions are explosive and others are not. The explosivity of an eruption depends on the composition of the magma. Eventually, some of the magma pushes through vents and fissures to the Earth's surface. Since it is lighter than the solid rock around it, magma rises and collects in magma chambers. ![]() Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. ![]()
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