Definition, Causes and Effects of Volcanic Eruptions Occurrence
Volcano is a place or a hole where incandescent rock and or gas, usually both, come out to the earth’s surface, and solid material that accumulates around the hole to form a hill or mountain ( Macdonald, 1972 ). Thus the focus of the understanding of volcanoes is on the hole and release of magma, while the shape of a landscape of hills or mountains is not a necessity, earthquake survival kit since many volcanoes are not forming a mountain.
However, because in Indonesia almost all mountain-shaped volcano then (wrongly) call it the volcano (volcano) or volcanoes. Volcanic eruption itself implies as an event that occurs due to deposition of magma in the earth were pushed out by a high pressure gas.
The occurrence of volcanic eruptions FACTORS CAUSE
Volcano may erupt as a result of increased mobility bouyancy and magma body. This happens under, in, and above the magma chamber . Magma chamber are being pressured by the rocks resulting in magma volume increases and eventually emerged as the eruption. Knowledge of plate tectonics is the beginning of solving the puzzle of natural phenomena including mountain ranges, continents, earthquakes, and volcanoes. Earth has a lot of fluids and water on the surface. Both of these factors greatly influence the formation and composition of the magma and volcanic locations and events.
Heat hot interior of the Earth is formed during the formation of the Earth around 4.5 billion years ago, along with the heat arising from natural radioactive elements, such as elements of the isotope K, U and Th with time. Earth at the time formed more heat, but then cooled gradually in accordance with the development of its history. The cooling occurs due to the release of heat and intensity vulkanisma on the surface.
Propagation of heat from the earth to the surface in the form of convection, where materials are heated on the base coat, the depths of 2,900 km below the earth moving and narrowed spreads around. On the upper mantle, about 7-35 km below the earth, these materials cools and becomes solid, then sank back into the convection flow. Lithosphere includes the crust too, generally have a thickness of 70-120 km and split into several large fragments called tectonic plates.
The plates are moving together and also penetrate into the direction of mantle convection. Part pedestal melengser lithosphere above the zone of weak upper mantle, which is also called astenosfir. Astenosfir weak parts occurs at or near the melting temperature that starts to happen, kosekuensinya some parts astenosfir melt, although most are solid. Continental crust has lk.35 km thick, low-density and aged 1-2 billion years, while the thinner oceanic crust (circa. 7 km), more dense and are not older than 200 million years. Continental crust position is on top of the oceanic crust due to differences in specific gravity, and both floats on astenosfir.
IMPACT CAUSED volcanic eruption
Volcanic eruptions can cause various effects ata u result. Impact of volcanic eruptions can influence directly or indirectly and nature can be destructive (negative) or be a blessing (positive) to the surrounding community. The negative impact / danger of a volcanic eruption is as follows:
falling pyroclastic : pyroclastic fallout from the eruption occurred which form columns of smoke high enough, when the energy runs out, the ashes will be spread in the direction of the wind and then fall back to earth. Ashfall is not a direct danger to humans, but the ash deposition will shed leaves and small trees so destructive agro and at a certain thickness can knock down the roof of the house. Distribution of ash in the air can darken the earth while threatening danger to the flight path.
Pyroclastic flows (hot clouds) : pyroclastic flows can occur due to debris Plinian eruption columns of smoke, eruption directly to one direction, glowing lava dome or lava tongue and flow at ground level (surge). Pyroclastic flow is largely controlled by gravity and tends to flow through the low-lying areas or valleys. High mobility pyroclastic flow is affected by the release of gases from magma or lava or of the heated air at the time of flow. The flow velocity can reach 150-250 km / h and a range of flow can reach tens of kilometers although moving on water / sea.
Her flow of lava : lava leleran a concentrated liquid and hot lava can destroy everything in its path infrastructure. Lava flow speed depends on the viscosity magmanya, the lower the viscosity, the more far-reaching stream. The temperature at the time of erupted lava ranging between 800-1200 C. In general, in Indonesia, her flow of lava the volcano erupted, medium magmanya composition, so the movement is quite slow, so that people can avoid terjangannya.
Lava eruption : lava eruptions have occurred at the volcano crater lake. If the volume of water in a crater large enough would be a direct threat to the eruption of hot mud spill. Poisonous volcanic gases : Toxic gases are generally present at active volcanoes in the form of CO, CO2, HCN, H2S, SO2, etc., at concentrations above the threshold can kill. Flash floods : flash floods caused by avalanches of volcanic material on the slopes of volcanoes long since saturated water or high rainfall. Mud flow here is not so thick as lava, but quite dangerous for the people who worked on the river when suddenly mud flow occurs.
Lahar rain : rain lava occurs when sediment loose material from the eruption of volcanoes which deposited on the tops and slopes, transported by rain or surface water. The lava flow is a stream of highly concentrated sludge that can transport material of various sizes. Boulders more than 5 m in diameter can float in the mud flow. Lava can also change the topography of the river in its path and damaging infrastructure. Volcanic avalanches : volcanic avalanches can occur as a result of volcanic eruptions, explosions of water vapor, alteration of volcanic rocks on the body so that it becomes brittle, or exposed to strong intensity earthquakes. This volcanic avalanches are rare in the general volcano resulting in disaster-prone area maps do not include the hazards of volcanic avalanches.
In addition to the negative impact (harm) above, volcanic eruptions also had a positive impact (blessing) if only to residents in the surrounding areas, such as; Lands affected by the result of volcanic volcano is very good for agriculture because the soil naturally become more fertile and can produce plants that are much more qualified, Material volcanic form of sand and stone have economic value that can be an alternative to a new livelihood to the locals as sand miners and stone, Although forest ecosystems damaged but in time will grow more trees that form a new forest ecosystems are also new, after the mountain erupted usually found geysers or hot springs coming out of the earth with a regular or periodic basis and contain specific minerals good for skin health.