火山碎屑流可以穿过水。这并不表明任何火山碎屑沉积可以穿过水。高能源需要一个火山口形成爆炸和高温流需要能给高的能量。穿越水也不能表明每个材料在一个流过去的水。逐渐流动材料数量减少。远端存款淤泥砂大小pumicious谷物。注意,浮石能溢出水由于其高的多孔结构。这是笔记标题为《* *》的火山碎屑流和激增水:一个例子从1883年喀拉喀托火山喷发* ....火山碎屑流和激增,在海上旅行.......距离80公里能量流动分散远离火山的速度超过100公里/小时,逆流而上到80公里从源代码。 The flows retained temperatures high enough to burn victims on the SW coast of Sumatra..... Here more details from the same paper; 15 km from the source flow deposited 1-2 m pyroclastics on Sebesi island.flows were moving with sufficient energy to pass over the 832-m peak of Sebesi island, inferring a maximum velocity of 320 km/h. 20 km from the source massive and poorly sorted features of the deposits indicate suspension sedimentation from the basal part of a high-particle-concentration flow. Density assumed < 1000 kg/m 3, the maximum particle concentration would be 45%. Temperature 500 C 40 km from the source temperature fall to 100-200 C. At this distance from Krakatau the deposition of tephra was not significant (several centimeters) implying that the particle concentration had been significantly reduced to perhaps only a few percent. 60 km were apparently more dilute and cooler. few cm in thickness material deposited. The distal deposits exhibit a decrease in sorting coefficient, median grain size, and thickness with increasing distance from Krakatau Some notes on mechanism from the same paper If the flow is at high temperature it will vaporize the underlying water and result in (a) expansion of the gas/particle mixture, (b)an increase in the turbulence, and (c) a decrease in friction. All of these effects will enhance the support of particles and thus reduce the amount of deposition. Druitt and Sparks(1984)have proposed that peak magma discharge occurs at the time of caldera formation, as the subsiding volcanic edifice exerts a dynamic pressure on the underlying magma chamber. The increase in magma discharge at Krakatau led to a high flux of pyroclastic flows into and over the sea. Widespread reports of mud rain closely associated with the 10 a.m. flow is attributed to the formation of a large co-ignimbrite plume laden with moisture from pyroclastic flows and surges which traveled over the sea. The transfer of heat from the flows to the sea surface led to the production of steam. As sedimentation reduced the flow's density, a moisture-rich buoyant plume lifted off, carrying fine-grained tephra and steam. Secondary phreatic explosions from shallow and proximal submarine pyroclastic flows may also have contributed tephra and steam to the plume, Reference *Carey, S., Sigurdsson, H., Mandeville, C. et al. Bull Volcanol (1996) 57: 493. https://doi.org/10.1007/BF00304435
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