Formation of the Aira Caldera, Southern Kyushu, ∼22,000 Years Ago
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Abstract:
This chapter contains sections titled: Introduction Precaldera Events The Osumi Pumice Fall Tsumaya Pyroclastic Flow Kamewarizaka Breccia Ito Pyroclastic Flow Nature of the Magma Formation of the Aira Caldera Post-Aira Caldera Activity Funnel-Shaped Underground Structure of the Aira Caldera and Other Japanese Calderas ConclusionKeywords:
Caldera
Pumice
Breccia
Breccia
Pumice
Debris flow
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Petrochemistry
Pyroclastic fall
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Pumice is abundant in many ancient sequences of marine pyroclastic rocks and is regarded as important evidence that contemporaneous, or nearly contemporaneous, volcanic activity was the source of at least some of the fragmental debris. The pumice in many such sequences of rocks, however, is easily overlooked, chiefly because most marine pyroclastic rocks have been altered or metamorphosed to varying degrees, masking or obliterating the delicate cellular structures of the original pumiceous material. With care, however, and with the knowledge that pumice-rich rocks commonly occur toward the top of thick, vertically graded beds of lapilli tuff and tuff breccia, the elusive pumiceous fraction of most sequences of rocks can generally be recognized. Hand-lens examination of wetted specimens in the field will usually reveal the wispy and ragged outlines of some of the pumice that is present. More detail can be seen in thick sections and in conventional thin sections of pumiceous rocks. In general, the pumice in more altered and metamorphosed rocks can be seen by careful examination of hand specimens or thick sections; the pumice in relatively unaltered rocks can best be seen in thin section. Examples of pumice-rich rocks from the Precambrian of Arizona, the Cretaceous of Puerto Rico, and the Tertiary of Japan are described and illustrated.
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Lapilli
Pumice
Pyroclastic fall
Peléan eruption
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Pyroclastic fall
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Pyroclastic fall
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Pumice
Pyroclastic fall
Peléan eruption
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Volcano represent channel of systems fluid (lava), which has a depth up to 10 km from the earth surface. One ofthe active volcanoes is Mount Rinjani which recorded the eruption was 9 times from 1846 to 1994. The result ofthe eruption of Mount Rinjani is pyroclastic rocks dominated by pumice, which accumulated at lot of areas ofresearch that will be determined by the density value calculation method. The resulting rock density values canbe used to see the spread of the volcanic eruption material with simulation software based on data Hazmaperuption in 1994. The result of this research is the density of pumice and simulated the spread of the eruption ofMount Rinjani 1994. The density of pumice is about 693 kg/m3 and deployment simulation shows the distributionof the eruption of Rinjani to the diameter size of the fine dust (<1/16 mm) spread towards the Northwest (NorthLombok) with total mass about 6,38x109 kg and diameter size of lapilli (2-10) mm spread around the center ofthe eruption (Mount Rinjani) with total mass about 5, 16x109 kg.
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Abstract The widespread shower-bedded deposits of Rotoehu Ash consist of multiple airfall pyroclastic units (tephras) which underlie, are interbedded within and mantle the less widespread rhyolitic pyroclastic flow deposits of the Rotoiti Breccia Formation (late Pleistocene). No significant time intervals are recorded within the Rotoehu Ash, showing that the thick pyroclastic flow breccia deposits enclosed by the Rotoehu Ash units were also erupted in a short time interval. Recognition of the multiple nature of Rotoehu Ash has proved necessary in correlation of breccia deposits in the Rotorua area.
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Volcanic ash
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