Ī brief lull was shattered by a tremendous explosion at about 8:00 a.m. The explosions continued through the next day and night. The phreatic explosions had finally given way to magmatic explosions as magma reached the surface. The following morning, parts of the eruption plume became incandescent, signifying that the character of the eruption had changed. The explosions resumed the night of 5 May. The tsunamis swept along the coast, damaging buildings and boats. The massive flow buried about 150 people and generated a series of three tsunamis as it hit the sea. Mount Pelée remained relatively quiet until the afternoon of 5 May when a mudflow swept down a river on the southwest flank of the volcano, destroying a sugar mill. Saint-Pierre received its first ash fall on 3 May. Some of the afflicted residents panicked and headed for the perceived safety of larger settlements, especially Saint-Pierre, about 10 km (6.2 mi) south of Pelée's summit. Heavy ash fell, sometimes causing total darkness. Lightning laced the eruption clouds and trade winds dumped ash on villages to the west. The intensity then subsided for a few days until early May, when the explosions increased again. Within days, the vigor of the explosions exceeded anything witnessed since the island was settled by Europeans. Eruptive activity began on 23 April as a series of phreatic explosions from the summit of Mount Pelée. The 1902 eruption of Mount Pelée was a volcanic eruption on the island of Martinique in the Lesser Antilles Volcanic Arc of the eastern Caribbean, which was one of the deadliest eruptions in recorded history. 2, these small-scale pyroclastic flows are roughly classified into three types by their origin: a) generated by the non-explosive, gravitational collapse of a lava dome (Merapi type), b) generated by the partial fracture and fall of a lava dome due to a volcanic eruption (Pelée type), and c) generated by the fountain collapse of an eruption column after a volcanic eruption (Soufriere type). In the volcanology, a pyroclastic flow with a bulk volume of 100,000-100 million m3 is called a small-scale pyroclastic flow. The pyroclastic flow was once called a volcanic clastics flow, but the shortened name "pyroclastic flow" is used these days. 2 Generation of pyroclastic flows (by Macdonald)īoth the lower and upper layers are high temperature and high speed. The upper layer is a low-density flow composed of primarily small size volcanic ash that sweeps down the hill floating in the turbulent volcanic gas.įig. The lower layer is a dense flow composed of relatively large size sediment. In terms of the structure, the pyroclastic flow is roughly divided into the lower layer (debris avalanche) and the upper layer (dust storm), a shown in Fig. Like other flowing bodies that flow down by gravity, pyroclastic flows flow down topographically low areas, but they easily run over low ridges because their speed is so high. Therefore, even among the sediment-related disasters caused by volcanic eruptions, pyroclastic flows are feared as one of the deadliest phenomena that have devastating impacts on both humans and houses. A combination of high temperature, high speed, and a large volume of sediment causes severe damage to the flowing areas. In general, the temperature of a pyroclastic flow is as high as 100-1000℃ and its speed is 10-100 m per second or more. A pyroclastic flow refers to a phenomenon in which hot lava pieces, pumices, and ash from a volcanic eruption run down the hillside floating in the generated hot volcanic gas.
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