|
Strombolian eruptions are relatively mild explosive with a VEI volcanic explosive index of about 2 to 3 volcanic eruptions, and are named after the Italian volcano Stromboli, which is the type volcano for this style of eruption. Strombolian eruptions consist of ejection of incandescent cinder, lapilli and lava bombs to altitudes of tens to a few hundreds of metres. The eruptions are small to medium in volume, with sporadic violence. Giuseppe Mercalli witnessed eruptions at Stromboli and Vulcano in 1888-1890. The characteristic features of eruptions that he observed at Stromboli were different from those of eruptions at Vulcano. To distinguish between the two types of eruptions, Mercalli defined Strombolian eruptions as "...''Mildly explosive at discrete but fairly regular intervals of seconds to minutes''..." The tephra typically glows red when leaving the vent, but its surface cools and assumes a dark to black colour and may significantly solidify before impact. The tephra accumulates in the vicinity of the vent, forming a cinder cone. Cinder is the most common product; the amount of volcanic ash is typically rather minor. The lava flows are more viscous, and therefore shorter and thicker, than the corresponding Hawaiian eruptions; it may or may not be accompanied by production of pyroclastic rock. Instead the gas coalesces into bubbles, called gas slugs, that grow large enough to rise through the magma column, bursting near the top due to the decrease in pressure and throwing magma into the air. Each episode thus releases volcanic gases, sometimes as frequently as a few minutes apart. Gas slugs can form as deep as 3 kilometers, making them difficult to predict.〔http://www.sciencemag.org/cgi/content/abstract/317/5835/227〕〔http://www.cosmosmagazine.com/node/1456〕 Strombolian eruptive activity can be very long-lasting because the conduit system is not strongly affected by the eruptive activity, so that the eruptive system can repeatedly reset itself. Monogenetic cones, usually erupt in the strombolian style. For example, the Parícutin volcano erupted continuously between 1943-1952, Mount Erebus, Antarctica has produced Strombolian eruptions for at least many decades, and Stromboli itself has been producing Strombolian eruptions for over two thousand years. The Romans referred to Stromboli as the "Lighthouse of the Mediterranean." ==See also== * Types of volcanic eruptions 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「strombolian eruption」の詳細全文を読む スポンサード リンク
|