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A Surtseyan eruption is a type of volcanic eruption that takes place in shallow seas or lakes. It is named after the island of Surtsey off the southern coast of Iceland.〔(Island Building Events )〕 These eruptions are commonly phreatomagmatic eruptions, representing violent explosions caused by rising basaltic or andesitic magma coming into contact with abundant, shallow groundwater or surface water. Tuff rings, pyroclastic cones of primarily ash, are built by explosive disruption of rapidly cooled magma. ==Characteristics== Although similar in nature to phreatomagmatic eruptions, there are several specific characteristics:〔(Surtseyan Eruptions )〕 *Physical nature of magma: viscous; basaltic. *Character of explosive activity: violent ejection of solid, warm fragments of new magma; continuous or rhythmic explosions; base surges. *Nature of effusive activity: short, locally pillowed, lava flows; lavas may be rare. *Nature of dominant ejecta: lithic, blocks and ash; often accretionary lapilli; spatter, fusiform bombs and lapilli absent. *Structures built around vent: tuff rings 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「Surtseyan eruption」の詳細全文を読む スポンサード リンク
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