Violent Basaltic Explosive Volcanism: A Case Study Of The 1886 Tarawera Eruption, New Zealand

夏威夷霍顿大学玄武岩火山作用被认为是最典型的产生熔岩渗出，最具爆炸性的表现形式，从温和的斯特龙博利活动到更有活力的火喷泉喷发。然而，一些玄武岩喷发现在被认为是极其猛烈的，即产生广泛的蒸汽岩浆、次普林尼期和普林尼期瀑布沉积。这些喷发是特别危险的，因为玄武岩岩浆在喷发前的上升速度可能非常快（发出警告的时间短至几个小时），因为它们的前兆可能被忽视或误解。在这个建议中解决的主要问题是：是什么条件导致玄武岩浆采取喷发风格更典型的化学演化，高粘度岩浆？可能的机制（单独或共同作用）是：（1）岩浆和水之间的相互作用，（ii）非常快速的上升产生延迟的脱气开始，然后异常快速的“失控”的囊泡在浅层次的导管，（iii）微晶结晶和脱气的岩浆在上升过程中导致粘度增加。我们的目标是建立1886年塔拉韦拉火山爆发的普林尼阶段的触发机制。这个建议将测试的假设，这一阶段是一个后果的流变变化在岩浆上升，伴随着早期（预破碎）之间的相互作用玄武质熔体和含水流纹岩单位形成的导管壁或后期阶段岩浆水的相互作用。

AbstractEAR-0125719HoughtonUniversity of HawaiiBasaltic volcanism is most typically thought to produce effusion of lava, with the most explosive manifestations ranging from mild Strombolian activity to more energetic fire fountain eruptions. However, some basaltic eruptions are now recognized as extremely violent, i.e. generating widespread phreatomagmatic, subplinian and Plinian fall deposits. These eruptions are particularly dangerous because the ascent rate of basaltic magma prior to eruption can be very rapid (giving warning times as little as a few hours) and because their precursors may be ignored or misunderstood. The main question addressed in this proposal is: what are the conditions that cause basaltic magma to adopt an eruption style more typical of chemically evolved, highly viscous magma? Possible mechanisms (acting singly, or in concert) are: (1) interaction between magma and water, (ii) very rapid ascent producing a delayed onset of degassing then exceptionally rapid "runaway" vesiculation at shallow levels in the conduit, (iii) microlite crystallization and degassing of the magma during ascent leading to increased viscosity. Our goal is to establish the triggering mechanism for the Plinian phase of the 1886 Tarawera eruption. This proposal will test the hypothesis that this phase was a consequence of either rheologic changes during magma ascent that accompanied early (pre-fragmentation) interaction between the basaltic melt and water-bearing rhyolitic units forming the conduit walls or late-stage magma water interaction.