Explosive-effusive volcanic eruption transitions caused by sintering.
Explosive-effusive volcanic eruption transitions caused by sintering.
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DOI：
10.1126/sciadv.aba7940
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发表时间：
2020-09
期刊：
影响因子：
13.6
通讯作者：
Tuffen H
中科院分区：
文献类型：
--
作者：
Wadsworth FB;Llewellin EW;Vasseur J;Gardner JE;Tuffen H
当火山口被烧结的火山碎屑材料堵塞时，火山爆发就会变得喷发或结束。长期以来，硅质火山活动一直被认为是剧烈爆炸或温和喷发的。然而，最近的观察表明，爆发性行为和情绪化行为可以同时发生。在这里，我们提出流纹质岩浆供给地面喷发通常在上升穿过上地壳的过程中碎裂，而喷发喷发是由于管道堵塞和更深的隐秘碎裂的火山碎屑产物的烧结造成的。我们的建议得到以下方面的支持：(i) 流纹质熔岩的挥发性已耗尽； (ii) 结构证据支持溢流产物的火山碎屑起源； (iii) 数值模型表明，≲10−5 m 的小灰颗粒可以在破碎和表面之间的可用时间内扩散脱气、粘附和烧结至低孔隙率； (iv) 从爆炸性喷发和明显喷发性喷发推断的上升速率可能会重叠。我们的模型协调了之前矛盾的观测结果，并提供了一个新的框架来评估地球上最猛烈火山喷发的物理、数值和地球化学模型。
Explosive volcanic eruptions become effusive, or end, when the vent becomes plugged with sintered pyroclastic material. Silicic volcanic activity has long been framed as either violently explosive or gently effusive. However, recent observations demonstrate that explosive and effusive behavior can occur simultaneously. Here, we propose that rhyolitic magma feeding subaerial eruptions generally fragments during ascent through the upper crust and that effusive eruptions result from conduit blockage and sintering of the pyroclastic products of deeper cryptic fragmentation. Our proposal is supported by (i) rhyolitic lavas are volatile depleted; (ii) textural evidence supports a pyroclastic origin for effusive products; (iii) numerical models show that small ash particles ≲10−5 m can diffusively degas, stick, and sinter to low porosity, in the time available between fragmentation and the surface; and (iv) inferred ascent rates from both explosive and apparently effusive eruptions can overlap. Our model reconciles previously paradoxical observations and offers a new framework in which to evaluate physical, numerical, and geochemical models of Earth’s most violent volcanic eruptions.
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