Acute sedimentation response to rainfall following the explosive phase of the 2008–2009 eruption of Chaitén volcano, Chile
Acute sedimentation response to rainfall following the explosive phase of the 2008–2009 eruption of Chaitén volcano, Chile
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2008-2009 年智利 Chaitén 火山喷发爆发阶段后对降雨的急性沉积响应
DOI：
10.1007/s00445-013-0723-4
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发表时间：
2013
影响因子：
3.5
通讯作者：
H. Moreno
中科院分区：
文献类型：
--
作者：
T. C. Pierson;J. Major;A. Amigo;H. Moreno
2008-2009 年智利南部 Chaitén 火山（南纬 42.83°，西经 72.65°）爆发时，持续 10 天的爆发阶段覆盖了 77 平方公里的陡峭、雨林覆盖的 Chaitén 河流域，火山灰厚度为 3 至 >100 厘米；主要是细到极细的流纹岩灰在爆炸阶段的后半段落下。在主要爆炸活动停止后的几天内，降雨落在灰烬覆盖层上，产生了超浓缩流火山泥流，紧接着是一场复杂的、多天的泥泞洪水（水流接近稀化超浓缩流）。这次火山泥流洪水事件中流动的沉积物使 Chaitén 河道充满了高达 7 m 的沉积物，将 Chaitén 镇（火山下游 10 公里）埋在高达 3 m 的沉积物中，并导致河道下游 3 公里冲破该镇。尽管沉积反应的性质和速度都不是前所未有的，但它们在几个方面是不寻常的：(1) 在 50-70 米宽的 Chaitén 河道中，近 70% 的沉积物（近 5 m）是由火山泥流引起的，估计是由大约 24 小时内 20 毫米的降雨量引发的。接下来的 24-36 小时内又发生了 2 m 的沉积。 (2) 对城镇的直接损害是由泥沙洪水事件的泥沙泛滥阶段造成的，而不是泥沙阶段。 (3) 从山坡侵蚀并输送到 Chaitén 河道的沉积物体积至少为 3–8 × 106 m3，大约是覆盖 Chaitén 河流域的最小火山灰体积的 15–40%。 (4) 对降雨的剧烈沉积反应似乎是由于灰烬层的厚度和细度（抑制雨水渗透）以及盆地山坡的陡峭造成的。其他可能的因素，例如先前形成的灰壳、疏水表面层的形成或截雨植被的大规模破坏，都没有发挥作用。
The 10-day explosive phase at the start of the 2008–2009 eruption of Chaitén volcano in southern Chile (42.83°S, 72.65°W) blanketed the steep, rain-forest-cloaked, 77-km2 Chaitén River drainage basin with 3 to >100 cm of tephra; predominantly fine to extremely fine rhyolitic ash fell during the latter half of the explosive phase. Rain falling on this ash blanket within days of cessation of major explosive activity generated a hyperconcentrated-flow lahar, followed closely by a complex, multi-day, muddy flood (streamflow bordering on dilute hyperconcentrated flow). Sediment mobilized in this lahar-flood event filled the Chaitén River channel with up to 7 m of sediment, buried the town of Chaitén (10 km downstream of the volcano) in up to 3 m of sediment, and caused the lower 3 km of the channel to avulse through the town. Although neither the nature nor rate of the sedimentation response is unprecedented, they are unusual in several ways: (1) Nearly 70 percent of the aggradation (almost 5 m) in the 50–70-m-wide Chaitén River channel was caused by a lahar, triggered by an estimated 20 mm of rainfall over a span of about 24 h. An additional 2 m of aggradation occurred in the next 24–36 h. (2) Direct damage to the town was accomplished by the sediment-laden water-flood phase of the lahar-flood event, not the lahar phase. (3) The volume of sediment eroded from hillslopes and delivered to the Chaitén River channel was at least 3–8 × 106 m3—roughly 15–40 % of the minimum tephra volume that mantled the Chaitén River drainage basin. (4) The acute sedimentation response to rainfall appears to have been due to the thickness and fineness of the ash blanket (inhibiting infiltration of rain) and the steepness of the basin’s hillslopes. Other possible factors such as the prior formation of an ash crust, development of a hydrophobic surface layer, or large-scale destruction of rain-intercepting vegetation did not play a role.
2008 年 5 月智利 Chaitén 喷发的火山灰地层和喷发量
影响因子：
3.5
作者：
Alfano F
通讯作者：
Alfano F