Timing, Distribution, and Volume of Proximal Products of the 2006 Eruption of Augustine Volcano
Timing, Distribution, and Volume of Proximal Products of the 2006 Eruption of Augustine Volcano
复制标题
2006 年奥古斯丁火山喷发的时间、分布和近端产物量
DOI：
10.3133/pp17698
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发表时间：
2010
影响因子：
5.2
通讯作者：
R. Mcgimsey
中科院分区：
文献类型：
--
作者：
M. Coombs;K. Bull;J. Vallance;D. Schneider;E. E. Thoms;R. Wessels;R. Mcgimsey
在2006年奥古斯丁火山爆发期间和之后，我们利用观测飞行、倾斜和航空摄影、红外成像、卫星数据和实地调查，编制了新熔岩和流动沉积物的地质图和年表。经过大约6个月的火山活动后，爆发阶段开始于2006年1月11日的两次爆炸（事件1和2），产生了富含雪的雪崩;很少或没有年轻岩浆喷发。地震活动表明，一个小的熔岩圆顶可能在1月12日挤出，但如果是这样，它随后被摧毁了。1月13日至14日的一系列六次爆发（事件3-8）在300米以上的上侧翼产生了广泛但薄（0-30厘米）的火山碎屑流沉积物，以及沿着火山大部分侧翼向下流动的叶状0.5至2米厚的火山碎屑流。在1月14日至17日之间，一个光滑的熔岩瓣在大约400米宽的山顶火山口的东半部形成，只有部分被后来的沉积物覆盖。1月17日的一次爆炸（事件9）在新的熔岩穹丘上打开了一个火山口，并在西南侧产生了弹道坠落存款和火山碎屑流。在1月17日至27日期间，一个碎石熔岩圆顶溢出。1月27日，爆炸事件10产生了一个火山碎屑流，在北-西北侧留下了一个富含致密碎屑的存款。紧接着火山碎屑流，一个巨大的4.7公里长的火山碎屑流席卷了北侧。1月27日和28日的三次爆炸产生了未知但可能是少量的岛上沉积物。阿拉斯加火山观测站，美国地质调查局，4200大学路，安克雷奇，AK 99508。2阿拉斯加火山观测站，阿拉斯加地质和地球物理调查局，3354学院路，费尔班克斯，AK 99709。3美国地质调查局，Cascades火山观测站，1300 SE Cardinal Court，温哥华，WA 98683。爆炸阶段喷发的物质体积，包括圆顶、水流和瀑布沉积物（华莱士等人，该体积），为30×106 m3致密岩石当量（DRE）。喷发的连续阶段（1月28日至2月10日）开始于为期4天的几乎连续的块和灰流，这些块和灰流沉积了小的单个流瓣，累积形成了山顶北部和东北部的风扇。1月30日，一个较大的火山碎屑流在西北侧形成了一个辫状存款。在此期间，大约有9×106 m3（DRE）的岩浆喷发。2月2日左右，岩浆流量减弱，向北的熔岩流流出，到2月10日达到约900米的长度。在连续阶段的后半段，大约有11×106 m3（DRE）的岩浆喷发。经过23天的中断，熔岩渗出重新开始在3月初（溢出阶段），并伴随着频繁（但体积较小）块和灰流。从3月7日到14日，挤压明显增加;两个块状熔岩流瓣，每个数十米厚，沿着火山的北部和东北侧移动;一个新的山顶熔岩圆顶比2006年前的山顶高出约70米。这一阶段产生了26×106 m3（DRE）的熔岩。3月16日左右，活跃的喷发已经停止，但在4月和5月，来自北部熔岩流西缘的三次重力崩塌产生了额外的块和灰流。2006年火山爆发的基本顺序与1976年和1986年的火山爆发非常相似。
During and after the 2006 eruption of Augustine Volcano, we compiled a geologic map and chronology of new lava and flowage deposits using observational flights, oblique and aerial photography, infrared imaging, satellite data, and field investigations. After approximately 6 months of precursory activity, the explosive phase of the eruption commenced with two explosions on January 11, 2006 (events 1 and 2) that produced snow-rich avalanches; little or no juvenile magma was erupted. Seismicity suggests that a small lava dome may have extruded on January 12, but, if so, it was subsequently destroyed. A series of six explosions on January 13–14 (events 3–8) produced widespread but thin (0–30 cm) pyroclasticcurrent deposits on the upper flanks above 300 m altitude and lobate, 0.5to 2-m-thick pyroclastic flows that traveled down most flanks of the volcano. Between January 14 and 17, a smooth lava lobe formed in the east half of the roughly 400-m-wide summit crater and was only partially covered by later deposits. An explosion on January 17 (event 9) opened a crater in the new lava dome and produced a ballistic fall deposit and pyroclastic flow on the southwest flank. During the interval from January 17 to 27, a rubbly lava dome effused. On January 27, explosive event 10 generated a pyroclastic current that left a deposit, rich in dense clasts, on the north-northwest flank. Immediately following the pyroclastic current, a voluminous 4.7-km-long pyroclastic flow swept down the north flank. Three more explosive blasts on January 27 and 28 produced unknown but likely minor on-island deposits. The cumulative 1Alaska Volcano Observatory, U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508. 2Alaska Volcano Observatory, Alaska Division of Geological and Geophysical Surveys, 3354 College Road, Fairbanks, AK 99709. 3U.S. Geological Survey, Cascades Volcano Observatory, 1300 SE Cardinal Court, Vancouver, WA 98683. volume of erupted material from the explosive phase, including domes, flows, and fall deposits (Wallace and others, this volume), was 30×106 m3 dense-rock equivalent (DRE). The continuous phase of the eruption (January 28 through February 10) began with a 4-day period of nearly continuous block-and-ash flows, which deposited small individual flow lobes that cumulatively formed fans to the north and northeast of the summit. A single larger pyroclastic flow on January 30 formed a braided deposit on the northwest flank. Roughly 9×106 m3 (DRE) of magma erupted during this period. Around February 2, the magma flux rate waned and a northward lava flow effused and reached a length of approximately 900 m by February 10. Approximately 11×106 m3 (DRE) of magma erupted during the second half of the continuous phase. After a 23-day hiatus, lava effusion recommenced in early March (the effusive phase) and was accompanied by frequent (but volumetrically minor) block-and-ash flows. From March 7 to 14, extrusion increased markedly; two blocky lava-flow lobes, each tens of meters thick, moved down the north and northeast flank of the volcano; and a new summit lava dome grew to be ~70 m taller than the pre-2006 summit. This phase produced 26×106 m3 (DRE) of lava. Active effusion had ceased about March 16, but, in April and May, three gravitational collapses from the west margin of the north lava flow produced additional block-and-ash flows. The basic sequence of the 2006 eruption closely matches that of eruptions in 1976 and 1986.