The Geomorphology, Structure, and Lava Flow Dynamics of Peralkaline Rift Volcanoes From High-Resolution Digital Elevation Models
The Geomorphology, Structure, and Lava Flow Dynamics of Peralkaline Rift Volcanoes From High-Resolution Digital Elevation Models
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DOI：
10.1029/2018gc008085
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发表时间：
2019-03-01
影响因子：
3.5
通讯作者：
Mather, Tamsin A.
中科院分区：
文献类型：
--
作者：
Hunt, Jonathan A.;Pyle, David M.;Mather, Tamsin A.
来自火山的详细地形数据可以提供对控制火山活动和危险的关键见解。通过遥感数据生成的高分辨率数字高程模型，可以比较难以接近的大型火山的地貌和结构。我们介绍了埃塞俄比亚主要裂谷中的三座过碱性火山(Fentale、Corbetti和Gedemsa)和阿法尔裂谷(Dabbahu)的一座火山的新地形数据，结合野外观察，揭示了以前未发现的火山口后沉积和陨石坑。喷口和陨石坑的位置与裂谷平行断层以及不同方位的裂谷切割构造对齐。火山口的形状由与这些结构的相互作用控制。在过去的150KYR期间，这些火山喷发的相对频率和类型差异很大。Gedemsa现在基本上不活跃；Fentale拥有许多小规模喷发的沉积物(<；0.1公里(3))；而Corbetti已经产生了几次大喷发(类似于0.4-0.5公里(3))。Corbetti和Fentale的过碱性流纹岩沉积物的形态计量学，包括OGIES和堤坝，对流变学提供了限制。类似于10(8)-10(11)PAS的Fentale侵位粘度与钙碱性流纹岩相似或更低，与实验和理论研究一致。这里提供的观察结果对埃塞俄比亚裂谷的危险评估具有重要意义，并突出了构造特征在控制埃塞俄比亚主要裂谷火山活动的位置、规模和类型方面的重要性。简单语言摘要我们使用从太空或飞机捕获的图像创建了高分辨率地形图，以调查埃塞俄比亚的四座火山，这四座火山很大，在某些情况下无法进入，这给研究它们带来了挑战。这些火山位于大裂谷，非洲大陆在那里被一分为二。我们已经确定了以前火山喷发的沉积物，计算了它们的大小，并比较了每一座火山的典型喷发。在一些火山，每次喷发的位置与地球表面的裂缝平行。在其他地方，位置与现在被埋藏的老断层排成一条线。大型陨石坑的形状也受到了断层的控制。冷却的熔岩流动的形状表明，由于裂谷中发现的不同寻常的熔岩成分，芬特莱的熔岩可能比典型的熔岩更具流动性。我们的研究突出了有关裂谷中的火山的关键问题。我们为评估位于人口不断增长和基础设施脆弱的每一座火山的未来危险提供了重要的观察结果。
Detailed topographic data from volcanoes can yield key insights into the controls on volcanic activity as well as hazards. High-resolution digital elevation models generated from remote sensing data enable comparison of the geomorphology and structure of large and inaccessible volcanoes. We present new topographic data for three peralkaline volcanoes in the Main Ethiopian Rift (Fentale, Corbetti, and Gedemsa) and one volcano in the Afar Rift (Dabbahu), combined with field observations, reveal previously unidentified post-caldera deposits and craters. Vent and crater locations are aligned with rift-parallel faults and also with rift-cutting structures in a variety of orientations. Caldera shape is controlled by interaction with these structures. The relative frequency and type of eruption varies greatly between these volcanoes over the past 150 kyr. Gedemsa is now largely inactive; Fentale hosts deposits from many small volume eruptions (< 0.1 km(3)); while Corbetti has produced several large eruptions (similar to 0.4-0.5 km(3)). Morphometry of peralkaline rhyolite deposits at Corbetti and Fentale, including ogives and levees, provides constraints on rheology. Emplacement viscosities of similar to 10(8)-10(11) Pas at Fentale are similar to or lower than calc-alkaline rhyolites and consistent with experimental and theoretical studies. The observations presented here have significant implications for hazard assessment in the Ethiopian rift and highlight the importance of structural features in controlling the location, magnitude, and style of volcanic activity in the Main Ethiopian Rift.Plain Language Summary We created high-resolution topographic maps using images captured from space, or from aircraft, to investigate four Ethiopian volcanoes, which are large and in some cases inaccessible presenting challenges to studying them. These volcanoes are located in the Great Rift Valley, where the continent of Africa is splitting in two. We have identified deposits from previous eruptions, calculating their size and comparing typical eruptions for each volcano. At some volcanoes, the locations for each eruption line up parallel to fractures in the Earth's surface. In other places, locations line up with older faults that are now buried. The shapes of large craters have also been controlled by faults. The shapes of cooled lava flows suggest that the lava at Fentale may have been more fluid than typical lavas, owing to the unusual composition of lava found at rifts. Our study highlights key questions about volcanoes in rifts. We provide important observations for the assessment of future hazards at each volcano, located among a growing population and vulnerable infrastructure.