Biass S, Houghton B F, Llewellin E W, Curran K C, Thordarson T, Orr T R, Parcheta C E, Mouginis-Mark P
Department of Earth Sciences, University of Hawai'I at Mānoa, Honolulu, HI 96822 USA.
Department of Earth Sciences, University of Geneva, CH-1205 Geneva, Switzerland.
Bull Volcanol. 2025;87(4):30. doi: 10.1007/s00445-025-01817-0. Epub 2025 Mar 31.
Basaltic lava flows can be highly destructive. Forecasting the future path and/or behavior of an active lava flow is challenging because topography is often poorly constrained and lava has a complex rheology and emplacement history. Preserved lavas are an important source of information which, combined with observations of active flows, underpins conceptual models of lava flow emplacement. However, the value of preserved lavas is limited because pre-eruptive topography and, thus, syn-eruptive lava flow geometry are usually not known. Here, we use tree-mold data to constrain pre-eruptive topography and syn-eruptive lava flow geometry of the July 1974 flow of Kīlauea (USA). Tree molds, which are formed after advancing lava encloses standing trees, preserve the lava inundation height and the final preserved thickness of lava. We used data from 282 tree molds to reconstruct the temporal and spatial evolution of the ~ 2.1 km-long July 1974 flow. The tree mold dataset yields a detailed dynamic picture of staged emplacement, separated by intervals of ponding. In some ponded areas, flow depth during emplacement (~ 5 m) was twice the preserved thickness of the final lava (2-3 m). Drainage of the ponds led to episodic surges in flow advancement, decoupled from fluctuations in vent discharge rate. We infer that the final breakout occurred after the cessation of fountaining. Such complex emplacement histories may be common for pāhoehoe lavas at Kīlauea and elsewhere in situations where the terrain is of variable slope, and/or where lava is temporarily perched and stored.
The online version contains supplementary material available at 10.1007/s00445-025-01817-0.
玄武岩熔岩流具有高度破坏性。预测活跃熔岩流的未来路径和/或行为具有挑战性，因为地形通常限制条件较差，且熔岩具有复杂的流变学和就位历史。保存下来的熔岩是重要的信息来源，与对活跃熔岩流的观测相结合，为熔岩流就位的概念模型提供了支撑。然而，保存熔岩的价值有限，因为喷发前的地形以及同期喷发的熔岩流几何形状通常并不清楚。在这里，我们利用树模数据来约束美国基拉韦厄火山1974年7月那次熔岩流喷发前的地形和同期喷发的熔岩流几何形状。树模是在前进的熔岩包围直立树木后形成的，它保留了熔岩淹没高度和熔岩最终保存厚度。我们利用来自282个树模的数据重建了1974年7月那次约2.1千米长的熔岩流的时空演化。树模数据集呈现出了一个详细的阶段性就位动态图景，中间有积水间隔。在一些积水区域，就位期间的流动深度（约5米）是最终熔岩保存厚度（2 - 3米）的两倍。积水的排出导致了流动推进的间歇性激增，与喷口排放速率的波动解耦。我们推断最终的突破发生在喷泉停止之后。对于基拉韦厄火山以及其他地形坡度多变和/或熔岩暂时停歇和储存的地方的绳状熔岩来说，这种复杂的就位历史可能很常见。
在线版本包含可在10.1007/s00445 - 025 - 01817 - 0获取的补充材料。
