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[MIS16-P03] Constraint on the formation conditions of rootless cones in the Kenya Rift
Keywords:Mars , water, rootless cone, Kenya
When lava covers water-saturated layers, successive explosions occur by water vaporization. This process leads to the formation of cone-shaped landforms (rootless cones). The existence of possible rootless cones has been reported in many regions on Mars, such as Elysium Planitia (e.g., Fagents and Thordarson, 2007). Since surface and/or subsurface water/ice was consumed during the formation, rootless cones have been focused as key features for estimating the past surface/subsurface environments of Mars. Therefore understanding rootless cones would drive comprehensive studies on Martian history, including the subsurface environment, and exploring possible habitable worlds.
The formation of rootless cones does not necessarily occur whenever lava meets water. Considering the abundance of water and volcanoes on Earth, many opportunities for rootless cone formation are expected. However, actually, rootless cones have been reported in extremely limited regions, such as Hawaii and Iceland (Noguchi & Kurita, 2016). This implies that the formation conditions of rootless cones are intricate, involving factors such as the lava-water ratio, watery environments, the chemical composition of lava, and topographic settings. Constraining these factors and conditions could contribute to estimating the environmental conditions during the formation of rootless cones and understanding why rootless cones are abundant on Mars and less on Earth.
To constrain the factors and conditions in the formation of rootless cones, it is necessary to compare parameters between lavas with and without rootless cones emplaced in similar environmental conditions in the same region. In this study, we focused on four volcanoes located in the Kenya Rift. where there are abundant opportunities for lava-water interactions. The targeted volcanoes include Silali, Emuruangogolak, Namarunu, and Barrier. The studied area is currently extremely arid, it is thought that it was a water-abundant environment in the past (Dunkley et al., 1993). In this region, rootless cones are found on lava on the southern foot of Emuruangogolak volcano and the northern foot of Silali volcano.
In this study, we conducted literature research and GIS analyses to create a dataset compiling the chemical composition (major elements), formation age, and topographical data of selected lavas which have been reported to have an opportunity to meet water in Dunkley et al., 1993. The chemical composition and formation age data were collected from Dunkley et al., 1993, Black et al., 1998, and Rogers et al., 2000. The average slope angle and Topographic Wetness Index (TWI) for each lava were calculated using DEM. TWI calculations followed the methodology outlined by Kopecký et al., 2021.
We conducted principal component analysis and hierarchical cluster analysis on the created dataset. By principal component analysis, we extracted parameters with significant factor loadings and created combinations of parameters for use in cluster analysis. We performed cluster analysis using the created parameter combinations (utilizing Euclidean distance and Ward's method) to investigate whether lavas with rootless cones are classified into the same cluster. The results revealed that terrain parameters are essential for classifying lava with rootless cones into the same cluster.
This study revealed that slope and TWI play important roles in determining whether rootless cones are formed or not. In other words, in the studied region, rootless cones are distributed in areas with wide and uniformly flat watersheds, indicating that this geographical and topographical environment is conducive to triggering rootless volcanic eruptions.
The formation of rootless cones does not necessarily occur whenever lava meets water. Considering the abundance of water and volcanoes on Earth, many opportunities for rootless cone formation are expected. However, actually, rootless cones have been reported in extremely limited regions, such as Hawaii and Iceland (Noguchi & Kurita, 2016). This implies that the formation conditions of rootless cones are intricate, involving factors such as the lava-water ratio, watery environments, the chemical composition of lava, and topographic settings. Constraining these factors and conditions could contribute to estimating the environmental conditions during the formation of rootless cones and understanding why rootless cones are abundant on Mars and less on Earth.
To constrain the factors and conditions in the formation of rootless cones, it is necessary to compare parameters between lavas with and without rootless cones emplaced in similar environmental conditions in the same region. In this study, we focused on four volcanoes located in the Kenya Rift. where there are abundant opportunities for lava-water interactions. The targeted volcanoes include Silali, Emuruangogolak, Namarunu, and Barrier. The studied area is currently extremely arid, it is thought that it was a water-abundant environment in the past (Dunkley et al., 1993). In this region, rootless cones are found on lava on the southern foot of Emuruangogolak volcano and the northern foot of Silali volcano.
In this study, we conducted literature research and GIS analyses to create a dataset compiling the chemical composition (major elements), formation age, and topographical data of selected lavas which have been reported to have an opportunity to meet water in Dunkley et al., 1993. The chemical composition and formation age data were collected from Dunkley et al., 1993, Black et al., 1998, and Rogers et al., 2000. The average slope angle and Topographic Wetness Index (TWI) for each lava were calculated using DEM. TWI calculations followed the methodology outlined by Kopecký et al., 2021.
We conducted principal component analysis and hierarchical cluster analysis on the created dataset. By principal component analysis, we extracted parameters with significant factor loadings and created combinations of parameters for use in cluster analysis. We performed cluster analysis using the created parameter combinations (utilizing Euclidean distance and Ward's method) to investigate whether lavas with rootless cones are classified into the same cluster. The results revealed that terrain parameters are essential for classifying lava with rootless cones into the same cluster.
This study revealed that slope and TWI play important roles in determining whether rootless cones are formed or not. In other words, in the studied region, rootless cones are distributed in areas with wide and uniformly flat watersheds, indicating that this geographical and topographical environment is conducive to triggering rootless volcanic eruptions.