9:30 AM - 9:45 AM
[MIS12-03] Rootless cones in the southwest of Emuruangogolak Volcano, Kenya
Keywords:rootless cone, Kenya, Mars, Emuruangogolak Volcano
The formation condition of rootless cones (pseudocraters) is still in an enigma. In simple, they are formed by continuous explosive interactions of molten hot lava and external water. Therefore, possible rootless cones on Mars have been thought to be evidence of not only volcanic activity but also subsurface water-ice in the last 100 Ma (e.g., Greeley and Fagents, 2001). The explosive interaction (hereafter rootless eruption) does not always occur where lava meets water. For example, in the 2014-2015 Holuhraun eruption, effused lava flowed into a glacial river, but rootless eruptions that form conical mounds did not occur (Dundas et al., 2020). To constrain occurrence conditions of rootless eruptions, we have to survey the environment of rootless cone fields in detail.
Here I report a rootless cone field in the southwest of Emuruangogolak Volcano, Kenya. Emuruangogolak Volcano is a shield volcano with ~40 km extent and locates in the Great Rift Valley. This volcano is characterized by a 5 x 3.5 km summit caldera, trachytic and basaltic lava flows emanated from NNE and SSW flanks and inside of the caldera, and lateral cones/maars in the NNE-SSW trend. In the west of the volcano, a seasonal river, Suguta is located. Tiny ponds are distributed in the southwest of the volcano. In the previous report, rootless cones have been identified but never described in detail (Dunkley et al., 1993). Therefore, I described spatial distribution, bottom/crater diameters of rootless cones using high-resolution (~1 m/pixel) satellite images on Google Earth Pro.
In the Emuruangogolak rootless cone fields, 919 rootless cones were identified. They can be divided into three major localities: north, east, and west. They are split by subsequent lava flows. The lava that rootless cones are located on has been described as “Upper Basaltic Lavas” emplaced during the upper Pleistocene to recent (Dunkley et al., 1993). Since several cones are destroyed and buried by subsequent lava flows and fluvial deposits, the original amount of rootless cones in this field considered being larger than today. The bottom diameter of rootless cones in this field ranges from 3.9 m to 164.4 m, and its average is 28.2 m. For the crater diameter, it ranges from 1.4 m to 98.0 m, and 14.2 m on average. The bottom diameter to crater diameter ratio (Dcr/Dco) ranges from 0.15 to 0.75 and has 0.50 on average. In the presentation, I describe regional differences of these geomorphometry and compare them with the other rootless cone fields on Earth and Mars.
Here I report a rootless cone field in the southwest of Emuruangogolak Volcano, Kenya. Emuruangogolak Volcano is a shield volcano with ~40 km extent and locates in the Great Rift Valley. This volcano is characterized by a 5 x 3.5 km summit caldera, trachytic and basaltic lava flows emanated from NNE and SSW flanks and inside of the caldera, and lateral cones/maars in the NNE-SSW trend. In the west of the volcano, a seasonal river, Suguta is located. Tiny ponds are distributed in the southwest of the volcano. In the previous report, rootless cones have been identified but never described in detail (Dunkley et al., 1993). Therefore, I described spatial distribution, bottom/crater diameters of rootless cones using high-resolution (~1 m/pixel) satellite images on Google Earth Pro.
In the Emuruangogolak rootless cone fields, 919 rootless cones were identified. They can be divided into three major localities: north, east, and west. They are split by subsequent lava flows. The lava that rootless cones are located on has been described as “Upper Basaltic Lavas” emplaced during the upper Pleistocene to recent (Dunkley et al., 1993). Since several cones are destroyed and buried by subsequent lava flows and fluvial deposits, the original amount of rootless cones in this field considered being larger than today. The bottom diameter of rootless cones in this field ranges from 3.9 m to 164.4 m, and its average is 28.2 m. For the crater diameter, it ranges from 1.4 m to 98.0 m, and 14.2 m on average. The bottom diameter to crater diameter ratio (Dcr/Dco) ranges from 0.15 to 0.75 and has 0.50 on average. In the presentation, I describe regional differences of these geomorphometry and compare them with the other rootless cone fields on Earth and Mars.