Contrasting styles of post-caldera volcanism along the Main Ethiopian Rift: Implications for contemporary volcanic hazards

Abstract

The Main Ethiopian Rift (MER, ~7-9 °N) is the type example of a magma-assisted continental rift. The rift axis is populated with regularly spaced silicic caldera complexes and central stratovolcanoes, interspersed with large fields of small mafic scoria cones. The recent (latest Pleistocene to Holocene) history of volcanism in the MER is poorly known, and no eruptions have occurred in the living memory of the local population. Assessment of contemporary

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

“…Fontijn et al, 2018; Figure 4). Their lower FeO content compared to all other samples, and relatively high SiO 2 , K 2 O, and Al 2 O 3 , match the composition of products of Corbetti volcano, the silicic center approximately 80 km south of Aluto, 50 km south of ABII, and 60-km south of LLIII (Fontijn et al, 2018;Martin-Jones et al, 2017). Their lower FeO content compared to all other samples, and relatively high SiO 2 , K 2 O, and Al 2 O 3 , match the composition of products of Corbetti volcano, the silicic center approximately 80 km south of Aluto, 50 km south of ABII, and 60-km south of LLIII (Fontijn et al, 2018;Martin-Jones et al, 2017).…”

“…However, ABII-08-16 and LLII-09-74 have a clearly different glass composition and componentry (Figures 3; 4). ABII-08-16 and LLLII-09-18 are also the only two samples that contain no dense material, including no crystals ( Figure 3); the lack of crystals is consistent with most eruptions of Corbetti (Fontijn et al, 2018;Mohr, 1966;Schmincke, 1974). ABII-08-16 and LLLII-09-18 are also the only two samples that contain no dense material, including no crystals ( Figure 3); the lack of crystals is consistent with most eruptions of Corbetti (Fontijn et al, 2018;Mohr, 1966;Schmincke, 1974).…”

“…There is also evidence of lower-magnitude postcaldera activity at the Tullu Fike complex immediately north of the caldera, which may be the source of late Quaternary pumice deposits located in the caldera walls (Fontijn et al, 2018;Mohr et al, 1980). It has produced several silicic Holocene eruptions, which have generated aphyric obsidian flows and/or pumice fall deposits and are documented in terrestrial sections and lake sediment cores up to 167 km from the volcano (Fontijn et al, 2018;Martin-Jones et al, 2017;Rapprich et al, 2016). It has produced several silicic Holocene eruptions, which have generated aphyric obsidian flows and/or pumice fall deposits and are documented in terrestrial sections and lake sediment cores up to 167 km from the volcano (Fontijn et al, 2018;Martin-Jones et al, 2017;Rapprich et al, 2016).…”

“…Most of these centers experienced mid-Pleistocene caldera-forming eruptions followed by lower magnitude events, some of which have extended into the Holocene . Shala caldera (approximately 40 km south of Aluto) has experienced limited postcaldera activity, with the possible exception of scoria cones to the south of the caldera (Fontijn et al, 2018;Mohr, 1971;Trua et al, 1999). Shala caldera (approximately 40 km south of Aluto) has experienced limited postcaldera activity, with the possible exception of scoria cones to the south of the caldera (Fontijn et al, 2018;Mohr, 1971;Trua et al, 1999).…”

“…A subset of these tephra deposits was chemically analyzed and correlated by Fontijn et al (2018), who proposed an initial Holocene tephrostratigraphic framework for the volcano. A subset of these tephra deposits was chemically analyzed and correlated by Fontijn et al (2018), who proposed an initial Holocene tephrostratigraphic framework for the volcano.…”