History of scoria‐cone eruptions on the eastern shoulder of the Kenya–Tanzania Rift revealed in the 250‐ka sediment record of Lake Chala near Mount Kilimanjaro

Abstract

Reconstructions of the timing and frequency of past eruptions are important to assess the propensity for future volcanic activity, yet in volcanic areas such as the East African Rift only piecemeal eruption histories exist. Understanding the volcanic history of scoria‐cone fields, where eruptions are often infrequent and deposits strongly weathered, is particularly challenging. Here we reconstruct a history of volcanism from scoria cones situated along the eastern shoulders of the Kenya–Tanzania Rift, using a sequence of tephra (volcanic ash) layers preserved in the ~250‐ka sediment record of Lake Chala near Mount Kilimanjaro. Seven visible and two non‐visible (crypto‐) tephra layers in the Lake Chala sequence are attributed to activity from the Mt Kilimanjaro (northern Tanzania) and the Chyulu Hills (southern Kenya) volcanic fields, on the basis of their glass chemistry, textural characteristics and known eruption chronology. The Lake Chala record of eruptions from scoria cones in the Chyulu Hills volcanic field confirms geological and historical evidence of its recent activity, and provides first‐order age estimates for seven previously unknown eruptions. Long and well‐resolved sedimentary records such as that of Lake Chala have significant potential for resolving regional eruption chronologies spanning hundreds of thousands of years.

A 3000-year record of vegetation changes and fire at a high-elevation wetland on Kilimanjaro, Tanzania

“…On Kilimanjaro, high-elevation paleoenvironmental studies have characterized late Pleistocene and Holocene vegetation and climate change derived from soils (Zech, 2006; Zech et al, 2011; Montade et al, 2018), sediments (Coetzee, 1967; Schüler et al, 2012; Schüler, 2012), and glacial ice (Thompson et al, 2002; Gabrielli et al, 2014), and are also informed by records from nearby Lake Challa (Table 1) (Verschuren et al, 2009; Barker et al, 2011; Nelson et al, 2012; Martin-Jones et al, 2020). Archaeological evidence and oral tradition summaries show a long and varied history of land use on and around Kilimanjaro (Fosbrooke and Sassoon, 1965; Odner, 1971; Mturi, 1986; Clack, 2007, 2009), though as yet, there are no published archaeological sites above 2000 m asl.…”

Crossing new frontiers: extending tephrochronology as a global geoscientific research tool

“…Beyond the well‐studied European region, Martin‐Jones et al . (2020) demonstrate how long‐lake sequences can be used to reconstruct the timing and frequency of volcanism in the East African Rift, an emerging hot‐spot for tephra studies with volcanological, archaeological and palaeoenvironmental focusses (e.g. Poppe et al ., 2016; Campisano et al, 2017; Fontijn et al ., 2018).…”

“…(1) Patton Seamount, North Pacific Ocean (Aoki, 2020) (2) Mount St. Helens, USA (Foo et al, 2020) (3) Azores archipelago (Wastegård et al, 2020) (4) Iceland (Meara et al, 2020) (5) Hekla volcano, Iceland (Larsen et al, 2020) (6) Loch Ashik, Scotland (Pyne-O'Donnell and Jensen, 2020) (7) Llyn Llech Owain, South Wales (8) Western Norway and Iceland (Saxby et al, 2020) (9) Eifel Volcanic Field, Germany (Förster et al, 2020) (10) Arma Veirana and Riparo Bombrini, Italy (Hirniak et al, 2020) (11) Central Mediterranean Sea (Insinga et al, 2020) (12) Ciomadul volcano, Eastern Carpathians, Romania (Harangi et al, 2020) -"Tephra Hunt in Transylvania" field conference venue (13) Lake Chala, Tanzania/Kenya (Martin-Jones et al, 2020) (14) Toba caldera, Sumatra (4+5)…”

“…Poppe et al, 2016;Campisano et al, 2017;Fontijn et al, 2018). Martin-Jones et al (2020) identified nine visible or cryptotephra deposits in sediments from Lake Chala that can be linked to volcanic activity in the Mt Kilamanjaro (Tanzania) and the Chyulu Hills (Kenya) volcanic fields. These correlations support documented evidence for recent volcanism and provide an insight into the timing and frequency of volcanic activity in the region that can now be used to assess the potential future hazard to local populations.…”

A Lake Record of Geomagnetic Secular Variations for the Last 23 ka From Lake Chala: Toward a Composite Directional Lake Record of the Earth's Magnetic Field for Equatorial East Africa

“…Kilimanjaro (Figure 1). The lake is currently the object of extensive multidisciplinary studies for reconstructing the climate and environmental history of East Africa (e.g., Barker et al., 2011; Baxter et al., 2023; Maitituerdi, 2022; Meyer et al., 2020; Verschuren et al., 2009; Wolff et al., 2011) and to reconstruct the volcanic history of surrounding scoriae cone fields (Martin‐Jones et al., 2020). In 2016, in the framework of the ICDP DeepCHALLA Project, a 214.5 m long record of lacustrine sediments was sampled.…”