A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa: reply

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Maselli, V., Oppo, D., Moore, A. L., Gusman, A. R., Mtelela, C., Iacopini, D., Taviani, M., Mjema, E., Mulaya, E., Che, M., Tomioka, A. L., Mshiu, E., & Ortiz, J. D. A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa: reply. Geology, 49(1), (2021): E516-E516, https://doi.org/10.1130/G48585Y.1.We appreciate Somerville’s (2020) interest in our work, and the opportunity to further expand the discussion about the occurrence of a trans-oceanic tsunami in the Indian Ocean generated by a megathrust earthquake ~1000 years ago. Somerville suggests a connection between the inferred tsunami deposit presented by us (Maselli et al., 2020) and a tsunami event reported to have occurred in Nagapattinam (India) in the year 900 CE and described in Kalaki Krishnamurty’s book (Rastogi and Jaiswal, 2006)

A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Maselli, V., Oppo, D., Moore, A. L., Gusman, A. R., Mtelela, C., Iacopini, D., Taviani, M., Mjema, E., Mulaya, E., Che, M., Tomioka, A. L., Mshiu, E., & Ortiz, J. D. A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa. Geology, 48(8), (2020): 808-813, doi:10.1130/G47257.1.The December 2004 Sumatra-Andaman tsunami prompted an unprecedented research effort to find ancient precursors and quantify the recurrence time of such a deadly natural disaster. This effort, however, has focused primarily along the northern and eastern Indian Ocean coastlines, in proximal areas hardest hit by the tsunami. No studies have been made to quantify the recurrence of tsunamis along the coastlines of the western Indian Ocean, leading to an underestimation of the tsunami risk in East Africa. Here, we document a 1000-yr-old sand layer hosting archaeological remains of an ancient coastal Swahili settlement in Tanzania. The sedimentary facies, grain-size distribution, and faunal assemblages indicate a tsunami wave as the most likely cause for the deposition of this sand layer. The tsunami in Tanzania is coeval with analogous deposits discovered at eastern Indian Ocean coastal sites. Numerical simulations of tsunami wave propagation indicate a megathrust earthquake generated by a large rupture of the Sumatra-Andaman subduction zone as the likely tsunami source. Our findings provide evidence that teletsunamis represent a serious threat to coastal societies along the western Indian Ocean, with implications for future tsunami hazard and risk assessments in East Africa.This work was funded by the National Geographic Society (grant N. CP-R008–17). Maselli acknowledges support from the Canada First Research Excellence Fund through the Ocean Frontier Institute. We are extremely grateful to the editor, two anonymous reviewers, J. Bourgeois, G. Eberli, A. Prendergast, and C. Gouramanis for all the suggestions provided, which greatly improved the quality of the manuscript. We would like to thank the United Republic of Tanzania and the University of Dar es Salaam for allowing us to perform the field work activity. This is ISMAR Bologna scientific contribution number 2024

Maritime community settlement history in Pangani Bay, Tanga coastal region, Tanzania

Many Zanjian settlements (8th to 13th centuries AD) on Tanzania’s coast are considered to have collapsed and not regarded as belonging to the formation of the Swahili culture (13th to 16th centuries AD). With this regard, Swahili traditions found on Tanzania’s coast are seldom linked to local Zanjian precursors but to external influence especially from Lamu archipelago on the Kenya coast. Nevertheless, new archaeological evidences from Pangani Bay on the northern coast of Tanzania suggest that the external influences to cultural continuity and change from Zanjian to Swahili periods are overemphasized. This conclusion is grounded on archaeological field works conducted in the surrounding of Pangani Bay in 2010 and 2012, where major Swahili sites directly overlie Zanjian sites without recognizable changes of the cultural materials. The study compares and contrasts cultural materials (in particular pottery) and remains of economy and trade (fauna and glass beads) traditions from both Zanjian and Swahili phases. The aim of this comparative analysis is to trace change and continuity of archaeological traditions for better understanding the origin of Swahili culture in Pangani Bay. In this endeavour, the analysis of ceramic, faunal remains and glass beads from Pangani Bay proposes negligible differences of materials and economical traditions from the late 1st to 2nd millennia AD. That is, local ceramic styles by Swahilis show only minor differences to those used by their ancestors, while fauna data suggest a similarity in subsistence economy between Zanjian and Swahili periods. Correspondingly, glass bead data indicate that although maritime trade became highly sophisticated during Swahili time, early involvement into oceanic far distance trade contact began in the Zanjian period. Thus, this thesis conveys all issues together. It presents research objectives, field work methods as well as analysis and interpretation of the results, with a main focus on ceramic, fauna and bead data. With the support of archaeological evidences, the current work concludes that there is more continuity than change in most of the Zanjian traditions that facilitated the origin of Swahili culture in Pangani Bay

African Archaeology Without Frontiers: Papers from the 2014 PanAfrican Archaeological Association Congress

Confronting national, linguistic and disciplinary boundaries, contributors to African Archaeology Without Frontiers argue against artificial limits and divisions created through the study of ‘ages’ that in reality overlap and cannot and should not be understood in isolation. Papers are drawn from the proceedings of the landmark 14th PanAfrican Archaeological Association Congress, held in Johannesburg in 2014, nearly seven decades after the conference planned for 1951 was re-located to Algiers following the National Party’s rise to power in South Africa. Contributions by keynote speakers Chapurukha Kusimba and Akin Ogundiran encourage African archaeologists to practise an archaeology that collaborates across many related fields of study to enrich our understanding of the past. The nine papers cover a broad geographical sweep by incorporating material on ongoing projects throughout the continent including South Africa, Botswana, Cameroon, Togo, Tanzania, Kenya and Nigeria. Thematically, the papers included in the volume address issues of identity and interaction, and the need to balance cultural heritage management and sustainable development derived from a continent racked by social inequalities and crippling poverty. Edited by three leading archaeologists, the collection covers many aspects of African archaeology, and a range of periods from the earliest hominins to the historical period

African Archaeology Without Frontiers: Papers from the 2014 PanAfrican Archaeological Association Congress

Confronting national, linguistic and disciplinary boundaries, contributors to African Archaeology Without Frontiers argue against artificial limits and divisions created through the study of ‘ages’ that in reality overlap and cannot and should not be understood in isolation. Papers are drawn from the proceedings of the landmark 14th PanAfrican Archaeological Association Congress, held in Johannesburg in 2014, nearly seven decades after the conference planned for 1951 was re-located to Algiers following the National Party’s rise to power in South Africa. Contributions by keynote speakers Chapurukha Kusimba and Akin Ogundiran encourage African archaeologists to practise an archaeology that collaborates across many related fields of study to enrich our understanding of the past. The nine papers cover a broad geographical sweep by incorporating material on ongoing projects throughout the continent including South Africa, Botswana, Cameroon, Togo, Tanzania, Kenya and Nigeria. Thematically, the papers included in the volume address issues of identity and interaction, and the need to balance cultural heritage management and sustainable development derived from a continent racked by social inequalities and crippling poverty. Edited by three leading archaeologists, the collection covers many aspects of African archaeology, and a range of periods from the earliest hominins to the historical period