OR/14/005 Introduction

Vye-Brown, C, Crummy, J, Smith, K, Mruma,A and Kabelwa H. 2014. Volcanic hazards in Tanzania. Nottingham, UK, British geological Survey. (OR/14/005).

The United Nations Office for Disaster Risk Reduction (UNISDR) has invited the BGS/Bristol — led Global Volcano Model (GVM) to work with the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) to provide an assessment of global volcanic hazard and risk for the 2015 Global Assessment of Risk Report (GAR15). The GAR programme evaluates risk and identifies global challenges with reports released every two years to implement the Hyogo Framework for Action (HFA) that aims to substantially reduce disaster losses by 2015 by building the resilience of nations and communities to disasters. Volcanism along the East African Rift (EAR) varies hugely in terms of spatial and temporal variability as well as eruptive styles and products. However, there are limited data available on the EAR to characterise and define the potential hazards based on past events or to consider the future consequences of such hazards.

This report presents the results of a pilot study on volcanic hazard analysis in Tanzania with a case study on Mt Meru. The aim of the study was to establish science-based evidence for volcanic hazards and their impacts in Tanzania to provide a case study example for the GAR15 report that could be expanded and applied to the rest of Africa in the future. Data requirements for such analysis include:

• understanding the in-country monitoring capacity
• identifying needs for capacity development
• communication and response to volcanic eruptions and unrest
• assistance for hazard management
• how to support the integration of volcanic hazards into the Tanzanian Disaster Risk Reduction (DRR) programme.

There is no dedicated or mandated volcano observatory in Tanzania, however the Geological Survey of Tanzania (GST) have the responsibility for providing advice on the character and impact of volcanic eruptions. The Tanzanian Meteorological Agency (TMA) liaises with the regional Volcanic Ash Advisory Centre (VAAC) in Toulouse to provide information on the dispersion of ash. This report considers the current situation and infrastructure as part of an assessment of volcanic hazard and risk and in collaboration with both GST and TMA makes recommendations for future work.

Tanzanian volcanoes

There are ten active Holocene volcanoes listed in the Global Volcanism Program (GVP) database for Tanzania (Figure 1). These form two clusters in the northern and southern parts of the country marking the southern portion of the East African Rift Valley. The northern volcanoes are Mt Kilimanjaro, Mt Meru and Ol Doinyo Lengai, while the southern volcanoes are clustered around Rungwe Volcanic Province. Of Tanzania’s Holocene volcanoes, only the carbonatite volcano of Ol Doinyo Lengai is known to be currently active. However, at the time of writing, the lack of volcano monitoring in proximity to any of these volcanoes means that any state of unrest is unreported and the potential for an eruption may be underestimated.

Figure 1    Location map of Tanzania’s active volcanoes. Data from the Smithsonian Institute GVP.

The majority of Tanzania’s Holocene volcanoes are explosive in nature, with effusive lava dome growth and lava flows. The three northern volcanoes (Mt Meru, Mt Kilimanjaro and Ol Doinyo Lengai), and Mt Rungwe and Mt Kyejo in the south, are stratovolcanoes characterised by pyroclastic cones and lava domes. Mt Kilimanjaro and Mt Meru also have craters resulting from edifice collapse. Three of the southern volcanoes (Igwisi Hills, Izumbwe-Mpoli and an unnamed volcano) are pyroclastic and tuff cones. Mt Ngozi is a shield volcano with a summit caldera. Only SW Usangu Basin is entirely effusive, characterised by lava dome growth.

Although Tanzania’s largest cities are situated more than 30 km from the volcanic centres, the prevalence of numerous rural communities in Tanzania mean that seven of the Holocene volcanic centres have more than 100 000 people living within a 30 km radius. Of these, two have more than 300 000 people within a 10 km radius (Source: Smithsonian Institute GVP 2013).

There is no record of fatalities as a result of volcanic activity although there are reports of injuries and loss of livestock associated with the 2007 eruption of Ol Doinyo Lengai. The Disaster Management Unit (DMU) of Tanzania wrote a report to the Prime Minister’s Office in response to this eruption, recommending a series of restrictions on access, regulation of official local guides, first aid stations and shelters be implemented on Ol Doinyo Lengai. At the time of writing those recommendations have yet to be actioned. The lack of fatalities known as a result of past eruptions may be due to recording and epistemic uncertainty that requires consideration when analysing the impact of past eruptions.

Volcanic hazards and disaster risk reduction strategies

UN ISDR is the lead organisation for global governance of Disaster Risk Reduction (DRR) and so has great influence on policy development, international collaboration among nations and decision-making on priorities and actions by nations. UN ISDR and the GAR reports are also highly influential among NGOs, other international agencies (e.g. the World Bank, the European Space Agency) and the private sector.

GVM and IAVCEI (the international volcanology body — International Association of Volcanology and Chemistry of the Earth’s Interior) have been jointly commissioned by UNISDR to produce the volcano chapter for the GAR15 study. Volcanoes have not been considered in previous GAR reports so this is a unique opportunity for the international volcanological community to make a broad global assessment of volcanism in the context of DRR and to present the state-of-the art in volcanic hazards and risk assessment. The volcano model will complement other models in the report on: earthquakes, floods, cyclones and extreme weather, tsunamis, exposure and risk. GAR13 was launched in May 2013. It looks at how public regulation and private investment shape disaster risk. GAR15 will be launched at the World Disaster Programme meeting in 2015 and will develop 'Ready to use risk data'. The GAR15 task force has been tasked to produce the assessment of volcanic hazard and risk by April 2014.

We are building on the methodology employed in the World Bank funded GFDRR report (Aspinall et al. 2011) to evaluate volcanic risk and are working in collaboration with volcanologists worldwide to build this model. This methodology is being modified by a GVM task force on volcanic indices. Volcano data from key databases, such as the database of Smithsonian's Global Volcanism Program and VOGRIPA, will be used to provide a synoptic assessment of global volcanism from a hazard and risk perspective. The products of the GAR15 study will include a general synoptic document for a non-technical readership, and a more detailed technical report which gives the evidence that supports the global assessment, including: global, regional or local analysis on volcanoes and volcanic hazards, case studies that are through to be illustrative of key issues, good practice or methodologies in hazard and risk assessment. References to key publications and authoritative web sites, specialised background papers and data collation forming individual country profiles will also be presented and digitally accessible. The reported work in Tanzania will form the basis for one of these country profiles and is the first profile to be completed for the GAR15 report.