Spatio-temporal modeling of built-up land expansion (2005–2055) in the eruption prone area of Gamalama volcano, Ternate island, Indonesia

Ternate Island, a volcanic island dominated by the still-active Gamalama Volcano in North Maluku Province, Indonesia, faces complex dynamics in built-up area development driven by accelerated demographic growth and economic activities, particularly in the trade and tourism sectors. The limited availability of flat land has resulted in increasingly intensive expansion of settlements and infrastructure on the volcanic slopes, areas inherently characterized by high volcanic hazard vulnerability. This study employs a Cellular Automata-Markov Chain modeling approach based on multi-temporal satellite imagery and driving variables, including elevation, slope, distance to road networks, and economic center locations, to analyze land cover change dynamics during the periods 2005, 2015, and 2025 and to model projections for 2035, 2045, and 2055. The results demonstrate significant expansion of built-up land from 2005 to 2055. The rate and spatial distribution of built-up land development within disaster-prone zones Prone Zones I and II underscore the urgency of implementing risk-based spatial planning policies, including stringent restrictions on development in hazardous areas, the development of adequate evacuation infrastructure, and the enhancement of community preparedness capacity. The contributions of this research are highly relevant to sustainable regional planning in tropical volcanic areas with high disaster risk, while also emphasizing the importance of integrating disaster mitigation strategies and climate change adaptation into the spatial planning policies of Ternate Island.