Search

Studying past eruptions provides a unique opportunity to improve understanding of volcanic hazards, especially in Indonesia, where volcanic eruptions are frequently deadly and destructive. As part of a recent approach to identifying and characterizing past volcanic events, we present the first reconstruction of the eruptive history of the Ternate and Tidore Islands (North Maluku, Indonesia) for the last 22,000 years cal. BP. This interdisciplinary study (geomorphology, tephrochronology, sedimentology, geochronology, geochemistry) consists of the first stratigraphic and chronological continuum from eruptive deposits established in a set of fifteen sections in Ternate, Tidore and Maitara islands. Sedimentological and geochemical data from tephrostratigraphy studies and radiocarbon dating suggest that these islands experienced at least four major explosive events from c. 22,000 to 740 years cal. BP. The earliest event is a Plinian eruption leading to the caldera formation of Telaga volcano on the island of Tidore, c. 22,000–17,500 cal. BP. The Gamalama volcano on Ternate, whose current eruptive activity is essentially strombolian or phreatomagmatic, experienced as well a pumice eruption dated to c. 18,000 cal BP. A third event dated to c. 14,500-13,000 cal. BP, associated with a succession of abundant pyroclastic deposits of scoria, pumice, and ash, is related with the phreatomagmatic eruption at the origin of the formation of the Ngade maar on Ternate Island. Although no eruptions of Kie Matubu volcano on Tidore Island have been filled out by people since their presence in the region from the 16th century, this survey identifies two late Holocene eruptions, c. 2500 cal BP and 740 cal BP. This chronostratigraphic framework from the late Pleistocene to recent eruptions in North Maluku region provides new perspectives in managing predictive and warning information for potential eruptions that may occur on these small, vulnerable volcanic islands in the future.

Tidore and Hiri Islands in North Maluku Province is the result of a complex tectonic setting. In contrast with Ternate Island and its well-known volcano, Gamalama volcano, there is still a lack of research about volcanic information or volcanic landform in Tidore and Hiri Islands. Even though the two islands also have volcanoes, i.e., Hiri and Tidore/Kiematubu volcano. This study aims to provide geomorphological information, especially in Tidore and Hiri Islands, since this information is hard to find whereas it is very important to disaster mitigation and landuse planning. We used remote sensing images, digital elevation models (DEM), and geological maps to classify geomorphological information of the small island of Tidore and Hiri in the North Maluku based on geomorphological aspects, i.e., morphology, morphogenesis, morpho-chronology, and morpho-arrangement. As a volcanic island, the slope in Tidore and Hiri Island is dominated by a slightly steep (8°-16°) and a steep slope (16°-35°), while the relief is dominated by hills and mountainous. Volcanic landforms on Tidore and Hiri Islands are characterized by relatively symmetrical cone-shaped volcanic cones, which are accumulations of falling pyroclastic material and lava ejected from magma vents. Volcanic islands include the case of Tidore and Hiri Island have radial centrifugal river flow patterns. The material on Tidore and Hiri Islands is dominated by Holocene volcanic rocks. In Tidore, there is alluvial material on the west and east coasts of the island. This study result also can be developed into more detailed geomorphological maps, or landscape evolution in a volcanic island, or spatial planning.

Kiematubu volcano is often considered as non-volcanic, even though it consists of basalt material, since it has never erupted before. In fact, that small volcanic islands have a high risk due to their restriction on means and resources. The study aims to assess the social vulnerability of the community in Tidore Island that may be exposed to the eruption of the Kiematubu volcano. There has not been previous research in Tidore Island regarding volcanic vulnerability yet. The social vulnerability is an initial assessment of disaster management, which will affect in optimizing community’s capacity then minimizing the disaster impacts. Social parameter of demographic condition, health facilities, and education facilities was weighted to assess social vulnerability. The result shows that the social vulnerability class of Tidore Island is dominantly low, approximately 80%, the rest is middle and high, with a percentage of 13% and 7%, respectively. Mostly, the low vulnerable villages are due to less population density. However, the highly vulnerable villages, Gamtufkange and Indonesiana, consist of very high and high population density. The southeast part of Tidore Island, where both villages are situated, is the center of human activities, such as governmental, trades, and education.