Gamalama Volcano is a volcano island which is nearly circular in shape with 5.8 km in radius and covered about 105 km² of the entire area. This volcano island is known as Ternate island. Ternate city which is located in the southeast coast of Ternate Island, is the capital city of North Maluku Regency. Half of the population of Ternate Island live in Ternate city, whereas the rest live in along the coast which are mostly as fishermen or farmer. Gamalama Volcano is a stratovolcano, where is positioned at 0o48' S and 127o19.5' E and the highest peak is 1715 m above sea level is composed of lava, pyroclastic and lahar from three generation of volcanoes which is reflected by three crater rims on its summit. The position of these crater rims reflects the direction of the movement of its eruption point the south to the north. The youngest crater rim where part of its eruption activity occured during historic time, is located in the north known as Mt.Arfat or Piek van Ternate, it is circular in shape of 300 m in diameter and 1715 m in high above sea level. The morphology of the summit area, shows the crater rims are facing northward, and act as the barrier of eruption material distribution in the form of flowing mass. Most of the distribution of its eruption products will be distributed toward this point except the ejected material which are generally distributed to all direction. So, the north part is the most dangerous area toward eruption. Precursory to eruption show that tectonic earthquake and volcanic earthquake are the common phenomena which are usually occur. This may because Gamalama volcano is located in an active tectonic earthquake zone. The analysis result of seismicity, recorded by the seismograph show that the dominant tectonic earthquake is always accompanied by presence of volcanic earthquake. It is assumed that tectonic earthquake has triggered the volcanic activity which is followed by eruption. The seismicity data show that since 1990, every eruption was preceded by the increase amount of tectonic earthquake intensity. On the other hand, the very pronounce change of the activity of Gamalama since 1990 are the amount of ash eruptions, that these phenomena were never recorded during its activity history. There are nine craters, i.e.: Arfat Crater, Madiena, K1, K2, K3, K4, Laguna Lake, Tolire Jaha and Tolire Kecil (Kusumadinata, 1979). Nowadays, the point of eruption or the active cone is Arfat Cone.

Historic eruptions

Gamalama is one of very active volcanoes in Indonesia. The first known eruption during historic time was in 1538. Its increase activities recorded until 1994 were 82 time, where 65 of them followed by the occurrence of eruption. From these eruption occurences, there were 15 times of them produced lava flows. In general, they were explosive eruptions which took place in the main crater, except the 1763 which was a flank eruption occurred in the north flank in the Sulamandaha area which produced lava flows. During the eruption of 1980, which took place in the central crater, there was a new crater formed located in the eastern part of the main crater. Based on the eruption history, the eruption period was short and generally took place just in few days. The eruption interval show at least 1 year of quiescene and 44 years in the longest period of quiescene or every 5.5 years on average. In general, the eruptions are in the form of ejected volcanic material of ash to boulder sizes which are frequently followed by volcanic bombs and in some eruptions were followed by lava flows. During the rainy seasons, this ash and rock boulders often form lahar, whereas pyroclastic flows have never been occurred. Although Gamalama erupts frequently, the character of its eruptions is not too hazardous. Human victims were claimed during the eruptions of 1673,1775,1838 and 1871. There were two persons injured and in 1838 while they were doing observation in the crater and around the summit areas, whereas during the 1871 activity one person killed and another one was wounded hit by the ejected rock. During the formation of Tolire Jaha and Tolire Kecil Maars in 1775, there were 141 people were missing at Soela Takomi area.