Samalas volcano on the Indonesian island of Lombok erupted in 1257. It had a probable Volcanic Explosivity Index of 7, making it one of the largest volcanic eruptions during the current Holocene epoch. Ash from the eruption fell as far as 340 kilometres away in Java; the volcano deposited more than 10 cubic kilometres of rocks and ash. It left behind a large caldera that contains Lake Segara Anak.
About 1257 Samalas eruption in brief
Samalas volcano on the Indonesian island of Lombok erupted in 1257. It had a probable Volcanic Explosivity Index of 7, making it one of the largest volcanic eruptions during the current Holocene epoch. The eruption may have helped trigger the Little Ice Age, a centuries-long cold period during the last thousand years. Ash from the eruption fell as far as 340 kilometres away in Java; the volcano deposited more than 10 cubic kilometres of rocks and ash. It left behind a large caldera that contains Lake Segara Anak. Other volcanoes in the region include Agung, Batur, and Bratan, on the island of Bali to the west. The oldest geological units on Lombok are from the Oligocene-Miocene, with old volcanic units cropping out in southern parts of the island. Since the destruction of Samalas, two new volcanoes, Rombongan and Barujari, have formed in the caldero. Most volcanic activity now occurs at the Barujar volcano with eruptions in 1904, 1906, 1966, 1994, 2004, and 2009; Rombongsan was active in 1944; Rujar is active in 2014; and Lombok is about 164 kilometres deep, the lower extremity of the Wadati–Benati zone is about 20 kilometres thick, and the crust beneath the volcano is about 160 kilometres deep. The eruptions are mostly dacitic, with a SiO2 content of 62–63 by weight. The volcanic activity is mostly calc-alkaline ranging from basalt over dacite and dacites to dacitite and basalt.
The volcano is 20 kilometres beneath the Earth’s surface, with the crust at the lower end of the Wadati-Benati zone about 164 kilometres thick. It is located in the Sunda Arc of Indonesia, a subduction zone where the Australian plate subducts beneath the Eurasian plate at a rate of 7 centimetres per year. Before the site of the eruption was known, an examination of ice cores around the world had found a large spike in sulfate deposition around 1257, providing strong evidence of a large volcanic eruption having occurred somewhere in the world. In 2013, scientists linked the historical records about Mount Samal as to these spikes. Mount Rinjani has also been volcanically active, forming its own crater, Segara Muncar, with Mount RinJani at its eastern edge. The remains of the volcano form the SegaraAnak calderA, with Mount Rin Jani at the eastern edge of the cal dera, and Rombonga at the western edge. The volcano may have been as tall as 4,200 ± 100 metres, based on reconstructions that extrapolate upwards from the surviving lower slopes; its current height is less than that of the neighbouring Mount Rin jani, which reaches 3,726 metres. Eruption columns reached tens of kilometres into the atmosphere.
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