1257 Samalas eruption

Caldera-forming eruption of Mount Samalas

A summit reconstructed at about 4,200 metres became the Segara Anak caldera. The year is nailed down four different ways; the day is not recorded at all.

The mountain that became a lake, 1257

Mount Samalas on Lombok erupted in 1257 through several phases: at least two Plinian fallout phases, an intervening water-influenced phreatoplinian phase, and voluminous pyroclastic-density currents produced when the eruption column collapsed.

The eruption destroyed the upper Samalas cone and formed the Segara Anak caldera. The pre-eruption summit has been reconstructed at about 4,200 metres above sea level.

How far the deposits reach

Ash blanketed Lombok and is preserved on Bali and Sumbawa; the deposit geometry also indicates fallout in eastern Java. That evidence shows ashfall on Sumbawa, not pyroclastic flows crossing the sea to it.

Pyroclastic-current deposits remain as much as 35 metres thick 25 kilometres from the caldera.

Estimates put the erupted magma at 40.2 ± 3 km³ dense-rock equivalent and the initial plume at 43 ± 8.6 km above sea level, classing the eruption at VEI 7.

A capital named in a chronicle, never located

Later Lombok chronicles say the eruption destroyed Pamatan, capital of the Lombok kingdom. Pamatan has not been archaeologically located, and the textual account remains only partly corroborated.

The Babad Lombok preserves social memory rather than eyewitness manuscripts; the versions modern researchers examined were probably compiled in the eighteenth or nineteenth century.

The year is supported by radiocarbon modelling, polar ice-core chemistry, historical climate evidence and the Lombok tradition — but no exact day survives, and the westward ash pattern only suggests the dry season, roughly May to October.

Sources

Researched 23 Aug 2026 6 sources 2 audit passes

How this was checked

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What the sources leave uncertain

The year 1257 is strongly supported by radiocarbon modelling, polar ice-core chemistry, historical climate evidence and the Lombok tradition, but no exact day survives.
The westward ash pattern suggests an eruption during the dry season, approximately May–October 1257.
The Babad texts preserve social memory rather than contemporary eyewitness manuscripts; versions examined by modern researchers were probably compiled in the eighteenth or nineteenth century.
Pamatan's destruction and reported human losses come from the chronicles. As of the 2022 study, Lombok had yielded little securely dated thirteenth-century archaeological material.