When a Giant Tsunami Rolled Over Southern Java, Pangandaran-Yogyakarta Hit

Paleotsunami research conducted along the southern coast of Java to Bali has uncovered strong indications that a major tsunami occurred around 400 years ago. Eko Yulianto, a researcher at the Geological Disaster Research Centre of the National Research and Innovation Agency (BRIN), explained that traces of the event can still be found and studied through various scientific evidence. This evidence was obtained through a combination of geological proof, marine microfossils, archaeology, and studies of coastal community cultural narratives. ‘The problem is that there are no historical documents that can explain when the last giant rupture actually occurred. If the megathrust earthquake happened before the historical writing period, its memory may have been lost from historical records,’ said Eko.

By 2026, the research team had conducted paleotsunami investigations at twelve main locations spread from West Java to Bali. In his presentation, Eko highlighted four representative locations: Cibuaya in Banten, Pangandaran in West Java, Kulon Progo in the Special Region of Yogyakarta, and Tabanan in Bali. In Pangandaran, researchers found a tsunami sand layer separating mangrove mud deposits from younger sediments above them. Radiocarbon analysis of plant remains beneath the sand layer indicates an age of around 400 years. This is the first indication that a large tsunami likely affected the southern coast of Java about four centuries ago. Another finding in Pangandaran came from a coastal swamp environment, showing repeated sediment layers. This structure is thought to have been formed by several successive tsunami waves in one major event.

Evidence pointing to the same time period was also found at the Batu Kalde Site in Pangandaran. Besides a cultural layer containing Hindu-Buddhist pottery fragments and mollusc shells, researchers discovered several collapsed stone structures. Although it cannot yet be confirmed as a tsunami impact, this condition opens up the possibility of an earthquake shock or large inundation occurring in the past. In Kulon Progo, located not far from Yogyakarta International Airport, the team found a sand layer containing various marine microfossils such as foraminifera, radiolaria, and ostracods. Interestingly, according to Eko, some of these organisms originated from a deep-sea environment. ‘The presence of deep-sea microfossils is strong evidence that the material was carried by a major marine inundation event and not by an ordinary coastal flood,’ Eko stated. Similar findings were also obtained in Cibuaya, Banten. At that location, a sand layer rich in marine microfossils was found directly beneath a layer of tree trunks buried in a swamp. Radiocarbon dating indicates the trees died about 300 to 400 years ago.

Meanwhile, in Tabanan, Bali, the research discovered an arrangement of boulders and tile fragments oriented towards the land. The structure indicates a very strong flow of water from the sea. ‘Based on its relationship with a volcanic ash layer suspected to be from the 1815 eruption of Mount Tambora, the estimated age of the tsunami event at this location again falls within the range of 400 years ago,’ Eko explained. After compiling radiocarbon data from various locations, the researchers found an interesting pattern. The ages of the tsunami deposits are not randomly scattered but are clustered in certain periods. The youngest cluster is around 400 years ago, while older clusters appear in the periods around 800-1000 AD, 100-300 AD, and 400-700 BC.

One of the most compelling findings from this research emerged outside the realm of geology. After finding indications of a large tsunami around 400 years ago, the researchers began to question whether traces of the event were still stored in the collective memory of coastal communities. The study was then directed at various traditional narratives developing on the southern coast of Java, including traditions concerning the Queen of the South Sea and the Serat Sri Nata manuscript. Eko said that when descriptions in the manuscript were compared with testimonies from modern tsunami victims, several striking similarities were found, such as unusual sea behaviour, a loud sound from the sea, strong winds, a dark atmosphere, mass panic, extensive damage, and many casualties. ‘This is certainly not proof that a specific tsunami event is actually recorded in the manuscript. However, this finding opens up the possibility that traditional narratives can store fragments of environmental memory that survive long after the physical event itself has disappeared from written history,’ he revealed.