The risk of large, devastating tsunamis in the South China Sea and its surrounding coastal region is commonly underestimated or unrecognized due to the difficulty of differentiating tsunami from storm deposits. As a consequence, few convincing records have documented tsunami deposits in this region. Here we report preliminary evidence from Xisha Islands in the South China Sea for a large tsunami around AD 1024. Sand layers in lake sediment cores and their geochemical characteristics indicate a sudden deposition event around AD 1024, temporally consistent with a written record of a disastrous event characterized by high waves in AD 1076. Heavy coral and shell fossils, which are older than AD 1024, deposited more than 200 meters into the island, further support the occurrence of a high-energy event such as a tsunami or an unusually large storm. Our results underscore the importance of acknowledging and understanding the tsunami hazard in this area.

Paleomonsoon strength is difficult to reconstruct. The strength of the East Asian monsoon and precipitation over large areas correlate well on a decadal time scale. Thus, monsoon strength can be reconstructed through proxies of sediments originating from large areas. In the present study, we investigated the characteristics of a sediment core from the Northern Yellow Sea Mud. The results showed that sedimentary characteristics are mainly controlled by discharge changes of the Yellow River. The relationships between median grain size (MZ), magnetic susceptibility (MS) and the SiO₂/Al₂O₃ ratio of sediments and spatially averaged precipitation around the Yellow River Drainage basin reveal that changes in MZ and MS are correlated with variation in precipitation. The agreement of temporal trends in MZ, MS and the monsoon strength index confirm that spatially averaged precipitation changes in the Yellow River Drainage basin on decadal time scale are driven by the monsoon strength. These characteristics of marine sediments from the Northern Yellow Sea Mud can thus be used as proxies for monsoon strength.