Explosive volcanic eruptions eject large quantities of ash into the atmosphere. The ash is dispersed by atmospheric winds over thousands of kilometres, until it falls out of the atmosphere and becomes incorporated in sediments within days, weeks or months of the eruption. As such, ash layers form instantaneous time-markers, even when the ash particles are too sparse to be seen with the naked eye. These invisible layers are called cryptotephras. The chemistry of the particles can indicate from which volcano the ash was erupted, and therefore it is possible to link cryptotephras across very large regions. Where the dates of the eruptions or cryptotephras are known, the ash layers also provide a means of dating the sediment in which they occur.

We aim to search for cryptotephra layers (tephra in concentrations too small to be visible to the naked eye) in peat and lacustrine sediments across a wide expanse of continental China (from north to south, and from the southeast to southwest) to investigate the potential of using this method for dating and correlating past environmental records. The presence of tephras could greatly improve the understanding of different climate systems in the region which will in turn help the interpretation of the main natural causes of climate change, and the impacts they have in different regions.