mayans

Via The Earth Story:

The cave has already been used in research on Saharan dust transport across the Atlantic since its depths make an ideal sediment trap, and now new work has confirmed the inference from other sources that the Maya civilisation fell after a series of long droughts. They used a series of sediment samples from the epoch of their demise (around 800-1000 CE) and compared the changing ratios of aluminium and titanium, which reveal periods of heavy rainfall from tropical cyclones (the source of most of the water that kept the Mayans alive).

These indicated several long periods of drought at the time of their slow downfall that eked out over two centuries as the inter tropical convergence zone shifted north and south, taking the rain giving cyclones with it. The science is simple, in times of greater rain, more of the volcanic rocks in the area are weathered, and the water flows into the sea dumping its sediment and accompanying titanium with it. Analysing through the core allows the shifting rainfall densities to be tracked over time.