Using tree-ring analysis to evaluate intra-eruptive lahar activity in the Nexpayantla Gorge, Popocatépetl volcano (central Mexico)

Lahar activity is one of the most important processes capable of mobilizing large volumes of sediment and producing devastating effects on human populations and infrastructure. Estimating the frequency, distribution and climatic controls on lahar activity is necessary for understanding how sediment is mobilized from hillslopes to channels and how the landscape is modified by this type of process. In this study we evaluate the intra-eruptive lahar activity in the Nexpayantla Gorge (NW of Popocatépetl volcano, central Mexico) by using a dendrogeomorphological analysis of growth-ring records of Abies religiosa trees (n = 100). Based on the identification of 322 growth disturbances (GD) and field evidences we identify 23 intra-eruptive lahars that occurred from 1959 to 2013. By analyzing the lahar chronology and climatic data, we observed that ~ 83% of lahar activity coincides with moderate to strong cold and dry phases of El Niño-Southern Oscillation. Based on the seasonal timing of GD we explored the intra-annual lahar activity. We found that ~ 43% of the lahars occurred in the latewood season (from July to October) when the mean summer monthly rainfall is > 120 mm. Approximately 37% of lahars occurred during the first heavy rainfalls (from March to June) which corresponds to the earlywood season. The remaining 20% of the lahar activity corresponds to the dormancy period (winter season), when snowmelt and/or occasional strong rainfalls (> 100 mm day− 1) occur. The GD indicate that in Nexpayantla Gorge intra-eruptive lahar activity takes place around every two years. We also found that the effects of lahars are concentrated around the transitional and depositional zone of Nexpayantla Gorge.