Recurrent historical lahars in Jamapa Gorge, Pico de Orizaba volcano, Mexico: Geological and dendrochronological evidence

Lahars are a recurring phenomenon in volcanic areas and have a high potential to cause economic losses and fatalities. In recent decades, tree-ring records combined with stratigraphic correlations have proven valuable for reconstructing the spatiotemporal occurrence of these events. This study analyzes lahars exposed in the upper Jamapa Gorge, located on the northern flank of Pico de Orizaba volcano, at elevations between 3760 and 4000 m above sea level. We employed an unmanned aerial vehicle (UAV) to generate an orthomosaic and a digital elevation model (DEM), enabling the production of a detailed geological map of the study area. Fieldwork included the construction of stratigraphic columns, the collection of volcaniclastic samples, and dendrochronological sampling of 163 Pinus hartwegii tree cores. Stratigraphic analysis identified three distinct ancient terraces formed by lahar activity, composed of heterolithological massive deposits made of boulder-gravel fragments supported by a coarse sandy matrix. The terrace tops are semi-flat and currently colonized by Pinus hartwegii . We generated three tree-ring chronologies providing minimum ages for terrace formation of ≤292, ≤96, and ≤79 years. The lahar deposit dated at ≤96 years correlates with the Mw 6.4 Jalapa earthquake of January 3rd, 1920, whereas the ≤79 years deposit may be associated with extreme rainfall produced by a category 3 hurricane in September 1931. The oldest deposit (≤292) may be related to snowmelt processes or extreme rainfall events. These results provide new insights into the historical occurrence of lahars in Mexican volcanoes, which have been comparatively understudied. Establishing more accurate lahar chronologies is essential for improving hazard assessments, as these events pose significant risks of damage to infrastructure and populations located at the base of active volcanoes. • Stratigraphic analysis revealed three ancient terraces formed by lahar activity. • The trees suggest minimum formation dates of the terraces at ≤292, ≤96, and ≤78 years. • This analysis is an opportunity to investigate historical lahars in Mexican volcanoes.