Spatio-temporal reconstruction of lahars on the southern slopes of Colima volcano, Mexico – A dendrogeomorphic approach

• Historical records of lahar occurrence and distribution are scarce in volcanic environments
• Based on tree-ring data, we present evidence for lahars at Colima volcano since AD 1969
• The tree ring reconstruction improves the record of lahar activity for the volcano

Historical records of lahar occurrence and distribution are typically scarce in volcanic environments, even more so if they occur outside of human settlements. In the context of hazard assessment and process understanding, documenting their temporal frequency and drivers of activity might be crucial. On forested volcanoes, lahars may significantly damage trees along their flow paths, and sometimes even eliminate entire forest stands. This study is based on growth disturbances in trees affected by lahars (i) to assess the potential of dendrogeomorphic techniques in lahar research and (ii) to analyze the temporal frequency and spatial patterns of lahars at Montegrande and Arena, two of the most active of the ephemeral streams on the southern sector of Colima volcano. A total of 78 Pinus leiophylla live trees were sampled along the ravines, yielding evidence for 20 lahar events after the AD 1913 eruption, adding seven events to the historic records. Although the number of lahars reconstructed with tree-ring records can only be considered as a minimum frequency, the method clearly improves the local lahar chronology. Despite the scarcity of meteorological records at the study sites, the timing of reconstructed lahars points to heavy rainfalls after explosive activity as the main driver of events.