  Understanding past volcanic eruptions is essential to improve the resilience
of societies to future events and to establish appropriate response plans. For
volcanoes which are not the most active (one eruption every 30 yrs or less),
documentation of past eruptions is often scarce, especially for those preceding
modern measurements, making sometimes challenging the connection between
studies such as those based on ash deposits and more recent observations. In
this study we show that tree-ring growth records can help to constrain the size
of basaltic events over a time-span of approximately 100 years. In order to
validate our approach, we sampled pine trees along the north-east rift zones of
Mt. Etna and show the growth of these trees has been impacted since 1925, and
that erupted volumes correlate with change in tree-ring growth (r>0.7, p<0.005,
n=14 events and 48 trees sampled). We propose that tree growth is enhanced by
transport of fluids (water, nutrients within the water and potentially SO2/CO2)
within the subsurface before magma reach the surface. These results suggest
that trees growing on volcanoes may be useful in documenting past volcanic
activity and in understanding the role of deep magmatic sources in the
preparation of magma intrusions.
