Study of lava dome growth and its partial destruction during September 2016 to February 2017 at Volcán de Colima, Mexico

The most recent eruption at Volcán de Colima, occurred between September 2016 and February 2017. During that period, lava effusion generated a dome, lava flows and rockfalls. Subsequently, explosive activity was observed for several months. The increase in seismic energy during the first days of October 2016, also led to a precautionary evacuation of a nearby community. Elevated levels of SO₂ flux were observed during the peak effusive phase in the early days of October, resulting in acid rain towards the southwest of the volcano. An analysis of the Frequency Index (FI) of discrete seismic events showed a change from low frequency energy to a high frequency energy; for several volcanoes this has proved to be a valuable indicator for assessing the transitions between ductile behaviour to a brittle state. For volcanic monitoring, it is crucial to comprehend parameters related to the transition from effusive to explosive activity. Additionally, the occurrence of seismic event families indicates a repetitive non-destructive source with events sharing similarities in waveform and spectral characteristics. Locating rockfalls through the amplitude attenuation method proves effective in identifying areas where lava flows, rockfalls, or Pyroclastic Density Currents (PDCs) occur. Photogrammetry was utilized to calculate the volume and effusion rate during the initial effusive stage, yielding a value of 1.3 m³s^-1, consistent with typical rates for lava dome growth. Significant temperature variations were predominantly observed during the southward extension of lava flows and following explosive events. A combination of techniques is essential for a comprehensive evaluation of volcanic activity levels at Volcán de Colima and other volcanoes.