# The 2014 Effusive Eruption at Stromboli: New Insights from In Situ and Remote-Sensing Measurements
## 3 Results
occurred at 05:08 and the amplitude reached a peak at around 05:24, a few minutes after the opening of vent V2 at 05:16. After a pause of about 8 min, the landslide activity resumed at 05:32 and lasted for about 1 h, before reaching a stationary level (slightly higher than the value observed before 05:08) and possibly related to the ongoing lava flow (Figure 7C). The GBInSAR recorded a large loss in coherence at the NEC-talus and the SdF area, consistent with the onset of the effusion (Figure 5D). At 05:29 the flow had travelled the Pianoro flat surface and at 05:30 started to expand along the SdF steep slope (Supplementary Materials). Here it formed at least 5 lava flow branches (Supplementary Materials), reaching the coast with a hot avalanche 30 min later (Table 1, Supplementary Materials). The landslide activity resumed at 05:32, and the collapse lasted for about 1 h, coherent with several landslides' pulses (Figure 8). By 06:24 several lava branches reached the sea, forming a lava fan \(\sim\)500 m wide (Table 1, Supplementary Materials). Effusive and explosive activity declined between 7 and 8 August 2014, with only one lava flow active along the coast and deeper magma level within the feeder conduit, evidenced by more collimated jets produced during the explosive activity at the summit vents (Table 1, Supplementary Materials). Figure 6: Thermal images recorded by the SCT camera located at Labronzo, \(\sim\)100 m a.s.l. (see Figure 1b for location), showing the hot ”gravel flows” that reached the sea on 6 August 2014, at 14:05 (**A–D**), 14:06 (**E–H**) and 14:07 (**I–L**), spreading on the sea surface. Temperature is in \({}^{\circ}\)C. The velocities of the three landslides of hot blocks in the frontal region were 9.8 m s\({}^{-1}\), 5.9 m s\({}^{-1}\) and 9.8 m s\({}^{-1}\), respectively, based on web-cameras measurements. Loss in SAR coherence persisted until 8 August 2014 on the whole scene illuminated by the GBInSAR device. In the crater terrace, the coherence increased again since 9 August 2014 when no explosive activity was observed from the monitoring cameras, and the GBInSAR recorded displacement away from the sensor until late September indicating deflation of the summit. The images recorded by the thermal camera located at II Pizzo (SPT; see Figure 1B for location) showed significant morphology changes of the summit craters since 9 August 2014, showing that the apex of cones and hornitos within NEC1, NEC-hornito and SWC had been removed by the several collapses and hot \"gravel flows\" of the previous days. The thermal images displayed also a much lower temperature of the whole crater area, indicating a decline in the explosive activity. Likewise, the rate of effusion decreased significantly from the previous day, with only one wider lava flow starting from the eruptive fissure and replacing the 4-5 branches of the previous day. This flow was reaching the coast forming a narrow channel apparently cooling down, with overflows sometimes spilling over the channel levees. Figure 7: Plot of the high-frequency (>10 Hz) seismic amplitudes averaged over 10 s windows (station STR8, EW seismic component) for: (**A**) details referred to the time interval 10:00–18:00 of 6 August 2014, highlighting the signals associated with landslides that occurred soon after the onset of the overflows, whose onset is marked by orange vertical lines; (**B**) the time interval 10:00 on 6 August 2014–10:00 on 7 August 2014; (**C**) details referred to the time interval 03:00–10:00 of 7 August 2014, highlighting the signals associated with landslides that occurred at the opening V1 and V2 vents (red vertical lines). Until 15 October 2014 the GBInSAR recorded displacement towards the sensor, indicating inflation of the crater area. Afterwards, very low displacement rate (<0.05 mm/h) oscillating between away and towards the sensor, have been recorded. In the SdF area, after the onset of the 2014 flank eruption, the radar recorded a very low coherence for three days; this was related to the initial fast-moving lava flow.