Reventador volcano (Ecuador): lava dome continues to grow, ongoing explosions

Source: Volcano Discovery - Tom Pfeiffer, 2/02/13

The activity of the volcano remains strong. The new summit lava dome continues to grow and produce explosions and feed active lava flows on the upper flank.

During the afternoon of 31 Jan, an strong emission column of steam and moderate ash content could be observed rising 3.5 km above the crater.
Seismic activity remains at a high level, with a daily average of 20 earthquakes related to fluid pressurization and movement inside the volcano, and a daily average of 29 explosions since 22 January.
IGEPN and the National Risk Management conducted a scientific helicopter overflight of the volcano on 29 Janand published the following informative report (translated):

Since November 2002, Reventador's activity has been characterized by periods of high and low activity levels. A marked increase of seismic and surface activity occurred on 21 Jan. Reports received from residents located near the volcano indicated the presence of glowing material in the crater and on the flanks during the nights of 21, 22 and 23 January.
On 22 Jan, activity further intensified and produced explosions with loud bellowing noises. Associated with this activity was a strong seismic signal of constant fluid movements inside the volcano in the form of long-period events, low frequency tremor, tremor and explosion signals.
From 22 Jan until now, there have been frequent signals of low-frequency tremor of high energy.

It was found that the reported incandescence during 22 Jan came from a new lava flow on the southeastern flank, which had a width of about 350 m and a length of approximately 1.1 km and continued to advance. There were also smaller lava flows, less than 200 m long, on the north and south sides.
Compared to the situation in past November, the lava dome in the summit crater has significantly increased its size. Its present height exceeds the eastern summit by at least 100 m. It has nearly filled the crater created by the explosion in November 2002.
It was also evident that at least one lava flow had been generated between the months of November and December, and descended the northern flank of the cone reaching approximately 1.3 km length.

During the overflight, an explosion was observed as well that generated a column of steam and ash rising at least 1.5 km above the crater.
SO2 gas measurements were attempted, but the weather conditions during the flight did not allow to use the mobile DOAS.

Since November 2002, the volcano has produced over 20 lava flows, mainly on the north, south and southeast flanks of the volcano. These lava flows have remained inside the caldera, which is an area without population or any kind of infrastructure.
However, IGPEN stresses that close monitoring is necessary to asses the stability and growth of the lava dome in the crater, because a partial or total collapse of the dome could generate pyroclastic flows that directly affect the area of ​​the caldera and in some cases beyond, especially on the eastern side.