Update [11/17/2013 – 14:20]: Volcano Discovery claims that eruptions are continuing at the southeast cone of Mount Etna, with reasonably elevated tremor levels still
detected. We will continue to provide updates on the change in amplitude of the tremor.
Original Article [11/17/2013 – 09:35]: Europe’s largest and most active volcano, Mount Etna, has erupted once more, producing a beautiful nighttime display, as it ejected a looming column of ash and gargled up intensely hot lava. An expansive plume of smoke and ash could be seen filling the skies of the island of Sicily, Italy.
Mount Etna is a composite volcano, comprised of numerous layers of solidified lava, pumice, tephra and ash and is the tallest active volcano in Europe, measuring close to 11,000 feet tall. Etna is in a state of almost perpetual activity, with one of the most recent eruptions – occurring Oct. 26, of this year – culminating in the closure of airspace around Sicily.
The Events Leading up to the Explosive Eruption
According to Volcano Discovery, who has been monitoring the tremor signals around Mount Etna for some time, the volcano has been demonstrating intermittent strombolian
explosions from the southeast crater. Strombolian explosions are defined as relatively minor volcanic eruptions, hurling tephra, lava bombs and the pyroclastic material cinder several hundred meters into the air.
On Sunday Nov. 11, 2013, a series of strombolian explosions were evident from the southeast crater. That same day, photographer and volcanologist Tom Pfeiffer snapped images of Mount Etna springing back to life, puffing out a series of smoke rings. Speaking to the National Geographic, he had the following to say:
“We could hear explosions and spot the occasional ash plume… Suddenly I saw a perfect steam ring racing over the sky. And soon after that a second one, and a third one.”
Many had speculated that, based upon the tremors and strombolian explosions witnessed throughout much of the past week, a paroxysm was likely. Paroxysms are characterized as the explosive phenomenon observed during an eruption, constituting the most dangerous and violent phase, where lava fountaining and emission is evident; the volatile event can also be accompanied alongside the release of reasonably large tephra columns.
A paroxysm was recorded on Nov. 11, generating a series of perfect smoke rings, but quickly died down by Wednesday, with a few low level tremors still detectable. Volcano Discovery explained the impact of the previous paroxysm on the lava flow of the southeast cone:
“The latest paroxysm has greatly enlarged the field of young lava flows south of the SE cone, including the upper sections of the access road… The last recorded signal from the Torre del Filosofo seismic station (ETFI), showing the tremor intensity at unprecedented levels. If the eruption size is more or less proportional to the integral of the tremor amplitude, this illustrates the size of the paroxysm”
Increasing activity was noted during Wednesday afternoon, with two active vents sighted. Weak strombolian explosions persisted through the remainder of the week, until tremor activity began to rise on the Saturday, ominously signaling the arrival of another paroxysm.
Mount Etna’s Main Event
The main event took place around midnight and lasted for around five hours. Lava fountains spewed superheated material to heights of over 300 meters, sprinkling glowing lava over the darkened landscape. Lava flows were witnessed trickling down Mount Etna’s peak, with a total of three flows.
However, based upon the latest tremor reports, it seems likely that another paroxysm could be imminent. The southeast crater continued to yield recurrent strombolian explosions in the aftermath of Sunday morning’s breathtaking spectacle, in a similar vein to the previous paroxysm.
The volcano was created around one million years ago and has a history of brutal eruptions. In 122 BC, one such eruption vented so much volcanic ash across the town of Catania that the civilians became exempt from paying taxes to Rome, for close to a decade.
These types of eruptions are relatively common for Mount Etna, and a history of dangerous events were witnessed throughout the 20th century. In 1971, lava engulfed the Etna Observatory and endangered the lives of several nearby villages on the volcano’s east flank. However, the longest eruption was yet to come; in 1979, the volcano produced a forceful eruption that lasted a duration of 13 years.
Similarly, the 1991 to 1993 eruption placed residents of the town of Zafferana at grave peril, until redirection efforts were coordinated by engineers; this resulted in the destruction of only a single building. An eruption that transpired during 1992 is considered the last major eruption, however.
The Associated Press indicates that the latest violent eruption did not endanger any villages spread across the mountain slopes, and no evacuation order was necessary. However, the airport in the city of Catania, located on the east coast of Sicily, claims some airspace sectors have been closed off to flights.
The latest eruption represents the sixteenth paroxysmal explosion to have been documented in 2013. Mount Etna is a constant concern for local authorities, since a quarter of the island’s population inhabits Etna’s slopes. In addition, many of the residents rely upon the rich soils for agricultural purposes, stemming from past volcanic activity.
By James Fenner
The Wall Street Journal