Earthquake swarm at Chile's San Pedro volcano

Earthquake swarm at Chile's San Pedro volcano

An earthquake swarm with possibly hundreds of small quakes has been detected at Chile's San Pedro-Pellado (or Tatara-San Pedro) volcano. Not many details about this activity are available and reports are in parts contradictory, as the Wired Eruptions Blog points out:

Apparently, the SERNAGEOMIN has been monitoring an earthquake swarm at Chile’s Tatara-San Pedro (also known as San Pedro-Pellado), possibly numbering in the hundreds of small earthquakes over the last few days. The reports are a little scant and the information coming from different parts of the Chilean government are contradictory: the regional governor of the area was quoted as saying that “it is of volcanic earthquakes, so we are on alert” while the regional director from ONEMI said “at first thought that we were facing a volcanic earthquakes, but known reports of the analysis has led to the conclusion that we were facing tectonic type earthquakes“. The article in La Tercera also mentions that the volcano hasn’t erupted in “decades”. If this is renewed activity at the volcano, it is potentially the first in recorded history.

There is little known about the eruptive history of the volcano except that it most likely has erupted during the past 10,000 years and can be considered an active volcano. Any reawakening would thus mark its first historic eruption, something that would remind what has happened at Chaitén volcano in 2008.

The San Pedro-Pellado volcanic complex (also known as San Pedro-Tatara) has been active from the Pliocene to the Holocene. The Tatara-San Pedro edifice overlies the deeply eroded Pellado stratovolcano; both were constructed within the 6 x 12 km Río Colorado caldera, which formed during an eruption about 0.5 million years ago.

The Tatara basaltic-andesite shield volcano at the western end of the complex contains stacked sequences of up to 100 or more lava flows forming up to 1500 m of relief. The glacier-filled summit crater of the 3621-m-high dominantly andesitic San Pedro stratovolcano, which overlies the Tatara edifice, contains a young scoria cone that was the site of the most recent eruptions from the volcano.

A major Holocene east-flank debris avalanche filled the Río de la Puente valley to the south and was followed by eruptions originating within the avalanche scarp low on the east flank that produced lava flows down the Estero Pellado drainage. No historical eruptions have been recorded, but fumaroles are found SE of Pellado.


Featured image: Tatara-San Pedro seen in February 2006. Image by Michael Dungan (Univ. Geneva)


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