Earthquake and Volcano Watch – El Hierro Earthquake Swarm

Posted on October 4, 2011

0


  • The IGN have reported surface deformations of up to 35mm in El Hierro.
  • This morning the number of earthquakes on the island had exceeded 9250, 1172 of which occured last week.
  • Earthquakes around the volcano (which has had one historic eruption, in 1793, for a month) have continued at a depth of around 10-14km.

 

The History of El Hierro

El Hierro is situated in the most southwestern extreme of the Canaries.  The  island was formed after three successive eruptions, and consequent accumulations, the island emerged from the ocean as an imposing triangular pyramid crowned by a volcano more than 2,000 metres high.

The volcanic activity, principally at the convergence of the three ridges, resulted in the continual expansion of the island. A mere 50,000 years ago, as a result of seismic tremors which produced massive landslides, a giant piece of the island cracked off, crashed down into the ocean and scattered along the seabed. This landslide of more than 300km3 gave rise to the impressive amphitheatre of the El Golfo valley and at the same time caused a tsunami that most likely rose over 100 metres high and probably reached as far as the American coast.

According to the Global Volcanism Program, the massive Hierro shield volcano is truncated by a large NW-facing escarpment, seen here from the east, which formed as a result of gravitational collapse of the volcano. The steep-sided 1500-m-high scarp towers above a low lava platform bordering 12-km-wide El Golfo Bay, which is barely visible at the extreme left. Holocene cones and flows are found both on the outer flanks and in the El Golfo depression. The last eruption, during the 18th century, produced a lava flow from a cinder cone on the NW side of El Golfo.

According to ElHierro.com: “Although over 200 years have elapsed since the last eruption, El Hierro has the largest number of volcanoes in the Canaries with over 500 open sky cones, another 300 covered by the most recent outflows, and some 70 caves and volcanic galleries, notably the Don Justo cave whose collection of channels surpasses 6km in length.”

El Hierro is located south of Isla de la Palma (population 86,000), currently the most volcanically active of the Canary Islands.  About a half a million years ago, the volcano, Taburiente, collapsed with a giant landslide, forming the Caldera de Taburiente. Since the Spanish occupation, there have been seven eruptions.

http://www.irishweatheronline.com/news/earth-science/geology/earthquake-swarm-continues-on-el-hierro-canary-islands/40626.html

 

Posted in: Random