Hierro Volcano | John Seach


El Hierro, Canary Islands, Spain

27.73 N, 18.03 W
summit elevation 1500 m
shield volcano

El Hierro volcano is the westernmost, youngest and smallest of the Canary Islands. In the 2nd century A.D., Ptolemy considered it the western-most position of the world.

El Hierro Island covers an area of 278 sq km, and contains three well-defined ridges, arranged at approximately 120 degrees. According to the hotspot model of volcano formation, the current location of the Canary islands hotspot is under Hierro Island.

El Hierro volcano is still in its juvenile stage of shield growth, and has been modified by gravitational spreading which caused gigantic landslides. There are three volcanic structures on El Hierro Island - elongated topographic ridge (the Southern Ridge) and two semi-circular volcanic cones (Tinor volcano, El Golfo volcano).

Tinor Landslide was the earliest and directed to the northwest of Hierro Island.

El Julan produced a 15 km wide embayment in the southwest of the island. The landslide was approximately 60–120 cubic km in volume, and covered 1600 sq km of ocean floor.

Las Playas Landslide directed SE and had a volume of 25-35 cubic km.

El Golfo, Debris Avalanche
El Golfo is a major debris avalanche on the northern flank of Hierro Island, dated about 13,000 years ago. It has a width of 15 km and a scarp height of 1000 m. The landslide deposited 150-180 cubic km of debris on the seafloor down to a depth of 3000 m.

2013 Earthquake Swarm
An earthquake swarm began at El Hierro volcano on 18th March 2013. The swarm suggested magma intrusion 16 to 25 km below the volcano. The earthquakes were felt by residents in the  Golfo/Frontera area of the island. On the 21st March some earthquakes were shallow with a focus at 2 km. The renewed seismic activity indicates eruptions at El Hierro volcano may not be finished. On 23rd March earthquakes were measured at a depth of 12-14 km indicating a migration towards the surface. On 23rd March 164 earthquakes were recorded. On 26th March two populations of earthquakes were recorded - shalow earthquakes further from the island and deeper earthquakes (7-10 km) closer to the island. On 27th March seismic activity caused rockfalls on El Hierro Island in the El Golfo area. The seismic crisis released more energy than the earthquakes prior to the 2011-12 eruption.

2011-12 Eruption
An earthquake swarm occurred at El Hierro volcano in July 2011 with 720 earthquakes measured in a week. The earthquakes were measured between magnitude 1-3, and most were at a depth of 5-15 km. The swarm occurred at El Golfo in the northwest of the island at the location of a landslide that created a 100 metre high tsunami about 50,000 years ago. The earthquakes were continuing at the end of September and some evacuations were ordered for people living near the volcano.

An undersea eruption began off the coast of El Hierro Island, Canary Islands on 10th October 2011. Initial reports placed the eruption site a few kilometres off the south coast of the island at a depth of about 450 m. The eruption was only been confirmed from seismic activity.

Further reading
Becerril, Laura, et al. "Volcano-structure of El Hierro (Canary Islands)." Journal of Maps 12.sup1 (2016): 43-52.

Becerril, Laura, et al. "Three-armed rifts or masked radial pattern of eruptive fissures? The intriguing case of El Hierro volcano (Canary Islands)." Tectonophysics 647 (2015): 33-47.

Prates, G., et al. "Enhancement of sub-daily positioning solutions for surface deformation surveillance at El Hierro volcano (Canary Islands, Spain)." Bulletin of volcanology 75.6 (2013): 724.

Hierro Volcano Eruptions

2011-12, 1793, 1692?, 1677?