The submarine eruption south of
El Hierro Island could be in a process of change: While visible activity on the sea surface above the vent, as well as harmonic tremor signal (thought to be more or less proportional to erupting magma flux) have nearly ceased, the number of earthquakes under the island has increased sharply since yesterday.
 |
New bathymetric map (9-13 Feb 2012 survey) published by IEO. |
On 15 February, more than 20 quakes were measured. Most of the earthquakes were very small, well below magnitude 2, and were clustered beneath the NW and SW sectors of the island at depths of around 10 km. There is no conclusive interpretation of this measurement. A possible (and usually assumed) scenario is that rising new magma from the mantle reservoir is creating new intrusions and rupturing rock to create pathways in the crust under El Hierro, not using the same paths as until now. That would explain why less magma is currently being erupted at the current vent(s). In that scenario, the eruption will continue, perhaps even from a different vent, and an increase in magma output is going to be expected any time soon. However, this is speculation.
The earthquakes could as well be related to some other (known or unknown) process, e.g. gravity-induced adjustments that respond to pressure changes and occur within previously ruptured areas of the crust beneath the island...
The eruption has once again paused or perhaps even stopped. There is no longer any significant tremor signal and only a very weak stain can be seen on the ocean. Small earthquakes continue, however, suggesting that it is probably once again only a pause in the eruption. On the other hand, the clear trend of decreasing overall activity over the past 3 months is continuing as if the eruption ends with a very long decreasing tail. The submarine eruption south of El Hierro Island could be in a process of change: While visible activity on the sea surface above the vent, as well as harmonic tremor signal (thought to be more or less proportional to erupting magma flux) have nearly ceased, the number of earthquakes under the island has increased sharply since yesterday.
On 15 February, more than 20 quakes were measured. Most of the earthquakes were very small, well below magnitude 2, and were clustered beneath the NW and SW sectors of the island at depths of around 10 km...
The Instituto Espaniol de Oceanografia (IEO) has published the results of a recent bathymetric survey of the submarine topography of the ongoing eruption south of La Restina (see map). The data were collected on board the Spanish Ramón Margalef research vessel during 9-13 February. The most interesting finding is perhaps that the submarine edifice, which sits on the steeply descending floor of a submarine canyon, and is about 100-150 m tall, has not grown significantly in height over the past weeks and there is a secondary prominent vent that has accumulated enough lava to form a small flank cone about 80 m tall and peaking at 200 m depth. The depth of the principal vent is still at about 120 m below sea level. If current eruption rates continue, it seems extremely unlikely that the eruption, within a foreseeable time, is able to breach the surface to produce Surtseyan explosions or even form a new island. Whether magma-water explosions can breach the surface depend on mainly 2 factors: the water depth, i.e. containing water pressure, and the flux of magma. Both parameters are probably long outside the range to produce significant explosions visible at the surface... - Volcano Discovery.
WATCH: The Guardia Civil's video from their last overflight showing the vent area near La Restinga.