photo: livescience
A small underwater volcanic eruption in the summer of 2012 under a Canary island is highlighting a process by which all islands are born through underwater volcanic activity.
This one however poses some problems.
Lo Hierro volcano lies partially underneath an existing island and along a plate boundary. In the last eruption, which occurred a few months ago, the lava that spewed from it was a modest affair, only enough to fill 120,000 swimming pools.
But the volcano is in shallow waters, and a larger eruption could cause disaster. The volcano is being carefully monitored, and its changing shape plotted with sonar instruments, to predict any bulging or curvature that could bely a sudden more explosive eruption.
El Hierro, which is also the name of the island, is the last of the islands to form, and therefore its youngest geologically.
The latest eruption, which was very modest, happened on the west coast near the village of La Restinga, which had to be evacuated.
The volcano underneath the island is about 150 meters (490 feet) high and almost peeking through the ocean surface.
As exciting as it is to watch the volcano grow and rise from the sea, it is nevertheless the most dangerous phase, as underwater explosions can become incredibly forceful. And this is but one of the volcanic peaks below the sea. There are 200 other cones in the island's underwater flanks.
The cone of the volcano has inflated and deflated with each eruption. In November of 2011, a second vent, which is the cone itself, opened up, but landslides partially obstructed the vent, which was transformed into fissure eruptions, with four vents in place of the initial one.
Floating rocks have been found in the water above the volcano called "restingolites", which are rocks with a white core filled with air bubbles and a dark color rim of basanite, a different composition that its core. This has opened up new possibilities as scientists try to understand the nature of the rock formations.
The constant spewing of lava is at this time very modest, so that to form an island of the size of El Hierro it would take the volcano about 125 years. But at the same time, the volcano keeps spewing lava, which can kill fish and plankton. The water at one point was nearly 65 degrees F, and the ph plummeted to 2.8.
A new eruption however is feared. In the past couple of days an unusual pattern of tremors has put the whole island on alert. An earthquake of magnitude 4.3 and very many aftershocks which followed, are bringing renewed concerns that a larger more devastatin eruption could take place. Already ships and even commercial flights have been rerouted.
A volcano expert on the island, J. Carlos Carrecedo has said that a ball of magma was rising to the surface and that there was no way of knowing if it would break through the crust. But he warned that the eruption could only be days, if not months away.
Source: Live Science
Daily Mail/3.27.13
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