Tuesday, November 8, 2011

El Hierro Eruption Enters Surtseyan Phase

It could be just a matter of hours or days before the volcano at El Hierro breaks the ocean surface in what is referred to as a "Surtseyan Eruption" phase. The volcano had a period where it looked like it was calming down a few weeks ago, but as some astute volcanologists pointed out, the ongoing quake swarm meant anything but calming down. A couple weeks ago, quakes were detected that indicated not one, but two magma chambers coalescing into one, which would increase the volatility of the eruption when the two magma types mix.

The eruptive phase currently underway seems to indicate that another eruption has already (or will soon have) started to the north of the El Golfo region of the island (the site of a massive landslide over 50,000 years ago). The activity to the south of La Restinga has continued unabated, and the locals are marveling at what they call the "Jaccuzzis" in the water off the coast. The Jacuzzis they refer to are the underwater plumes of superheated water and ash that resemble the surface water of a jacuzzi spa.

In the past few days there have been reports of ejecta actually breaking the water's surface, and pyroclastic rocks that formed underwater are beginning to wash up on shore. Thus scientists can predict that the eruption will soon overpower the pressure of the surface water, and begin to erupt ash and gas above the ocean, eventually leading to either 'ephemeral islands', or, as they have been speculating, a "Surtseyan" eruption.

The term Surtseyan is a reference to the Icelandic island of Surtsey, whos birth in the 1960's was the first historically witnessed account of a volcano breaking the surface of the ocean to rapidly form a volcanic island. This island was quickly 'built' by the eruption, and as a result has undergone extensive erosion since its birth, and unless it erupts again (which is unlikely for Surtsey) will likely erode and be swallowed by the sea within decades. This could be true of the El Hierro eruption, but the lava types and eruption types above water have yet to be determined.

If the El Hierro/La Restinga volcano does break the surface, it will likely start with large ash emissions, due to the water hitting the molten lava, and quickly build an ephemeral island. If the eruption continues and the ocean is cut off from the eruption crater, more solid and viscous lavas could be erupted onto the surface, creating a much more stable island.

There are many similarities to Icelandic and Hawaiian volcanoes in this eruption, but more so with Hawaiian style island building. Off the southern coast of the big Island of Hawaii, a small volcano is quietly erupting named Loihi. However due to the depth it is erupting at, it is not expected to break the oceans surface for over 10,000 years! The Canary Islands, much like Hawaii, are part of a slowly moving 'hotspot' or mantle plume, the same as Hawaii. It is quite likely that activity over time will migrate to the SW, the same as Hawaii, building small-medium sized volcanic islands as the eons pass.

Keep your eyes peeled on the webcams, as you might be lucky enough to witness the birth of new land!

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