Trying to keep up with the news at El Hierro in the Canary Islands is hard - the seismicity and tremor has been almost nonstop for 6 months now and over the last few weeks, the submarine eruptions have waxed and waned - but now we seem to have entered another period of strong submarine activity (see above), which might possibly be closer to the ocean surface.__
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UPDATE 3:15 EDT: It looks like the phreatomagmatic explosive activity is beginning south of El Hierro. Prensa El Hierro tweeted (translated): "Juan Manuel Santana have just announced that produce water columns and ash." La Restinga is being evacuated as a precaution. Some new video/images of the area shows small explosive plumes/jets from the ocean surface that suggest the eruption is enterting a Surtseyan phase. Here is a live feed of TV from El Hierro with updates.
The current activity is pretty clear from a linear vent on the seafloor (see right) and there are very prominent bubbling areas where the volcanic tephra and gases are rising - with some excellent video to show that activity. This vent, as I've mentioned before, is likely to be very similar to what we see at Kilauea during new fissure vent eruptions - albeit that this one is under the sea. At the depths that the material is eruption (few hundred meters), the eruption is likely not highly explosive but plenty of shattered basaltic (or basanitic) glass is being produced as the lava hits the cold ocean water. Now, it does appear that the bubbling is more intense (video) - and more of it - so if these vents do begin to get close enough to the surface to produce ocean-surface explosions, we might expect something like the 2009 Hunga Tonga Hunga Ha'apai activity, also know as Surtseyan eruption. There has been more of the floating, dark pyroclastic material (see below) as well from the renewed activity at El Hierro.
All of this new activity has prompted the PEVOLCA to indefinitely close the tunnel to Frontera after earthquakes as large as M4.4 have occurred on El Hierro. New evacuations have also been called for people living on the southern end of the island due to the renewed eruptive activity. The government and IGN have had to quell rumors that eruptions have started to the north of El Hierro as well but there is no evidence of any activity other than the submarine eruption south of La Restinga. However, IGN "expects" eruptions to propagate northward
The tremor continues underneath El Hierro, so we haven't likely seen anything close to the end for this eruption.
{Special thanks to @suw, @lumifg, @teideano, @rschott amongst others for information/images in this post.}
