We saw a lot of steaming, bubbling and even some small explosive activity at El Hierro over the weekend – not much has changed since Saturday, but I wanted to share this great set of image. On the left is the bubbling ocean south of El Hierro – amusingly termed “jacuzzis” by many readers. On the right is a thermal image of the jacuzzi showing just how warm the ocean water has become due to the eruption with is likely sources at least 50-100 meters below the ocean surface.
As you can see, some of the ocean water on the edges is 25°C or colder while in the middle of the “Jacuzzi” (video), the ocean water is at least 35°C – that is a ~10°C change in the ocean temperature. Now, remember, that is a column of ocean water maybe 10 meters across (a bit of a wild guess on my part) and 50-100 meters deep. Rough estimate of the ocean of water in the column at any given moment might be 3900 to 7900 m3 of ocean water. It takes a lot of heat to warm up that much water, but erupting basalt/basanite might be as hot as 1100°C to 1200°C – so raising seawater temperature 10°C in that relatively small volume of water isn’t too hard. As the eruption becomes shallower, the jacuzzis will likely be the source of explosive phreatomagmatic (water and magma) eruptions – some area look close to this (see below).
There are also some new images of the floating pyroclastic chunks that have been coughed up during this eruption – and they continue to look as strange as they sound (see below) with a mixture of light rhyolite/phonolite that is highly vesicular (filled with bubbles) and dark basalt/basanite (that is also full of bubbles). There is an unsubstantiated report of a “big rock” being ejected from the eruption, but no image (or size) so far.
So far it seems that the change from submarine to Surtseyan eruption has slowed at El Hierro, but we’ll keep an eye on whether the eruption begins to break the surface if magma continues to flow.