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97564
From: ao, [DNS_Address]
Subject: Iceland’s Reykjanes Peninsula is primed for another eruption.
Here’s a recent interferogram spanning Dec 21 to Dec 29 and showing the amount of uplift over the newly emplaced magmatic system since the cessation of activity on the 20th. I have yet to see any reference to the scale of their rings, but here, with data from the same source, I'm used to one cycle of colors being equal to 1.65 centimeters (or 0.65 inches) rise or fall over the time bracketed by the two dates. Though I've see outputs of data associated with this event where there’s only one cycle of color and a scale bar, this source presents what I infer are the standard but without a reference. As folks that follow such things know there have now been four eruptions in the area, and each has had its own unique characteristics, although the first three were in many ways similar, the most recent has changed considerably. Early on, during the onset of all this activity, it was noted that this new series is sourced from the underlying mantle plume (hot spot) rather than magmas associated with the spreading apart of the North American and Eurasian plates. At that time it was speculated that a new shield volcano would take shape over the coming years, decades, centuries, and what we are seeing now is but the tip of what’s to come. Interestingly the first eruptions in this series originated, the magma accumulated and erupted from, a strikingly deep point, more or less 10 kilometers below the surface. And, the lavas that were erupted we hotter, and denser, and not as gas rich, as I am accustom to in Hawaii. One might recall the way the first eruption took a long time before it got to a gas rich fountaining phase. It had fountains, but for the most part lava streamed out of the ground. And that same pattern, sourced from deep, hotter, denser, and not as volatile, repeated with the volume and duration of each event diminishing over time. And then this new eruption started, and instead of rising from the same depth all the way to the surface the magma stopped along the way. And the lightbulb went off, well yeah, of course the system is going to build a shallow magma chamber. Where the first three events required the energy to break a path through the crust, now that the earth is shattered, fracture, loosened, by the repeated build up and release of pressure, now the magma can rise to the surface in a more natural way. Magma, lava as it surfaces, is driven, the energy that it takes to move is derived from the expansion of its parts, that once set in motion (by whatever melted it in the first place) will not cease until it reaches a state of equilibrium with it’s environment. Within the earth the expansion pushes the surrounding environment aside, and because the magma as it expands becomes, by volume, lighter than the surrounding environment, it rises. The amount of magma that accumulates and the distance it rises is equal to the resistance it encounters. As such the earlier phases of activity had to accumulate enough energy to break through a lot more rock. And when they did, they didn’t have enough time, or space, to decompress as they rose to the surface. With the fourth phase of activity, the pre-eruptive sequence began similar to the first three in that it originated from the same depth, but instead of accumulating the same amount of magma before it started, and rising directly to the surface, it started earlier and then it stopped at about 3-4 km below the surface, and accumulate the energy it would use to rise to the surface. When this latest eruption finally surfaced it wasn’t fooling around. The stop along the way allowed the magma time to continue to expand so it was lighter, cooler, and it was now, unlike when it was sourced directly from depth where the pressure is too great, it was filled with gas right from the get go. And the expanding gas added the energy it took to break open and flood that fissure with those spectacular fountains. But it was very short lived. Since the end of that phase the magma continues to accumulate at the shallower depth. And will probably cycle in fairly short order. As it is, right now, as much magma as was erupted has been replaced.. so if things were to repeat themselves then we might think there's soon to be enough energy to erupt again. Maybe even within days.. |
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[97573]
97573
From: chaskuchar@stcharlesmo, [DNS_Address]
Subject: Re: Iceland’s Reykjanes Peninsula is primed for another eruption.
| interesting |
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None
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