Who doesn’t dream of escape? Perhaps you have a mind-numbing job, a repressive social environment, or a damp and cold house. It may be an escape in (and from) a computer game, trying to reach the exit while being chased by your real-time friends becoming virtual enemies. Sometimes we need to escape from a dream, an unrealistic and damaging expectation of life. We may look forward to a better future, while forgetting that our life is the here and now. Terry Pratchett wrote about it in a children’s book, Only you can save mankind. It is about games and dreams as escapism from real life. The children have only vaguely fleshed-out personalities: they are forgotten by a world that is dealing with more important things. They come to life only in their video games, and it provides their ultimate escape.
Volcanoes too go for escape. The purpose of lava is to recreate the land: it should not be locked up inside a crater. The local people see things different, of course: it is a damaging inconvenience to have your property being claimed by lava, just for the purpose of recreation. And us, volcano watchers, are in two minds. Like Jonny in the book, we see both the game of lava and the events in the real world. It excites and frightens in equal measure.
The Geldingadalir eruption was exceptionally well placed for the purpose of isolation from the real world. The cone erupted on the side of an elevated plateau, Fagradalsfjall, in an area where a number of valleys had been eroded into the ancient lava shield. The valleys vary in depth, but have in common that they lack a direct outlet. Geldingadalir consisted (note the past tense) of two valleys with a small ridge in between. The volcano first erupted on this ridge. It was presumably a pressure ridge as it was located on – but perpendicular to – the Reykjanes fault. The lava flows remained confined to these two valleys. But they were also within walking distance of the main road. You can’t get more tourist friendly than that. In this perfect lava video game, there was to be no escape for the lava, and civilization was saved.
After a while the eruption upped its sticks and moved to higher ground next to Geldingadalir, from where it eradicated the original valleys and began to fill two others: Meradalir and Natthagi. Natthagi is a deep lying valley reaching for the coast, with an outlet only a little higher than the bottom of the valley. Escape from here seemed inevitable, but it was stopped by a combination of Icelandic engineering (the wall – from now on an essential part of any Simcity game) and volcanic temper (it stopped erupting in this direction). This saved – for now – the coastal road, a historic farm, and the newly build wall. The flows continued into Meradalir, a deep double valley separated from the lowlands beyond by a ridge. The steep ridge comes from an ancient eruption underneath the ice of the ice age – we think 35,000 years ago, based on the movement along the fault. This ridge became a useful location to put viewing cameras. The lava slowly filled up the valleys but it had a long way to go. The confinement remained.
But if the eruption continues, it is inevitable there will be an escape attempt. There are some places in Meradalir where the natural barrier is potentially overtoppable. At the moment the lava no longer seems to reach these places, because of a somewhat lower eruption rate and perhaps because of increased viscosity of the flows – they don’t look as runny as before. In the last week some of the flows have been notably sluggish. But at other times it is flowing like there is no tomorrow.
Assuming the eruption continues, where would an escape be most likely to happen? Where should we send the engineers to game a solution? Where are the danger points? And which property is ok for building a hotel?
To flow where none have flowed before
Let’s first look at the current extent of the flow. The image below is a preview of a Skysat (Planetlab) image obtained August 14, during a period of clear weather. (This probably counts as an extreme weather event in Iceland.) The image itself is high resolution (0.7 m/pixel) but is commercial and requires a hefty payment – after all, these satellites are not free to build, launch or operate. The preview shown here is of much lower resolution, but it gives a good indication of the most recent size of the lava field.
In this image, some of the hills look dark enough to be confused with lava, because of the shadow. The sun was fairly low in the southeast when this image was taken. In Natthagi, the dark and smooth-grey is lava, and the stripy lighter grey is the shadow of the ridge on the right.
For a while lava flowed into Natthagi. The lava came close to the exit from this valley but had not quite reached it when the volcano changed direction. Over the past weeks, the eruption has left Natthagi alone and the lava has instead gone east, into Meradalir. Not all the lava went down: a fair amount remained close to the cone and build up an embankment and a shield. The embankment contains the main outflow channel. The new parasitic vent is growing on the side of this embankment. To the east of the cone the lava shield has been rapidly rising. This rise has already eradicated one hill, which first turned into an escarpment with the lava lapping against the ridge, and then was swamped by overtopping lava. The transmitter which had been mounted on this hill became the subject of a rescue attempt, not entirely successful. The rest of the lava has been flowing into Meradalir, first into the western valley and later extending into the eastern one.
The best map of the lava field is from http://www.viewsoftheworld.net/?p=5783, dated to 27 July. (The flow has thickened since but expansion has been very limited.) To the east and north of the lava flow (the ‘hraun’) is the old shield of Fagradalsfjall (which we estimate at 100,000 years old, dating from the previous interglacial). (Note that our ages come from assumptions on what lines up with what across the Reykjanes fault, and should be taken with caution and not as scientific fact.) This fjall acts as a block. Various other ridges contain the flow but these have some gaps. I have indicated the potential routes where the lava may flow through the gaps and perhaps escape. The coast lies waiting.
The current flows are down the slope into Meradalir. Natthagi is not being resupplied. The picture below is a screenshot from one of the many drone views. It shows how well developed the cone has become. The route to Natthagi would start at the back, to the south, were the cone is highest and best protected. There is no sign that a collapse here is likely. The outflow is the weak part of the cone, but any potential break here (perhaps related to the current parasite vent) will still feed towards Meradalir. A reinstatement of the Natthagi supply route can not be excluded, but it does not appear likely or imminent.
There have been some excellent views of the lava flows recently – as well as some very foggy days. Below is a combination of daytime view of the field on Aug 15, and a night-time view of the lava flows. The hot flows are white. Mostly it follows the northern edge of Meradalir, fed by the embanked lava river coming off the cone. This flow first runs southeast and turns northeast where it enters the slope down to Meradalir. This turn is a memory of the transmitter hill which blocked this direction before being overtopped. There is now also a flow going south and turning southeast. Finally, there has been a small flow going northwest, visible on some satellite images, but no other indications that we are missing lava.
The way out
Let’s go through the possible escape routes via Meradalir. For an overview of Meradalir, this Gutntog drone video covers it well and it is worth watching.
Starting along the northern edge, lava has entered a small canyon between two ridges. The lobe is just outside of the cameras: the Meradalanuknur_SV camera is on the adjacent ridge but on the wrong side. The following image is taken from the drone video, showing this lobe – and lava flowing past it.
The Jul 27 map shows that the lava had at this time reached the contour level at 140 meters. It has expanded further since dat date. This is evident in the overlay with the Skysat image of Aug 14: it is now approaching the 160 meters contour. The flow can expand further by about 1 kilometer if it reaches 170 meters. That is about the limit. The plateau beyond is at 200 meters: if it were to reach that height here, there would be serious outflows elsewhere. We can expect significant expansion of this lobe but not an escape.
North by northeast
A bit further east is a second lobe going north to northeast. It is running into a steep upward slope, requiring 60 meters of ascent, indicated by the arrow. This flow did not expand in the period 27 July to 14 August. The Skysat map and the July map overlap perfectly, following the 140 meter contour. However, a lava flow reached this area on Aug 15, when the flow expanded as indicated by the red hashed area. The area of the red arrow was out of sight of the camera. It may have expanded there as well. It seems plausible that the 150 meter contour had been reached here. However, the confining slope is too steep and high. This is not the way out.
The eastern valley – northeast
Next we come to the second valley of Meradalir. This is a fairly narrow basin running southwest to northeast. The lava has not expanded here between July 27 and Aug 14: the flows have not reached this second valley, possibly because the eruption rate reduced a bit in this phase. The current level is around the 130 meter contour. That is 45 meters above the original deepest point – in most of the valley the lava is currently some 35 meters thick, and in places more. (As an aside, at that thickness it will take a long time to cool down. Even after a month of down time, and a solid looking crust, most of the lava underneath may still be liquid. Don’t go there.)
This region has a number of potential escape routes which are coming into range.
Starting with the northeastern tip of the lava, there is a plateau further northeast at an elevation just over 150 meters, which is about 20 meters above the current level of the lava. This plateau is fairly wide and would give a large surface to expand into, of 500 by 500 meters, doubling the surface area of this second valley. Once it has covered this space, there is a path around the big hill to the east, where there is a shallow descent to the south. This escape route is slow, because of the wide area to be covered and because of the shallow slope.
The second valley – the routes south
There are three other escape routes from the valley, as indicated by the arrows. These are easier and more likely.
The clearest exit is in the middle of the valley. Here, the saddle in the confining ridge is less than 10 meters above the current lava surface. Crossing this saddle will bring the lava into a new valley running to the south-southeast, sloping down to the south. It is the lowest of the exits, but the saddle is narrow and this might restrict the outflow, at least for a while. However, it is the most likely path out.
The southern tip of the lava has two ways out. The lava here is at 125 meters elevation. To the southwest the saddle is 25 meters above the current lava; to the southeast the exit is some 20 meters above. These two exits have the advantage of being the shortest route to the coast and bringing a wider flow channel, but it is higher than the central way out.
Going out, may be some time
In conclusion, none of the three routes appear imminent because lava has not reached here for some time. Some outflow will happen here with a 5-10 meter rise in level, and a major outflow will occur if the level reaches 20 meters higher, to the 150 meter contour .This level has been reached in the western valley of Meradalir, but not yet in the eastern valley. If the lava flows reach this second valley again, the lava could reach this level quite quickly. The required volume is 1km by 0.5 km by 20 meters (the rough size of the eastern valley), or 0.01 km3. The eruption is producing that much in about 10 days. Of course only a fraction of the lava will reach far enough. Once it gets here again, a minor outflow may happen in a week and a major escape could occur in 2 months.
And that seems to be it: none of the available routes is likely in the near future. The nuclear option would be the flow being completely redirected away from Meradalir. However, a look at the contour maps shows that the old Geldingadalir and the valley-with-no-name (named Sydri-Meradalur on the map) are filled to between 210 and 230 meters, while the flow into Meradalir begins at 200 meters, which is considerably lower. Gravity favours Meradalir, and using the first law of physics (‘Einstein is always right’), gravity always wins. In Meradalir the flows should remain confined for the next month.
Does this mean the coast is clear? Not quite. The recent re-arrangement of the volcanic cone has indicated another possibility. Over the past month the embanked lava channel has channeled the flows largely to the northern side of Meradalir. But the new vent, and holes on the side of the cone and embankment are now providing a route that runs along the southern edge of wide slope into Meradalir.
It is visible on the image at the beginning of this post. It is a shorter route into the eastern valley, although so far it hasn’t reached that. However, the region along this side where the 150 meter contour has been reached has expanded to the entrance point of the eastern valley.
This opens a potential short cut. The new flow is coming down along the high hill where the contours drops from 200 meter to 150 meter. The hill ends at 180 meters. There is a passage at the 180 meter contour, in a place where the lava has already reached the 170 meters. It would not take much to enter this gap.
The arrows indicate the flow paths this could open up. It provides a shorter route into the eastern valley. It is not without problems: the gap is narrow, and may be higher or more restricted than apparent from the maps.
After the exit
An escape can therefore happen if the eruption continues as it is at the moment, perhaps by early Autumn. It brings the lava into a long, open-ended valley. It is still quite a distance from here to the coast. Progress may not be fast and the lava may get stuck if the flows are not voluminous enough, so that they solidify before getting to the exit. That would be the preferable outcome, of course, leaving both the virtual tourists and the locals happy, the former with some brilliant views, and the latter by keeping their property safe from recreation. Everyone wins in this game of life.
But if the flows heads for the coast here, it would be harder to stop it by building a wall. Simcity-Volcano has just become a lot more complicated.
Albert, August 2021