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Observations for 2023 September 06


Got a late start to another busy day. Arrived at Haukadulur and parked in the northeast parking area, away from the tourist traps and bus parking areas. Almost immediately saw an eruption of Strokkur from our car. We got long series of eruptions, much on video.

A few years back I came across a recent paper published in Geophysical Research Letter titled "Eruption Interval Monitoring at Strokkur Geyser, Iceland". One of the most interesting pieces of information in it is that over the course of a year, their monitoring recorded 73466 eruptions, and that 23331 of those eruptions had more than one burst. There was even a single six burst eruption recorded. (Based on the statistical model, a seven burst eruption should also occur ever 12 years or so.) Also, the time between eruptions correlated to the number of bursts, but not to the number of bursts in a subsequent eruption.

We saw mostly one burst eruptions from Strokkur. There were a few with two bursts, with the second coming as soon as the first burst completed, to as much as 20 seconds later. (It's annoying when you stop the video only to miss the second burst becuase it took so long.) We only saw one three burst during the day, which based on the previously mentioned paper, was expected for the amount of time we were there.

Strokkur eruption. 2023-Sep-06:10:34, 2B. Video by H.Koenig.

The sizes of the eruptions varied considerably. Up close, some were just "tall." From a distance, I think we saw several that were over 30 meters high. On the otherhand, some were disappointingly small. In one case, I doubt the height was over 4 meters. Looked like a Grand Boop. When there were two bursts, one of the bursts could be tall, but not both, unless it was one of the cases when it was more like a second jet developing through the first jet.

Intervals ranged from two to seven minutes after a one burst eruption, but most of those were three minutes or less. If there was a second burst, then the interval lenghtened out to seven to ten minutes.

Geysir was quietly overflowing. What was surprising is that it is developing a shelf along the edge of the crater, and the overflow terrace has developed scallops well down the hillside.

Didn't see much else. Alfaauga was active, and we saw a few eruptions. The pool over the vent fluctuates until boiling starts on the side, which leads into an eruption. The durations were from over two minutes (it was in eruption) to a single burst. Didn't try to get any intervals, as it is located on the main path between the buildings and Strokkur, which is a crowded, busy area. (And Strokkur had our attention.)

Littli and Smiður were perpetually spouting to about a meter, and up at the top of the hill, Haìhver, while spouting continuously, did seem to vary from almost quiet to bursting well over a meter high.

We finally left after over five hours and 52 eruptions of Strokkur seen.

Arrived at Hveravellir about an hour and a half before it got dark, and after taking care of necessities like eating and checking in, had maybe half an hour of light to do a quick investigation. Nothing there erupts to much more than a meter, and the intervals are extremely short, but in that time saw close to two dozen eruptive vents and features, including at least three or four geysers. There was one feature erupting about every minute, draining after the eruption. The pool of Rauðihver would pulsate over the vent, then have a couple or so bursts. The tallest feature was a pool south from Öskurhóll, which was splashing almost two meters high at times. Should have plenty of time to investigate these further tomorrow.


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Observations for 2023 September 05


The first stop of the day was at Hveradalir, located to the north of Route 1 west of Hveragerði. This is an area of frying pans, mudpots and fumaroles with a walkway through it on the edge of a well developed geothermal powerplant.

The walkway crosses a lagoon, which the information sign says is artificial. After that, the next main attraction is a large mud pot upslope from the walkway which has built a several meter high cone,and was in the process of occasionally flinging mud onto the walkway. Beyond that is a powerful fumarole and an eruptive feature. The latter is active inside a stone and cement box with a hole in the side which allows water to escape the box. The fumarole is loud, and I couldn't see any actual steam coming from it, a sign that it is highly superheated. To get to the end of the walkway requires passing through the fumarole' steamcloud, a slightly scary experience.

Hveradalir mud pot
Hveradalir fumarole and box spouter

On the way back along the walkway, at the point where the walkway first crosses over the lagoon, we noted a small vent bubbling away. This activity was intermittent, and every minute or so it would increase to the point some splashes were getting to about 5cm high. Then the activity would cease for a few tens of seconds, only to start the cycle again.

The next stop was the Hveragerði Geothermal Park. I wasn't expecting much here as I knew about the changes after an earthquake 15 years ago when most of the pools empty and dried up. What I didn't expect was that there is an active, erupting feature there. It's probably artificial, and erupting borehole, but it is still a fascinating feature with a distinctive and unique eruption.

We saw four eruptions over about an hour period, the interval was about twenty minutes. There's just some rocks piled around the vent, probably the remnants of a borehole, and there is splashing about 1/2 meter high begins about five minutes after the eruption. This activity gets a bit stronger over then next fifteen minutes, but not by much. Suddenly, one of the splashes triggers an eruption, which lasts at most five seconds. There is a roar as water is expelled up to ten meters high, and just as suddenly drops down to nothing. According to the little map we got at the entrance, this is Eilifur Goshver/Eternity Geyser.

There's a second active feature, a small pool which splashes away and is located next to the cafe/greenhouse entrance to the park. It looks like it's probably a natural feature, as I didn't seen any evidence of concrete or other building materials around it. When I recorded the last eruption we witnessed, I decided I wanted a distant shot, so was standing about 25 meters from the Eilifur with the small pool in the foreground. As the eruption started, the pool suddenly increased in activity and force and the splashing was well over a meter high for just as long as the eruption lasted. Then it reverted back to its previous splashing.

Eilifur Goshver/Eternity Geyser at Hveragerði Geothermal Park

The next stop was a thermal area up on the hillside north of town. Over about 100 meters is a line of mudpots and acidic springs. At the northern end are signs with names for some of the features: Reykjamóri, Leirgerður and Skjálfti. Based on these, I think it was Skjálfti that was having eruptive episodes. This feature contained opaque, brownish red water which was boiling up and splashing from every locations. Every minute or two the activity would get stronger in one of the vents, and the splashing would be one or two meters high.

Skjálfti north of Hveragerði

The final stop of the day was to see Littli Geyser at Gamla Laugin/Secret Lagoon in Fluðir. It, along with several other boiling springs, are on the grounds of the spa and provide some of the waters used.

The vent is maybe 25 cm across, and there are two deeply incised runoff channels leading from it. Most of the time there is water flowing down one of these channels, and the vent is in a constant agitation to maybe 25cm high.

Based on an hour and a half's observations, Little has three sizes of eruptions. The minor is shorter and not as tall, and the vent almost immediately resumes overflow and splashing. The larger eruption lasts longer, is taller and the vent drops below overflow and refills over about a minute. The major eruption is the tallest and longest, with some of the eruption getting to about four meters high. After the eruption the vent drains with the usual array of sounds.

All but one series consisted of two minor eruptions about two minutes apart, and then two minutes after that, a major eruption. It takes about five minutes between a major and the next minor. The time we saw the intermediate eruption, it was after the first minor eruption, and it was followed by another minor and then a major.

Littli Geysir at Gamla Laugin/Secret Lagoon in Fluðir

Near Litli are some deep boiling springs. One had collapsing bubbles at the bottom, maybe 1/2 meter below the surface. There's also another boiling spring, Vaðmálahver between the spa and the Litlà-Laxa River.


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Observations for 2023 September 04


Visited our first Iceland thermal features today. Gunnuhver sits in the middle of a production geothermal field. The activity consists of a perpetual spouter which has jets of water up to 8 meters high. The vent is obscured by the remnants of a boardwalk which it destroyed earlier this century.

Nearby is a large mound of siliceous sinter. It's old and heavily eroded, but there are still rock fragments featuring flow patterns and terracettes.

To the west of the recent volcanic activity is Seltún, south of Kleifarvatn. There's a large parking lot along with plumbing facilities which may or may not be open.

Next to the parking lot is a large muddy spring which was erupting gray water to about 1/2 meter. A boardwalk trail continues up the hillside past more large acid sulphate springs and numerous small spouters.

Across the road is another small thermal area consisting of two large mudpot craters. They were more of a pool than a mudpot, probably thanks to the heavy rains in the couple of days prior to our visit.

Behind the plumbing facilites is an old geothermal well. When I first looked at it, there was occasional noise coming from below ground as it there was some sort of eruption going on. About twenty minutes later, I stopped by again and the feature was quiet.


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Size Comparison of Thermal Areas


While preparing for another attempt at visiting the thermal areas of New Zealand and Iceland, as well as the western U.S., it occurred to me that it shouldn't be too difficult to compare the sizes of the various area. In The Transactions Vol. 7, T.Scott Bryan does a comparison of the size of some thermal areas. He just presents some basic line drawings, while I figured I could download satellite maps set to the same scale, which would give a lot more details.

The two areas I couldn't include completely are the Upper and Lower Geyser Basins. They are huge compared to everywhere else. Instead I limited them to Geyser Hill/Old Faithful areas and the Fountain Paint Pots. The only other thermal area presented here that doesn't quite fit is Waimangu, where I wasn't able to include the lakeside thermal area.

Update: Added Mickey H.S., and Steamboat Springs.