Watching “N.O.T. Geyser” grow at West Thumb

by | Dec 6, 2016 | Geyser Watch

This summer a new geyser broke out at West Thumb Geyser Basin just north of Thumb Geyser. People not familiar with geyser basins often assume that they’re fairly static, and that after all these years, we know much about how thermal features work. The truth is that we don’t know a lot about our world, even in Yellowstone.

New thermal features show up while others disappear or go dormant. Thermal energy shifts cause this.

So with this new geyser at West Thumb, the chances are that it’s not here for long as the energy may shift away from that area, but for now, it’s been fun watching this one develop.

Click on the photos to bring them up larger or hover over them to see the caption.


The location of this geyser inspired Ranger Ben Hoppe to give it an informal name of “N.O.T. Geyser” (North Of Thumb). Other informal suggestions have been given of “Waterfall Geyser” from a few visitors for the way the water has carved a pretty impressive channel that makes it look like a waterfall flowing into Thumb Geyser. Also suggested was “Slurry” (by Pat Snyder) in reference to how the water looks like slurry used in making ceramics. And a friend of mine suggested “Muddy Waters”.

Time will tell what it will end up being called – assuming it continues long enough for that to happen. It is likely that the energy will shift again and leave yet another hole in this upper area of West Thumb Geyser Basin.


“N.O.T.” Is located North of Thumb Geyser. As you stand on the boardwalk directly facing Thumb Geyser, it is at about 1:00 and is behind the Unnamed Thermal Feature (UTF) that’s to the right of Thumb Geyser.

Behind it has been a set of what were three joined pools (usually empty) that at the beginning of the summer 2016 season were separated from the vent that has developed into “N.O.T. Geyser” by a berm of dirt and grass. That is now gone and “N.O.T.” has joined the other pools.

Detail of a map of West Thumb Geyser Basin (Yellowstone Lake would be to the right, or east)
25 Sept 2014 - Thumb Geyser (left blue pool)


“N.O.T.’s” vent stood empty for most of the past decade that I have been tracking the changes at West Thumb through photos. The photo collection goes back to 2005, though I have yet to go through each visit to verify this. For now I’ve focused on the past three or four years.

19 Oct 2014 – Water was seen in “N.O.T.’s” vent, but it wasn’t overflowing into Thumb Geyser and the berm between it and the other joined vents was still in place. This rest of the photos show it empty as seen from the boardwalk.

2015 – no photos showed any water visible from the boardwalk.

2016this is when things get interesting.

Prior to the end of June 2016, no water was visible from the boardwalk in N.O.T

26 June 2016 – Water visible in “N.O.T.” as well as a bit of water in the three joined pools to the west of it. At this point, “N.O.T.” wasn’t connected to the other three joined pools – that berm of dirt and grass was still in place.

23 July 2016 – Water in “N.O.T.” was overflowing into Thumb Geyser, and it had connected with the other three joined pools. “N.O.T.” was sending up lazy bubbles. A small channel had been carved by the runoff channel into Thumb Geyser, but the water in Thumb didn’t look murky at all. As far as I can tell, this is near the start of the activity from “N.O.T.”

The UTF Next to Thumb Geyser is in the foreground. "N.O.T. Geyser" is the pool located behind it.
Thumb Geyser (in the foreground) 23 July 2016
"N.O.T. Geyser" 23 July 2016
"N.O.T. Geyser" 23 July 2016 as seen from the top boardwalk (closest to the parking lot)


12 August 2016 – Bubbling seen in N.O.T. and the runoff channel was slightly larger. The water in Thumb Geyser was slightly murky.

Other observations:

  • Dampness showed at the bottom of “Oil Slick”
  • No water seen in Ephedra.
  • Percolating Spring at least had steam coming from the vent at the bottom, but no visible water and I didn’t take any notes saying that it was gurgling that day.
  • The UTF across from Blue Funnel Spring was full, overflowing (with a rather large wet area to the north) and bubbling in two spots. Many of these have been basically empty since 2013.
12 Aug 2016 - Thumb Geyser, "N.O.T. Geyser", and the UTF Next to Thumb Geyser
12 Aug 2016 - "N.O.T. Geyser"

20 August 2016 – While in a class with the Yellowstone Association, we stopped by West Thumb where N.O.T. was boiling and splashing up 6 to 8″. The water in Thumb Geyser was murky and the pools immediately behind Thumb Geyser had mostly drained. No ‘high water mark’ showed in Thumb Geyser.

Other observations:

  • Dampness showed in Perforated Pool and the sun showed reflections of water on the wall inside the main vent.
  • Percolating Spring had water in the bottom as well.
20 Aug 2016 - The smaller pools behind Thumb Geyser drained and "N.O.T." Geyser was boiling.
20 Aug 2016 - Boiling in "N.O.T." Geyser.

21 August 2016 – Ben Hoppe reported seeing N.O.T. Erupt and there’s good reason to believe this very well could have been the first eruption; if not, then it was at least one of the first. When I arrived after the end of my class at 1830, the water in the crater was down 6-8″ below overflow, but water was still visible as seen from the top boardwalk.

Other Observations:

  • I visited West Thumb to find “oil” (not really oil, I think) on “Oil Slick” but perhaps this is the same phenomenon that gave rise to its nickname.
  • The UTF next to Thumb Geyser had milky colored water visible in it.
  • No visible water in Epehdra.
  • The water level in Blue Funnel Spring was below the line of orange microbes.
  • Thumb Geyser had muddy water with a higher white line showing where it had filled to.
21Aug 2016 - Thumb Geyser and "N.O.T. Geyser".
21Aug 2016 - A view of the "N.O.T. Geyser" area from the top boardwalk closest to the parking lot.

22 August 2016 – Went in this day specifically to sit in the area around Thumb Geyser, and never did see an eruption, though I only had a couple of hours to give to it.

22 Aug 2016 - Thumb Geyser
22 Aug 2016 - "N.O.T. Geyser" as seen from the top boardwalk

23 August 2016 – Ben Hoppe invested quite a bit of time and observed four eruptions 3 to 4 hours apart. Thanks so much to him for this valuable information!

25 August 2016 – I had met a friend at West Thumb where we caught the start of a major eruption that lasted longer than the hour time we had to stay there. The crater was empty when we arrived, and while I was checking on the surrounding area. The most surprising change was the drop in water levels in the UTFs above Collapsing Pool (and behind some trees). This could just be a coincidence, but the sudden drop is interesting to note.

Soon we could hear boiling from “N.O.T.” And within a couple of minutes, it quickly filled the crater with an eruption that must have started at depth.

It took 8 minutes before the eruption filled enough to start draining into Thumb Geyser. The milky colored eruption reached 3-4 feet high and was perhaps about as wide and seemed to only come from one vent.
• As the eruption continued, I noticed the water in Ephedra rose as did water in the UTF next to Thumb Geyser.
• There was a ‘high water mark’ in Thumb Geyser and after an hour of watching the eruption, it still had at least a foot to go to reach that mark. Since the time we had to watch was up, we left with the eruption continuing just as strong as when it had started.

25 Aug 2016 - "N.O.T. Geyser" as seen from the top boardwalk not long before the eruption started.
25 Aug 2016 - Thumb Geyser not long before the eruption of "N.O.T. Geyser" started.
25 Aug 2016 - A few minutes into the eruption of "N.O.T. Geyser" before it had reached overflow.


3 Sept 2016

Went in to see what was happening. “N.O.T.” did not erupt while I was there. But talked with Ranger/Paramedic Sam who had visited with a gal who was a ranger in the 1950s who said the pools around the Mimulus area were not there, but instead, it was a field (which would make sense with the old boardwalk shown from then). I asked my friend who was a ranger back then and he honestly doesn’t remember.

Other Observations:

The area on the south side continues to lose water, though the water in the Thumb Paint Pots area is still high – if not a bit higher than last visit.

  • Percolating has more water in it – and splashes up to 6″ or so.
  • “Oil Slick” has water in the bottom with bubbles rising in a couple of spots.
  • The sun was shining into “Footprint” – the far vent – and no water was seen in it.
  • Ephedra was empty.
  • Not was only sending up a bit of steam.
  • A small vent between the UTF Next to Thumb Geyser and the boardwalk had opened up (was full of dirt before).
3 Sept 2016 - Thumb Geyser area
3 Sept 2016 - "N.O.T. Geyser"


From the start of September, the reports came less frequently – but often once a day. Shorter eruptions were reported, possibly indicating a change to different behavior that’s not unusual with new geysers.

6 Sept 2016 – The eruptions observed by Ben Hoppe elicited this note from him:

1115 eruption: Noted that the eruption was very violent – much more so than recent eruptions. Estimated height 6-7′ at some points.


1940 eruption: Eruption was more vigorous than any I have observed. Saw one burst up to 5′. Usually quiet for a few seconds followed by periods of more intensity. Eruption ended at 1948.

This very well might have been when the eruptions shifted from the milky/light colored eruptions that only came from one vent to the darker, muddier looking eruptions that seemed to come from two vents.

18 Sept 2016

Heading in again for more observations of N.O.T. And caught a short eruption that started as I was at the Thumb Paint Pots spur on the boardwalk. Didn’t take many photos as I was explaining about the new geyser to some visitors.

  • The three-lobed spring at the top had water levels lower than I think I’ve ever seen in them. Ben said they drained on Friday (16 Sept 2016). Sam concurred it was sometime between Thursday and Friday, but was definitely down on Friday. He mentioned that they were actually back up a bit from the lowest level he saw.
  • Top Mud Pot was burping and then drained and changed to a hissing like a fumarole or steam phase. A mud pot geyser? Seemed to be behaving like one – filling, bubbling and then draining. I watched this twice and let Sam and Mike know.
  • Percolating was even a bit more full and still splashing up 6″ or so.
  • “Oil Slick” seemed to be at about the same level.
  • Perforated Pool was steaming.
  • No water visible in Ephedra from the boardwalk.
  • Blue Funnel Spring had more bits of microbe lining that had lifted.
18 Sept 2016 - Thumb Geyser, "N.O.T. Geyser" and the UTF Next to Thumb Geyser
18 Sept 2016 - Thumb Geyser, "N.O.T. Geyser" just after the end of the eruption - showing the waterfall of water into Thumb Geyser.


13 Oct 2016

  • Another trip in to document the small shifts at West Thumb. No eruption from N.O.T. while there.
  • “Oil Slick” has a few more inches of water and is boiling harder.
  • Somewhere across from Blue Funnel Spring, there’s something boiling below any visible level.
  • Water is boiling fairly hard in Ephedra at a low level.
  • Steam rising from the far vent of “Footprint” – think this is the first time I’ve seen that since it drained (in 2013?).
13 Oct 2016 - Thumb Geyser and part of "N.O.T. Geyser"
13 Oct 2016 - "N.O.T. Geyser's" crater as seen from the top boardwalk

23 Oct 2016

Stopped by West Thumb on my way back from a trip to the Upper Geyser Basin to check on things. We had good moisture since the last visit and quite a few thermal features had recharged and filled with more water, showing that surface water does make a difference. “N.O.T.” did not erupt while I was there.

  • Thumb Geyser was still full of muddy water.
  • Gurgling heard in Perforated, though the light was not right to be able to see into the main vent.
  • Percolating water’s seemed to be higher, and photos show the water level about 2-3″ higher.
  • Boiling continues to be seen in “Oil Slick”.
  • Boiling also still seen in Ephedra.
  • A Spot still sending up bubbles in Blue Funnel Spring.
23 Oct 2016 - "N.O.T. Geyser's" crater as seen from the top boardwalk


5 Nov 2016 – the last visit of the year that I took full documentation photos.

As I drove up, “N.O.T.” was in eruption. I caught the last 6 minutes. This eruption was quite dark and definitely coming up from two vents rather than just the one. Lots of steam with the cooler air temperature, but that, plus the lower light made for some nice photos.

  • Side ledge in Percolating is just above the water line now – and sizzling like a small frying pan. The bursts from the vent that’s now underwater still occasionally disturb the water surface.
  • Boiling in Ephedra still.
  • Bubbles still rising in Blue Funnel Spring – a bit harder than on the last visit.
  • Bubbles also seen in Seismograph Pool (probably not related, but a change, nonetheless).

6 Nov 2016 – just made a quick stop to see if I might be lucky enough to catch an eruption of N.O.T. No such luck. Took a few photos, but no notes.

Looking forward to any and all notes from anyone heading into West Thumb this winter.

5 Nov 2016 - "N.O.T. Geyser" in eruption
5 Nov 2016 - Thumb Geyser's water level after an eruption of "N.O.T. Geyser"
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