| Note ID | Start Time (US/Mountain) | End Time (US/Mountain) | Entrant | Note |
| 38563 |
21 Apr 2025 @ 1500 |
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skibumbrendan |
I went to check it out while hiking to Black Sand Basin. While I was next to it, I felt the ground shake like an explosion went off under my feet. Then, it aggressively started to boil. It was super weird. I've never felt something like that in all the time I've spent in the park, so I figured it was noteworthy. |
| 36746 |
04 Sep 2024 @ 1415 |
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kc |
4 ft. boil |
| 36744 |
04 Sep 2024 @ 1322 |
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kc |
Nice thumps and boils! |
| 36544 |
25 Aug 2024 @ 1140 |
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BrianR |
Only one weak thumping episode with a weak boil in the 15 minutes of observation. There is a 2ft log floating in the pool |
| 35181 |
13 Jun 2024 @ 1547 |
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CrisG |
thumps again at 1551 |
| 33117 |
19 Dec 2023 @ 1507 |
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mhreed |
Activity appears unchanged. Clusters of thumps at variable intervals (on the order of minutes) and variable strength. |
| 28212 |
11 Sep 2023 @ 1104 |
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Pholli |
black sand pool had an eruption of ~5ft following a very large thump! |
| 26906 |
08 Jul 2023 @ 1450 |
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nails |
Thumping |
| 26877 |
07 Jul 2023 @ 0847 |
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nails |
Thumping |
| 26343 |
15 Jun 2023 @ 1554 |
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CrisG |
thumping |
| 26193 |
09 Jun 2023 @ 1423 |
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CrisG |
thumping |
| 23711 |
10 Sep 2022 @ 1549 |
10 Sep 2022 @ 1603 |
ThomasR |
Strong thumps at 1550 and 1600 with large boiling up to approx. 1 foot. Smaller boils with weak thumps in between. |
| 19427 |
10 Sep 2021 @ 1201 |
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CrisG |
thumping |
| 19062 |
25 Aug 2021 @ 1520 |
25 Aug 2021 @ 1550 |
BrianR |
5 good thumping episodes, one with 4 ft boil |
| 18437 |
15 Jul 2021 @ 1658 |
15 Jul 2021 @ 1708 |
nails |
Thumping. |
| 18136 |
25 Jun 2021 @ 1001 |
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CrisG |
great thumping with nice boil at 1001 |
| 18166 |
25 Jun 2021 @ 1001 |
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CrisG |
great thumping with nice boil at 1001 |
| 16207 |
20 Sep 2020 @ 1743 |
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DanS |
Thumps and vigorous multipoint boils |
| 16151 |
17 Sep 2020 @ 1037 |
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kc |
7 ft burst in the middle of Pool. No thumps prior. |
| 16111 |
13 Sep 2020 @ 1610 |
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Graham |
Watched for 15m and no noisy thumps. Could feel some vibration on the railing. Sinter rim is dry indicating no high water. |
| 14979 |
14 Jul 2020 @ 1033 |
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nails |
Thumping |
| 14098 |
23 Jan 2020 @ 1144 |
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Graham |
Big thumps 1144, 1150, 1151, 1157 with big boil. |
| 11477 |
01 Jun 2019 @ 1432 |
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kc |
Almost entire pool burst violently to about 7 feet. Several big chunks of edge broke off. Total surprise. Thump happened as it was calming. |
| 11388 |
27 May 2019 @ 1515 |
27 May 2019 @ 1549 |
StephH |
Good thumps and bubbles every four to seven minutes. |
| 10796 |
25 Dec 2018 @ 1500 |
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Janet Jones |
Visitor report that mild thumps were happening every 3-5 minutes. |
| 10005 |
03 Sep 2018 @ 1230 |
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BobInSLC |
6-8 foot boil, after 45 minutes of waiting. thumping every 4 minutes or so. |
| 8410 |
02 Jun 2018 @ 1026 |
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kc |
Wide boil over 12 feet. Broke off multiple big chunks of edge. Was preceded by a mild thump. |
| 8407 |
02 Jun 2018 @ 0720 |
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steve |
Black sand pool is less active. I observed it from 0720 to 0752. I had no thumps until 0737 when I had 3 thumps followed by a boil. Just after that was one thump followedby a stronger boil. At 0745 there was one thump and a boil. At 0747 was a thump with no boil. At 0750 was a strong boil without a thump. Then at 0751 was a strong thump with no boil. |
| 4053 |
06 May 2017 @ 0957 |
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sfavor |
intermittent boiling. very nice shade of blue today. |
| 2786 |
24 Apr 2016 @ 1448 |
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User34 |
Thumps and heavy boiling |
| 2747 |
17 Apr 2016 @ 1145 |
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mhreed |
Thump cycles every 1-8 minutes, with one exceptionally loud cycle causing boiling to 2+ feet. |
| 2166 |
20 Aug 2015 @ 1013 |
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Choward |
There was a tree trunk floating in the pool. thumps every 2-3 minutes. |
| 1188 |
08 Jul 2014 @ 1200 |
08 Jul 2014 @ 1800 |
JSJ |
Black Sand Pool is still having relatively frequent subterranean thumping, followed by moderately small to moderately large roiling in Black Sand Pool - observed mid-afternoon on 8 July 2014. |
| 1067 |
11 May 2014 @ 0000 |
11 May 2014 @ 2359 |
WillBoekel |
Still nicely thumping :) |
| 1217 |
02 Jun 2013 @ 0000 |
02 Jun 2013 @ 2359 |
JSJ |
Black Sand Pool - moderately frequent subterranean thumping. Each thumping event was followed by energetic roiling-boiling at the surface of the pool, lasting for about 15 seconds or so. |
| 15829 |
31 May 1997 @ 0827 |
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JarnoO |
murky H2O; visibility ≤1ft |