Last Known Eruption
3y 147d 6m ago

Latest Eruptions

Eruption DurationInterval
03 Oct 2020 @ 0848 wc4y 83d 15h 11m
12 Jul 2016 @ 173711d 21h 32m
30 Jun 2016 @ 200530d 1h 25m
31 May 2016 @ 18403h 41m
31 May 2016 @ 14595m 26m
31 May 2016 @ 1433423m
31 May 2016 @ 1410527m
31 May 2016 @ 1343323m
31 May 2016 @ 132026m
31 May 2016 @ 125423m
31 May 2016 @ 123142y 277d 20h 52m
27 Aug 2013 @ 153914y 310d 2h 7m
25 Oct 1998 @ 123251d 23h 8m
03 Sep 1998 @ 1424 ie2y 6d 22h 28m
27 Aug 1996 @ 1556 ie227d 23h 37m
12 Jan 1996 @ 1519 ie23h 43m
11 Jan 1996 @ 153625m
11 Jan 1996 @ 15112h 52m
11 Jan 1996 @ 12195d 3h 12m
06 Jan 1996 @ 09074d 21h 44m
01 Jan 1996 @ 11232h 0m
01 Jan 1996 @ 09233d 22h 12m
28 Dec 1995 @ 111125m
28 Dec 1995 @ 10461d 1h 30m
27 Dec 1995 @ 091621h 6m
26 Dec 1995 @ 1210 ie33m
26 Dec 1995 @ 11372h 1m
26 Dec 1995 @ 0936 ie21h 33m
25 Dec 1995 @ 120324m
25 Dec 1995 @ 11393d 17m
22 Dec 1995 @ 112217m
22 Dec 1995 @ 1105 ie17m
22 Dec 1995 @ 1048 ie1d 35m
21 Dec 1995 @ 1013 ie53m
21 Dec 1995 @ 092023h 48m
20 Dec 1995 @ 093219h 50m
19 Dec 1995 @ 13422h 50m
19 Dec 1995 @ 105214m
19 Dec 1995 @ 1038 ie20h 20m
18 Dec 1995 @ 1418 ie19m
18 Dec 1995 @ 135910m
18 Dec 1995 @ 13491d 1h 43m
17 Dec 1995 @ 120614m
17 Dec 1995 @ 115221h 40m
16 Dec 1995 @ 141213m
16 Dec 1995 @ 13591d 2h 32m
15 Dec 1995 @ 11271h 59m
15 Dec 1995 @ 0928 ie49m
15 Dec 1995 @ 08395d 22h 6m
09 Dec 1995 @ 103321h 40m
08 Dec 1995 @ 1253 ie1y 185d 2h 23m
06 Jun 1994 @ 11307d 23h 35m
29 May 1994 @ 1155262d 18h 52m
08 Sep 1993 @ 170321d 2h 11m
18 Aug 1993 @ 145221m
18 Aug 1993 @ 143129m
18 Aug 1993 @ 140239d 5h 27m
10 Jul 1993 @ 0835268d 13h 58m
14 Oct 1992 @ 1837 ie71d 22m
04 Aug 1992 @ 18151d 21h 58m
02 Aug 1992 @ 2016:5011m 38s
02 Aug 1992 @ 2005:1211m 38s
02 Aug 1992 @ 1953:3411m 25s
02 Aug 1992 @ 1942:0911m 50s
02 Aug 1992 @ 1930:1911m 22s
02 Aug 1992 @ 1918:5712m 7s
02 Aug 1992 @ 1906:507h 32m 35s
02 Aug 1992 @ 1134:1512m 5s
02 Aug 1992 @ 1122:1012m 20s
02 Aug 1992 @ 1109:5012m 20s
02 Aug 1992 @ 1057:3011m 34s
02 Aug 1992 @ 1045:5616m 21s
02 Aug 1992 @ 1029:3511m 35s
02 Aug 1992 @ 1018:0012d 16h 55m 11s
20 Jul 1992 @ 1722:4910m 16s
20 Jul 1992 @ 1712:3310m 33s
20 Jul 1992 @ 1702:009m 7s
20 Jul 1992 @ 1652:5319d 20h 49m
30 Jun 1992 @ 200311m
30 Jun 1992 @ 195211m
30 Jun 1992 @ 194111m
30 Jun 1992 @ 193010m
30 Jun 1992 @ 19207d 5h 55m
23 Jun 1992 @ 13254d 1h 58m
19 Jun 1992 @ 112712m
19 Jun 1992 @ 111522m
19 Jun 1992 @ 105312m
19 Jun 1992 @ 104110d 17h 20m
08 Jun 1992 @ 172113m
08 Jun 1992 @ 170812m
08 Jun 1992 @ 165613m
08 Jun 1992 @ 164311m
08 Jun 1992 @ 163212m
08 Jun 1992 @ 162013m
08 Jun 1992 @ 160715y 347d 21h 39m
29 Jun 1976 @ 1828 ie3h 28m
29 Jun 1976 @ 1500 ie1h 35m
29 Jun 1976 @ 1325 ie1y 7d 20h 7m
22 Jun 1975 @ 17181h 47m
22 Jun 1975 @ 15311y 317d 18h 59m

Interval Statistics

Interval Count100
Min9m
Max15y 347d 21h 39m
Mean172d 5h 24m
Median1h 41m

Latest Notes

Note IDStart Time (US/Mountain)End Time (US/Mountain)EntrantNote
33945 28 Jan 2024 @ 0944 --- JarnoO (wc) Water level noticeably lower. Vertical edge visible, with no water even touching the white geyserite deposits on the shore. North Sister has a yellowish hue to it in the Mugwump - MYR-1 - Little Brother area; Three Crater, the unnamed southern vent of North Sister, and Middle and South Sisters are still pale blue.
25259 28 Apr 2023 @ 1248 --- JarnoO (wc) Of North Sister, only Three Crater still has blue water, the remainder (including the unnamed southern vent, which had blue water on the 17th) is orange. Middle and South appear to still have blue water.
25176 17 Apr 2023 @ 1315 --- JarnoO (wc) Aside from Three Crater and the unnamed southern vent of North Sister, North Sister has orange water.
22774 22 Jul 2022 @ 1151 22 Jul 2022 @ 1159 JarnoO (wc) Northern part of North Sister (from Mugwump to just north where Little Brother's channel joins the pool) rainbow-colored in the most literal sense. Little Brother itself still erupting every minute or so, remainder of the North Sister pale blue. A few minutes later the whole pool was brought into view, which is also pale blue.
18499 18 Jul 2021 @ 1305 --- JarnoO (wc) Mugwump to Little Brother to north rim area is completely green and possibly lined with yellow at the edges - either way a pretty sight. Three Crater area and remainder of North Sister has a teal-ish color to it. Did not see the color of Middle and South Sisters.
16387 10 Oct 2020 @ 1156 10 Oct 2020 @ 1200 JarnoO (wc) Two conewalkers. 1156:41 one of them came from between the North Sister-Basin Spring trees and headed out of frame (maybe for runoff pictures or Basin Spring itself). Back in frame 1157:00 and headed between the trees again. 1157:30 the other one headed straight for North Sister at Mugwump's side, with the other one joining 1½m later. It appears both were capturing "that one video". Both later headed behind a tree blocking direct view of the southern tip of North Sister. They later headed for safe ground @ 1159:48 and started running as well, with them reaching the road just 15 seconds later.
16322 03 Oct 2020 @ 1424 03 Oct 2020 @ 1425 JarnoO (wc) Two conewalkers touched water twice of North Sister's pool at Mugwump's side. Were still at the pool's edge when the cam panned to Castle @ 1425, but gone by the time Mugwump had its 1431 eruption.
15668 21 Aug 2020 @ 1545 21 Aug 2020 @ 1548 JarnoO (wc) Conewalking at Three Sisters in progress. Two people came within a mere foot or 15 (originally estim. 2-3, later revised based on satellite imagery) of North Sister, at Mugwump's side. Back on safe ground early 1548.
7727 21 Oct 2017 @ 1315 21 Oct 2017 @ 1450 DanS No eruptions in Three Sisters group 1315-1450.
7418 26 Sep 2017 @ 1253 --- Tara Bacteria has returned to the Mugwump side of North Sister. Middle Sister remains active.
5220 22 Aug 2017 @ 1040 22 Aug 2017 @ 1150 Tara Middle Sister is active today and was probably active prior to this based on observations from me, Rocco Paperiello, and David Schwarz, who saw one eruption on 8/21/17. Middle Sister eruptions consist of a single burst that may vary in height from 2 to 8 feet. Mugwump has been inactive for a number of days but is still hot. MYR-1 has been seen boiling but no eruptions have been reported. Three Crater is still frequent and sometimes having energetic eruptions to as much as 6-8 feet.
4880 11 Aug 2017 @ 1220 11 Aug 2017 @ 1321 JSJ Overflow from North Sister's basin caused by splashing eruptions of Three Crater Geyser. Trickling overflow also occurs intermittently between eruptions through a border notch just north of Mugwump Geyser.
4873 10 Aug 2017 @ 1710 --- Tara Something is erupting in North Sister that was creating some overflow as of 8/8/17, though less runoff than when Mugwump was active in 2016. The bacteria in Mugwump was present at that time but is now gone. i have yet to catch the erupting feature so I am not sure if it is Mugwump, MYR-1, or something else.
3496 14 Aug 2016 @ 1733 14 Aug 2016 @ 1751 JSJ Well-developed steamnado over the Three Sisters Spring complex at 1733. Another one at 1751.
3005 07 Jun 2016 @ 1708 07 Jun 2016 @ 1711 JSJ Heavy pulsing event from North Sister Spring (= vent at 44°, 27' 37.08" North latitude, 110° 50' 12.71" West longitude) from 1908 to 1911.
15178 23 Jan 1996 @ 0000 23 Jan 1996 @ 2359 JarnoO near full
15177 22 Jan 1996 @ 0000 22 Jan 1996 @ 2359 JarnoO vents almost joined by pool
14456 31 Dec 1995 @ 1200 --- JarnoO not observed since 12/28; {generic time}
497 06 Oct 1975 @ 0000 06 Oct 1975 @ 2359 BoekelUpload Three Sisters area springs;1st overflow since 6/30/75 Tremor
No attachments for this geyser.
Baseline does not exist.