Last Known Eruption
1y 22d 15h 39m 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
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.