Last Known Eruption
3y 241d 11h 4m ago

Interval Statistics

Interval Count100
Min1m
Max1y 261d 20h 39m
Mean7d 7h 39m
Median3m

Latest Notes

Note IDStart Time (US/Mountain)End Time (US/Mountain)EntrantNote
17197 26 May 2021 @ 1800 26 May 2021 @ 1858 JSJ In very light roiling and/or light bubbling at 1800. Small, brief doming at 1858.
13099 07 Aug 2019 @ 1900 07 Aug 2019 @ 1926 JSJ No activity at all from Middle Sister, but I've seen pauses much longer than this recently. No other activity in the entire Three Sister complex, except Three Crater eruptions.
13083 06 Aug 2019 @ 1505 06 Aug 2019 @ 1808 JSJ All closed intervals. Occasional blipping or roiling in lieu of an eruption. All eruptions were single brief bursts, with one double burst. One or two were ~2-3 seconds in duration.
13054 05 Aug 2019 @ 1203 05 Aug 2019 @ 1341 JSJ All closed intervals. Some roiling and blipping events. All eruptions were single short bursts of varying sizes.
13027 04 Aug 2019 @ 1027 04 Aug 2019 @ 1625 JSJ All closed intervals. Under constant observation during this time.
12384 06 Jul 2019 @ 1305 --- DanS Domed water. Did not erupt.
9091 09 Jul 2018 @ 1145 09 Jul 2018 @ 1218 Micah Kipple Occasional bubbling vent just on the south edge of the crater towards south sister.
5288 23 Aug 2017 @ 1117 23 Aug 2017 @ 1155 Tara Under observation during this time, no eruptions.
14373 31 Aug 1995 @ 0000 31 Aug 1995 @ 2359 JarnoO active
EntrySourceLinkComment
06 Aug 2019 @ 1505 JSJ https://www.youtube.com/watch?v=_iWPkqVV0Sc#t=4m02s Clips 17-37 of this video compilation (= time stamp 4:02 to the end) show Middle Sister Spring eruptions on 6 August 2019.
04 Aug 2019 @ 1027 JSJ https://www.youtube.com/watch?v=_iWPkqVV0Sc Clips 1-16 of this video compilation (= beginning to time stamp 4:01) show Middle Sister Spring eruptions on 4 August 2019.
Baseline does not exist.