Go Giant! Giant Geyser Continues Eruptions

Giant Geyser in Yellowstone’s Upper Geyser Basin erupted again on Thursday, September 10, 2026, after dark. The eruption was illuminated by flashlights and caught on the live streaming webcam, much to the delight of giddy geyser gazers who had watched the area for days and waited in hopes of an eruption. One of them triangulated the height as 215 feet. Giant is one of the largest geysers in the world.

This is the fourth eruption this season, and the interval between those eruptions is shortening. This means it is quite likely that Giant Geyser, one of the largest geysers in Yellowstone, is entering another active phase.

The first eruption was seen on the streaming webcam on June 26. The second occurred 52 days later on August 17. The last two eruptions, one on August 30 and the most recent on September 10, were 12 (almost 13) and 11.5 days apart. These last two intervals of 11-13 days between eruptions match many of the typical intervals seen in 2018 and 2019.

Can Giant be Predicted?

The short answer is no. However, assuming the eruptions continue and looking at these data points – keeping in mind we’re looking only at two here – means watching more closely now and for the next week. If the timing aligns with the two data points we have, then the week of September 20-26 is a possible window of opportunity.

Old Faithful, a predictable geyser, gives you a 20-minute window of opportunity to erupt. Predictably, geysers usually don’t share their water chamber with other geysers, making the recharging phase much easier.

But when geysers share water, it’s much more complex, with one geyser’s eruption drawing water from another. Giant is one of those that shares its water with many others, including Grotto Geyser, Marathon Pool, and more. This has been determined over years of observations by geyser enthusiasts.

How Long Will an Active Phase Last?

Again, short answer: we really don’t know. Looking back at the last two active phases, one in 2018-2019, and previously in 2007-2008, it’s hopeful that this will last at least through next summer.

As we learn more about the rhythm Giant might find by looking at the intervals between eruptions, it should become a bit easier to get the window of opportunity for an eruption down to fewer days. But it still takes commitment to giving time in the area.

Stay Tuned

I’ll keep watching the reports coming in. I’m excited at the possibility of seeing Giant Geyser again and will keep you updated on what is learned.

[Community Contributor]

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