Sept 28, 2015, 5:03 am: The second largest active geyser in the world, Giant Geyser, erupted in Yellowstone early Monday morning. The impressive spray lasted for about an hour. Luck would have it that there was a full moon illuminating the scene, so the webcams in Yellowstone's Old Faithful area caught the show.
At the start of the below video (courtesy of Geyser Observation and Study Association), Oblong geyser is erupting. The Giant Hot Period is at 0503 (possibly Mastiff). Giant appears to start about 0506 or 0507, but it is hard to tell for certain.
Giant geyser's previous reported eruption was on January 22, 2010, the second in that month. This makes a break of 5 years and 250 days before Monday's event.
The below video shows a previous eruption from June 6, 2006
Giant Geyser is a cone-type geyser in the Upper Geyser Basin of Yellowstone northwest of Old Faithful Geyser. It's cone is about 12-feet tall. An eruption can reach up to 250-feet in height, then dropping to about 100-feet for the hour-long duration. In comparison, Old Faithful's eruptions top out at 140-feet.
Giant Geyser is the namesake for the Giant Group of geysers, which includes Bijou Geyser, Giant Geyser, and Mastiff Geyser. Giant Geyser is also the namesake for the Giant Platform, a raised stone structure incorporating all these geysers.
Learn more about Yellowstone geysers and hot springs