I was very lucky to see an eruption of Grand Geyser. This is one that only goes off about twice a day, and the predictions given by the park service cover a four hour interval. As it happened, I was nearby when it started to erupt. In addition, the sun peaked through the clouds during this eruption for about the first time all afternoon, creating the rainbow seen here. The eruption was quite impressive, lasting for 10 or 12 minutes.