If you are in Yellowstone’s Upper Geyser Basin waiting for Grand Geyser to erupt, and hear a nearby geyser gazer announce “Waves on Grand,” get your camera ready - chances are the eruption you’ve been waiting for is just moments away.
The eruption of Grand actually involves three geysers; viewed from the boardwalk they are Vent (left), Turban (center), and Grand (right). Like several geysers in the Park, Grand geyser has indicator events that can help gazers determine if an eruption is ready to start or if it has been delayed.
The primary indicator for Grand’s eruption are the cycles involved in refilling Grand’s pool after the previous eruption. In his book, “Geysers of Yellowstone, Forth edition,” T. Scott Brian describes the process as follows:
“During the long quiet period after an eruption, Grand slowly fills with water. The first overflow is about 4 hours following the previous eruption. There is little variation to this figure. From then until the time of the next activity, the water slowly rises and falls in sympathy with the eruptions of Turban Geyser. Each cycle, from high water through low water as Turban plays and back to high water, takes exactly the same amount of time as that particular cycle of Turban-usually between 17 and 22 minutes. This water level variation allows the geyser gazer to judge how near Grand is to an eruption. Stand where you can see the outermost part of the basin where small ridges of sinter project through the water. Use them to gauge the level of the pool. If the water level drops enough to clearly expose the ridges and stop almost all overflow when the time for Turban to play is approaching, then you know there will be at least one more cycle of Turban before Grand erupts. Finally will come a cycle when the water level does not appear to drop at all. Now is the time to watch closely. Very small at first waves begin to wash across the surface of the pool because of pulsations over Grand's vent. Soon the waves become obvious as the water level continues to rise and discharge becomes heavy. Only rarely will the wave action start without a consequent eruption.”
Because of steam around Grand’s pool, the waves are sometimes hard to see. If you open this video to the full-screen mode and look closely at around the 48-second mark, you will see small waves rolling over the sinter ridges closest to the pool’s center just prior to Grand's eruption.
16 сен 2024
