We visited Iceland in 2015. Being interested in geology — and Iceland having been formed only 25 million years ago — created the perfect match.
The country is filled with volcanoes, lava fields, glaciers, waterfalls and even several locations where you can actually see two tectonic plates — the North American plate and the Eurasian plate — moving slowly apart at the rate of 0.98 inches per year.
My most astonishing moment, however, came during a visit to the Geysir geyser. Clearly this geological feature is the source for the eponymous word “geyser,” which derives from the Old Norse geysa meaning “to gush.” Despite having seen other geysers elsewhere, Geysir is impressive.
The first eruption was as expected. While waiting for the next eruption, I saw instead of a simple water column, an enormous blue bubble of water fill the entire pool, rising upward until it broke up and became a part of the rising water fountain.
I was in shock. Despite the presence of numerous other tourists, no one else seemed to have noticed this unusual and completely unexpected phenomenon.
Even though we waited around for a considerable period of time afterward in the hope of both seeing the bubble again and getting the corroborating evidence of a photograph, all we saw was the usual spout of boiling water. Without the photo, I was sure that no one would believe my story.
I have since learned that while this bubble phenomenon is not unknown, it is relatively rare. Iceland is not nearby, but Yellowstone National Park is a common destination for geysers and associated geothermal phenomena. According to Dirk Niermann, who has done extensive photography of geothermally active areas, Great Fountain Geyser, Fountain Geyser, Morning Geyser, Deep Blue Geyser and Morning’s Thief Geyser of Yellowstone occasionally exhibit this bubble activity as well.
The Lewis and Clark expedition travelled immediately north of Yellowstone in 1806. A member of their expedition, John Colter, returned to the area in 1808, entering Yellowstone itself. When he returned with accounts of geysers, mudpots and thermal pools, he was not believed, and the area was laughingly known as “Colter’s Hell.” Over time, there were further explorations, and in 1872, President Ulysses S. Grant created the Yellowstone National Park, the first park so designated in the United States.
There are only approximately 50 known geyser fields worldwide, all associated with active volcanic areas and hotspots — and most have only single-digit active geysers. Yellowstone is in a class of its own, having 300 to 500 geysers in nine geyser basins.
Generally, geysers are categorized as two types — fountain and cone geysers. Both involve pools of water at the surface. Fountain geysers erupt from within those pools, and Grand Geyser of Yellowstone is a superb example.
Cone geysers have a nozzle-like structure formed over time from the mineral-rich water, rising above the pool, through which the water explodes. The age of the cone is commensurate with its size — larger is older.
Old Faithful, probably the most famous geyser in Yellowstone, is an example of a cone geyser.
Three conditions must be met in order to have geysers.
They are heat, water and a plumbing system, which in this case, means a series of pipes — although in this case, these pipes are carved out of the underlying stone.
Heat is supplied by subsurface liquid rock, called “magma,” when it lies below the Earth’s surface, and “lava” once it reaches the Earth’s surface.
Three processes create volcanic conditions:
• Convergent Plate Margins — This is where tectonic plates push into each other, being forced to slide under the other. The friction involved partially melts the subducting plate, and the magma rises to the surface. Examples include geysers in Chile, Mexico and Japan.
• Divergent Plate Margins — Tectonic plates can also separate. This thinning of the crust causes cracking or rifting, allowing magma to again move upward to the surface. Volcanoes along divergent margins can be found in Iceland and Kenya.
• Hotspots — Just as the name implies, they represent locations where plumes of extreme heat rise up directly from the mantle layer. (The outer layer, between five and 25 miles thick, that we live on is the crust. The mantle, lying below it, is 1,800 miles thick, and is divided into the upper and lower part. The lower mantle’s rock flows like asphalt and underlies the process of plate tectonics.)
The hotspots are stationary positions in Earth’s globe, and as the tectonic plates move over them, it creates volcanic conditions.
It is believed that the Hawaiian islands were created by successive eruptions as the plates moved along over a hotspot.
Yellowstone is another example of such activity.
Have a thought or comment for Sura Jeselsohn? Email her at email@example.com.