Green Scene

Even when man stops, nature keeps geysers going

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As I was preparing this column, we were more than a week into the government shutdown. One agency that I wanted to query was the National Park System.

The shutdown was so absolute that a park employee I attempted to reach told me that “due to the lapse in appropriations, I am prohibited from conducting work as a federal employee, including returning phone calls and emails, until further notice.”

In a previous column, we covered heat sources as one of the necessary conditions for geyser creation. Clearly, the second necessary condition is a water supply. Many geysers are near large water supplies such as rivers and presumably draw from them. However, since there are also geysers in desert areas such as El Tatio in Chile’s Atacama Desert, river water is clearly not the only possible water source.

Instead, other sources include precipitation — either rain or snow — that percolates into the groundwater through sand, gravel and fissures. Parenthetically, there are indications that some of the sand and gravel left behind as glaciers retreat form part of the piping system which will later be used for the upward motion of the geysers.

At Yellowstone, it is estimated to hundreds of years (some tests show up to 500 years) for precipitation water to enter the groundwater system, become heated, and then reappear as a geyser. Therefore, yearly fluctuations in precipitation do not have an immediate effect on geysers.

A plumbing system is the third necessary condition for geyser creation — heated water under pressure must have an exiting pathway. Without said system, the naturally heated water would simply flow out at the surface resulting in hot springs. While there are several hypothetical models for the shape of the underground piping, they all include a lower reservoir for water collection, a long standpipe through which the waters erupt — a narrowing at some point near the opening of the outside, and a side chamber called a “bubble trap.”

It also is important to note that this system needs to be watertight. This is accomplished by the silica, which dissolves out of surrounding rhyolite (a silica-rich volcanic rock) being re-deposited on the walls of the standpipe and on the surface surrounding the geyser where it is known as sinter or geyserite.

The essential point regarding the process of eruption is that water at the bottom of the standpipe is under greater pressure than water at the top. This means that as the reservoir water is heated, its boiling point rises considerably above the usual boiling point of 212 degrees at sea level.

As the water starts to boil in the bottom chamber, it pushes bubble of steam upward, which are caught in the bubble trap (essentially an underground bend or loop). These bubbles help heat the upper waters, which are at a lower pressure than the bottom waters.

“Eventually, the steam bubbles trigger sudden boiling at the top of the column, releasing pressure on the water below and allowing it to boil (up) as well,” according to Michael Manga of UC Berkeley. “The column essentially boils from the top downward, spewing water and steam hundreds of feet into the air.”

While we are all familiar with hot water geysers, it should be noted that cold water geysers exist as well. Examples include Crystal Geyser in Utah and Brubbel Geyser in Germany. In these cases, the propellant is carbon dioxide, which dissolves in groundwater. Magma below the geyser area is the source of the carbon dioxide gas.

While we are “visiting” Yellowstone, we should mention a few other geothermal phenomena there:

 

Hot springs

Water is heated by magma and rises to the surface because of unrestricted access. These are quiescent springs. When there is some boiling, it is due to mild obstruction, and these are called vigorously boiling hot springs. Sulfurous hot springs are yellow due to percolation through sulfur deposits.

 

Fumaroles

Derived from the Latin fumariolum, meaning “vent hole for smoke,” with fumus being Latin for “smoke.”

It would ordinarily be a hot spring, but since there is only minimal amount of water present that, boils away, just leaving gases to vent at the surface.

 

Mod pots

Plopping mud is created when small amounts of heated water containing sulfuric acid combines with volcanic ash and other fine soil particles.

Paint pots are a colored subcategory when the soil which, lacking sulfur, instead contain iron oxides, potassium or magnesium.

Alas, while geysers are of great scientific interest, the blue dome phenomenon has only been noted, not investigated, thus far. Manga suggests the phenomenon requires a large geyser with a surface pool.

Dirk Niermann believes that a smooth and symmetrical shape of both the orifice and the standpipe are causative factors.

I simply feel privileged to see one!

Have a thought or comment for Sura Jeselsohn? Email her at greenscenesura@gmail.com.

CORRECTION: Geysers can be found in many places around the world, including deserts like Chile’s Atacama Desert. Green Scene in the April 4 issue misstated this fact.

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