Drawing Gas from a (Yellow) Stone
By Matthew Tyler, Marine Biology and Environmental Science, 2017
The recent release of helium gas from Yellowstone National Park rock has received perhaps undue attention from two groups of people: those familiar with the massive Yellowstone super-volcano, who think this phenomenon signifies the end of the world as we know it, and those familiar with the helium shortage in the U.S., who think this can be used to bolster the supply.
A study from the journal Nature, as well as input from its authors, explains that both of them are wrong: the former because, as lead author Jacob Lowenstern says, “This really isn’t a volcano story.” The giant magma chamber under the park could cause worldwide devastation if it erupted, but the release of gases does not indicate this being an imminent danger.
The geysers for which Yellowstone is famous have been erupting since before the area’s discovery by explorers in 1809, and for the same reason as the helium degassing: heat from magma. As for the latter group, Yellowstone is a protected national park, and extracting helium would not be economically viable.
An important distinction to make about the gas release is that “recent” refers to the geological timescale. Helium has been coming out of Yellowstone’s geysers for two million years. What is notable is that the radioactive helium-4, formed by the decay of uranium, is leaving the crust hundreds of times faster than it is formed, on the order of 60 tons per year.
Given that Yellowstone is one of the oldest areas of continental crustal rock in the world, this helium may have formed billions of years ago and been trapped underground ever since.
Why is it being released? The current theory is that the movement of the volcanic hotspot under the crust caused the release through rock metamorphism: volcanic heat turned sedimentary stone into metamorphic rock, warping it in the process and giving the helium a channel to the surface.
Coauthor Bill Evans attempted to put this process in simple terms: “Think of it this way: You have these old crustal rocks just sitting around for hundreds of millions, perhaps billions of years…They have this boring little existence, and then suddenly somebody puts the heat on under them and they start giving up all their long-held secrets.”
The release of helium at Yellowstone is not something the public needs to worry about, but hopefully it will present geologists with an abundance of data on dynamic earth processes.
This article was originally published in NUSci Issue 19.