Old Faithful is one of Yellowstone’s biggest geysers and the most active in the national park. Geysers like Old Faithful erupt whenever water and steam get trapped in a tight spot deep below the geyser’s blowhole.
The mix of water and steam builds in pressure until it finds its way to the surface where a tall stream of scorching hot water blasts hundreds of feet in the sky.
However, the regularity of its eruptions have become more infrequent in the past few decades, and scientists want to know why.
In the 1950s, the interval between eruptions (IBE) was on average every 60 to 65 minutes, but since 2001, it erupts on average every 90 to 95 minutes.
To understand why, researchers from the US Geological Survey (USGS) collected samples of mineralised wood from the mound which Old Faithful sits on.
The mound now is lifeless, as trees or plants cannot grow with the constant bombardment of scalding, alkaline-rich water.
But the discovery of the mineralised wood means that at some point, trees did grow there.
By dating the wood, scientists were able to determine that the now barren mound once had trees growing there from around 1233 to 1362 AD.
USGS geologist Shaul Hurwitz told Science: “When I submitted the samples for radiocarbon dating I didn’t know whether they would be hundreds or thousands of years old.
“It was an ‘aha!’ moment when they all clustered within a hundred-year period in the 13th and 14th centuries.”
At the same time, Earth was going through a brief warm patch known as the Medieval Climate Anomaly.
This led to droughts across the planet, including Yellowstone, where, consequentially, water failed to seep into and recharge the geysers.
Palaeoclimatologist Cathy Whitlock from Montana State University, who wasn’t involved in the study, explained to Inside Science: “It’s the time when we have things like grapes growing in Northern England and a loss of sea ice that allowed people to discover Greenland.
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“We know in Yellowstone it was both warmer and drier. The upper tree line was higher up the slopes and there is evidence of more fires during that period.”
As a result, with the world warming due to climate change, scientists believe geysers such as Old Faithful will go quiet once again.
The USGS scientists wrote in the journal Geophysical Research Letters: “Climate models project increasingly severe droughts and large fires by mid-century leading to a major transformation of Yellowstone’s ecosystems.
“Periods of decreased precipitation have been shown in modern observational records to result in less frequent eruptions of Old Faithful Geyser, while the new 14C dates of mineralised wood suggest that severe, long-duration drought events can lead to Old Faithful Geyser eruption cessation.”
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