“Since its first known eruption 16.5 million years ago, it (Yellowstone) has blown up about a hundred times….The last eruption was a thousand times as that of Mount St. Helens (in 1980), the one before that was 280 times as big and the one before that was so big that no one knows how big it was” Bill Bryson - ‘A Short History of Nearly Everything’
My previous post about the Icelandic Geysers reminded me of my visit to Yellowstone Park in Wyoming USA in 1995 and the spectacle of an ever higher tower of boiling water and steam than the one that we had seen today.
Yellowstone was designated as a National Park in 1872 when President Ulysses S Grant signed a new law ordering ‘the tract of land lying near the headwaters of the Yellowstone River to be set apart as a public park’ and in so doing it became the first National Park in the USA and indeed the world.
The park is sensationally beautiful with stately snow capped peaks, lush meadows with lazy herds of grazing bison, meandering rivers like sapphire ribbons amidst the yellow-green prairie and tumbling streams, a magnificent sky blue lake and bounteous wildlife.
But there is danger too because Yellowstone is what is called a caldera (from a Latin word for cauldron) which is a volcano that collapses rather than builds a mountain and it sits precariously on top of a reservoir of restless molten rock about two hundred kilometres below the surface of the earth that rises here close to the fractured surface and is the reason for all of the geysers, bubbling mud pots and hot springs that are scattered liberally around the park and belch and spit continuously.
The magma chamber is about sixty- five kilometres across and about twelve kilometres thick so that is something to bear in mind when wandering about leisurely admiring the scenery because if (when) it goes off again it is going to be rather uncomfortable for anyone standing nearby.
There are more geysers and hot springs at Yellowstone than in all of the rest of the World put together and whilst we were there we obviously stopped off to see the most well-known and reliable geyser in the park. Old Faithful is a popular tourist spot where the geyser erupts promptly every seventy minutes or so and there are grandstands arranged an appropriate distance away from the boiling steam for the visitors to sit and admire the spectacle. An eruption can shoot anything from 3,700 to 8,400 gallons of boiling water to a height of fifty five metres and can last from one to five minutes. The average height of an eruption is forty four metres and that’s about the equivalent of about ten London double decker buses.
Previously the most famous geyser in the park was Excelsior, which used to erupt regularly to a height of a hundred metres but, as with the Great Geysir in Iceland, in 1888 it just stopped and didn’t erupt again for a hundred years. One day Old Faithful will no doubt just stop in exactly the same way.
The biggest geyser in the park and indeed the world is the Steamboat geyser which blows to a height of one hundred and twenty metres but this spectacle is most infrequent and inconveniently unpredictable and you really wouldn’t want to sit waiting for it because that could waste more than half of your life away.