The American painter Anne Coe called Yellowstone ‘the place where the centre of the Earth finds an exit and gives us a glimpse of its soul’. As I stand on the edge of Old Faithful — the centrepiece of the Upper Geyser Basin, the largest concentration of geysers on Earth — I know what she means. It’s winter. Steam billows from the valley like bonfires; the ground hisses, shaking like marching drums beneath my feet. Suddenly a super-heated plume of water erupts 90ft in the air. I watch it crystallise in the freeze and fall like shards of glass. It’s spectacular, and unnerving, like a gasp from the underworld. But Old Faithful’s fame rests in its reliability, spouting like clockwork every 90 minutes.
This 3,468sq mile wilderness, where bison and wolves roam free, is America’s first national park, established in 1872 after fur trappers returned east with seemingly tall tales of a magical landscape where the ground bubbled and jets of scalding water shot hundreds of feet into the air. But they were right, Yellowstone is magic. There are over 10,000 hydrothermal features here: a tapestry of bubbling pools, hot springs and vents, plus the world’s largest collection of active geysers. I find pools of pure sapphire, boiling mud pots of cinnamon and rainbow slicks of bright red, orange and green, like an abstract painting. Some geysers look like castle turrets; others beehives; some sparkle like stars; others fizzle or scream like a gale. But what’s most astonishing is that they’re alive with microscopic artists — the bands of colour in their superheated waters created by thermophilic microbes. The most beautiful of all: the Grand Prismatic Spring, the largest hot spring in the US at 90 metres across. Like a vast tie-dye painting, concentric rings of rainbow colours spread out from a cobalt centre; viewed from above, a blue-eyed giant seems to be staring up from beneath the Earth.
That night, I lie down next to Black Sand Pool, a geyser on the edge of the basin; nothing but stars and steam all around. A low-pitched sonic boom shoots up from deep below and punches me in the back. I jump up; I’m no longer visualising the world beneath my feet as solid ground; instead, I’m seeing a precarious honeycomb filled with fire and unfathomable force. “It’s like there’s a monster trying to get out,” my guide Alex laughs. And he’s right, there really is a monster. Yellowstone sits on top of one of the world’s largest active supervolcanoes. When, not if, it explodes it will take half the country with it and shroud the planet in ash and darkness. But that’s why the national park is so special. This is creation at work, the world at its most primal; ever-changing, with me, a mere ant, on its skin. Coe was right: it’s a glimpse into the soul of the Earth itself.