Lava Creek Tuff, Volcanic rock formation in Yellowstone National Park, US
Lava Creek Tuff is a volcanic rock formation that stretches across Wyoming, Montana, and Idaho, made of consolidated ash with gray and reddish tones. The formation appears as tall cliffs and outcrops, where the layers are clearly visible stacked one above the other.
The formation emerged from a massive volcanic eruption around 640,000 years ago, which spread huge amounts of ash across the region. This eruption created the Yellowstone caldera, one of the largest volcanic structures in North America.
The name comes from Lava Creek, which flows through the area, though the deposit itself formed from ash rather than flowing lava. Visitors today see reddish and gray layers in the rock face, created by different temperatures as the material settled and cooled.
The deposits are well exposed at Tuff Cliff along the Gibbon River, where the layers stand openly visible. The cliffs are best viewed from the road, though some areas require short walks over uneven ground.
The rock walls sometimes show glassy areas where the ash was so hot it fused into a smooth surface as it cooled. These glassy zones appear darker and smoother than the surrounding gray ash.
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