North America 2024

Yellowstone National Park – Mammoth Hot Springs – Grand Canyon, Yellowstone

A winter scene? No, the white is the result of volcanic activity. The limestone, calcium carbonate, has reacted with carbonic acid, the result of CO2 from the mantle vents reacting with water. The result is a white rock called travertine. When bacteria feeds off the sulphuric acid and hydrogen sulphide in the erupting water spouts, it colours the travertine with a bacterial layer. Here an entire hillside has been formed in this way.

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