The Great Sand Dunes National Park conserves America’s largest sand dune.

Sand dunes have been formed by sediments from the surrounding mountains filling the valley over geologic time. When lakes in the valley disappear and recede, what is left is the sand and the sand is blown towards the Sangre de Cristos. This formed the now-famous sand dunes.

The parts that make up the Great Sand Dunes system are the dune field, the sand sheet, the sabkha (a mud or sand flat where minerals and salts accumulate from evaporation), and the mountain watershed.

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Photo Credit: Photo by Patrick Myers, National Park Service