The roving rocks of Racetrack Playa are a mystery even to NASA:

The rocks are famous because they move, leaving tell-tale trails in the clay, like this one. This happens at several playa in California and Nevada. There’s no record of anybody seeing one of the rocks move, and scientists aren’t quite sure how it happens. But they know that it’s not the work of animals, gravity, or earthquakes.

Eerie images from a bomb test in Nevada in 1955.

Now that he’s got your attention with his spectacular photos, geoscientist Kristian Klepp would like to teach you something. At least that’s the general idea behind his very cool website www.lichtjahre.eu.

About the site:

The aim is to increase public awareness of the earth system, so that people can develop a clearer understanding of the planet. Over 200 images of spectacular landscapes accompanied by scientific explanations illustrate the perpetual change of our planet through the eons of time.

These images of the explorers of the American West are part of a much larger photo collection put together by the Mail of the first ever taken of this newly discovered territory. Timothy O’Sullivan worked alongside government teams as they explored Arizona, Nevada, Utah and the rest of the west as they sought to assess the land’s natural resources. He had earlier covered the U.S. Civil War and was one of the most famous photographers of the 19th century.