Mudcracks: Now and Then

August 05, 2022



Photographer: Marli Miller
Summary Author: Marli Miller

One of the wonderful things about sedimentary rocks is that they record the conditions at Earth's surface when they’re deposited -- and one of the most recognizable features are mudcracks. As we all can see, mudcracks form as wet, fine-grained sediment dries out, as shown by the top photo of a shoreline in the Amargosa Valley of southeastern California (taken in April 2022).

The bottom photo shows mudcracks in the Proterozoic-age Snowslip Formation of Glacier National Park in Montana (taken in July 2013). These rocks, deposited in northern Montana's Belt Basin between about 1.4 and 1.5 billion years ago, likely formed near the shoreline of a shallow inland sea where the sediment was similarly periodically wet and dry.

Amargosa Valley, California Coordinates:  36.58001, -116.44487

Glacier National Park, Montana Coordinates: 48.7596, -113.7870

Related Links:

Mudcracks near Trona, California

Marli’s Website