Rectilinear cracks in the bedrock at the Chirup soil target, just east of Kimberley, opened up cracks that have let the soft, fine soil drop down between the bedrock blocks.
NASA caption: This image was taken by Front Hazcam: Left B (FHAZ_LEFT_B) onboard NASA’s Mars rover Curiosity on Sol 589 (2014-04-03 09:15:53 UTC).
More Sol 589 images (from all cameras), and Curiosity’s latest location map.