Today's Image of Mars comes from HiRISE and shows part of Cerberus Palus that is broken up and blocky. What you see was likely once a flat surface that broke apart; just under the surface was probably a freezing mudflow. The pieces of that flat surface began flowing apart on top of slushy material. When the slushy material eventually froze it would have expanded and forced its way up between broken, drifting pieces, pushing them even farther apart.
Cerberus Palus is 480km across and located in the Elysium quadrangle of Mars. Clicking on this image will take you to a similar image showcased by Mars Travel, since the original HiRISE image does not currently have a caption.