In an incredible feat of technology and timing, the HiRISE camera captured at least four avalanches/debris falls in action on the surface of Mars. According to the HiRISE team:

 

“Material, likely including fine-grained ice and dust and possibly including large blocks, has detached from a towering cliff and cascaded to the gentler slopes below. The cloud is about 180 meters across and extends about 190 meters from the base of the steep cliff. Shadows to the lower left of each cloud illustrate further that these are three dimensional features hanging in the air in front of the cliff face, and not markings on the ground (sun is from the upper right)…
 
From top to bottom this impressive cliff is over 700 meters tall and reaches slopes over 60 degrees. [source]

 

The HiRISE (High Resolution Imaging Science Experiment) is a 65 kg (143 lb), US$40 million camera on board the Mars Reconnaissance Orbiter. It consists of a 0.5 m (19.7 in) aperture reflecting telescope, the largest so far of any deep space mission, which allows it to take pictures of Mars with resolutions of 0.3 m/pixel (about 1 foot), resolving objects below a meter across. [source]