Cool image time! The Mars Odyssey science team has released this very interesting image, cropped on the right, of an avalanche debris pile formed when the large section of cliff on the left broke off and collapsed into the valley below. The valley is called Tiu Valles and is located close to Mars’ equator.
The wide spread of the debris is an indication of several things. For one, it illustrates the light Martian gravity, which allowed the debris to flow much farther than it would have on Earth.
For another, the spread of the debris pile suggests to me that the material that fell was very crumbly. It might have been able to hold together as a cliff for a long time, but when it collapsed the material broke apart almost like sand. Think of a sand castle you might have built as a kid on the beach. With a little moisture you can pack the sand to form solid shapes, but if your shape breaks apart the sand falls not as large blocks but as crumbly soft and loose sand. That is what appears to have happened here.
There is also the suggestion to me that water might have been involved somehow in this collapse. I am not a geologist so this speculation on my part is very unreliable. However, the shape of the debris pile suggests a liquid flow. The flow itself wasn’t liquid, but liquid might have somehow been involved in causing this geological event. We would need a geologist however to clarify these guesses on my part.