As one gets used to the idea that there is quite a bit of CO2 on Mars, the notion those are flows of material on a "bed" of gas makes more sense.

Now, I'm not sure of the term, maybe "hyperclastic". Just before Mt. St. Helens "blew", the internal heat of the mountain turned the water under the surface mud and rocks into steam.

The debris rode out on a bed of steam, and rode a long ways. I've walked completely around St. Helens, 3 day trip, and I can vouch for the volume and distance.

Mighten the flows on Mars have some geological similarity to those off volcanoes which superheat the water under the material on the sides which would be distinguishable from a liquid flow?

I obviously don't have the slightest idea what they might be, possibly riding UP a slight hill after the "runout". The gaseous CO2, or gaseous water, would have less friction than a liquid flow.

Interesting thoughts you have on this, though.

Arf