It has to do with the scale and physics of the motion. When you film an avalanche from far away, it appears to descend very slowly at the normal replay rate. But if you made your typical science fair volcano on a tabletop, the foam descends a lot more quickly at the same time scale.
The fact that those objects have different scales and speeds does not mean that faster objects automatically appear smaller. You pointed out a correlation.
If we are pointing out random anecdotal examples, ice cubes melt slowly, and don't appear huge to the observer.
I have to disagree both in the case of animals and the volcano example. With animals, there are real underlying physics principles that dictate the strength-to-weight ratios at various scales that lead to smaller animals being able to move more quickly (muscle strength is proportional to cross section, while mass is proportional to volume).
In the case of the avalanche, the force at work is the same (gravity) it's just that we are zooming way out and so crossing the same distance takes much more time.
