"Flying sand and walking stone" is a famous Chinese proverb, which describes how a powerful storm could be like.
Characters are in the artwork.
1, Fly or Flying, big seal script
which is a flying bird.
2, Sand, big seal script
The left is character Water
the middle is river, the four dots are water drops. ancient Chinese got water from the river, so river + water drops = character water.
other four dots are sand, which means that the sand is located near the river (on the beach). I added much more sand in the air.
3, Walk or Walking, bronze script
the top is a person who is walking, the bottom is a foot.
4, Stone, big seal script
厂 means the cliff, the 口 is the stone, which is quarried from a cliff of mountain. I added many more rolling stones