Jack1111, I think what you are seeing are the prop tips hitting the ground and throwing dirt to the side.
Take from another forum :-
"great care must be taken on runup because if the tail begins to rise the limited prop clearance and high polar moment produces an inevitable strike no matter how quickly the throttle is closed."
"Yes, you had to be careful on take-off with any Spit, and hold the nose up a bit to keep the prop tips off the ground."