EMPLOYEE WAS USING A LOADER TO CLEAR ROCKS FROM AREA AROUND DRILLING RIG. WHILE BACKING UP, THE FRONT LEFT WHEEL WENT OVER TOP OF 18"" ROCK CAUSING THE LOADER TO LUNGE TO THE SIDE. THE EMPLOYEE WAS LOOKING OVER HIS RIGHT SHOULDER AND THE MOTION CAUSED WHIPLASH TO HIS NECK. AN HOUR LATER THE PAIN WORSENED. HE WAS TAKEN TO THE HOSPITAL FOR EVALUATION AND RELEASED WITH RESTRICTIONS.