Rolling Downhill

At first just a pebble, rolling along the ground. Then as it picks up speed, and the slope of the land gradually turns downward, bits of moss and dirt begin to cling to it. Soon it enlarges. The ground continues to slope downhill, the gradient more severe, the speed of the roll becoming faster with the decline. The pebble now has become the size of a large rock and still it rolls ever onward. Once it started downhill, nothing was going to stop it short of a large barrier. The rock has become a boulder, racing down the slope crushing all in its path. Grass, dirt, small bushes, all are caught in the tumble and become part. Only the bottom will stop the fall.