The answer is Erosion, which is the the gradual destruction or diminution of something -- in this case, rocks. I hope this helps! For reference/perspective, sand is the product of rock erosion, because it's really just tiny remnants of crushed rock. Those "small pebbles" could be sand, but you'd have to emphasize just how small they are -- one grain of sand is just that: a grain
"mi casa es tu casa" is how you spell it
ur answer would be a steam engine.
i really hope this helps
