They change shape due to a number of reasons.
The easiest reason to understand why they change is that they erode.
The coasts around the the world erode due to waves hitting cliffs, the wind batting against the coasts etc. Over a long period of time we can see that they change in shape.
(sorry I don't know why they move)
Splattered, splatter, and will be splattering. future progressive verbs usually include "will" and "be" and have the verb ending in "-ing"
