a wooded area is a kind of place & if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past & fossils of seashells are found in a wooded area ->  the wooded area used to be covered by water in the past  the wooded area used to be covered by water in the past & if something used to be in the past then that something has changed -> the place has changed from being covered by water to a wooded area