Describe the process of a cast forming, indicating when the mold has formed and when the cast has formed
The remains of a plant or animal are encased in sediment and the sediment eventually hardens into rock. As the remains of the plant or animal disintegrate, a hole is left in the rock, in the shape of the original remains. That is the mold. The mold might fill up with sediment later and when the sediment hardens, it forms a cast.