GEOLOGY

Detailed explanation-1: -A mold is a hollow area in rock in the shape of an organism or part of an organism. A mold forms when the hard part of an organism, such as a shell, is buried in sediment. Later, water carrying dissolved minerals may seep into the empty space of a mold.

Detailed explanation-2: -Sometimes when an animal dies and its body decays, it can leave an imprint in the sediment. If this imprint fills in with minerals from sediment and groundwater, it can harden to form a fossil. This fossil is called a cast fossil. The fossilized imprint is called a mold fossil.

Detailed explanation-3: -A cast forms as the result of a mold. Water with dissolved minerals and sediment fills the mold’s empty spaces. Minerals and sediment that are left in the mold make a cast.

Detailed explanation-4: -Sometimes, open pores in the rock let water and air reach the organism or part, causing it to decay or dissolve. What is left behind is a cavity in the rock where the organism or part was. This empty space is called a mold. A mold shows the original shape and surface of the organism or part.

Detailed explanation-5: -Rock that fills in the mold resembles the original remains. The fossil that forms in the mold is called a cast (Figure below). Molds and casts usually form in sedimentary rock. With compression (Figure below), an organism’s remains are put under great pressure inside rock layers.