The diagram shows a shell fossil. Which type of fossil is shown? O mold O cast O trace O imprint
The Correct Answer and Explanation is:
The correct answer is: Mold fossil.
Explanation
Fossils are the preserved remains or traces of ancient organisms, and they come in various types. Among the most common are mold, cast, trace, and imprint fossils. Understanding the differences between them helps identify which type of fossil is represented in a diagram, such as a shell fossil.
A mold fossil forms when an organism, like a shell, is buried in sediment and then decays or dissolves, leaving behind a hollow impression or cavity in the rock. This cavity preserves the shape and surface details of the original organism. Over time, the surrounding sediments harden, maintaining the hollow shape. Mold fossils often show detailed external features of the organism and are essentially negative impressions.
A cast fossil, on the other hand, forms when that mold later becomes filled with minerals or other sediments. These materials harden inside the mold and create a positive replica of the original organism. So while a mold is like a footprint in mud, a cast is like pouring plaster into that footprint to make a 3D model.
A trace fossil records the activity or behavior of an organism rather than its physical form. Examples include footprints, burrows, or coprolites (fossilized dung).
An imprint fossil is similar to a mold but is usually a flatter, surface-level impression, like a leaf or a feather pressed into soft sediment.
Given that the diagram shows a shell fossil, and assuming it displays a hollow impression without the actual material of the shell present, it is most accurately described as a mold fossil. It captures the external shape and surface detail of the shell after the organic material has decayed, leaving a void in its place.
Therefore, the correct fossil type for a shell-shaped cavity in rock is a mold.
