Question

how are casts formed by decaying organisms?

organisms turn into rock over time.
organisms leave carbon residue on a rock.
organisms leave impressions in sediment that hardens into rock.
impressions left by organisms are filled in with sediment that hardens into rock.

Explanation:

Define mold and cast formation

A mold fossil forms when an organism is buried in sediment and decays, leaving a hollow impression. A cast fossil forms when minerals or sediment fill this hollow mold and harden into rock, replicating the original shape.

Evaluate the given options

• Option 1 describes petrifaction/permineralization.
• Option 2 describes carbon film formation.
• Option 3 describes mold formation (the impression itself).
• Option 4 describes cast formation (filling the impression with sediment that hardens).

Select the correct option

Option 4 correctly describes how casts are formed.

Answer:

• (A) Organisms turn into rock over time.
• (B) Organisms leave carbon residue on a rock.
• (C) Organisms leave impressions in sediment that hardens into rock.
• (D) Impressions left by organisms are filled in with sediment that hardens into rock (Correct answer)