How are fossils primarily formed?

Fossils are primarily formed by the process of being buried in sediment. When an organism dies, its remains are often quickly covered by layers of sediment, such as mud, sand, or silt. This rapid burial is crucial as it protects the remains from decay and scavenging. Over time, additional layers of sediment accumulate on top, applying pressure that eventually compresses the lower layers, leading to lithification. This process transforms the sediment into rock and can result in the preservation of the original biological material as a fossil.

This method is fundamental to fossilization because it allows for the gradual replacement of organic materials with minerals, effectively preserving the shape and sometimes the structure of the original organism. Other methods, like ice preservation or mummification, are less common and usually pertain to specific environments that do not contribute to the broader fossil record found in sedimentary rock layers.