03. Fossil formation

Fossils are the preserved remains or traces of once living organisms, such as plants or animals.

Fossils are most often found in sedimentary rock. Fossils are never found in igneous or metamorphic rock. Sometimes fossils are found in other materials, such as tar, amber or ice.

Fossils are important because they give us information about the organisms that lived in the

past.

There are several types of fossils:

Mold Fossil

- A mold fossil is an impression of a once-living organism.

- A mold fossil forms when an organism dies and its hard parts are buried in mud, clay or other material that turns to rock. Over time, the hard parts dissolve, leaving behind an impression or mold of the once-living organism.

Cast Fossil

- A cast fossil is a “filled in” mold fossil.

- A cast fossil forms when an organism dies, its hard parts form a mold fossil in rock and then the mold is “filled in” with some sort of mineral. This leaves behind a cast of the original organism.

Trace Fossil (Imprint)

- A trace fossil or imprint is an “indirect” fossil. It is a fossil of biologic activity, not a fossil of a body structure.

- A trace fossil can be an impression (such as a footprint or feeding mark), a nest or burrow made by a once-living organism.

True Fossil

- A true fossil is the actual organism or part of the organism.

- True fossils form when the organism does not decay and its body parts are preserved. True fossils often form when an organism gets trapped in ice, tar or amber. The original features of the organism, like its color and shape, remain intact.

- Bones, teeth and eggs are types of true fossils. These are the actual body parts of a once-living organism, and thus are considered to be true fossils.

- True fossils are the best fossils because they give the most information.

Petrified Fossil

- A petrified fossil is different from other fossils.

- A petrified fossil forms when the organic matter of a dead organism or part of a dead organism is replaced by minerals and turned into stone.

Activity:

Use the information above to complete the "Types of fossil" Flip-flap sheet.

Activity:

In a group, produce a simple A3 sheet (Google Slide or Google Drawing) that gives photographic examples and explanations for each of the types of fossil.

Activity:

Look at the instructions on how to make a model fossil: https://www.wikihow.com/Make-Fossils use a piece of A4 paper to draw up a plan of what you will make a fossil of, and how you will do this. Submit it so the resources can be prepared for next class.