Fossil Formation

mold

A mold is a hollow area in sediment in the shape of an organism or part of an organism. A mold forms when the hard part of the organism, such as a shell, is buried in sediment.

carbon film

An extremely thin coating of carbon on rock. all living things contain carbon. When sediment buries an organism, some of the materials that make up the organism evaporate, or become gases. These gases escape from the sediment, leaving carbon behind. Eventually, only a thin film of carbon remains.

cast

A cast is a solid copy of the shape of an organism. A cast is the opposite of its mold. Both the mold and cast preserve details of the animal's structure.

evolution

Evolution is the gradual change in living things over long periods of time.

sedimentary rock

Sedimentary rock is the type of rock that is made of hardened sediment. Recall that sediment is the material removed by erosion. Sediment is made up of rock particles or the remains of living things. Sandstone, limestone, and coal are examples of sedimentary rocks. Most fossils form from animals or plants that once lived in or near quiet water such as swamps, lakes, or shallow seas where sediments build up.

What are the different kinds of fossils?

Fossils found in rock include molds and casts, petrified fossils, carbon films, and trace fossils. Non rock fossils form when the actual remains of organisms are preserved in substances such as tar, amber, or ice.

How do fossils form?

Most fossils form when living things die and are buried by sediments. The sediments slowly harden into rock and preserve the shapes of the organisms.

paleontologist

Scientists who study fossils are called paleontologists. Paleontologists collect fossils from sedimentary rocks all over the world. They use this information to determine what past life forms were like. They want to learn what these organisms ate, what ate them, and in what kind of environment they lived.

What does the fossil record tell about organisms and environments of the past?

The fossil record provides evidence about the history of life and past environments on Earth. The fossil record also shows that Earth's surface has changed over time.

extinct

The fossil record shows that millions of types of organisms have evolved. But many others have become extinct. A type of organism is extinct if it no longer exists and will never again live on Earth.

petrified fossil

The term petrified means "turned into stone." Petrified fossils are fossils in which minerals replace all or part of an organism. These fossils formed after sediment covered the wood. Then water rich in dissolved minerals seeped into spaces in the plant's cells. Over time, the minerals come out of solution and harden, filling in all of the spaces. Some of the original wood remains, but the minerals have hardened and preserved it.

fossil

the preserved remains or traces of living things.

trace fossil

trace fossils provide evidence of the activities of ancient organisms. A fossilized footprint is one example of a trace fossil. From fossil footprints, scientists can find answers to questions about an animal's size and behavior.