How Fossils Form in Rocks — Reading Comprehension

Fossils are the remains or traces of plants and animals that lived long ago. Most fossils are found in sedimentary rocks. These rocks form from layers of sand, mud, and small pieces of rock called sediment.

When a plant or animal dies, its soft parts usually decay or are eaten by other animals. Sometimes, the hard parts, like bones, shells, or wood, are quickly buried by sediment. Over time, more layers of sediment pile on top, pressing down and protecting the remains. This process is called fossilization.

As the layers build up, minerals in water seep into the remains. The minerals replace the original material, turning bones or shells into rock. This creates a petrified fossil. Sometimes, only an impression or shape is left behind, which is called a mold. If the mold fills with more minerals, it forms a cast fossil.

Fossils can tell us a lot about ancient life and Earth's history. For example, dinosaur bones, ancient leaves, and even footprints have all become fossils. Scientists called paleontologists study fossils to learn about animals and plants that lived millions of years ago and how the planet has changed.

Not all living things become fossils. Fossilization is rare because most organisms decay before they can be buried. The best places to find fossils are where sediment builds up quickly, like riverbeds, lakes, and shallow seas.

Interesting Fact: Some fossils are so tiny that scientists need microscopes to see them, while others, like dinosaur skeletons, can be longer than a school bus!

What are fossils?

Where are most fossils found?

Who studies fossils?

What helps protect animal remains?

Why is fossilization rare?

What forms a cast fossil?

Fossils are always big. True or false?

What does 'sediment' mean?