What Is a Fossil?

Fossils are evidence of what life was like long ago. The oldest fossils are over three billion years old and the youngest fossils are about 10,000 years old.

Scientists that study fossils know that creatures that lived at different times in past were different. Most fossils are from creatures that no longer live on the planet because they have become extinct. Many of the extinct ones are somewhat similar to creatures that live today.

It takes special conditions for a fossil to form. Hard parts made of mineral, like shells and bones, are more likely to become fossils. Soft parts, like skin, organs, and eyes, usually don�t become fossils.

Trace fossils are clues that show how animals lived. For instance, if you were to make footprints on the beach today and the beach sand eventually became a sedimentary rocks, your footprints would be trace fossils in the rock. This doesn�t happen very often. Think about all the people, dogs, crabs, birds and other animals that walk over a beach each day. Few, if any, of those footprints will become fossils someday. Most of them are washed away by wind and waves.

Last modified June 11, 2009 by Jennifer Bergman.

Shop Windows to the Universe Science Store!

The Fall 2010 issue of The Earth Scientist, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

What Is a Mineral?

Minerals are the building blocks of rocks. There are many different types of minerals. All of them are solid and all are made of atoms of elements. Minerals can grow even though they are not alive. Most...more

Early Whales Gave Birth on Land

Scientists discovered two fossil whales in 2000 and 2004 in Pakistan. They dug up the fossils, transported them back to labs, cleaned off the fossils and then worked on the fossils for a few years. Their...more

Dinosaur Discovery Helps Solve Piece of Evolutionary Puzzle

Scientists have discovered a new species of dinosaur called Haplocheirus sollers (which means simple, skillful hand). These dinosaurs lived during the Late Jurassic time period and are part of the family...more

Scientists Use T. rex Bone to Link Dinosaurs to Birds

For a long time, scientists have thought that birds are dinosaurs' closest living relatives. They came up with this hypothesis based on the shapes found in bird and dinosaur skeletons. Now scientists...more

Finding the Four-Footed Ancestors of Whales

Scientists have known for a long time that whales, the largest marine mammals, have distant relatives that lived on land millions of years ago. A team of scientists has been searching for fossils to better...more

Some Sedimentary Rocks Are Made of Fossils!

Rocks made of fossils are called organic sedimentary rocks. This picture shows one place where organic rocks are being made on the Earth today. This is a coral reef where the skeletons of coral, clams,...more

How Many Species Have There Been on the Earth?

Scientists are interesting in knowing how many species can fit on the Earth. The number of species is called diversity. If there are a lot of species, then diversity is high. If there are few species,...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF