What Is a Fossil?

The leg and shoulder bones of a large Sauropod dinosaur preserved at Dinosaur National Monument (Colorado, USA) Click on image for full size (52 Kb) Courtesy of Dinosaur National Monument

Fossils are evidence of ancient life preserved within sedimentary rocks. They are clues to what living things, ecosystems, and environments were like since life has existed on this planet. The oldest fossils are mats of blue-green algae that lived as much as 3.5 billion years ago. The youngest fossils are animals that lived approximately 10,000 years ago, before the beginning of recorded history.

Scientists that study fossils know that the types of creatures have changed dramatically over the millions and millions of years of Earth history. Most fossils are from animals, plants and other organisms that no longer live on the planet because, like dinosaurs, they have become extinct. In fact, about 99% of fossils are from extinct organisms. Many of these extinct species, or types of life forms, are similar to species that live today.

It is not just scientists that are able to find fossils! In some areas of the world, the rock exposed at the surface is made almost entirely of fossils making them easy to find. In other places, the rocks at the surface are not the type of sedimentary rocks where fossils are typically preserved. However, you can still find fossils in your local science or natural history museum. Even if you are from a place where fossils are difficult to find, you probably rely on fossils everyday by using fossil fuels such as oil, gas, or coal to power cars, lights, and heat or cool your house. Fossil fuels are organic carbon from plants and marine life that lived millions of years ago.

Body fossils are the preserved remains of actual organisms. Most living things never become fossils because it takes special conditions for a fossil to form. Parts made of mineral such as shells and bones are much more likely to become body fossils than soft tissues, such as skin, organs, and eyes, which usually decay. Animals like jellyfish, which have no bones, are rarely preserved.

Trace fossils are indirect evidence of ancient life. For instance, if you were to make footprints on the beach today and the beach sand eventually became cemented together forming a rock called sandstone, your footprints, if left undisturbed, would be in the rock and would be called trace fossils. 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. Other examples of trace fossils include crab burrows, dinosaur bite marks, and bear claw starches on the walls of caves.

The leg and shoulder bones of a large Sauropod dinosaur preserved at Dinosaur National Monument (Colorado, USA) Click on image for full size (52 Kb) Courtesy of Dinosaur National Monument

Fossils are evidence of ancient life preserved in sedimentary rocks. On Earth, they are clues to what living things, ecosystems, and environments were like in the past. The oldest fossils are from mats of blue-green algae that lived over three billion years ago. The youngest fossils are from animals that lived before the beginning of recorded history, 10,000 years ago.

Scientists that study fossils know that the types of creatures that lived on the planet at different times in Earth history have changed quite a bit over millions and millions of years. Each unique type of life form, whether alive today or extinct, is called a species. Most fossils are from species that no longer live on the planet because they have become extinct. Many of these extinct species are somewhat similar to species that live today.

Fossils are not always big dinosaur bones or fancy shells like the ones found in museums. In fact, if you think you have never found a fossil, think again! You probably rely on fossils everyday by using fossil fuels such as oil, gas, or coal to power cars, lights, and heat or cool your house. Fossil fuels are organic carbon from ancient plants and marine life that lived millions of years ago. So, every time you pull into a gas station, think about the fossils that are filling the tank!

Body fossils are remains of actual organisms. Most living things never become fossils. It takes special conditions for a fossil to form. Hard parts made of mineral such as shells and bones are much more likely to become body fossils than soft tissues, such as skin, organs, and eyes, which usually decay. This means that animals like jellyfish, which have no bones made of hard mineral, are rarely preserved.

Trace fossils are clues to how ancient animals lived. For instance, if you were to make footprints on the beach today and the beach sand eventually became cemented together forming a rock called sandstone, your footprints would be in the rock as well. They would be trace fossils and evidence that you were once there. 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. Other examples of trace fossils include crab burrows, dinosaur bite marks, and bear claw starches on the walls of caves.

The leg and shoulder bones of a large Sauropod dinosaur preserved at Dinosaur National Monument (Colorado, USA) Click on image for full size (52 Kb) Courtesy of Dinosaur National Monument

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.