HOW ARE FOSSILS MADE?

INTRODUCTION

     What is a fossil? The word fossil literally means "dug up." A fossil is any remains or traces of past life that has been preserved in the record of the Earth's rocks. 

     You might just think of bones when you hear the word fossil, but fossils may come from any part of a living organism's remains. This includes shells, teeth, bones, plant or animal tissue, and even bacteria.

     Fossils are not just formed from the left over parts of plants and animals. Fossils can also include traces or evidence of life, such as footprints or worm holes.

PIECES OF A PUZZLE

     There are several ways that fossils can be formed. Most fossils are the leftover remains of plants or animals that lived long ago. Fossils generally look similar to how the plant or animal looked when it was alive, except now it is turned to stone. 

     Sometimes the entire skeleton of an animal may be preserved as a fossil, such as in the fossils discovered at the Ashfall Fossil Beds.

    Paleontologists (scientists who study the history of life on Earth through fossils) often discover only small pieces, and put together the pieces like a puzzle to discover the ancient history of life on Earth.

TURNED TO STONE

     The most common way that fossils are made is when the substance that shells or bones or teeth were made of is replaced by rocky materials such as quartz or pyrite. This is called petrification, which means "turning to stone." Even wood can be turned to stone by the process of petrification.

     But how does it work? Well, dissolved minerals are carried by ground water which fills up the space inside the cells of plants or animals. The minerals crystalize inside the cell spaces and eventually form rocks in the shape of the animal or plant. 

TRAPPED!

     Most creatures do not turn into fossils. They quickly rot and decay after they die. But some do not decay if they get covered in a layer of sediment right away before they can start decaying.

     For example, this is what happened to the animals from the Ashfall Fossil Beds in Nebraska. They were buried by ash from a volcanic eruption about 12 million years ago.

     Sediment is tiny pieces of rock, mud, and sand. The sediment may get squished together under the ground or under the sea and turn into rock with the creature trapped inside. It can take from 10,000 to 500,000 years for a fossil to be made.

A STICKY SITUATION

     Not all fossils are turned to stone. Another type of fossil can be made when an insect gets trapped in the sticky liquid of a pine tree, and the liquid gets buried under the ground. 

     Years later the tree will die and rot away, but the insect and sticky liquid may become fossilized. The insect is still trapped inside the sticky liquid that has turned to an amber colored stone.

     Amber is rock that looks like orange or light brown glass, with the creature trapped inside!

BURIED IN ICE

     Sometimes the soft tissues of a pre-historic animal can also be preserved. This includes the remains of organisms such as skin, muscles, fur, hair, and internal organs, such as the heart and brain.

    Usually these body parts quickly decompose after an organism dies. However, under special circumstances an animal may be quickly buried in a low oxygen environment, such as by being frozen in ice, which stops the animal from decomposing or being eaten by other animals.

     Lyuba is a baby woolly mammoth who lived more than 40,000 years ago. In 2007, Lyuba's body was discovered in the melting permafrost of Siberia. Lyuba's complete body, including her skin, internal organs, and even her mother's milk within her stomach, were preserved in the ice for more than 40,000 years! 

CONCLUSION

     In conclusion, fossils can be formed in many different ways. Discovering and studying the fossil remains of plants and animals helps us to uncover the hidden mysteries of life on our planet Earth.