Fossils: Life of the Past
by Lynne M. Clos
(NOTE: you must click on the individual screens to see the pictures. This screen gives the full text so you can read it in uninterrupted fashion. Text is divided up on the individual screens so that pages will be in the right order when you cut and assemble the booklet.)
Fossils tell us about plants and animals that lived and died a long time ago. Fossils may be bones, footprints, or the
imprints of shells or leaves which have turned to stone.
Sometimes, after an animal dies, its body is covered with earth before it has had time to decay. A leaf may fall into a lake
and become covered with mud. Footprints on a beach may harden in the sun and later become covered with another layer
of sand.
Many more layers of mud and sand accumulate, burying the plant or animal far below the ground. After a very long time
-- millions of years -- both the mud and the plant or animal remains turn to stone. The bone, shell, or leaf has become a fossil.
Sometimes, slowly, the wind and rain wash away the layers of rock covering the fossil, leaving it lying on the surface of
the ground. Other times hammers, shovels and other tools must be used to dig the fossil out of the rock. People interested
in fossils, called paleontologists, collect the fossils and study them to learn about the plants and animals which lived long,
long ago.
Different types of plants and animals lived at different times in the past. Scientists can examine certain chemicals in
some rocks, called isotopes, to learn how long ago the rocks formed and how old the fossils in, or associated with, those rocks are.
Knowing the ages of different fossils allows us to learn how life on earth has changed over long spans of time.
Many of the plants and animals which lived in the past were very different from those which are living now. In rocks
which formed on the ocean floor, squidlike animals called ammonites and buglike trilobites are commonly found as fossils.
These animals are now extinct, meaning that none of them are still alive today.
Things were different on the land, too. Dinosaurs lived in forests and meadows instead of the animals like deer, buffalo
and wolves which live there today.
For a long time, there were no plants with flowers. Pine trees, cycads, and ferns covered the land instead.
About 65 million years ago, all of the dinosaurs died. No one knows for sure why. After this happened, their place was
taken by animals with fur, called mammals. Most of the large animals alive today are mammals.
Even though we have learned a lot about the life of the past by studying fossils, there is still much for us to learn.
Hunting for fossils can be hard work, but it is also a lot of fun. Maybe you, too, will someday find a fossil which will add to
our understanding of the history of life on earth.
© 1995 by Lynne M. Clos. This book may not be republished by any other party; however, as long as it is used
for educational purposes and no profit is involved, all or part of it may be freely reproduced and distributed.
Lynne M. Clos holds a master's degree from the University of Colorado in museum studies with a specialization in
vertebrate paleontology. She lives in Boulder, Colorado, with her husband, Chris, and two daughters, Allison and Mattie. She has
done research on fossil lizards and has a particular interest in igniting a love of fossils in young children, who are potential
future paleontologists.