Mark Stephen Fowler, age 11, of Houston, Texas, for his question:

What exactly are fossils?

The word fossil means something that has been dug up from the ground. In science it has a special meaning. It means something that has been preserved or buried for a long, long time and that particular something must once have been alive. It may be the remains of ancient animal life. Plant life or animal and plant life mixed together. Fossil remains may also be the imprints of ancient living things left to harden in the mud.

The most spectacular fossils are the bones of the monster dinosaurs. There are also fossilized dinosaur eggs, footprints and imprints of skin. There are fossils of great mammoths preserved in northern glaciers. These are fossils of animal life. Coal is the fossil remains of ancient forests. Amber is ancient resin which is the fossil remains of ancient conifer trees. Sometimes insects were trapped in the amber and we have a plant and animal fossil in one piece. Petroleum is thought to be the remains of ocean life, tiny animals and tiny plants.