Jerry Clark, age 13, of Shreveport., La., for his questions
Why are there no plant fossils?
Who says there are no plant fossils? Coal, petroleum, amber like frozen honey, the so called lead in a pencil, the scouring powder we use to clean the bath tub all these and many more are fossil materials which came from ancient plant. Once in a while we find the imprint of a fern frond in a stone or lump of coal. In desert regions, whole tree trunks have been turned to stone. These petrified forests are also the fossil remains of ancient plants.
There have always been many more plants than animals on the earth. Yet few plants are as durable as., say, the bones of a dinosaur. Most vegetation is fragile and tends to decay rapidly. When it does not decay, it tends to pack down in crumpled layers. When conditions are right, this vegetation goes through chemical changes and becomes something else. This happened to the massive beds of vegetation which finally became our seams of glossy black coal. This fossilizing process continues even after the ancient forest has become coal. Finally, the coal becomes soft, waxy graphite, the so called lead used to make pencils.
Petroleum, we suspect, was formed from the teeming plant and animal life in ancient shallow seas. These little plants, perhaps somewhat like our one celled algae, thrived and grow fat under the summer suns of millions of years ago. Their fatty remains were buried and through chemical changes became petroleum and natural gas.
Amber comes from ancient conifer trees. Like modern conifers, these trees were full of tangy resins. When such a tree was damaged, a gob of resin oozed out to eoyer the wound, In time the tree decayed, but the r amber remained to become a beautiful plant fossil.
Much of our cleansing powder is made from diotomeceous earth which is the fossil remains of ancient diatoms. These tiny plants, which encase themselves in shells like microscopic jewel boxes, teemed in the ancient seas, just a s they do today. Their jewel like shells, made of silica which is the same mineral from which an opal is made, sifted through the water and made great piles on the sea floors. When this debris becomes dry land, it is diatomeceous earth. The little diatom cases with their buttons and spikes are used to scour our sinks and bath tubs.
Perhaps the most dramatic plant fossil is petrified wood. This was formed when ancient logs fell into stagnant water where there were no decay bacteria. In time, water dissolved the plant cells and replaced them molecule for molecule with dissolved chemicals: The final petrified wood is a perfect copy of the original plant in semi .precious opal, agate and jasper.