When we find fossil ferns in the rock we call coal, we discover again how lively a planet this is. We also discover that life doesn't just live here--it helps build the earth.We have a habit of thinking of Earth as inert and dead--just rock. But that habit of thinking can get in the way of understanding how Earth works. In fact, much of the Earth we know has been created by living organisms.
Beginning about 340 million years ago, and continuing for 60 million years, land life on earth found its way onto barren land and colonized it. Plants formed great swampy forests of tree ferns, conifers, and horsetails. Insects rapidly developed many forms, and amphibians became large creatures that looked somewhat like alligators.
The plants that formed these vast forests grew using sunlight, just as plants do now. As plants in these forests died, lots of them were covered by water and became, over a long time, beds of peat. Over a long time, these peat beds were covered with mud and sediments. The weight of these materials on top of the peat squeezed the water out of the peat. Later pressure and heat slowly, slowly transformed the peat into coal. This process has been going on ever since. The "younger" coal beds we discover today are poor-quality coal for burning. The oldest coal is the best coal.
Life creates other parts of the earth's crust, too. In the oceans, for billions of years, shell-building algae and zooplankton have been living and dying and falling to the ocean floor, where their shells eventually became limestone, chalk, and other kinds of rocks.
Some of them transformed into natural gas and petroleum--life created the oil and gas we all depend on.
Sea life, in the form of ancient iron-concentrating bacteria, has also created the deposits of iron that we mine. Fossil shark teeth are frequently found in iron mines.
Other bacteria concentrated aluminum from seawater and created the bauxite deposits we mine now for beverage cans and airplane skins.
Life created all the petroleum, all the coal, and all the natural gas there is.There are many other examples.
The point is that Earth's crust is partly the result of life. So Life doesn't just use Earth as a stage where it plays out its dramas. Life creates some of the stage.
Earth spent hundreds of millions of years putting sunlight energy into the bank in earth's crust. All the oil, coal, and natural gas that exists comes from organisms that transformed solar energy into their bodies. This vast bank of stored energy in the earth's crust is now quickly being withdrawn by our civilization.
Top of Page