Most people as they walk along this Chicago beach never notice me lying here with the other pebbles, although I'm certain you'll agree that I am more attractive than most of my pebble relatives. This is really quite amazing, considering some of the terrible experiences I have had. I don't look my age at all. In fact, my friends tell me I look younger every day. Perhaps that is because I am constantly growing smaller and smaller instead of just plain growing.
You certainly could never tell by looking at me that I am very old, and yet I have been wearing away to this day, for many ages since I was formed. The earth itself was very young at that time and looked quite different from the world of today. This was the somber, strange, lifeless world of the Archeozoic era.
My career didn't start here in Chicago but up north quite a way, in what is now the south of Canada. At that time I was not a pebble because, you see, pebbles are pieces of larger rocks that have been broken into bits. The breaking-up process is called erosion. It is accomplished by forces of nature like the wind and the water. You could never have a pebble without first having a larger rock, just as you could never have a cake crumb if you had not had a cake from which that crumb had broken.
The very first things that I can remember happened long before I was a pebble. I was still part of a huge mass of rock underneath the surface of the earth. Men have been able to dig quite deep into the earth's crust, but even the deepest mine or hole made by man goes down only about three miles. I was more than thirty miles down, where the temperature is so high that the rocks may be melted. This liquid rock, or magma, is hotter than the red-hot lava coming from a volcano. I was a tiny part of a magma that was pushing its way up to the surface of the earth along the weak places in the rock layers above. Should a magma reach the earth's surface it may cause a volcanic eruption, but most magmas harden underground.
Gradually I felt the magma stop moving and, after what seemed to me like ages, it appeared to be getting slightly cooler. Though I thought at first that this might be my imagination, I soon realized that I could not move around as I had been doing because I was truly cooling and becoming harder. The rock, with me as a part of it, had become solid. 1 was caught in a dark prison in which there was no space to move and from which there seemed to be no way to escape.
It was very uncomfortable at first, but one can get used to almost anything in time, and in a few hundred million years I felt quite at home in my cozy little place in the dark. Everything there was quiet and still. I was surrounded by the familiar rock I had known since the time, ages ago, when it had hardened from liquid magma. I did not know then of the surface of the earth somewhere up above me. As I lay deep in the earth's crust I never imagined the strange but wonderful adventures I would have in ages to come.
- River Journey
- My First Living Friend
- Jet-Propelled Shellfish
- Chicago's Coral Cities
- Undersea Animal Gardens
- Visitor From The Swamp Forest
- Chicago's Great Ice Sheet
How Igneous Rocks are made.
A geology learning resource.
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