Kurt Ege, age 11, of Duluth, Minnesota, for his question:
Are any mountains being made at present?
The earth's rocky crust fits around the planet somewhat like a ripped and wrinkled jacket. The rips are deep cracks down to the dynamic mantle layer below. The wrinkles are ranges that form when the ragged fragments push together and overlap. The restless crust has been creating mountains here and there through billions of years and the process still goes on.
Right now, scientists are adjusting their minds to the idea that the continents really do drift around the globe. Every previously held idea about mountains and other geological events is being re evaluated. lie know now that the land masses are rafts of crustal material, inching around in slow motion on global tours. The earliest known mountains arose more than two billion years ago. The most recent range began to grow less than a million years ado. It is still growing.
Previously, mountain making was explained by upsets in the weight of the earth's crust. The major ranges arose from geosynclines, long shallow seas that accumulated enormous masses of sediments. These factors are indeed part of the picture. But the more complete story shows how these and other mountain making events are caused by movements of the six major crustal plates.
The Alps and the Apennines, the Caucasus and Pyrenees are fairly young mountains, of the same vintage as the mighty Himalayas. They were born during the Tertiary period that ended about a million years ago. All these mountains were uplifted by a crashing of continental rafts. Africa and the Mediterranean region helped to push up the Alpine hump in central Europe. A continental crash between Eurasia and India humped up the high Himalayas.
The mountains born during that period are young and still growing. On the far side of the world, the western ranges of North and South America, are several million years older though still young as mountains go. .Earthquakes and volcanic activity indicate that this region is still in the mood for mountain making. The earth's latest upheaval is the Coastal Range of California.
Earth scientists now suspect that the western edge of the continent is colliding with the great crustal plate that forms the bed of the Pacific. Great slabs overlap in massive sandwiches. As they bend and buckle, they hoist up the young and growing Coastal Range.
Every era has built its mountains and such gradual upheavals are continuous. Earth scientists have traced the pattern back through the past 200 million yegks: But older ranges seem to follow another pattern. It is suspected that mountain making regions may change with changes in the earth's magnetic field. But at present, scientists have a few answers and a zillion questions on this subject.