Becky Norris., Age 13, Of Portland, Ore., for her question:
What was the Laramide Revolution?
A revolution makes us think of political unrest and a topsy turvy change of goyetents. The laramide revolution, hawever, was an event in the restless geological history of our globe, and the topsy turvy change took place in the earth's crust. It gave birth to our rocky mountains.
The most dramatic revolutions of the world take place slowly in the earth's crust. Mountains rise and fall, glaciers tear at the rocks, the seas flood the land and recede. Wind and water are forever shifting the weight of the earth's crust. And, geologists suspect, there arc forces deeper in the earth operating to readjust these changes and keep the over all weight of the crust in balance.
The laramide revolution was one event in this geological warfare. The surface events which caused it began with the cretaceous period, about 130 million years ago. Where the proud. Rockies now stand, a shallow ditch called a geosyncline stretched from Mexico to Alaska.. The seas crept up from the gulf of mexico and finally linked with the waters of the arctic.
For millions of years, the geosynclinc of the west collected the silty sediments drained from 400 million square miles of soggy soil. In the center of the ditch, the sedimentary layers became six to eight miles thick. This extra weight upset the balance of the earth's crust and set in motion the forces which operate to readjubt the crustal balance.
The floor of the geosyncline began to arch up in long ridges. The present Rockies were being born. As the ridges grew higher, many of them cracked open in deep faults. In many cases, pressures from below forced one side of a fault up and over the opposite side. Deep crustal layers formed 500 million years ago were lifted and shoved over the young rocks formed during the cretaceous period.
The revolutionary upheaval took millions of years. When it was finished, the massive rockies reached from Alaska to Mexico, and the weight of the earth's crust in this area was again in balance. The, earth moving event formed the continental divide of North America and some of its greatest upheavals centered around the laramie mountains of Wyoming and Utah.
We can trace many of the faults of the laramide revolution and see how the thick crustal layers of rock were, pushed up and over one another. One fault runs 200 miles from utah up into canada. In glacier national park, deep layers formed more than 500 million years ago were lifted up to the surface. Later, one of these massive crustal blocks was shoved across the young cretaceous deposits for a distance of 35 miles