James J. Scroggins, age 12, of Tallassee, Alabama, for his question:

Is Niagara Falls really eroding?

The news from Niagara is far from good. The falls, naturally, are falling and gradually eroding as they have through thousands of years. Now we are told that more serious erosion threatens the cliffs around them where millions of visitors stand to admire the tumbling torrents. Fortunately, an enormous engineering project is planned to reinforce the rocky foundations before anything happens to threaten the view.

In 1969, the U.S. Army Corps of Engineers performed the impossible task of turning off Niagara Falls. At least they stopped the American side of the great waterfalls. They did it by building a dam up the river and diverting this portion of the stream to another channel. The reason for this fantastic operation was to survey the possibility of future erosion both under and around the falls.

American and Canadian geologists have been concerned about erosion in this region for a long time. In the 1950s, a joint engineering project was undertaken to reduce the natural erosion that normally occurs under the falls and in the river bed below the plunging cataract. The more recent survey was concerned with possible erosion in the cliffs facing the falls.

The survey took several years and the report was not pleasant. The engineers found cracks and fissures deep in the rocky formations. This sort of erosion threatens future rockslides. However, wouldn't you know, those same engineering geniuses suggested a remedy.

Right now, the American Falls have been turned back on. But not, we hope, for long. The anti erosion project calls for shutting off the water again while mighty cables and other means are installed deep in the weakened rocks. The proposed project to be undertaken jointly by the United States and Canada is expected to cost $38,500,000.

This sort of erosion in the cliffs around the falls is rather new. However, erosion in the Niagara region is an old old story going back several thousand years to when the falls were formed after the last ice age. The cascading cataracts, of course, tumble over steep cliffs into the bed of the Niagara. From time to time chunks tumble down from the cliff faces    and the falls inch back down the river.

During an average year, the cliffs behind the tumbling waters are eroded from a few inches to three or four feet. As in all waterfalls, the pressure of the tumbling water weakens and washes away the cliffs and gouges deep pits in the river bed below the falls.

In the case of Niagara, erosion is speeded up by the particular rock formation. The river bed is surfaced with a layer of durable dolomite limestone, laid down some 300 million years ago. Below this tough layer are weak shales, very prone to erosion. This undermines the dolomite, leaving ledges jutting out at the tops of the cliffs. From time to time these tumble down in rock slides. However, geologists estimate that the falls will take about 27,000 years to erode back as far as Lake Erie    and the proposed engineering project may preserve the stupendous view even longer.