Unearthing secrets of Niagara Falls: The 1969 'shutdown' that transformed an icon

Relatively young in geological terms, Niagara Falls came into existence around 12 thousand years ago, following the retreat of the last glaciation. Since its formation, the waterfall has been pushed back about 7 miles upstream from its original location due to rock erosion.

The most pressing issue for the waterfall is the constant undercutting of its base, leading to a rapid retreat of the edge. But the rate of rock erosion has dramatically slow down due to a series of engineering works performed over the last century.

The most significant and visually dramatic occurred in 1969 when the waterfall was "shut down" for several months using a temporary dam built upstream. Large boulders obstructing the river bed were simultaneously removed, allowing ship cruises to pass right under the fall.

Engineers unearthed two bodies and an innumerable amount of coins at the bottom of Niagara during the "shutdown". They discovered that the entire chunk of rock could not be moved, leaving tourists with an unsightly cliff to behold.

Thus, photos from this period have garnered attention even today. They depict the dramatic transformation of one of the world's most famous waterfalls, triggered by the dumping of 30 thousand tons of rocks.

The New York Times reported that more than 100 thousand people turned up to see the waterless waterfall on the first weekend of June 1969. This was double the number of visitors from the same weekend in the previous year.

Engineers examined boulders for the next five months, but it was only in 1974 that they deduced that these boulders were integral to the waterfall's support. Even though the erosion continues at a reduced pace, predictions indicate Niagara may vanish in about 15 thousand years.