英語聽力文摘652 尼亞加拉大瀑布正在慢慢消失

Niagara Falls has been a famous honeymoon spot for over a hundred years: some honeymooners have been more faithful to it than to each other.

When The Falls Formed

Since the falls were formed during the late Pleistocene period, about twelve thousand years ago, they have been subject to the force of erosion. As they erode, the falls are moving upstream, so they will one day disappear into Lake Erie.

Like all waterfalls, Niagara erodes because water wears away the softer rock at the base of the cliff, where a turbulent pool forms below the waterfall. Because erosion affects the base of the cliff, the old cliff face will collapse and the new edge will be slightly upstream. The rate of erosion depends on factors like the volume of water going over the edge, the height of the drop, and the type of rocks that make up the base of the waterfall.

Water Volume

At Niagara, the volume of water is very high. In fact, one-fifth of the world’s fresh water empties from the Great Lakes Superior, Huron, Michigan, and Erie over the falls into Lake Ontario. Niagara is the second largest waterfall in the world.

Before you cancel your honeymoon suite with the heart-shaped tub, keep in mind that in the past 12,000 years the falls have moved about seven miles upstream and, at this rate, they will disappear into Lake Erie in just under 23,000 years. Enough time to visit on a honeymoon–and even a second honeymoon.