RATE OF EROSION OF NIAGARA FALLS
毫无疑问，尼亚加拉大瀑布是大自然中最伟大的奇迹之一。环保主义者担心加拿大和美国的瀑布侵蚀率。然而，在过去五十年中，侵蚀速度已经放缓。
现在的尼亚加拉马蹄瀑布、美国瀑布和新娘面纱瀑布的位置正是过去发生的侵蚀所致。从历史上看，瀑布的侵蚀速度一直在每年3英尺左右。在过去的12,300年间，它已经侵蚀了11.4公里。在过去的200年里，尼亚加拉瀑布已经从安大略湖向伊利湖方向撤退，年侵蚀率为5英尺。然而，自1942年以来，侵蚀率已经下降。由于补救措施得当，目前的侵蚀率已降至每年约1英尺。
尼亚加拉瀑布侵蚀的原因
由于水的冲击和流动，薄弱的岩石被打破并被带走。
由于这个地区的寒冷天气，岩石的不断冻融导致了破损。
在脆弱的岩层上下发生岩石坠落。
当水舔着岩石中的裂缝时，强化岩石的矿物也会被冲走。
大约11000年前，尼亚加拉大瀑布的位置介于今天的安大略省Queenston和纽约州的Lewiston之间。从那以后，由于侵蚀导致其现在的位置，瀑布向南退缩。今天侵蚀率下降的原因之一是由于其目前的位置。
减少侵蚀的原因
水流过石灰岩盖层岩石，比其他岩石更耐腐蚀。未来许多年，当瀑布达到较软的岩层时，侵蚀速度将再次增加。
由于水力发电厂的发展，瀑布的水流量已经下降。这些都是通过尼亚加拉河沿岸的引水来创造的。水流量减少导致侵蚀减缓。
工程师们还在定期开展工作，通过修复故障和修建水下堰等各种补救措施来降低侵蚀速度。
尼亚加拉大瀑布的未来
由于环境方面的努力，预计侵蚀率将进一步下降。研究数据表明瀑布的侵蚀率可以将有望下降到10年内减少1英尺。然而，人们永远无法预测未来，气候变化将在决定陨落的未来方面发挥关键作用。一次重大的岩石坠落也可能改变瀑布的侵蚀速度。有一些科学家推测，尽管美国瀑布的侵蚀速度很慢，但它在2000年内可能会干涸。考虑到所有因素，即使在减少侵蚀的情况下，尼亚加拉大瀑布也可能在大约5万年后不再存在。
简而言之，尼亚加拉大瀑布不会很快消失，但它的未来谁也无法预测。
What is the future of the falls?
- The falls will continue to erode, however, the rate has been greatly reduced due to flow control and diversion for hydro-power generation.
- Recession for at least the last 560 years has been estimated at 1 to 1.5 metres per year.
- Its current rate of erosion is estimated at 1 foot per year and could possibly be reduced to 1 foot per 10 years.
- The current rate of recession is unclear; assessing its value remains the responsibility of the International Joint Commission. The International Boundary Waters Treaty stipulates the minimum amount of flow over the falls during daytime, nighttime and the tourist season.
- Erosive forces include the action of frost from the spray, the dissolving action of the spray itself, and abrasion action of the softer shales by fallen limestone boulders.
- No one knows when the next major rock fall will occur in the Horseshoe Falls; the effect could be to speed up erosion. A stable position is abandoned when the crest line develops a notch configuration and the Falls retreats relatively rapidly until a new stable position is attained.
- It’s also possible that the current or future flow and volume of the river will not be sufficient to carve out a deep enough plunge pool to accommodate rock falls; in this case, the Canadian Falls could be supported by talus in much the same way as the American Falls.
- The Cascade Rapids above the Falls are about 15 metres (50 ft.) higher than the falls today; once that ledge has been breached, the falls will have an extra 15 metres of force.
- Climate change is also an influencing factor on the future of the Niagara River as an integral part of the Great Lakes Basin; models indicate a drying up of the Basin.
- Isostatic rebound continues to affect the Great Lakes Basin and consequently the flow of water through the Niagara River.
- All things considered, scientists speculate that perhaps 2,000 years from now the American Falls could dry up. It is a stationary feature collapsing by rock falls and landslides, carrying less than seven percent of flow before diversion; this bit of water is shallow and spread out, therefore ineffective as a major erosive power.
- As a dry falls, it could appear like the Glen does today.
- The Horseshoe Falls will notch back for about 15,000 years, traveling back about four miles to a softer riverbed (from the southern end of Navy Island to Buffalo/Fort Erie the riverbed is no longer the erosion-resistant limestone but soft Salina shale) after which the rate of erosion will change significantly (remember the bedrock tilts downward to Lake Erie).
- The falls could be replaced by a series of rapids.
- 50,000 years from now, at the present rate of erosion, the remaining 20 miles to Lake Erie will have been undermined. There won’t be a falls anymore, but there will still be a river at work.
Source: Niagara Parks Commission
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