Angel Falls
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Hidden in a wilderness region, called the Gran Sabana, in Venezuela.
They tumble 1000 meters off the edge of an escarpment of the mysterious Auyan Tepuy, a sandstone mesa of 700 sq kms. The Angel Falls were discovered by accident in 1935 by Jimmy Angel (1899-1956), an American adventurer and bush pilot who operated in Central and South America.
Discovery
Last summer I made an excursion to view the Falls and learned of the exciting history of their discovery.
Jimmy Angel owned a Fokker monoplane of 1930's vintage, capable of carrying 3 passengers and freight. He became a legendary figure in Venezuela, in his quest for gold and daredevil flying.
While flying up the Devil's Canyon sector of Auyan Tepuy he spotted amongst the clouds an impressive waterfall that hurtled into space to spray the jungle below.
In 1937 he tried to land his plane on top of the flat-topped mountain close to the Falls, but ended up in a bog. He and his passengers had to abandon the plane and proceed on foot. A near vertical kilometer of cliff was descended to reach the jungle below. After 11 days of bushwhacking they reached an Indian village on a river that lead to civilization.
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Near midnight I booked into the Hotel Italia on the waterfront of the Orinoco River at Cuidad Bolivar, after a long, air-conditioned bus ride from Caracas.
Carlos, the manager, greeted me.
"Want to join a tour group to see the Angel Falls?" he asks, "Come and see me in the morning."
That's service for you!
The Tour
The tourist entry point is the isolated village of Canaima located at a beautiful spot on the Rio Carrao where a series of cataracts plunge into an extensive lagoon. This is Canaima National Park of 3 million hectares and there is no road access. The airstrip perimeter is a clutter of light planes of amazing variety. Twice a day a jet from Caracas disgorges tourists who are shuttled off to up market, air-conditioned accommodation.
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Canoe access to the Angel Falls is restricted to the rainy season, June to November. Thanks to El Niño, the rains had continued and the river was negotiable at the end of November, but only just. Alternatively, weather permitting and with absence of cloud, you can fly by the Falls, but blink and you've missed them.
The Rio Carrao is up to 200 meters wide and leads straight to Auyan Tepuy. We donned lifejackets and huddled under canvas drapes to shelter from the spray as we roared up several scary rapids. Towards dusk we pulled into the bank at Camp Orquidea - a jungle camp beneath towering rocky bluffs.
The shelter was open-sided with a thatch roof. Sandstone floor paving stones show ancient ripple marks. Other tour groups used the camp. About 50 hammocks complete with mosquito nets awaited our tired bodies. Soon the kitchen was a hive of activity and we enjoyed spaghetti bolognaise by candle light, joined by a group of 20 Italians who raged into the night.
Next morning our canoe headed up the tributary Rio Churan to take us deep within the mountains. Rapids were more frequent and frightening. Huge sandstone blocks stud the river bed.
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Our guide explained that an hour's hike up through the jungle will bring us to the Mirador, a rocky outcrop from where we would see the Falls in their entirety. Up, and jungle, are the operative words - a tangle of lianas, fallen branches, mossy rocks and mosquitoes made progress miserable but it was worth the struggle. The cloud cleared from the tops.
A river took off into space high above. What a sight! A tremendous amphitheatre at the base of the Falls was a swirling mass of spray.
A DC3 tourist aircraft flew by, in and out of the cloud - Wow, I thought, I'm glad to be on tierra firma and not dodging mountains!
We clambered down the rocks to the stream and bathed in the first substantial pool below the Falls. The cool mountain waters cleansed us of sweat and grime and left us invigorated for the hike back and a welcome lunch at the boat landing.
The return journey next day by canoe down the Rio Carrao was a delight. Above the rapids, we were put ashore to hike for a few kilometers while the boteros took the boat down unladen for the water level had dropped considerably. The afternoon flight to Cuidad Bolivar by Cessna taxi gave us a bird's eye view of neighbouring mesas poking up from the jungle.
The Bay of Fundy
Iguaçú Falls
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LOCATION
The Iguaçú Falls are located in the Iguaçú National Park, at the border of Brazil and Argentina.
The Iguaçú Falls are located in the Iguaçú National Park, at the border of Brazil and Argentina.
DESCRIPTION
In a horseshoe form, 2,700 meters wide between the two countries, the Iguaçú Falls fill the visitors's view with the spray of 72 meter-high falls - the number of them varies between 150 and 300, depending on the flow of the Iguaçú River. The panorama overwhelms the onlooker with a sensation of fright, fascination and respect for the perfection of nature. A visit to the Falls and the contact with wildlife and the spectacle of the waters awake an emotion that many hope to experience once in a lifetime.
In a horseshoe form, 2,700 meters wide between the two countries, the Iguaçú Falls fill the visitors's view with the spray of 72 meter-high falls - the number of them varies between 150 and 300, depending on the flow of the Iguaçú River. The panorama overwhelms the onlooker with a sensation of fright, fascination and respect for the perfection of nature. A visit to the Falls and the contact with wildlife and the spectacle of the waters awake an emotion that many hope to experience once in a lifetime.
Krakatau (Krakatoa) Island
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On August 27, 1883, the Indonesian island of Rakata almost vanished. In fact, about 75% of the land area of Rakata no longer exists. It was the most violent volcanic eruption recorded in world history that caused the destruction, and left more than 30,000 dead.
Krakatau (Krakatoa) volcano was located on the island of Rakata, 40 km off the west coast of Java. Since early historic ages, violent volcanic activity has been known to exist in the region. The "great eruption" of Krakatau must have taken place around 416 AD, as reported in ancient Javanese scriptures. The eruption formed three Islands (Rakata, Panjang, and Sertung), and caused a 7 km long caldera (cavity) to form underneath Rakata. When Krakatau erupted again in 1883, the island virtually collapsed into its cavity, 300 m below sea level. So violent was the eruption that volcanic ash and debris reached as far west as Madagascar. Tidal waves resulted in the destruction of more than 150 villages, and were felt in France and England. In Australia, hundreds of kilometers away from the site, the explosion was heard.
Since the disappearance of Krakatau, smaller eruptions have been observed. The ocean floor has been since gradually rising, eventually giving birth in 1927 to a new island, north of what remains of Rakata. Today, Anak Krakatau (Son of Krakatau) rises more than 150 m above sea level and is two km in diameter.
Mount Fuji
Mount Kilimanjaro
Niagara Falls
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Geography of Niagara
The Niagara Region is located on a portion of a great plain which runs east to west from the northern Laurentian Highlands (Canadian Shield) approximately 161 kilometers north of Toronto, Ontario to the southern Allegheny Plateau which form the foothills of the Adirondack Mountains and the Appalachian Mountains.
The Niagara table land mass extends 100 kilometers (62 miles), both east and west from the Niagara River.
This plain is a small part of the Great Lakes low lands in which Lake Superior, Lake Michigan, Lake Huron, Lake Erie and Lake Ontario lie.
The areas north and south of the Great Lakes low lands are the high lands.
Climate in Niagara has been similar to the current weather patterns for the past 5,000 years.
Today the Great Lakes hold twenty percent of the worlds fresh water supply. Ninety-nine (99%) percent of this water is of glacial origin.
The Niagara Peninsula is actually an isthmus.
The Niagara Escarpment begins in Watertown New York, USA and ends on the Manatoulin Island in the Province of Ontario, Canada.
It is 1,609 kilometers in length and is the weathered edge of a very ancient sea bottom. Throughout its length from Hamilton, Ontario to Watertown, New York the escarpment ranges from 183 meters (600 feet) above sea level to 189 meters (620 feet) above sea level.
The Niagara Escarpment is the ultimate reason the Falls of Niagara was born. Without the escarpment, Niagara Falls may never have materialized. After millions of years, the Niagara Escarpment continues to erode in a southward direction.
The Niagara Escarpment was formed and existed before glaciations. The land that is now Southern Ontario emerged from the sea of the Paleozoic Era at least 245 million years ago or more.
The Ordovician and the Silurian rocks of the Niagara Escarpment are of the oldest found in Niagara dating back to 430 - 415 million years ago.
The escarpment is not a fault line or a rift line but was created through erosion. It is a "cuesta".
To understand the age of the Niagara Escarpment consider the following time line:
| TIMELINE | |
| YEARS AGO | EVENT |
| 430 - 415 million years ago | rocks of the Niagara Escarpment |
| 295 million years ago | Appalachian Mountains |
| 225 - 83 million years ago | Triassic, Jurassic Period (dinosaurs roam earth) |
| 83 - 60 million years | dinosaurs extinct |
| 1.5 million years ago | earliest man in Africa |
| 14 thousand years ago | continental glaciers in Northern Hemisphere at their maximum extension |
| 14 - 12 thousand years ago | Wisconsin Glacier cover - retreats |
| 12 thousand years ago | Niagara Falls begins |
| 12 - 11 thousand years ago | Lower Great Gorge |
| 10 - 6 thousand years ago | Whirlpool Rapids Gorge |
| 6 thousand years ago | modern Lake Erie |
| 5 thousand years ago | Upper Great Gorge |
The height of the Niagara Escarpment at Lewiston, New York is 76 meters (250 feet).
Five kilometers west of Lewiston, New York, the escarpment is so steep that it rises 73meters ( 240 feet) in 0.4 kilometers (1/4 mile).
The eastern portion of the Niagara Escarpment is higher than in the west. The escarpment at Watertown, New York is 147 meters (483 feet) above sea level while at Hamilton, Ontario the escarpment is 35 meters (116 feet) above sea level.
The ancient uplift and rising crust of the land in the eastern portion of North America is quite noticeable.
Only in Niagara can one find a gravel beach 147 meters (483 feet) above the nearest body of water.
A smaller Onondega Escarpment runs east - west is located along the northern shoreline of Lake Erie. Consisting of Onondega limestone cap rock, this escarpment runs through Buffalo, New York and Fort Erie, Ontario. This escarpment is most noticeable east of Buffalo, however rarely rises more than 10 meters.
Substantial breaks in the Onondega Escarpment have allowed Lake Erie waters to flow into the low lands of the Wainfleet Marsh 10,500 - 11,000 years ago and again 4,000 - 5,000 years ago during periods of time when the water level in the Erie Basin was much higher from the influx of waters from glacial Lake Agassiz.
Other physical breaks in this escarpment can be found at Lowbanks and Highway #58 in Port Colborne.
Between the Niagara Escarpment and the Onondega Escarpment is a relatively flat and poorly drained lowland called the Tonawanda plain.
It is said that the Earth was created 4,600 million years ago. Ever since that time, the forces of nature have been masterfully creating an artwork of ever changing landscape and seascape known as Niagara.
Eons ago, the Niagara area the bottom of an ancient tropical salt water sea. Ancient specimens are being found today deep under the soils of Niagara that are still today found at the bottom of our great oceans.
Approximately 65 million years ago at the end of the Cretaceous and the beginning of the Tertiary periods, scientists claim that a giant asteroid collided with the Earth in the area of the Yucatan Peninsula of Mexico. This collision resulted in a massive amount of debris being propelled into the atmosphere on a world wide scale which caused a catastrophic change in the climate and led to the extinction of the dinosaur and many other life forms.
This event continues to be re-examined and debated and will continue to be debated well into the future, however there is little doubt that the climate made a dramatic change to an era of the Ice Age.
A view of the rock strata along the Niagara Gorge
The Niagara Escarpment was covered with a sheet of ice 2 - 3 kilometers thick (Wisconsin Glacier) 23,000 - 12,000 years ago.
The last glacial ice age occurred during three distinct periods of time during the past 65,000 years. The glacier originated east of Hudson Bay in northern Quebec and Labrador. This great glacier was known as "the Wisconsin Glacier".
The last glacial ice age occurred during three distinct periods of time during the past 65,000 years. The glacier originated east of Hudson Bay in northern Quebec and Labrador. This great glacier was known as "the Wisconsin Glacier".
The early Wisconsin Glacier covered the Niagara District and most of the northern North America 65,000 years ago. This glacier remained for a period of approximately 15,000 years before retreating 50,000 years ago.
The middle Wisconsin Glacier advanced again over the Niagara District 40,000 years ago. It remained for approximately 8,000 years before retreating 32,000 years ago.
The late Wisconsin Glacier advanced again 20,000 years ago. It remained for approximately 8,000 years before beginning it's final retreat 12,000 years ago.
The plain of the lowest beach was 122 - 153 meters (400 - 500 feet) above present Lake Ontario (Lake Iroquois).
As the Glacier retreated, the water levels slowly lowered forming four lakes:
Glacial Lake Algonquin - ( area including Lake Superior, Lake Michigan and Lake Huron)
Glacial Lake Warren - small (Lake Erie)
Glacial Lake Iroquois - small (Lake Ontario)
Glacial Lake Tonawanda - area western New York
Glacial Lake Algonquin - ( area including Lake Superior, Lake Michigan and Lake Huron)
Glacial Lake Warren - small (Lake Erie)
Glacial Lake Iroquois - small (Lake Ontario)
Glacial Lake Tonawanda - area western New York
Glaciers ranged up to 4.8 kilometers (3 miles) thick. Ice at 1.2 kilometers (1 mile) thick would exert a pressure of 150 tons per square foot. It is estimated that the weight of the glacier depressed the earth 61 meters ( 200 feet). When the glacier retreated the land began to rise in what is referred to as glacial rebound.
As the late Wisconsin Glacier retreated northward, it created several outlets:
An outlet from Lake Algonquin (Lake Huron) to Lake Iroquois (Lake Ontario)
An outlet from Lake Algonquin (Lake Huron) through Lake Nippissing to the Ottawa Valley
An outlet from Lake Iroquois (Lake Ontario) through the Mohawk Valley (Rochester) to the Hudson River
An outlet from Lake Algonquin (Lake Huron) through Lake Nippissing to the Ottawa Valley
An outlet from Lake Iroquois (Lake Ontario) through the Mohawk Valley (Rochester) to the Hudson River
The rising of the lands from glacier rebound finally cut off these outlets with the exception of the Niagara River.
During the period of glaciation and shortly afterwards, the climate in Niagara was arctic. Vegetation was tundra and arctic fauna.
Lake Iroquois (Lake Ontario) was nearly the same depth as Lake Warren (Lake Erie). Following the retreat of the middle Wisconsin Glacier and ancient lake which occupied the present Lake Ontario basin was created. This Lake was called Lake Lundy. After the waters of Lake Lundy fell due to the reflex action of the land, it became a smaller lake named Lake Iroquois.
The depth of Lake Iroquois was much lower initially when Iroquois beach was created. The shoreline of Lake Iroquois was carbon dated at 12,000 years old with a degree of accuracy of plus or minus 450 years.
During the life of Lake Iroquois the northern shore rebounded at a greater amount than the southern shore. This resulted in the water levels continually rising along the southern shore causing increased erosion along the edge of the Niagara Peninsula.
Lake Iroquois was a pro-glacial lake. The northern shore of this lake was the southern edge of the retreating glacier.
The waters of glacial Lake Iroquois were held back by the ice of the giant glacier which lay across the St. Lawrence valley to the east. The only outlet for this lake was at Rome and Utica, New York where the water exited to the ocean through the Mohawk and Hudson River Valley.
Later this route shifted to a route north of the Adirondacks through the Champlain Valley. When this happened, the water level in Lake Iroquois dropped 15 meters (50 feet). When the Wisconsin Glacier had retreated north of the St. Lawrence Valley, Lake Iroquois's water level dropped to within several years to sea level.
Over the past ten thousand years, the lake water level has risen to its present level as the eastern end of current Lake Ontario continues its post glacial rebound uplift.
During the past 100 years, the post glacial rebound at the eastern end of Lake Ontario has resulted in the water level at the western end of this lake to rise 0.3 meters.
Glacial Lake Lundy
Fifty thousand years ago, a broad glacier pressed over the Niagara Escarpment holding back the melt waters to the South. This formed a large glacial lake named Lake Lundy.
As the glacier retreated northward, a lower water outlet was created at Rome, New York which resulted in the rapid draining of Lake Lundy. For a very long time after the glacier retreated, it held back the melt waters to such a great level that the Niagara Peninsula and Escarpment were covered by a large lake (Lake Ontario, Lake Huron and Lake Erie were one).
With the retreat of the glacier, the rising land separated both Lake Ontario and Lake Erie
Glacial Lake Tonawanda
Glacial Lake Tonawanda was created with the retreat of the last Wisconsin Glacier. The lake was located east of the Niagara River and covered most of the western New York area to Rochester.
Although large in area, it was shallow. The water along the eastern shore at Rochester, New York was only four feet deep.
At first Lake Tonawanda's only water outlet was the same as Lake Lundy, at Rome New York. Rising land in the east cut off this outlet, forcing waters to seek other outlets.
Lake Tonawanda had five water outlets over the 644 kilometer (400 mile) Niagara Escarpment. These outlets were located in Holley New York, Medina New York, Gasport New York, Lockport New York and Lewiston New York.
Only the outlet to become the main spillway was at Queenston - Lewiston. Here the draining waters flowed over the Niagara Escarpment. It is here where the water falls of Niagara were born. This water course continues to be the main outlet which exists today.
Lake Erie was still very large and the width of the Niagara River was much wider than it is today. The entire area where the Falls are today was under water. The water depth was 9 - 12 meters (30 -40 feet). The slope (glacial moraine) on the west edge of Queen Victoria Park (on top of which the Skylon Tower and Minolta Tower are now situated) was a river bank about 12,000 years ago before the gorge was created.
The retreating glacier was the cause of the reduction in size of this much wider and much deeper glacial river known as the St. David's River into what is now a smaller and shallower river known as the Niagara River.
As the glacier retreated north, the water followed to the much lower land recently uncovered. This caused the draining of the Lake Erie basin and Lake Tonawanda. As these waters drained, the river became much smaller resulting in the uncovering of land such as Niagara Falls, New York. Also uncovered was the present Grand Island and Three Sisters Islands and Queen Victoria Park in Niagara Falls, Ontario.
Birth of Niagara Falls
A view of Roy Terrace - the birth site of Niagara Falls
at the Niagara Escarpment (Queenston-Lewiston)
As the Glacier retreated, the upper Lakes began draining into the lower lakes at five to six locations across the Niagara Escarpment. Twelve thousand years ago, the Niagara River ultimately became the main water outlet over the Niagara Escarpment. The waters of a much larger Lake Erie began to flow over the escarpment into a larger Lake Iroquois (Lake Ontario).
The Niagara River began to flow from the Lake Erie basin through Lake Tonawanda and down the present path of the river to the escarpment.
At this time, the lake plain from Queenston to Niagara on the Lake was covered with the waters of Lake Iroquois (Lake Ontario). The height of the lake was within 11 meters (35 feet) of the average level of the Niagara Escarpment at Queenston, Ontario.
The height of the initial Niagara Falls was only 11 meters (35 feet) as it flowed over the Niagara Escarpment at Queenston to the waters of Lake Iroquois below. As the water flowed over the escarpment to the water below, the water began eating through the glacial material and the limestone rock of the Niagara Escarpment to begin the formation of the Niagara Gorge.
At this time, the lake plain from Queenston to Niagara on the Lake was covered with the waters of Lake Iroquois (Lake Ontario). The height of the lake was within 11 meters (35 feet) of the average level of the Niagara Escarpment at Queenston, Ontario.
The height of the initial Niagara Falls was only 11 meters (35 feet) as it flowed over the Niagara Escarpment at Queenston to the waters of Lake Iroquois below. As the water flowed over the escarpment to the water below, the water began eating through the glacial material and the limestone rock of the Niagara Escarpment to begin the formation of the Niagara Gorge.
The site of the birth of Niagara Falls was discovered by a geologist named Doctor Roy Spencer and today this site is known as "Roy Terrace".
The flow rate of water back then was only twenty-five percent of the present flow rate. Scientists have calculated that the volume of water flowing over the Falls initially was 37,500 cubic feet per second.
As the Glacier continued receding further north, it opened silt barriers allowing waters to drain to the ocean resulting in the lowering of the water levels of Lake Iroquois (Lake Ontario).
The rising of the northern crust of the earth, a reflex action to the weight of a Glacier a half a mile or more thick, caused a faster outpouring of Lake Iroquois (Lake Ontario). The lower 11.2 kilometer (7 mile) stretch of the Niagara River to Lake Ontario was once 19 kilometers (12 miles) long.
As the Glacier continued receding further north, it opened silt barriers allowing waters to drain to the ocean resulting in the lowering of the water levels of Lake Iroquois (Lake Ontario).
The rising of the northern crust of the earth, a reflex action to the weight of a Glacier a half a mile or more thick, caused a faster outpouring of Lake Iroquois (Lake Ontario). The lower 11.2 kilometer (7 mile) stretch of the Niagara River to Lake Ontario was once 19 kilometers (12 miles) long.
Scientists have suggested that the eastern part of the North American continent is still in the process of tilting as part of the glacial reflex action. As the crust of the earth rises along the eastern seaboard the water flowing from the Great Lakes system will become slower.
The beginning of the last glacial retreat began 12,000 years ago. The third and last Wisconsin Glacier retreated east of Hudson Bay in Labrador. As the glacier retreated, the land began to rise. The crust of earth rocks are elastic when bent over large sections.
The Whirlpool - St. David's Buried Gorge
The Whirlpool - St. David's Buried Gorge was a channel for an ancient river which existed before the advance of the third Wisconsin Glacier. It is believed that this gorge was buried in glacial silt during the retreat of this glacier 12,000 years ago and never reopened.
When the Falls of Niagara eroded the gorge back to the present day Thompson Point (where the Spanish Aero Car and the Whirlpool is located), the river found erosion of the rock much easier.
The Niagara River broke through a rock barrier which held back glacial debris which had been previously filled into what was the ancient gorge of the St. David's River. The waters of the Niagara River quickly flushed this area of all the glacial debris (what is today the Whirlpool) and changed direction to follow the ancient gorge a short distance in a southward direction.
It is believed that the Whirlpool Rapids Gorge which extended southward to the present Michigan Central Railroad Bridge, had also been carved from the rock from the ancient St. David's River which was also responsible for the carving out of the now filled in St. David's buried gorge.
The ancient Whirlpool Rapids gorge was 38 meters (125 feet) wide. During the advance of the late Wisconsin Glacier the ancient Whirlpool gorge and the St. David's gorge were filled with glacial debris.
At one moment in time, the ancient river did not make a dog leg turn at the Whirlpool but rather followed a relative straight line via the St. David's Gorge through the present Village of St. David's to the shore of Lake Iroquois (Lake Ontario).
The St. David's buried gorge existed 22,800 years ago. It was a small portion of an ancient drainage system which extended the width of the Niagara Peninsula from Low Banks at Lake Warren (Lake Erie) to St. Catharines at Lake Iroquois (Lake Ontario).
The St. David's Buried Gorge was found to be 1219 meters (4000 feet) long and 305 meters (1000 feet ) wide at the Whirlpool. The gorge was 91 meters (300 feet) deep. This gorge was 200 feet (60 meters) deeper that the current floor of Lake Ontario. The gorge extends into Lake Ontario 2.4 kilometers (1.5 miles) west of the present Niagara River.
When Ontario Hydro was building the intake water tunnels to feed the Sir Adam Beck Hydro-Electric power plant, it was forced to bring the tunnels to the surface while crossing the St. David's Buried Gorge because they could not bore into the glacial debris. Instead they had to build concrete flumes on each side of this crossing to prevent water from being siphoned away through the buried gorge.
In 1998, the Niagara Parks Commission remodeled a portion of the Niagara Parks Golf Course nearest Whirlpool Road. This project consisted of the removal of the second hole and the installation of a large pond. This area of the golf course was built on top of an area of the St. David's Buried Gorge known as Bowman's Ravine. The ravine had previously been used by the Canadian Niagara Power Company as a dumping area for rock debris taken from the wheel-pit excavation.
When the unlined pond which when filled with water, the water immediately leached away into the glacial debris of the buried gorge. This pond needed to be fitted with a liner to hold the water within the confines of the pond.
Smeaton's Ravine
The Smeaton's Ravine is located on the Canadian shoreline opposite the Ontario Hydro Floral Clock. It is the site of an infant water falls that began cutting a small gorge into the side of the existing Niagara Gorge. The gorge of Smeaton's Ravine measures 152 meters (500 feet) long and 46 meters (150 feet) wide. The water fall was only 40 feet to the water below. The source of this water was of the then much wider version of the Niagara River that had a small branch flowing in from the west adjacent to the Niagara Gorge.
Niagara Glen Terraces
The Niagara Glen is today a favorite site for thousands of visitors each year. It is a beautiful picnic area located on the top of the Wintergreen Flats and nature trails to the river below are well marked and plentiful.
This is the site of the Falls of Niagara 6,000 - 7,000 years ago. The water falls at this point was 37 meters (120 feet) to the water pool below.
Here also existed an ancient island similar in size to the present Goat Island. Water flowed around both sides of this island before falling over the edge of the Wintergreen Flats to the water below resulting in two separate water falls. The dual falls continued until the main gorge to the east eroded back far enough past the beginning of the island effectively cutting off the secondary flow to the west of the island. The Falls of Niagara became a single Falls once again.
Today the remnants of the ancient island lay below the Wintergreen Flats in two identifiable terraces.
They are:
Fosters Flats is the portion of the Niagara Glen closest to the river.
Wilson Terrace is the first level just below the Wintergreen Flats. This portion is the steepest and most demanding physically.
Today, the speed of the water flow past the Niagara Glen is 40 kilometers/hr (25 mph).
Wilson Terrace is the first level just below the Wintergreen Flats. This portion is the steepest and most demanding physically.
Today, the speed of the water flow past the Niagara Glen is 40 kilometers/hr (25 mph).
The word "glen" is a Scottish word for a steep sided narrow valley.
Devil's Hole Ravine
Devils Hole Ravine is located along the American shoreline of the Niagara River Gorge just north of the Niagara Glen. It is a deep, bowl shaped basin of the Bloody Run tributary from Glacial Lake Tonawanda.
After the Niagara River eroded the Niagara Gorge beyond Devils Hole, the waters of Lake Tonawanda was still draining. One of the secondary outlets was at Devils Hole where a water falls created a ravine perpendicular to the wall of the Niagara Gorge.
The flow of Lake Tonawanda diminished before this infant gorge could establish itself.
The name Bloody Run recalls the massacre of British soldiers by the Seneca Indians in 1763.
The name Bloody Run recalls the massacre of British soldiers by the Seneca Indians in 1763.
In 1841, Charles Lyell, a British scientist and a father of modern geology came to Niagara Falls. From observations of the rocks at the Falls and along the Niagara River, Lyell was able to demonstrate beyond a doubt that the cascading waters had eroded the gorge from the edge of the escarpment at Queenston - Lewiston to its present location.
Lyell's conclusions were supported by an equally distinguished pioneer American geologist, James Hall. His independent studies for the State of New York included the first accurate survey of the rim of the falls to establish a basis for measuring the rate of recession.
Niagara Falls has eroded 11.4 kilometers (7.1 miles) during the last 12,300 years.
Niagara Falls has eroded 11.4 kilometers (7.1 miles) during the last 12,300 years.
The slowing of the erosion rate is caused by two major factors:
1) the erosion resistant limestone cap rock the Falls of Niagara have been flowing over. This limestone layer began approximately ½ kilometer north of the Rainbow Bridge. As the Falls erode southward, the erosion rate will increase when it reaches Navy Island where the Falls reach a softer layer of rock.2) the development of hydro electric generating plants along the shoreline of the Niagara River have vastly reduced the rate of water flow through water diversion.
In 1938, the deepest flow of water at the crest of the Horseshoe Falls was recorded at 7.6 meters (25 feet). Hydro diversion has reduced the water rate of flow.
There was a single water falls 800 - 600 years ago. The separation of the water falls into the two current water falls: the American & Horseshoe Falls is remarkably new in terms of its 12,000 year history.
Recession of the waterfall brought the Falls of Niagara to the brink of the bedrock sill known as the Lyell / Johnson Ridge at Hubbard Point . The Lyell / Johnson Ridge was the location where the cap rock reaches it maximum height above sea level. This is the location the Falls of Niagara were at their highest. From this point the height of the Falls began to diminish as the cap rock drops dramatically in a southward direction to the site of the current location of the Falls.
Recession of the waterfall brought the Falls of Niagara to the brink of the bedrock sill known as the Lyell / Johnson Ridge at Hubbard Point . The Lyell / Johnson Ridge was the location where the cap rock reaches it maximum height above sea level. This is the location the Falls of Niagara were at their highest. From this point the height of the Falls began to diminish as the cap rock drops dramatically in a southward direction to the site of the current location of the Falls.
The crest line of water falls was relatively straight until after 1775 when the Horseshoe shape began to form.
Two thousand (2,000) years ago, the crest line of the Falls was located north of the current Rainbow Bridge.
Four thousand - five hundred (4,500) years ago, the crest line of the Falls was located north of the current Whirlpool Bridge.
The shape of the crest line determines its stability. The uniform Horseshoe shape of the crest line of the Falls provides greater stability.
The deepest plunge pools are carved out when the crest line of the Falls is relatively stable.
The American Falls has no regular mode of collapse. The present amount of water flowing over the American Falls is insufficient to erode the Irondequoit Dolostone (limestone) talus at the base of the Falls.
The rock surface reaches its maximum at Hubbard Point (along Canadian side of gorge). This point is known as the Lyell / Johnson Ridge.
The US Army Corps of Engineers uncovered a number of problems during the 1969 de-watering of the American Falls. They were:
1. a complex system of joints in the Lockport Limestone cap rock was uncovered. The joints were more numerous near the crest and reached vertically to shale level below increasing likelihood of undermining.
2.Ground water seepage into the numerous joints increased the hydrostatic pressure as did winter freezing forcing segments of the limestone to be forced further a part creating the possibility of further fracturing of this cap rock layer.
3.Weathering and Erosion:
(a) falling and flowing water carry broken or weakened pieces of rock away.
(b) some of the mineral deposits of the Lockport Limestone are washed away when water flushes through the fissures in the rock. These minerals which are normally used to maintain the strength and resilience when absent speed the fracturing process.
(c) wetting and drying of Rochester Shale - tests show that after approximately ten (10) such cycles, the Rochester shale will deteriorate naturally undermining the Lockport Limestone cap rock.
(d) freezing and thawing repeatedly forcing rock to separate and break away.
(e) rock falls that occur expose more weakened and vulnerable rock layers.
Instruments were installed on Prospect Point, Luna Island and Terrapin Point to monitor any future rock movements. Rock bolts, steel dowels and cable tendons were inserted in a pattern at Luna Island and the Bridal Veil Falls to solidify and stabilize the rock as much as possible. Drainage holes were drilled into the Limestone at the American Falls, the Bridal Veil Falls and Terrapin Point to relieve the hydrostatic pressure. Now its up to nature.
The rock talus at the base of the American Falls was left to the forces of nature. It was decided that to remove the talus would be too expensive and create too much of an artificial look. The water flowing over the American Falls is too little to erode the talus so it will be there until the American Falls remains as it is.Stress measurements taken near the crest of the American Falls measured 870 pounds per square inch parallel to the Niagara Gorge. Tensional forces measured near the crest of the American Falls equaled 300 pounds per square inch acting perpendicular to the gorge.A core sample taken from the bed of the American Falls reached the level of Queenston Shale at the depth of 359.2 feet.
In 1972, remedial work was conducted at the Bridal Veil Falls and Luna Island. This included the installation of steel dowel bolts and cable tendons. In addition a series of holes were drilled to relieve hydrostatic pressure.
| PUBLISHED RATES OF RECESSION OF NIAGARA FALLS | ||||
| From | To | Interval | American Falls | Horseshoe Falls |
| 1842 | 1875 | 33 years | 0.23 m/yr. | 0.61 - 1.34 m/yr. |
| 1842 | 1890 | 48 years | 0.20 m/yr. | 0.66 m/yr. |
| 1842 | 1905 | 63 years | very little | 1.16-1.61 m/yr. |
| 1842 | 1911 | 69 years | n/a | 1.52 m/yr. |
| 1875 | 1886 | 11 years | 0.03 m/yr. | 0.57 m/yr. |
| 1875 | 1905 | 30 years | n/a | 1.70-2.01 m/yr. |
| 1886 | 1890 | 4 years | 0.50 m/yr. | 1.52 m/yr. |
| 1905 | 1927 | 22 years | very little | 0.70 m/yr. |
m/yr. = meters per year (average)
From 1842 to 1905, the average rate of erosion of the Horseshoe Falls was 1.16 meters (3.8 feet) per year.
From 1906 to 1927, this rate of erosion was reduced to .70 meters (2.3 feet) per year. This reduction coincided with the large quantity of water being diverted for hydro-electric generation.
In 1896, Thomas Martin wrote that the annual recession of the American Falls was 7½ inches per year and the Horseshoe Falls was 2.18 feet per year.
From 1842 to 1905, the average rate of erosion of the Horseshoe Falls was 1.16 meters (3.8 feet) per year. From 1906 to 1927, this rate of erosion was reduced to .70 meters (2.3 feet) per year. This reduction coincided with the large quantity of water being diverted for hydro-electric generation.
The mean rate of erosion was 3.5 meters (5 feet) per year. Since 1942 the rate has been much slower.
Today, through increased water diversion and anti-erosion remedial steps, the rate of recession at the Horseshoe Falls has been reduced to a fraction of what it used to be. Today it is estimated that erosion of the Horseshoe Falls is less than one foot per year. In the future, through remedial efforts and further water diversion that the amount of erosion at the Horseshoe Falls has been projected to be reduced to approximately 1 foot every 10 years.Today, erosion of the American Falls is estimated at 3 - 4 inches every 10 years. The water flow which is regulated at a minimum level of 10% of the estimated 100,000 cubic feet per second during the summer (50,000 cubic feet per second during winter) is insufficient to cause major erosion.
Niagara River Drainage
The Niagara River drains an area of 254,708 square miles, including the Upper Great Lakes.
The surface area of Lake Erie is 87,845 square miles. It is the shallowest of all the Great Lakes, averaging 60 feet in depth.
The levels of the Great Lakes vary on an annual basis in relation to season, rainfall, evaporation and runoff. The highest water levels are found in mid-summer and the lowest water levels are found in mid-winter.
The internal time required for an increase supply of water to show its effect upon the level of Lake Erie is approximately 76 days.
The internal time required for a decrease in the supply of water to show its effect upon the level of Lake Erie is approximately 132 days.
The extreme variation of water levels in Lake Erie:
greatest variation between 1860 and 1907 was 3.89 feet
maximum one year range occurred in 1892 was 2.28 feet
minimum one year range occurred in 1895 was .87 feet
annual average Lake Erie level variation is 1.56 feet
maximum one year range occurred in 1892 was 2.28 feet
minimum one year range occurred in 1895 was .87 feet
annual average Lake Erie level variation is 1.56 feet
A variation in the level of Lake Erie of one foot at Buffalo, New York equates to a difference in the rate of water flow discharge from Lake Erie into the Niagara River of 20,000 to 25,000 cubic feet per second.
During storms, the water level of Lake Erie at each end may vary as much as fifteen feet.
The average annual rainfall in the Great Lakes equals 36 inches. The average annual evaporation rate in the Great Lakes equals 24 inches.
The water discharge of the Niagara River has been determined by measurements taken at the International Railway Bridge at Buffalo/Ft. Erie (1,800 feet south of Lake Erie). Measurements began in 1897 the engineering staff of the U.S. Great Lakes Survey.
The maximum monthly mean discharge of 257,000 cubic feet of water per second from Lake Erie occurred in March of 1896. This was equivalent to the entire surface of Lake Erie to a depth of 2.44 feet.
The average discharge of the Niagara River between 1860 and 1907 equaled 212,000 cubic feet of water per second.
Between 1860 and 1907, the greatest excess average for any month occurred in June of 1876 at 45,000 cubic feet of water per second or an increase in water flow of 21% (refer to maximum mean discharge).
The greatest average in excess water flow in any one year occurred in 1876 at 26,000 cubic feet of water per second or an increase of 12%.
The greatest water flow deficiency average for any month was March of 1896 at 43,500 cubic feet of water per seconds or a decrease of 21%.
The greatest water flow deficiency in any year occurred in 1895 at 31,800 cubic feet of water per second or a decrease of 15%.
In September 1999, Lake Erie's water level was at 571.19 feet (174.10m) above sea level. This was 4.3 inches (11 cm) below the long term average. Lake Erie's water level was the lowest that has been recorded since 1967.
In February 2000, Lake Erie water level was at 570.08 feet (173.76 m) above sea level. This was 9 inches (23 cm) below the February long term average. Lake Erie's water level was the lowest that has been recorded since 1967.
Summer of 1999 Great Lakes water levels were 16-24 inches (40-60 cm) below those levels recorded in 1998.
In flow water rates from Lake Erie into the Niagara River have been recorded as follows:
Sept. 1999 - Feb.2000 = average 173,400 cubic feet per second
March - August 1999 = average 186,100 cubic feet per second
1900 - 1989 = average 191,800 cubic feet per second
March - August 1999 = average 186,100 cubic feet per second
1900 - 1989 = average 191,800 cubic feet per second
The water out flow rates of the Niagara River at Queenston are as follows:
Sept.1999 - Feb.2000 = 184,000 cubic feet per second (greatest one month average = 188,930 cf/s)
March - August 1999 = 200,660 cubic feet per second (greatest one month average = 207,610 cf/s)
March - August 1998 = 244,620 cubic feet per second (greatest one month average = 256,000 cf/s)
March - August 1999 = 200,660 cubic feet per second (greatest one month average = 207,610 cf/s)
March - August 1998 = 244,620 cubic feet per second (greatest one month average = 256,000 cf/s)
Lake Erie Precipitation Rates are as follows:
Sept.1999 - Feb.2000 = 15.8 inches (40.2 cm) of rain
March - August 1999 = 15.9 inches (40.3 cm) of rain
1900 - 1995 = 19.1 inches (48.5 cm) of rain
March - August 1999 = 15.9 inches (40.3 cm) of rain
1900 - 1995 = 19.1 inches (48.5 cm) of rain
Lake Erie
Approximately ten thousand - five hundred (10,500) years ago, the water level of Lake Erie rose 3 - 4 meters above its present water level. At this time the Upper Great Lakes drained through North Bay and the Mattawa River, to the Ottawa River to the St Lawrence River Valley. This resulted in the water drainage through the Niagara River being reduced to only one tenth (1/10) of its present flow (representing only the drainage of Lake Erie). The reduction of water flow through the Niagara River continued for approximately six thousand - five hundred (6,500) years before the drainage route returned to its previous course through the Niagara River.
This water reduction through the Niagara River correlates to the narrowness of the Niagara River Gorge.
Isostatic rebound had lifted the land surrounding North Bay cutting off the out flow of water from the Nipissing Lakes (Upper Great Lakes). The rising waters on the southern shores of Lake Huron breached the Lake Huron moraine and discharged the entire flow into the Lake Erie basin. This new direction of flow was initially shared with an exit at the southern shore of current Lake Michigan. Over several hundred years, the water level of the Lake Erie Basin rose 3 - 4 meters increasing the flow through the Niagara River. This increased flow caused the rapid recession of the Falls of Niagara through the gorge south of the current Niagara Glen.
Glacial Lake Agassiz had a great influence on the Lake Erie basin.
Eleven thousand (11,000) years ago, pro-glacial Lake Aggassiz initially drained southward over a divide into the Mississippi River basin. As the divide rose from isostatic rebound, the entire flow of the Upper Great Lakes flowed into the Lake Erie basin through the Niagara River.
The increased flow into Lake Erie caused water levels to rise in the basin up to five (5) meters. Water levels of Lake Tonawanda increased accordingly.
Today, the winds can cause the water level in Lake Erie to rise 2 - 5 meters in several hours. Lake Erie is the shallowest of the Great Lakes with an average depth of sixty (60) feet.
Power of the Niagara River
A view of rock strata of the Whirlpool Gorge
above the Whirlpool Rapids
The average flow of water through the Niagara River equals 212,000 cubic feet of water per second, falling a distance of 325 feet from Lake Erie to Lake Ontario would yield a potential 8 million horsepower or 5,965,600 kilowatts.
The difference in elevation from Lake Erie to the base of the Falls of Niagara is a fall of approximately 226 feet.
The difference in elevation from the head of the upper rapids to the base of the Falls is a fall of 212 feet.
The difference in elevation from the Whirlpool Rapids to the mouth of the Niagara Gorge is a fall of 94.5 feet.
The difference in elevation from the head of the gorge (base of Horseshoe Falls) to Fosters Flats at the Niagara Glen is a fall of 78.5 feet.
The Ontario Hydro (Ontario Power Company) Generating Station at the base of the Horseshoe Falls operates under a normal head of 180 feet, utilizing only 85% of the available height of 212 feet.
.075 cubic feet of water per second = 1 horsepower
1 cubic foot of water dropping 170 feet = 25 horsepower
1 cubic foot of water dropping 1 foot = 0.147 horsepower
1 cubic foot of water = 59.5 pounds
A water discharge of 168,000 cubic feet per second falling 212 feet would yield 2,250,000 horsepower.
A horsepower is equivalent to 33,000 foot/pounds per minute or 550 foot/pounds per second.
In 1894 the average flow of water through the Niagara River was 270,000 cubic feet per second = 1,000,000,000 pounds per minute:
61.7 pounds per cubic foot of water X 60 seconds =
3,702 pounds per minute X 270,000 cubic feet of water =
999,540,000 pounds per minute
multiply by height of Falls (161 feet) = 160,925,940,000
divide by 33,000 = 4,876,543.6 Horsepower
Horsepower is a unit of power in the English system of units. It is equal to 33,000 foot pounds per minute or 550 foot pounds per second or approximately 746 watts. The term horsepower originated with James Watt, who determined by experiment that a horse could do 33,000 foot-pounds of work a minute in drawing coal from a coal pit.3,702 pounds per minute X 270,000 cubic feet of water =
999,540,000 pounds per minute
multiply by height of Falls (161 feet) = 160,925,940,000
divide by 33,000 = 4,876,543.6 Horsepower
To convert horsepower to watts (multiply by 745.7)
To convert kilowatts to horsepower (multiply by 1.341)
During the daytime between April 1st and October 31st each year, 100,000 cubic feet of water flow over the Falls of Niagara. Water diversion for Hydro generation is maintained at 112,000 cubic feet of water per second.
During the night between April 1st and October 31st of each year, 50,000 cubic feet of water flow over the Falls of Niagara. Water diversion for hydro generation is maintained at 162,000 cubic feet per second.
From November 1st to March 31st of each year, 50,000 cubic feet of water flow over the Falls of Niagara. Water diversion for hydro generation is maintained at 162,000 cubic feet per second.
Today hydro-electricity being generated at Niagara Falls as follows:
1) Sir Adam Beck Generating Station #1 = 403,900 kilowatts
2) Sir Adam Beck Generating Station #2 =1,223,600 kilowatts
3) Sir Adam Beck Reservoir Generating Station = 176,700 kilowatts
4) Ontario Power Generating Station = 132,500 kilowatts (25 cycle) Retired November 1999
5) Canadian Niagara Power Generating Station = 82,500 kilowatts (25 cycle)
6) Robert Moses Generating Station = 1,950,000 kilowatts
7) Robert Moses Reservoir Generating Station = 240,000 kilowatts
2) Sir Adam Beck Generating Station #2 =1,223,600 kilowatts
3) Sir Adam Beck Reservoir Generating Station = 176,700 kilowatts
4) Ontario Power Generating Station = 132,500 kilowatts (25 cycle) Retired November 1999
5) Canadian Niagara Power Generating Station = 82,500 kilowatts (25 cycle)
6) Robert Moses Generating Station = 1,950,000 kilowatts
7) Robert Moses Reservoir Generating Station = 240,000 kilowatts
A Total of 4,209,200 kilowatts are presently being generated
From September 1999 - February 2000, the average water diversion for hydro-electric power generation was as follows:
Sir Adam Beck #1 & #2 = 57,630 cubic feet per second
Robert Moses Power Station = 63,110 cubic feet per second
Canadian Niagara Power Station (Rankin Plant) = 1,380 cubic feet per second
Ontario Power Generating Station = 390 cubic feet per second (Sept.- Nov.)
Robert Moses Power Station = 63,110 cubic feet per second
Canadian Niagara Power Station (Rankin Plant) = 1,380 cubic feet per second
Ontario Power Generating Station = 390 cubic feet per second (Sept.- Nov.)
From March 1999 - August 1999, the average water diversion for hydro-electric power generation was as follows:
Sir Adam Beck #1 & #2 = 58,800 cubic feet per second
Robert Moses Power Station = 63,140 cubic feet per second
Canadian Niagara Power Station (Rankin Plant) = 560 cubic feet per second
Ontario Power Generating Station = 990 cubic feet per second
Robert Moses Power Station = 63,140 cubic feet per second
Canadian Niagara Power Station (Rankin Plant) = 560 cubic feet per second
Ontario Power Generating Station = 990 cubic feet per second
Rocks & Sedimentary Deposits
Where Rock and Power meet
A view of rock strata of the Niagara Gorge
at the Robert Moses Power Generating Station
The Niagara District sedimentary deposits include:
sandstone
shale
marine limestone
which was laid down during the Silurian period 430 - 390 million years ago.
sandstone
shale
marine limestone
which was laid down during the Silurian period 430 - 390 million years ago.
Throughout the ages, nature has in conjunction with the wind, water & ice created stratified layers of rock and earth in Niagara. The Niagara Gorge provides a snapshot of those layers which would otherwise go unseen.
Rock Layers from top to bottom are:
Silurian Age
Clinton Group
Lockport Limestone
Decew
Rochester Shale
Irondequoit
Neagha
Thorold
Medina Group
Grimsby
Power Glen
Whirlpool
Ordovician
Queenston
The base of the current Horseshoe Falls is at the lower portion of the Clinton Group of rocks.
The base of the Whirlpool is at the base of the Medina group of rocks.
The water level of Lake Ontario is at the rock strata of the Queenston Shale level.
As the water falls reached an area just south of the present Michigan Central Railway Bridge erosion slowed when it encountered the highest limestone ridge in the Niagara District. This limestone ridge extended to just north of present day Eastwood Avenue. The water falls at this point was 15 meters (50 feet) higher than the current water falls. Because of the greater height of the falls the gorge is deeper. At this time Grand Island & Queen Victoria Park was submerged under 30 feet of water.
Precambrian rocks record 80 -85 percent of the Earth's history.
The Phanerozoic Age (the era of well developed life) is recorded in only 15 -20 percent of Earth's history.
Fonthill Kame - Delta
The Village of Fonthill in the Town of Pelham (located approximately 20 miles west of Niagara Falls) is remarkable for what is known as a Kame - Delta . It was the pro-glacial delta of glacial Lake Warren. It was beach of this ancient glacial lake. Gravel's of this sea are found 242 meters (793 feet) above sea level. The steep northern slope marks point of contact with the ice field. The gentler southern slope is the lake ward slope of this glacial delta. This glacial lake was located east of the present day Great Lakes. It exited high over Lake Erie territory and exited into the Lake Ontario basin. It's beach was the last and highest of the gravel margins formed.
During the retreat of the Lake Erie ice lobe of the Wisconsin Glacier which covered the Niagara Peninsula, the southern limit of the ice field remained nearly stationary at the Niagara Escarpment. Melt water from the glacier formed a series of glacial lakes. This melting water flowing from the glacier carried large amounts of debris, laying down a series of layers forming the kame - delta.
The Fonthill Kame-Delta is the highest point of land in the Niagara area. Today this site is readily identified by the many transmission and microwave relay towers situated upon it.
Fossils of Niagara
Approximately 425 million years ago, Niagara was the bottom of an ancient tropical sea. Today fossils from that era can be found deep in the layers of rock of Niagara. Because of the depth of the Niagara Gorge, many of these fossils have been exposed along the walls of the gorge.
Fossils found are:
Trilobites (Trilobata) - sea floor crustaceans (425-240 million years ago) found in Rochester, Grimsby and Clinton layers of rock
Snails (Gastropoda) - spiral shells of snails found in Silurian rocks
Sea Lilies (Crinoidea) - sea floor starfish (425 million years ago) found in Rochester shale rock layer - still in existence at bottom of Atlantic Ocean
Horn Coral (Enterolasma Caliculum) grew on sea bottom (425-400 million years ago) found in Lockport and Clinton layers of rock
Lamp Shells (Phyla Brachiopoda) - clam like shells, eighty different species found in the Clinton & Rochester rock layers
Nautilus (Cephalopod) - ancestors of nautilus, squid & cuttlefish (425 million years ago) found in Medina and Queenston rock layers
Trilobites (Trilobata) - sea floor crustaceans (425-240 million years ago) found in Rochester, Grimsby and Clinton layers of rock
Snails (Gastropoda) - spiral shells of snails found in Silurian rocks
Sea Lilies (Crinoidea) - sea floor starfish (425 million years ago) found in Rochester shale rock layer - still in existence at bottom of Atlantic Ocean
Horn Coral (Enterolasma Caliculum) grew on sea bottom (425-400 million years ago) found in Lockport and Clinton layers of rock
Lamp Shells (Phyla Brachiopoda) - clam like shells, eighty different species found in the Clinton & Rochester rock layers
Nautilus (Cephalopod) - ancestors of nautilus, squid & cuttlefish (425 million years ago) found in Medina and Queenston rock layers
The Future of Niagara Falls
A view of Goat Island and it's rock structure - Niagara Reservation NY State Park
The future of Niagara Falls is not easily predicted. The Falls of Niagara as we know it today will remain as it is for thousands of years to come.
Erosion is the largest factor which will alter its appearance in the future. Some have estimated that the Falls would continue eroding southward for the next 8,000 years at which time it would reach the limits of Lake Erie.
The eastern seaboard of North American is today still rising from the glacial rebound effect. It has been suggested that as the land rises on the eastern seaboard that water flow to the ocean will slow and reverse so that in the future the Falls would be much diminished or cease to exist entirely.
Perhaps the most realistic outlook is that the Falls will continue to erode southward. There is no doubt that at some point in its future that the main Horseshoe Falls once it has eroded far enough south, will cut off the water flow to the American Falls. The Falls of Niagara will once again become one.
The greatest threat to the integrity of the Horseshoe Falls and the American Falls is rock falls. The American Falls has been the victim of many rock falls in the past. As the rock talus collects at the base, it reduces the distance of the water fall and creates more of a cascade effect.
In the future substantial rock falls may affect the appearance and change the Falls of Niagara to mere water cascades and/or rapids.
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