Reversing Falls Information
A Natural Wonder
Twice each day 100 billion tons of water, a volume equal to all of the world’s rivers … enters and exits the Bay of Fundy. At this location, water levels rise as much as 9 meters or 28 feet in a tidal cycle. Reversing Falls Rapids experiences two tidal cycles daily resulting in 2 low tides and 2 high tides. Each complete cycle is roughly 12 hours and 10 minutes. Between the tidal extremes is a calm period known as “slack tide”, this condition lasts for just 20 minutes and is the only time vessels can safely pass through the gorge.
Why Reversing “Falls” Rapids? If you could see beneath the water, you would find rocky ledges near the surface stretching from the pulp mill to the Reversing Falls bridge, these create the rapids. Then immediately after the bridge, the river bed plunges 60 meters or 200 feet into a massive pool, deep enough to cover the 15 story Saint John City Hall building.
Interestingly, five thousand years ago, sea level was 30 meters or 100 feet lower in this area. Native people living here at that time enjoyed an impressive waterfall!
Reversing Falls Rapids is a Natural Wonder. Amazingly this area has an equally incredible and much older geological story. Two ancient continents meet here in the gorge. The dark volcanic rock originated in today’s Africa and is about 515 million years old and the light grey rock is marble formed from ancient sea creatures. It is about 1.2 billion years old and originated near the South Pole! Visit the Stonehammer Geopark website for information about the Reversing Falls Rapids site and other geosites.
The Reversing Falls Rapids gorge through which the Saint John River flows was created 11,000 years ago. As the ice ages receded water flows increased off the land. The force of moving ice, water and sediment broke a new route to the ocean here.
Today the Saint John River has a large watershed of 56 thousand kilometers. The watershed reaches from Maine USA in the west and Quebec in the north to lands covering one-third of New Brunswick. All water passes through the narrow gorge here at the Reversing Falls Rapids and enters the Bay of Fundy!
Why do tides happen?
The answer to “why do tides happen” is GRAVITY … a natural phenomenon which attracts all things with mass like planets and stars to one another.
Our nearby moon has the greatest influence. As the moon orbits our planet, it pulls earth and water towards it. A bulge or “high tide” forms on the side of the planet facing the moon … and on the opposite side too as water at Earth’s center straightens out. Tidal strength varies. It’s greatest when Sun, Earth and Moon are aligned … causing a “spring tide”. Canada’s Bay of Fundy … a funnel-shaped arm of the North Atlantic has the highest tides in the world!
It happens here for two main reasons:
First the shape of the bay. The entrance is wide and deep. By contrast, the east end is narrow and shallow with no outlet. As the tidal waters flow in (an amount equal to the flow of all the world’s rivers) the water is squeezed upward … creating giant tides. Tides at the east end of the bay can reach 53 feet!
Secondly the bottom topography and timing of the tides work with the shape of the bay to create a natural resonance … a rocking effect that exaggerates the tides. As the tide retreats, the high waters at the east end collapse and rock back toward the entrance of the bay … intensifying the low tide.
Here at the Reversing Falls Rapids, there are three distinct tidal conditions:
LOW TIDE. As the water rushes out to the Bay of Fundy, dramatic whirlpools form.
SLACK or NEUTRAL tide is the time between low and high tides. Opposing forces are in balance, and waters are calm for about 20 minutes. This is the time vessels can safely sail through the gorge.
HIGH TIDE. A force strong enough to reverse the direction of the Saint John River and raise water levels as far away as Fredericton …. 90 kilometers to the north!
Only a strong spring snowmelt in the watershed can temporarily stop this phenomenon!
Tidal Information
The vertical line on the chart below indicates the current tide status. The valleys and peaks are the upcoming high and low tide extremes. Between high and low tide is SLACK TIDE, when Reversing Falls Rapids briefly becomes placid ! To see whirlpools … come at the low tide extreme. To see Reversing Falls Rapids in reverse … come at the high tide extreme. The pull of the Moon and the shape of the Bay of Fundy are the largest contributing factors to the famous Reversing Falls Rapids tides. Full moons, especially a harvest moon can produce swings in the water level of 9 meters or 28 feet.