Reversing Falls Rapids is the world’s greatest example of tidal impact upon a river.
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 nine 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 61 meters into a massive pool, deep enough to cover the 15 story Saint John City Hall building.
Interestingly, five thousand years ago, sea level was 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 500-million years old and the light grey rock is marble formed from ancient see creatures. It is about 1.2 billion years old and originated near the South Pole ! Also see 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-kilometres. The watershed reaches to Maine USA in the west and Quebec to the north, all water passes through the gorge here at the Reversing Falls Rapids !