The regular rise and fall of the ocean’s surface, known as the tide, is a predictable phenomenon driven by astronomical forces. While sea level changes modestly across most coastlines, certain geological configurations cause water to fluctuate dramatically. The vertical difference between high tide and low tide is called the tidal range. Most locations experience a modest range, often only a few feet, but select areas with specific coastal geography undergo extraordinary water movements, creating the world’s most extreme tidal ranges.
The World’s Most Extreme Tidal Location
The location that consistently holds the record for the highest tidal range on Earth is the Bay of Fundy, situated between the Canadian provinces of New Brunswick and Nova Scotia. This massive body of water experiences a staggering fluctuation, with the highest recorded tidal ranges approaching 16 meters (roughly 53 feet), particularly in the Minas Basin arm of the bay. The average tidal range in the Bay of Fundy is approximately 11.7 meters (38.4 feet).
The visual impact of this extreme water movement transforms the landscape twice daily. At high tide, water covers vast mudflats and fills rocky inlets. Just over six hours later, the tide recedes to expose a massive, barren seafloor that can stretch for miles, leaving boats resting on the ground. The sheer volume of water flowing into and out of the bay during each cycle is estimated to be around 115 billion tons, which is more than the combined flow of all the world’s freshwater rivers. This immense power has practical implications for navigation, requiring harbors to be specially engineered to handle the massive vertical movement, and it creates unique ecosystems adapted to the frequent, dramatic exposure of the intertidal zone.
Global Mechanics of Tidal Variation
The fundamental cause of all ocean tides lies in the gravitational interaction between the Earth, the Moon, and the Sun. The Moon exerts the strongest gravitational pull, creating a bulge of water on the side of Earth facing it. A corresponding bulge forms on the opposite side because the Moon’s gravity pulls the solid Earth away from the water. As the Earth rotates beneath these two bulges, most coastal areas experience two high tides and two low tides daily, a pattern known as a semi-diurnal tide.
The Sun also influences tides, though its effect is less than half that of the Moon due to its greater distance. The relative positions of these three celestial bodies modulate the tidal range over the course of a month. When the Sun, Earth, and Moon align in a straight line (during new and full moon phases), their combined gravitational forces create the maximum tidal range, known as a spring tide.
Conversely, when the Sun and Moon are positioned at right angles relative to the Earth, the Sun’s pull partially counteracts the Moon’s. This results in a smaller difference between high and low tides, known as a neap tide, which occurs during the first and third quarter moon phases. While these astronomical forces determine the global tidal potential, they only account for about one meter of tidal range in the open ocean. Local geography transforms this modest wave into the dramatic ranges seen in places like the Bay of Fundy.
Geographic Factors That Amplify Tides
The extreme tides in the Bay of Fundy result from how its specific geography interacts with the incoming tidal wave, not solely from astronomical forces. Three primary geographic factors amplify the tidal range.
Funnel Shape
The bay is shaped like a narrowing funnel. This progressively compresses the incoming water mass traveling from the wider Atlantic Ocean. This constriction forces the same volume of water into an ever-smaller area, causing the water level to rise dramatically higher than it would in a broad, open basin.
Shoaling
The depth of the bay also contributes to amplification. As the tidal wave moves into the shallower waters toward the head of the bay, a process called shoaling occurs. Shoaling forces the energy of the wave upward, further increasing its height.
Tidal Resonance
The most significant factor is tidal resonance, where the bay’s natural period of oscillation matches the timing of the ocean’s tidal cycle. The length and depth of the Bay of Fundy mean the time it takes for a tidal wave to travel from the mouth to the head and back is approximately 12.4 hours—the same interval between high tides. This near-perfect synchronization creates a sloshing effect that continually reinforces the incoming tide, magnifying the basic ocean tide into the immense vertical movement observed.