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Shubenacadie
River Adventure Tours
FAQs
What is a "tidal bore"?
A tidal bore is a natural phenomenon, which is seen in very few parts
of the world. The Bay of Fundy is particularly noted for its extremely
high tides, the highest in the world, and for its tidal bores.
As is generally known, the rise and fall of ocean tides is caused by
the gravitational "pull" of the moon on the earth's watery blanket.
At most places along the ocean shores, high tides occur regularly every
12 hours, 25 minutes.
In the open ocean the tide only rises and falls a fraction of a meter.
However, in most V-shaped bays and inlets the tide enters the broad
end and the water literally "piles up" as it moves up the bay. In certain
areas, such as the Bay of Fundy, the natural period of oscillation is
very, close to the tidal period and, just like water sloshing back and
forth in a bowl, the rise and fall of the tide is greatly amplified.
Thus, the tide water enters the bay at its widest point, and as it passes
along toward the head of the bay, it is in effect squeezed by the ever-narrowing
sides and by the constant "shallowing" of the bottom.
NASA photo from the Space
Shuttle (October 1994)
From Bottom to Top: the Minas Channel off the Bay of Fundy; Cape Split;
the Minas Basin; Cobequid Bay; and the Shubenacadie and Stewiacke River
System. The Town of Truro, Nova Scotia is visable at the head of Cobequid
Bay, to the far right is the city of Halifax.
"The largest tidal fluctuations in the world, sometimes exceeding 50
feet (15 meters), create a constant agitation in the sediment that is
suspended in these basins. This can be seen in the discoloration at
the head of the bay."
Click on the NASA photo above to zoom
in on the Shubenacadie River.
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At the very head
of the bay this advancing tide becomes a wave varying; from just a ripple
to several feet in height, and this wave continues into and up the rivers
which empty into the bay. This wave is referred to as a "Tidal Bore".
Thus, we have the phenomenon of a river changing its flow before your
very eyes, created by the tidal wave, or bore, flowing in OVER the outgoing
river water.
The height of the tidal bore increases with the range of the tide. The
range of the tide varies with the phases of the moon, the distance to
the moon and other factors. For information on tide times on the Shubenacadie
see our Schedule of Tides.
Information provided by
the Marine Environmental Data Service, Department of Fisheries and Oceans,
Ottawa, Canada.
The tidal bore on the Shubenacadie
River may appear inconsequential compared to the surge of water that follows
in its wake. |
