Gunkholing: The Tides Tell the Whole Story

Cape Cod Life  /  November/December 2020 /

Writer: Brian Shortsleeve

At low tide in Cape Cod Bay, the tidal flats in Brewster are visible for more than one mile starting at the beach.  Six hours later at high tide in Cape Cod Bay the water level has risen four feet at this beach and up to ten feet in Wellfleet and Provincetown.  Imagine the amount of water it takes to fill all of Cape Cod Bay to this extent in six hours.” Photo by Chris Seuffert.

We include the phases of the moon in the Cape Cod Life Seascapes Calendar because the phases of the moon are important to all of us. The gravitational force of the moon is so strong that it affects pretty much all of us individually. I don’t know a better way to put it than to say it impacts our nervous system and at the very least, “makes us more anxious at times”. When we are more anxious this can impact our lives in many, many ways, for example, in work performance and interpersonal relations. The Japanese Government has for many years allowed important business meetings to be scheduled so as not to coincide with the Full Moon or the New Moon.

To me, the most clear demonstration of the power of the gravity of the moon is to understand how the high and low tides so dramatically effect our harbors, bays, and beaches, in direct proportion to the phases of the moon. Locally, our two highest tides in the months of November and December this year occur on November 15th and December 14th, the exact dates of the New Moon in each of these two months. 

The majority of people feel the effects of moon pressure more so on either the date of the Full Moon or the date of the New Moon. I relate more to the New Moon. I start to feel it one or two days before the New Moon occurs.

I think the high and low tides, in relation to the moon phases, are the most visible demonstration of the power of the moon’s gravity. The measurable rise and fall of the tides is impacted greatly by the configuration of the shorelines boarding a body of water. 

Over a period of twelve and a half hours, at the majority of locations on Martha’s Vineyard, the rise and fall of the tide is between two and three feet. On Nantucket, three feet is pretty normal. On the south side of the Cape, Hyannis Port, and Pleasant Bay in Chatham, is three feet; Falmouth Heights is less than two feet. But in the enclosed areas in Buzzards Bay we start to get up to and over a four foot rise and fall. In Cape Cod Bay, the rise becomes more significant…in Wellfleet, ten feet and in Provincetown, just under ten feet. In Plymouth it is ten feet and from Boston on up to Portland Maine, the rise and fall is between nine and ten feet. By the time you get up to Eastport Maine, the rise in feet is eighteen and a half.

In the middle of the Bay of Fundy, every twelve hours, the tide raises and lowers the level of the water fifty-three and a half feet. In Saint John, New Brunswick, home to the famous “Reversing Falls”, normal rise and fall is twenty-one feet. At the head of the Bay of Fundy, at Burntcoat Head, Nova Scotia, the rise and fall is thirty-eight and a half feet. Here in the Minas Basin, every twelve and a half hours, 160 billion tons of water flow in and out with the tide. This is more water then all of the fresh water rivers in the world in total.

Across the Atlantic, from here on the northern coast of France at Mont-Saint-Michel, the tides rise and fall is just over fifty feet. Here it is said the rising tide comes in at the speed of a galloping horse.

If this isn’t enough to instill respect for the power of the moon, consider this: the moons gravitational effect is so powerful that we have what scientists call a “Land Tide or Earth Tide”. North America gets pulled toward Europe. At certain times of high tide, the Empire State Building in New York is measuredly closer to the Eiffel Tower in Paris.

Feeling anxious at certain times of the month?  Check your moon schedule in the Cape Cod Life calendar.

My Best,

Brian Shortsleeve,


Brian Shortsleeve

Brian Shortsleeve is the owner, publisher, and founder of Cape Cod Life Publications. His personal column, “Gunkholing,” has appeared in all issues of Cape Cod LIFE since the very first issue in 1979.