The Tides and Phases of the Moon

Earth's tides are influenced by the gravitational pull of both the moon and the sun. Because the moon is closer to the Earth than the sun, the effect of the moon is greater. Tide levels change on a daily basis and during the month. The highest tides occur when the moon and the sun both exert a gravitational pull on the Earth. This corresponds to the New Moon. A graph of the highest tide each day during a Moon cycle would have a peak at the New Moon, a trough at the first quarter, a lower peak at the Full Moon, and a second trough at the last quarter.

The high tide events are called spring tides. The term is unrelated to the season of the year. It comes from the German word "springen" which in English means to rise up.

Neap tides happen when the sun, moon, and Earth are at right angles to each other. This corresponds to the first and last quarter of the Moon. The smallest high tides result from the cancellation of gravitational forces.

A day is determined by the rotation of the Earth and is about 24 hours. The effect of the Moon is felt over a 26-hour time period. During the 26 hours, all points on Earth undergo a high-low-high-low tide cycle. The tide is high both where the Moon is closest to the water side and on the opposite side. Points in between experience low tides. The highest of the two high tides occurs when the Moon is nearest the shore. High tides are about 13 hours apart. Tides cycle in just over 6 hours.

Can the gravitational pull of the Moon also explain earthquakes? This question remains unanswered. More research is needed, but some scientists are investigating how the Moon may affect Earth's liquid aesthenosphere.

For an explanation of tides using an animated illustration go to "Why Tides?"

To learn more about the phases of the moon and how they are seen here on Earth, go to "Phases of the Moon."

To view the current Moon phase, visit the Naval Observatory.

To find out the tide levels for the Passaic River at the Belleville Bridge, visit "Current Tide Levels." Select "B" at the top of the page. Then find "Belleville" on the list. Click on "Belleville" to find out the tide levels for the Passaic River at that point. To confirm the effect of Moon phases on the tides, select a month of tide data. Graph the highest tide each day versus the day of the month. Then draw the New Moon, First Quarter Moon, Full Moon, and Last Quarter Moon along the top of the graph. You will see that the highest tide occurs under a New Moon.

For near real-time data on NJ coastal tides at Sandy Hook, Atlantic City, and Cape May, use the NOAA tide data. Click on the "select a station" bar. A US map should appear in the frame. Select NJ. This should generate a map of New Jersey. Choose a New Jersey station for data.

Thinking Question: The National Weather Center has issued a hurricane warning for the New Jersey coast. Under what lunar phase and tide conditions would the greatest flooding occur? Least? Using links on this page, search for what conditions were like when tropical storm Floyd hit our area in September 1999. As bad as the flooding was, could it have been worse? Why?

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