The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (more exactly, when the ecliptic longitudes of the Sun and Moon differ by 180°). This means that the lunar hemisphere facing Earth – the near side – is completely sunlit and appears as a circular disk. The full moon occurs roughly once a month.
The tide chart above shows the height and times of high tide and low tide for Half Moon Bay, California.
The combined gravitational force of the Moon and the Sun causes the tides in Earth's oceans. There are 2 high tides and 2 low tides every 24 hours and 50 minutes (lunar day). Because the tidal force of the Moon is more than twice as strong as the Sun's, the tides follow the lunar day, not the solar day. It takes half a lunar day, on average 12 hours and 25 minutes, from one high tide to the next, so we have high and low tides nearly twice a day. According to the National Ocean Service, there are some exceptions to the main rule of 2 tides every lunar day: there are a few places, for instance along the coastline of the Gulf of Mexico, where there is only 1 tide per day.
The moon and sun are primarily responsible for the rising and falling of ocean tides. However, for any particular spot on Earth’s surface, the height of the tides and their fluctuation in time also depend on the shape of your specific beach and the the angle of the seabed leading up to your beach, plus your larger coastline and the prevailing ocean currents and winds. This is the spring tide: the highest (and lowest) tide. Spring tides are not named for the season. This is spring in the sense of jump, burst forth, rise. Should you expect these extra-high tides on the exact day of a supermoon? Probably not.
The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Since the earth is rotating while this is happening, two tides occur each day. Isaac Newton (1642 -1727) was the first person to explain tides scientifically. The Proxigean Spring Tide is a rare, unusually high tide. This very high tide occurs when the moon is both unusually close to the Earth (at its closest perigee, called the proxigee) and in the New Moon phase (when the Moon is between the Sun and the Earth).
The Moon’s gravity pulls on the Earth, causing the water to swell in the direction of the Moon. The exact timing and number of high tides per day varies by location, and is affected by such factors as geography, the shape of the coastline, the salinity of the water, the time of year, and the weather, among other things. On average, though, most coastal areas experience one high tide every 12 and 1/2 hours, or about twice per day. Image showing the Ocean Tides and Currents
The side of the Earth facing the moon will have a tidal bulge called the direct tide. Similarly, on the opposite side of the planet, the ocean will also be bulging. This is called the opposite tide, and it happens because the inertial force of the Earth exceeds the gravitational force of the moon at this location. Therefore, high tides occur simultaneously on the the opposite sides of the Earth. The phases of the moon also affect tides. When the moon is at its full or new moon phase, high tides are at their highest, while low tides are lower than usual. Called spring tides, these tides occur when the sun, moon and the Earth all line up.
High tide (left) and low tide (right) in the Bay of Fundy in Canada. Photo by Samuel Wantman. High tides and low tides are caused by the moon. The moon's gravitational pull generates something called the tidal force. As the Earth rotates, your region of Earth passes through both of these bulges each day. When you're in one of the bulges, you experience a high tide. When you're not in one of the bulges, you experience a low tide. This cycle of two high tides and two low tides occurs most days on most of the coastlines of the world. This animation shows the tidal force in a view of Earth from the North Pole.