What causes tides?

The Pacific Ocean is in a constant state of flux. While winds and currents make waves, the sun and moon interact to cause daily fluctuations in ocean levels. The sun and moon both pull the surface of the earth towards them, and oceanic waters are particularly affected by this attraction. The gravitational pull on the oceans causes water to bulge towards the orbiting moon. The varying position of the moon creates high and low tides. The tidal bulge created when ocean waters are pulled toward the moon is the high tide. Between each high tide, there is a low tide. As the moon rotates around the earth each day, water is displaced from the side of the earth facing the moon and also from the side of the earth facing away from the moon. The bulging of the waters on both sides of the earth occurs in response to the moon’s orbit. Because each orbit takes 24 hours and 50 minutes, there are usually two high tides and two low tides each day. However, because each orbit takes slightly longer than 24 hours, the timing of the high and low tides shift each day. There is also variation in the tidal range. When the sun and moon are aligned - during the full moon and new moon - the gravitational pull on the earth’s water is greater, causing very high tides and very low tides called spring tides. By contrast, when the moon and the sun are not aligned - in the first and third quarter of the lunar cycle - their gravitational forces partially cancel each other out, and the tidal range is less. These tides are called neap tides.


Click on a section below to learn more about Pacific tides

Queen Charlotte Shelf
Queen Charlotte Sound
Vancouver Island