What Are Mixed Tides?

A mixed tide is a tidal cycle which consists of two unequal high tides and two unequal low tides in approximately a 24 hour period. Mixed tides are actually the second most common type of tidal cycle found on earth. This is a tidal cycle which varies in size. Mixed tides are harder to predict and responsible for the famous surfing waves of the west coast of the United States and Mexico.

A mixed tide is a tidal cycle which contains two unequal high tides and two unequal low tides. The most common type of tidal cycle is called a semidiurnal, which consists of two equal high tides and two equal low tides in a 24-hour-and-50-minute period. A mixed tide still has two high tides and two low tides per 24-hour-and-50-minute period, but these tides are not equal. There is a high high tide, a high low tide followed by a low high tide and a low low tide.

The moon's gravitational force is the main influence of a tidal cycle. Whether it is a semidiurnal tide or diurnal tide the pull from the moon and proximity of the moon to the earth is the largest factor to why tides occur. The second component to the tidal cycle is the gravitational pull from the sun. Just as the earth revolves around the sun, the moon revolves around the earth. The closer the moon is to the earth the greater the tides will be. The same goes for the closeness of the earth to the sun, although since the moon is in a closer proximity to the earth it has the greatest influence over the cycle of tides.

A mixed tide occurs in locations where there is a combination of a diriurnal and semidiurnal tide. Since a diurnal tide only has one high tide and one low tide during the typical tidal cycle and a semidiurnal tide has two high tides and two low tides during the same tidal cycle the combination of these two types of tides creates what is known as a mixed tide. This combination does not create even high tides or even low tides. There will be one high tide higher than the next high tide and one low tide that is lower than the following low tide.

Mixed tides are actually the second most common type of tides found in the world. Mixed tides can be found all along the west coast of the United States as well as Mexico, the Caribbean Sea and Arabian Sea. Where there are mixed tides, tide charts are an important tool to judge the time and height of the current tidal cycle.