Understanding Ocean Tides: Causes and Types

Understanding Tides: Definition and Causes

Tides are periodic and alternative movements of the rise and fall of the sea and large lakes.

They are produced by the gravitational attraction of the Moon and Sun on Earth, which causes changes in the ocean's level.

The Earth-Moon system revolves around a common center of gravity, causing every point on Earth to experience a centrifugal force opposite to the Moon's direction.

Types of Tides

Spring Tides

Spring Tides occur when the Sun, Moon, and Earth are aligned. In this configuration, the gravitational forces of the Moon and Sun combine, producing higher high tides and lower low tides than average.

• Conjunction (New Moon): The Moon is between Earth and the Sun.
• Opposition (Full Moon): Earth is between the Moon and the Sun.

Neap Tides

Neap Tides occur when the Moon and Sun form a 90-degree angle relative to Earth, typically during the Moon's first or third quarter phases (crescent or waning). In this case, their attractive forces counteract each other, diminishing the Moon's primary attraction. This results in tides with a smaller range than the average tidal range. Consequently, tidal currents are also lower due to the reduced volume of water movement.

Lunar Tides

The Moon, being much closer to Earth than the Sun, is the primary cause of tides. When the Moon is directly above a given point on Earth's surface, it exerts a gravitational force on the water, causing it to rise above its normal level, creating a high tide. Water on the portion of Earth farthest from the Moon is also subject to this attraction, forming a second elevation that creates another high tide. The wave crest directly beneath the Moon is called the direct tide, and the one on the diametrically opposite side of Earth is called the opposite tide.

Solar Tides

The Sun also causes the rise of two opposing wave crests, but as the Sun is much farther from Earth, its tidal force is approximately 46% smaller than the Moon's. The combined effect of the Moon's and Sun's forces results in a composite wave with two peaks, whose position depends on their relative alignment at any given instant. During periods of New Moon and Full Moon, when the Sun, Moon, and Earth are aligned, solar and lunar tidal waves coincide, reinforcing each other.