The regular rise and fall of ocean levels across the globe are known as tides. These natural phenomena are primarily influenced by the gravitational pull of celestial bodies. While different types of tides occur throughout the lunar cycle, this article focuses on neap tides.
What Are Neap Tides?
Neap tides are characterized by a minimal tidal range, meaning the difference between the high tide and the subsequent low tide is smaller than average. During a neap tide, the high tides are not as high as usual, and the low tides are not as low as usual, resulting in a more moderate fluctuation of sea level. The term “neap” itself comes from an Anglo-Saxon word meaning “without power,” reflecting the reduced intensity of these tides.
Neap tides occur twice each lunar month, approximately every two weeks. They happen about seven days after a spring tide, marking a period of moderate tidal activity.
The Moon, Sun, and Earth Alignment
Neap tides occur because of a specific alignment of the Moon, Sun, and Earth. This alignment causes the gravitational forces of the Sun and Moon to partially counteract each other. During a neap tide, the Sun and Moon are positioned at a right angle, or 90 degrees, relative to Earth.
This right-angle configuration happens during the first quarter and third quarter moon phases. At these times, the Moon appears “half full” from Earth. The gravitational pull of the Sun works against the gravitational pull of the Moon, reducing the overall tidal bulge. Instead of combining to create a larger pull, their forces pull the ocean’s waters in different directions, leading to a diminished tidal range.
Neap Tides Versus Spring Tides
To understand neap tides, it is helpful to compare them with spring tides, which are their opposite. Spring tides are known for having the greatest tidal range, featuring the highest high tides and the lowest low tides. This occurs when the Sun, Moon, and Earth are aligned in a straight line.
This straight-line alignment, known as syzygy, happens during both the new moon and full moon phases. In this configuration, the gravitational forces of the Sun and Moon combine, reinforcing each other to create a stronger pull on Earth’s oceans. Spring tides and neap tides each occur twice a month, alternating roughly every seven days.