Tidal cycles are the regular rise and fall of sea levels, primarily caused by the gravitational pull of the moon and, to a lesser extent, the sun on the Earth.
The Basics of Tides
Here's a breakdown of how it works:
- Lunar Influence: The moon's gravity exerts a significant force, pulling the Earth and its water towards it. This creates a bulge of water on the side of the Earth facing the moon.
- Inertial Force: An equal bulge occurs on the opposite side of the Earth due to inertia, as the planet is essentially pulled away from the water on that side.
Tidal Patterns
As the Earth rotates, different locations pass through these bulges, resulting in tides. The most common pattern is semi-diurnal tides, where two high tides and two low tides occur in a 24 hour and 50-minute lunar day.
Here’s what we know from the reference:
- Two High and Two Low Tides: Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas experience two high and two low tides every 24 hours and 50 minutes.
- Time Between High Tides: High tides occur approximately 12 hours and 25 minutes apart.
- Time from High to Low Tide: It takes about six hours and 12.5 minutes for the water at the shore to transition from high to low tide, and vice versa.
Tidal Cycle Timing
The lunar day is 24 hours and 50 minutes, not 24 hours, because the moon is also moving in its orbit around the Earth. This means each tide happens about 50 minutes later each day.
Additional Factors Affecting Tides
While the moon is the primary influence, several other factors can affect tides:
- Sun's Gravity: Although much farther away, the sun also influences tides, resulting in spring and neap tides.
- Spring Tides: Occur during new and full moons when the sun, Earth, and moon are aligned. These tides are higher than average.
- Neap Tides: Occur during quarter moons when the sun and moon are at right angles to each other. These tides are lower than average.
- Coastal Shape and Depth: The shape of coastlines and the depth of the ocean floor can also affect tidal patterns, leading to different tide heights in different locations.
- Local Weather: Wind and storm surges can temporarily raise or lower sea levels.
Summary of Tidal Cycle
| Aspect | Description |
|---|---|
| Cause | Primarily the moon's gravitational pull and, to a lesser extent, the sun's. |
| Pattern | Typically two high tides and two low tides every 24 hours and 50 minutes. |
| Timing | High tides occur 12 hours and 25 minutes apart; transitions between high and low tides take 6 hours and 12.5 mins. |
| Influences | Lunar cycle, solar cycle, coastal shape, ocean depth, local weather. |
| Example Tides | Spring tides (high high tides, low low tides) and Neap tides (moderate tides) |
