Low tides are caused by the Earth's rotation moving coastal regions away from the areas experiencing the Moon's direct gravitational pull, which creates tidal bulges of water.
Understanding Tides
Tides are the rise and fall of sea levels caused primarily by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth. While the Sun also exerts gravitational force, the Moon's influence is about twice as strong because it is much closer to Earth.
The Moon's Tidal Bulges
According to the provided reference:
The moon's gravitational pull or tidal force causes two bulges on Earth (and its water) — one at the point closest to the moon and the other on the direct opposite side of the planet.
These two bulges represent areas where the water is pulled outwards, resulting in high tide. One bulge is caused by the moon's direct pull on the near side of Earth. The bulge on the opposite side is a bit more complex; it's primarily due to inertia and the center of mass of the Earth-Moon system.
How Low Tides Form
As the Earth rotates on its axis, different locations move into and out of these tidal bulges.
As the Earth turns, a region gets closer to or further from the bulges.
When a coastal area is directly under or opposite the Moon, it passes through one of the high-tide bulges. The areas that are between these two bulges, approximately 90 degrees away from the Moon's direct line of pull, experience lower water levels.
The reference clarifies the relationship between distance from the bulge and tide level:
The further it is from one, the lower the tide.
Therefore, low tides occur in the regions positioned between the two main tidal bulges as the Earth spins.
Summary of Low Tide Formation
Here's a simple breakdown of how low tide occurs:
- The Moon's gravity creates two main bulges of high water (high tide) on Earth.
- One bulge is on the side of Earth closest to the Moon.
- The second bulge is on the side of Earth opposite the Moon.
- As the Earth rotates, coastal areas move relative to these stationary bulges.
- Low tide occurs in the areas between these two high-tide bulges, where the water level is relatively lower because it is further from the gravitational influence causing the bulges.
High Tide vs. Low Tide Location
You can visualize the tide levels relative to the tidal bulges caused by the Moon:
| Tide Level | Location Relative to Tidal Bulges (caused by Moon) |
|---|---|
| High Tide | Located within or near the two bulges |
| Low Tide | Located in the regions approximately 90 degrees away from the bulges |
Low tides are a natural consequence of the dynamic interplay between the Moon's gravity, the Earth's rotation, and the inertia of the water.
