WAVES AND TIDES

Definition: Waves are disturbances that transfer energy through a medium (such as water, air, or even space). In the context of the ocean, waves are surface oscillations of water caused primarily by wind.

Components of Waves:

1. Crest: The highest point of a wave.
2. Trough: The lowest point of a wave.
3. Wave Height: The vertical distance between the crest and the trough.
4. Wavelength: The horizontal distance between two successive crests or troughs.
5. Wave Period: The time it takes for two successive crests (or troughs) to pass a fixed point.
6. Frequency: The number of waves passing a fixed point per unit time.
7. Amplitude: The height of the wave crest above the average water level.

Examples of Waves:

• Ocean Waves: Created by the wind blowing across the surface of the sea. They can range from small ripples to large swells.
• Tsunami: A series of ocean waves with very long wavelengths caused by large-scale disturbances such as undersea earthquakes.

Formation of Waves: Waves are typically formed by the transfer of wind energy to the water. As the wind blows across the surface, it creates friction and pushes the water in the direction of the wind. The size and strength of the waves depend on the wind speed, duration, and the distance over which the wind blows (fetch).

Tides

Definition: Tides are the periodic rise and fall of sea levels caused by the gravitational interactions between the Earth, Moon, and Sun.

Components of Tides:

1. High Tide: When the sea level is at its highest point.
2. Low Tide: When the sea level is at its lowest point.
3. Tidal Range: The vertical difference between high tide and low tide.
4. Tidal Cycle: The regular pattern of tides, typically occurring twice daily (semidiurnal) or once daily (diurnal).

Types of Tides:

1. Spring Tides: Occur during the full moon and new moon phases when the Earth, Moon, and Sun are aligned, resulting in higher high tides and lower low tides.
2. Neap Tides: Occur during the first and third quarters of the moon when the Sun and Moon are at right angles relative to the Earth, leading to lower high tides and higher low tides.

Examples of Tides:

• Bay of Fundy: Known for having one of the highest tidal ranges in the world, with differences of up to 16 meters (52 feet) between high and low tide.
• Tidal Bores: A strong tide that pushes up a river, forming a wave that travels upstream. Examples include the Qiantang River in China.

Formation of Tides: Tides are caused by the gravitational pull of the Moon and the Sun on the Earth’s oceans. The Moon has a greater effect due to its proximity to Earth. The gravitational forces cause the water to bulge out on the side of Earth closest to the Moon, creating a high tide. Another high tide occurs on the opposite side due to the inertia of the water. As the Earth rotates, different areas pass through these bulges, experiencing high and low tides.

Example to Illustrate Waves and Tides

Example: A Day at the Beach

• Waves: Imagine you’re at the beach, observing the regular waves crashing onto the shore. These waves are generated by the wind blowing across the ocean’s surface. You can see the crests and troughs and measure the wave height and wavelength. If you time the interval between the arrival of successive waves, you’re measuring the wave period.

Tides: Over the course of the day, you notice the water level rising and falling. In the morning, the water is at its highest point (high tide), making it ideal for activities like swimming. By the afternoon, the water level has dropped significantly (low tide), revealing more of the beach and making it possible to explore tidal pools and exposed marine life. This cyclical change in sea level is due to the gravitational pull of the Moon and the Sun on Earth’s oceans.