WAVES
Wind-Generated Waves
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The most common type of ocean wave, created by the friction of wind blowing over the water's surface.
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The size and shape of the waves depend on wind speed, duration, and fetch (the distance the wind blows over the water). Stronger winds, longer durations, and longer fetches create larger and more powerful waves
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As the wind blows, it creates a disturbance in the water, transferring energy that propagates as waves. The water molecules themselves don't travel along with the wave, but rather move in circular orbits as the wave passes.
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Wind-generated waves can be further categorized into various types based on their size and shape:
- Swell: Long, rolling waves generated by distant storms, often traveling vast distances without losing much energy.
- Wind waves: Shorter, choppier waves formed by local winds.
- Breaking waves: When wind waves reach shallow water, they become unstable and collapse, creating the familiar whitecaps seen on beaches
Other Wave Types:
- Tsunamis: Giant waves caused by underwater earthquakes, volcanic eruptions, or landslides. They can travel across oceans at incredible speeds and have devastating consequences when they reach land.
- Tides: The rhythmic rise and fall of the ocean's surface, primarily caused by the gravitational pull of the moon and sun. While not technically waves, they significantly influence wave behavior in coastal areas.
- Seiches: Standing waves formed in enclosed bodies of water like lakes or bays, caused by sudden changes in atmospheric pressure or underwater disturbances
When you see a wave rolling in on the beach, it might seem like the water itself is traveling across the ocean. However, that's not quite the case! Here's what's really happening with the motion of waves and water molecules:
Wave Motion:
- Waves are actually disturbances that transport energy, not water itself. Imagine a long line of people standing shoulder-to-shoulder. If one person at the end suddenly pushes the person next to them, that "push" travels down the line as each person relays it to the next, but the people themselves only move slightly back and forth in place.
- Similarly, in a wave, the water molecules don't travel long distances. Instead, they move in circular orbits as the wave passes.
Two types of wave motion:
- Transverse waves: The water molecules move up and down, perpendicular to the direction the wave is traveling. This is the typical motion seen in wind-generated waves and swell.
- Longitudinal waves: The water molecules move back and forth, in the same direction as the wave is traveling. These are less common in open water but can occur in sound waves underwater.
Factors affecting wave motion:
- Wind: The primary force creating waves, with stronger winds generating larger and more powerful waves.
- Fetch: The distance the wind blows over the water, impacting wave size and strength. Longer fetches allow waves to grow larger.
- Water depth: As waves approach shallow water, they slow down, become taller, and eventually break due to changes in drag and pressure.
Water molecules:
- While not traveling long distances, water molecules in a wave undergo circular motion. The size of the circle determines the wave height.
- Deeper water allows for larger circular orbits and therefore higher waves.
- This motion also creates currents within the water column, transporting nutrients and affecting marine life.
Waves, whether in the ocean, air, or even light, exhibit several defining characteristics that help us understand their behavior and impact. Here are some of the most important:
1. Wavelength (λ):
- This is the horizontal distance between two consecutive repeated points on a wave, like the distance between two wave crests or two troughs. It represents the spatial extent of one complete wave cycle.
2. Frequency (ν):
- This is the number of wave cycles that pass a fixed point in one second. It is measured in Hertz (Hz) and determines the wave's pitch or how often it repeats. Higher frequency means more cycles per second and a higher-pitched sound or faster-moving wave.
3. Period (T):
- This is the inverse of frequency (T = 1/ν) and represents the time it takes for one complete wave cycle to pass a fixed point. It's measured in seconds and relates to the wave's speed – larger periods usually indicate slower waves.
4. Amplitude (A):
- This is the maximum displacement of a point on the wave from its resting position. For water waves, it's the vertical distance between the crest (highest point) and the trough (lowest point). Amplitude determines the wave's intensity or strength.
5. Wave Velocity (v):
- This is the speed at which the wave disturbance propagates through the medium. It is not the speed of the individual water molecules themselves, which only move in circular orbits as the wave passes. Wave velocity depends on the properties of the medium (e.g., water depth for ocean waves) and the wavelength
