How Waves Are Formed

Whether you’re a surfer, SCUBA diver, or enjoy spending your time in and around the ocean, you will have noticed the seemingly never-ending roll of the ocean, but have you ever stopped to wonder what these waves are and how ocean waves are formed?

From small ripples across the water’s surface to massive beach breaks and large rolling tsunamis, ocean waves can be found in various forms. Waves are, for the most part, formed from the transfer of wind energy along the surface of a water body. These are most commonly found in the ocean, but larger bodies of water, such as Lake Superior in North America, can form large waves due to wind and tidal activity.

Let’s take a deeper look into waves, what they are, how they are formed, and what impact they have on the ocean and its surrounding ecosystems.

What Is A Wave?

Before taking a look at how waves are formed, we need first to understand what a wave is, as well as the parts of a wave.

Waves are the result of the transfer of energy from one medium to another. This transfer of energy causes ripples in the medium (in this case, the ocean’s water) that spread outward from the point of origin.

This transfer of energy causes particles to heat up and begin vibrating at a faster rate. Energized particles, in this case, water particles, move up when they have high energy and drop when their energy is lower.

A simple way to understand this is by imagining you are holding a rope and shaking it up and down.

When you transfer energy from your body to the rope, parts of the rope move up and down, but the rope does not actually move forward.

Ocean waves work in much the same way. Although this gives the illusion that water is being pushed in a straight line, what is actually happening is that energized water particles are rising, passing their energy to the next particle, and then dropping down into the same space.

Simply put, waves are the result of a transfer of energy and not the forward movements of particles.

Parts Of A Wave

Waves have various components. Understanding what these are will help bring a deeper understanding of how waves are formed and why they act in the way they do.

• Crest: The highest point or peak of a wave.
• Trough: The lowest point of a wave 
• Equilibrium: The resting point of the medium
• Amplitude: Maximum distance from the equilibrium. This is used to determine the strength or intensity of a wave.
• Wave Length: The distance between two corresponding points on a wave
• Wave Height: The distance between the trough and the crest
• Period: The time it takes for one complete cycle (crest and trough) to pass a given point. 
• Frequency: The frequency of a wave refers to the number of complete cycles that occur per unit of time. As frequency increases, the period of the wave decreases.
• Phase: The phase of a wave describes the position of a specific point in its cycle

How Waves Are Formed

There are several types of waves that can be found in the ocean or large water bodies. Although most waves in the ocean are formed by energy transfer from wind, this is not always the case.

Furthermore, the source of a wave can and does change the wave’s characteristics.

Wind Generated Waves

Wind-generated waves, as mentioned above, are the most common type of wave found in the open sea. These waves are generated from the transfer of energy from the wind as it creates friction by running across the surface of the ocean.

Waves created by the wind can vary in size and energy, depending on factors such as wind speed, wind duration, and the distance that the wind blows.

These waves generally have shorter wavelengths and irregular shapes.

That said, waves generated from storms tend to form swell waves, which have longer periods and wavelengths. Swell waves can travel large distances and, when undisturbed, can increase in size and strength as they move across the ocean.

It is these swell waves that bring some of the largest surfable waves to coastlines, where they reshape the shoreline and provide recreation for surfers, bodyboarders, and swimmers.

Storm Surges

When severe weather patterns such as hurricanes and cyclones occur, large amounts of energy are added to the ocean surface, similar to wind-generated waves; however, with this surge comes a rise in sea level due to low atmospheric pressures.

This rise in sea level above the normal tidal level can lead to coastal flooding. Storm surges are among the most destructive wave types and can cause significant damage, especially when the surge occurs at the same time as high tide.

When this happens, surge tides can reach heights of 20 feet or more.

Seismic Waves

Seismic waves are those that are caused by seismic activity on the ocean floor, such as earthquakes, volcanic eruptions, and landslides. Waves like these are common around volcanically active areas such as the Ring of Fire and can cause great damage.

Unlike wind-generated waves, seismic waves occur when large amounts of water are displaced. This displacement results in large, long-period waves known as tsunamis or mega-tsunamis.

Tsunamis can travel for thousands of miles through the ocean before reaching land, often causing devastating effects on the coastline.

Unlike wind and swell waves, seismic waves don’t crash on the coastline. Instead, they roll over the shore, representing a massive rise in sea level, as opposed to the breaking waves that we are familiar with seeing close to shore.

Seiche Waves

Seiche waves (pronounced “saysh“) are standing waves that are found in closed or partially closed environments such as lakes, bays, harbors, and seas.

Standing waves occur when two waves of the same frequency and amplitude travel in opposite directions and interact with each other.

A seiche wave requires a closed or partly closed area in which waves can bounce off and travel back in the opposite direction.

These are long-period waves that can be caused by wind, atmospheric pressure, or seismic activity.

As seiche waves have such an extended period, typically exceeding three or more hours, they are often not noticed.

Gravitational and Tidal Waves

The gravitational pull of the moon and sun on the earth cause the level of the ocean to rise and fall. We know this phenomenon as tides or tidal movements.

Tidal waves are a lot smaller than previously mentioned waves and tend to have low energy and long wave periods.

Tidal waves can significantly change the depth of water, thanks to the push and pull effect of gravity. However, these waves are very different from wind-generated waves.

Large freshwater bodies, such as lakes and dams, can be affected by tidal waves. 

It’s also worth noting that rivers can experience waves caused by tides, known as tidal bores. When water is pushed up a river due to a high tide, it can cause a wave at its leading edge. These river waves are often enjoyed by surfers as they can last for long periods but are very rare and occur in only a few places on Earth.

Internal Waves

Internal waves, also known as gravity waves,  occur under the water surface and are caused by the interaction between ocean currents and stratification (the separation) of water layers due to temperature and salinity.

The interaction between water of different densities causes horizontal waves at slow speeds. The speed of these waves is determined by the density of the water levels, and in some cases, they can move vertically if the density of the layers constantly changes.

Factors Affecting the Size and Power of Waves in the Ocean

Various factors affect the speed, size, and power of a wave in the ocean, many of which combine to create complex wave patterns and variations that are often unpredictable. 

Although numerous undetermined factors can affect how a wave behaves, some of the more common influences on a wave’s characteristics include:

1. Wind Speed and Duration: The speed of the wind and how long it blows is one of the primary influences on a wave’s strength and height. The greater the wind strength, the more energy and, therefore, can transfer more to the ocean. Similarly, the longer the winds blow, the more time energy has to be transferred, thus resulting in larger waves.
2. Fetch: Wind fetch or fetch length refers to the distance of water that the wind has blown over without obstruction. Generally speaking, the longer the fetch, the more time waves have to generate energy from the wind, and therefore, a longer fetch results in larger wave size.
3. Water Depth: As waves approach shallow waters, the lower areas of the wave see a decrease in speed due to friction. Simultaneously, the height of the wave rises, causing a breaking peak. In the deepest parts of the ocean, waves are unobstructed and can travel for longer distances.
4. Ocean Floor Topography: The shape of the ocean floor can change both the direction and power of a wave. Topography, such as underwater mountains, canyons, and ridges, can concentrate, disperse, or bend waves, drastically changing the way they behave.
5. Currents: Currents can affect the characteristics of a wave in a variety of ways. When ocean currents flow in the same direction as the wind, it can increase the growth of a wave. Similarly, if a current flows in a different direction from a wave, it can decrease the wave’s size and or change its shape. This is often seen when rip currents flow through breaking waves on the shore.
6. Tides: As water depth changes with the tides, different tides can bring different effects to waves. High tide brings with it more water, which allows waves to travel further, and with more power. A low tide will bring the opposite effect.
7. Storm and Weather Systems: Intense low-pressure systems that bring with them storms can generate massive waves. These are the storm surges that we previously spoke about.

How Waves Affect The Ecology of The Ocean

Apart from bringing us recreational enjoyment, waves have a significant role to play in the wider ecosystem. 

From shaping and reshaping coastal habitats to mixing and dispersing essential nutrients, often forming sea foam, waves are a contributor to the formation and preservation of intricate ocean habitats such as coral reefs and the intertidal zone.

Waves aid in the dispersal of larvae and ocean plants.

Other marine animals, such as mammals and fish, rely on waves and tides for transportation and relocation, which is essential to maintain a balanced environment and mix the gene pool.

Much of the ocean relies on the energy generated by waves, and without them, the immense biodiversity found in the ocean would not exist.

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