What causes waves in the ocean? All you need to know
- The science behind ocean waves, known as oceanography, is a complex yet fascinating topic.
- Waves result from energy moving through water, which makes it flow in a circular manner.
- Various factors, including wind, the Moon, earthquakes, and underwater landslides, cause ocean waves.
The oceans, seemingly endless expanses of water, are in constant motion. From the gentle lapping of the tide to the ferocious crashing of a storm surge, the oceans are a force to be reckoned with. But what causes these intriguing waves, and how do they form?
The science behind ocean waves, known as oceanography, is a complex and fascinating topic that has captivated scientists and beachgoers alike for centuries. From the physics of wind-generated waves to the geological forces that trigger tsunamis, join Interesting Engineering (IE) as we discover the science of how ocean waves are made.
What's the tallest wave ever recorded on Earth? We'll reveal that too!
What are ocean waves?
Whether you're on the boat or at the beach, the ocean is constantly moving in the form of waves. These result from energy moving through the water, which makes it flow in a circular manner.
In reality, though, water doesn't actually travel in waves. Rather, waves transmit energy, not water, through the ocean; if unhindered, waves can cross an entire ocean basin.
What causes waves in the ocean?
Various factors, including wind, earthquakes, and underwater landslides, cause ocean waves.
The most common cause of waves is wind. When the wind blows over the ocean's surface, it creates friction between the wind and the surface of the water, causing ripples. These ripples then grow into larger waves as the wind continues to blow and can travel for thousands of miles across the ocean, leaving a trail of white foam in their wake.
Of course, if there is stronger wind, as in a hurricane, then a storm surge can result—a series of long waves created far from shore. As these waves move into shallower water, they intensify and grow bigger and more powerful.
Earthquakes can cause ocean waves too. When an underwater earthquake occurs, the energy released by the movement of the tectonic plates creates seismic waves that travel through the Earth's crust.
These waves can cause the ocean floor to move vertically, which results in the displacement of a large volume of water. This displacement creates a series of waves that travel away from the earthquake's epicenter.
Landslides are various types of ground movement, including rock falls, slope failures, debris flows, and slumps, and can also cause ocean waves. Wave generation occurs when a landslide displaces the water from above (subaerial) or below (submarine).
Various factors that cause an underwater landslide include tectonic activity and changes in water depth and sediment makeup.
Sometimes a landslide can lead to a tsunami wave depending on the amount of landslide material that displaces the water, the speed it is moving, and the depth it occurs in.
In fact, this was the case in 1979 along the coast of southern France during the construction of an airport runway in Nice. One hypothesis is that the activity from this project triggered a submarine landslide, which sent destructive tsunami waves into Antibes harbor. The amount of debris that plunged into the ocean was estimated to have a volume of 150 million cubic meters.
Debris from an erupting volcano falling into the ocean can also generate waves. While not technically landslides, icefalls, avalanches, and glacial calving—the breaking off of big chunks of ice from a glacier—can have similar effects to them in terms of creating waves.
The gravitational pull of the sun and moon on the Earth also causes waves. In fact, if you could view the Earth from space, you would see the oceans bulging out (this is a high tide). On the side of the Earth facing the moon, the moon's gravitational force pulls the ocean's waters slightly toward it, creating a bulge. On the opposite of the Earth, inertia creates a second bulge. These bulges move with the Moon, creating high and low tides.
Types of ocean waves
There are a variety of different types of ocean waves, each with its own unique characteristics. Some of the most common types of ocean waves include:
The most common type of ocean wave is the wind wave, also known as a surface wave. These waves are created by the wind blowing over the water's surface. They are characterized by their long wavelength and are usually the most common type of wave found in the ocean.
The speed and direction of the wind and the fetch (the distance over which the wind blows) determine the waves' size and shape.
Local winds, such as those blowing close to the shore, do not produce swells. Instead, these come about as a result of powerful storms interacting with a massive fetch of water in the open ocean.
These waves have a longer wavelength and are generally larger than wind waves.
They can travel great distances, often crossing entire ocean basins, and are often responsible for creating powerful surf breaks on distant shores.
Underwater earthquakes, volcanic eruptions, or landslides cause tsunami waves. These waves can be huge and destructive, with wavelengths of up to 100 miles and heights of over 100 feet. Tsunamis caused by earthquakes can travel up to 500 miles per hour in the deep ocean. The size and strength of a tsunami wave are determined by several factors.
This includes the magnitude of the earthquake, the depth of the focus of the earthquake, and the distance from the coast. The larger the magnitude of the earthquake and the closer it is to the coast, the more destructive the tsunami can be.
The 2004 Indian Ocean earthquake and tsunami serve as one tragic example. The tsunami was set off by a powerful undersea earthquake, measuring 9.1 on the Richter scale, that struck off the coast of Sumatra island. The quake caused the ocean floor to rapidly rise by up to 131 feet, triggering a massive tsunami. Within just 20 minutes of the earthquake, the first of several 100-foot waves were hitting the closest shoreline in Banda Aceh.
The tsunami waves continued to travel for another eight hours and 5,000 miles, striking Thailand, India, Sri Lanka, and, eventually, the coast of South Africa. Around 230,000 people died, and millions lost everything.
The interaction of different layers of water in the ocean causes internal waves. These waves have a much smaller amplitude (height) than surface waves and are not visible from the surface.
They can, however, significantly impact ocean currents and the distribution of marine life.
Lastly, tides are caused by the gravitational pull of the Moon and the Sun on the ocean. Tidal waves have a very long wavelength, and the height of the wave changes as the tide comes in and goes out.
Tidal waves are predictable and regular, producing high tides about every 12 hours and 25 minutes.
What is the tallest wave ever recorded on Earth?
Imagine standing at the base of a skyscraper that is 1,720 feet tall (that's nearly a third of a mile). Now, imagine that that skyscraper is not made of concrete and steel—but water.
This is the incredible height that the tallest wave ever recorded on Earth reached when a massive tsunami struck Lituya Bay, Alaska, in 1958.
The restricted inlet of the bay received an estimated 90 million tonnes of rock and 40 million cubic yards (30 million cubic meters ) of debris due to a landslide triggered by an earthquake. The consequent water displacement created a megatsunami that was heard as far away as 50 miles (80 kilometers) from its origin.
Additionally, the destructive force of this wave was so great that it completely stripped the trees from the hillsides surrounding the bay, leaving the area barren.
Ocean waves: concluding notes
The existence and majesty of ocean waves remind us of the raw, untamed forces that shape our planet. From the gentle lapping of the shore to towering tsunamis, ocean waves are a constant reminder that Mother Nature is an uncontrollable force.
Oceanographers worldwide continue to forward their knowledge on the dynamics of ocean waves. While the field is fascinating, studying waves is also essential for developing mitigation measures in the event that they do become destructive.
But putting natural dangers aside, we hope you take a moment to marvel at nature's breathtaking beauty the next time you're at the beach and see an ocean wave.