Water And Oceanography

What causes Ocean Waves

Sarah Sunshine's image for:
"What causes Ocean Waves"
Image by: 

I love the feeling I get when I look out over the ocean. Whether I'm in a plane or on the shore, I find its vastness to be simply awe-inspiring. There's almost nothing more magical than the ocean and all of its many properties- its incredible breadth and depth, the enormous number of species to which it is home, and, perhaps most enchanting, the waves.

The mechanism behind the production of actual ocean waves, not tides lapping at the shore as many people might envision waves, can be explained through simple physics. The water in the Earth's oceans should not be viewed as one single entity, as it is actually, analogous to all matter, composed of a series of many, many molecules. These molecules are in perpetual motion at a rate faster than that of a solid, yet still slower than that of a gas. The gas surrounding the oceans' water, what we know as air, is indeed made up of molecules, as well. Basic ocean waves are created when the molecules in the air, moving in patterns called wind, act upon those present in the water. This causes a transfer of energy, known as friction, to take place, in turn causing the water molecules in the ocean to move in a coordinated, up and down manner, which we perceive as oscillations, or waves.

Perhaps you've noticed waves similar to those found in the ocean on a lake, pond, or even a puddle. This can be attributed to the fact that wind, the cause of waves, is present all over the planet. Another interesting aspect of ocean waves is their non-uniformity- sometimes the surface of the ocean is almost as smooth as a sheet of glass, whereas at other times, the ocean waves are extremely choppy and may even be dangerous. As you surely know, weather, including the wind responsible for ocean waves, is ever-changing- for this reason are the waves of the ocean so very dynamic, as well. If, on any given day, the wind is particularly soft, there would be much less movement present in the air to act upon the molecules in the ocean, so the waves would, too, be calm. It would then follow that during a storm with heavy wind, the waves would be much more extreme.

Earlier in this article, I mentioned a distinction between waves and tides. As just discussed, waves are caused by friction between the air and the sea. Tides, on the other hand, are periodic variations in the water levels of the oceans which may be credited to the gravitational pulls of both the Sun and the Moon. Picture, if you will, our planet and Moon at any point in their cycles, on the Earth, both the points closest to and furthest from the Moon will have the highest tides, and the two points directly in between those will have the lowest tides. This is because of the gravitational force of the Moon exerted on the Earth- the Moon's gravitational pull causes a pinch at those points on the Earth at the ends of the axis formed perpendicularly to the axis through the earth at both its closest and furthest points from the Moon. This pinch moves water away from those two points it most affects, creating at those points a low tide and at the points closest to and furthest from the Moon, a high tide. Another way of understanding this phenomenon is through picturing, again, the Earth and the Moon, this time imagining as though the water closest to the Moon is being pulled the hardest towards the Moon, then followed by the earth itself, and then, lagging most behind, the water furthest from the Moon; this would also yield an image of two high points in the tide at the points closest to and further from the Moon.

The Moon has a greater effect on the Earth's tides than does the Sun, due to its closer proximity to us, but the Sun does still have a notable effect on the tides. At all times, the Earth is rotating (one full revolution per day), the Moon is orbiting around the Earth (approximately one full orbit every 29.5 days), and the Earth orbits the Sun (fully, once a year). Because of these facts, it would make sense that when the Earth, Sun, and Moon align in certain ways, significant tides would occur. The two basic types of tides caused by this alignment are Spring tides which are particularly high and Neap tides which are unusually low. Spring tides are those that are created when the Moon, Sun, and Earth are all in alignment, either with the Moon positioned between the Sun and Earth, as in a new moon, or on the side of the Earth opposite the Sun, as with a full moon. During these two points in the Moon's cycle around the Earth, the gravitational forces of the Moon and the Sun combine to bring about an even higher tide at those points of the Earth aligned directly with the Moon and Sun, than would occur during a typical high tide. Quite the reverse, the lowest possible tides, called Neap tides, are produced during quarter moons when the gravitational forces of the Sun and the Moon are working in opposition, as a result of their perpendicular positioning to one another, thus causing a counteraction between the two and lowering the overall level of the tide.

The link of tidal waves to the wax and wane of the moon is just one example of the manner in which everything in our world is inextricably bound. On Earth, there exists a complex interplay between all living things and natural phenomena- an incredible balance that is to be constantly respected and valued by all of her inhabitants.

More about this author: Sarah Sunshine

From Around the Web