Have you been to the ocean or even a large lake? Watching the rhythm of the water and tides can be soothing or even frightening because of their movement and the shape they undertake. They can be small with a particular rhythm or they can be large with rage-like progressions. Tides are one of the most important factors when discussing the relationship and movement of water across the ocean.
Waves give rhythm to the ocean and they transport energy over vast distances. Where they make landfall, waves help to sculpt a unique and dynamic mosaic of coastal habitats. They impart a watery pulse upon intertidal zones and trim back coastal sand dunes as they creep towards the sea. Where coasts are rocky, waves and tides can, over time, erode the shoreline leaving dramatic sea cliffs. Thus, understanding ocean waves is an important part of understanding the coastal habitats they influence.
When waves meet the shore, they are reflected which means that wave is pushed back or resisted by the shore (or any hard surface) such that the wave motion is sent back in the other direction. Additionally, when waves meet a shore, it is refracted. As the wave approaches the shore it experiences friction as it moves over the sea floor. This frictional force bends or refracts the wave differently depending on the characteristics of the sea floor.
Tides are the regular rising and falling of sea level caused by the effects of the gravitational attraction of the earth and moon, and the earth and sun. The solid Earth moves only minutely toward the moon and sun, but the liquid moves more. Gravitational attraction between two objects is regulated by the mass of the two objects divided by the square of the distance between them. So, although the mass of the sun is 27 million times greater than the mass of the moon, the moon has the dominant influence over the timing of the tides because the great distance to the sun diminishes its gravitational influence relative to the moon.
The timing of the arrival of the tidal wave shifts each day. As the earth spins to the east on its axis, the moon revolves around the earth in the same direction, but more slowly than the earth’s spins. Therefore, it takes an extra 50 minutes longer than the 24-hour day for the moon to catch up to the same location above the earth that it was the day before, resulting in the timing shift of the tides each day.
The height of a tidal wave is regulated by the relative position of the earth, moon, and sun. The gravitational force is strongest, and therefore the wave height highest, during the new and full phases of the moon when the earth, sun and moon are positioned in a line. The gravitational force is weakest during the quarter phases of the moon when a line connecting the earth, sun, and moon would construct a right angle.
Gravitational attraction is what sets the tidal wave in motion. The revolution speed of the moon around the earth regulates the timing of the wave, and the relative positions of the earth, moon, and sun regulate the wave height. However, the presence of the continents and the shape of the ocean basins alter the tidal wave from the ideal wave we would calculate if there were no other influences. Therefore, when predicting the arrival timing and height of a tidal wave, one must include local geographic influences on the wave. The resulting complexity leads to locations on the earth that experience one high tide (one peak and one trough of the tidal wave) or two peaks and troughs per day. Those with two peaks and troughs may have high tides of similar heights or very differing heights. The vertical distance between the peak and the trough may be just a few inches as in some parts of the Florida coast where you'd hardly notice the passing of the tidal wave, as oppose to a tidal wave as high as 55 feet, as in the Bay of Fundy, Canada, where the changing tide is hard to miss.
Tides are wonderfully complex and mesmerizing to watch even at their most frightening heights. They are one of nature’s beautiful sites but dangerous as well. The more we know about nature and its complexities the more opportunity we will have to predict their outcome and save lives. Tides are one of the most important factors when discussing the relationship and movement of water across the ocean.
Tide. (2011). Retrieved from Encylcopedia Britannica: http://www.britannica.com/EBchecked/topic/595148/tide
This online encyclopedia provided a lot of information on ocean tides and how they occur. This site gave incite to the gravitational pulls of the moon and sun and its relationship to tidal waves.
Peppas, L. (2008). Ocean, tidal, and wave energy: Power from the sea. (Vol. 8, pp. 1-32). Crabtree Publishing Company.
This children's book provides information on tidal waves along with information on the use of renewable resources. It presents physical and mathematical descriptions of several generic wave energy conversion techniques, along with their uses and performance characteristics, plus several electro-mechanical energy conversion techniques and worked examples.
Wikipedia (n.d.). Tsunami. Retrieved from http://en.wikipedia.org/wiki/Tsunami
This web site was a great web site to learn about tidal waves and tsunamis. There was many links present to further look deeper into tidal waves and tsunamis. This article also gave the history, how they are generated, characteristics, and how waves are formed based on aspects other than gravitational pulls. The animations provided on the web site were very helpful as well.
Walker, J. (2006). The Flying Circus of Physics/ Edition 22. Wiley, John & Sons, Incorporated.
This book was a great book to learn about various topics along with tidal waves and their complexities. They provide a question and answer for each topic. This would be a great book to have in your classroom.
Title Wave Settlement Services, LLC. (Producer). (2007-2008). Title wave. [Web Photo]. Retrieved from http://www.tidalwavesettlements.com/tidal_wave_1.jpg
Mel Schwartz. (Producer). (2011). Collapsing the wave: Creating new realities. [Web Photo]. Retrieved from http://blog.melschwartz.com/wp-content/uploads/2011/09/tidal_wave_1039.jpeg
Encyclopædia Britannica. (Producer). (2011). Tide. [Web Graphic]. Retrieved from http://www.britannica.com/bps/media-view/128174/1/0/0
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