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STRUCTURE AND MOTIONBy Kaila, Chelsey, Corey and Tessie

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What are tides?Tides are the periodic variation in the surface level of the oceans and of bays, gulfs, inlets, and estuaries, caused by gravitational attraction of the moon and sun.

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What cause tides?Tides are caused by gravity pulling on the bodies of water on the Earth and upon the Earth itself. There are 2 gravitational bodies that affect tides. The sun and the moon.

The Moon is much closer to the Earth so it has a much greater influence upon the tides. The earth and the moon are two great masses that have a great gravitational pull on each other. This is what keeps the moon in orbit around the earth, and it is also what causes tides to occur in the ocean. The moon’s gravity pulls on the earth, and pulls the water towards it. The water moves up into a slight bulge on the side of the earth that faces the moon. At the same time, there is a force pulling water out in the opposite direction of the moon.

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Spring TidesSpring tides occur during the full moon andthe new moon. When it’s a full or new moon, the gravitational pull of the Moon and Sun are combined. At these times, the high tides are very high and the low tides are very low. Spring tides are especially strong tides. They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides.

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Neap TidesNeap tides occur during quarter moons. During the moon's quarter phases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are very weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to oneanother.

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The geometric relationship of the Moon and the Sun to specific locations on the Earth's surface results in thecreation of three different types of tides.

1 Diurnal tides (Solar Tides) Solar Tides occur in parts of the northern Gulf of Mexico and Southeast Asia. These kind of tides have one high and one low water per tidal day.

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2 Semi-diurnal tides (Lunar Tides) Lunar tides have two high and two low waters per tidal day. They are common on the Atlantic coasts of the United States and Europe.

3 Mixed tides During mixed tides high-water and low-water differ extremely. In these tides we have a higher high water and lower high water as well as higher low water and lower low water. The tides around west coast of Canada and the United States are of this type.

The Proxigean Spring Tide is a rare, unusually high tide. This occurs when the Moon is unusually close to the Earth and in the New Moon phase (when the Moon is between the Sun and the Earth). The proxigean spring tide occurs at most once every 1.5 years.

 

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What is a wave?

A wave is one of a series of ridges that moves across the surface of a liquid.

What causes waves?

Waves are causedby the wind blowingon the surface ofthe water. Theheight of wavesdepends on the force of the wind.Waves can alsooccur by themovement of platescreating what wecall a tsunami.

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Two types of waves :

Ripple Waves & Swells

Ripple Waves: Also known ascapillary wavesappear on smoothwaters. These wavesdie out when thewind stops blowing.Surface disturbance or tension can causethe waves to move. They are small, surface water waves with a very short wavelength.

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Swells:

Swells are formed when seas move away from their point of origin. For example by a tropical storm or wind system. Due to this, they are far more stable in direction and frequency than normal oceanicwaves. Separatingnaturally as perdirection and wavelength. Swells are usually significantly largerthan normal waves and have along wavelength.

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The three ways a Tsunami can be formed are: volcanic eruptions, earthquakes (causes plates to shift) and by landslides. All of the these, in some way or another, cause a large body ofwater to be displaced. This water has to find some place to go to, and that’s how a Tsunami is created. Tsunami’s are a collection of waves somejoining to make massive waves.when Tsunami’s reach land instead of slowing down and eventually stopping like smallerwaves, they continue on todestroy whatever is in there path.

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Energy from the sun isn't evenly distributed, most of the energy enters the Earth at the equator. This causes large temperate differences between the equator and the poles. Movement of air and oceans is controlled by these temperature differences and the result is a transfer of heat from the equator to the poles. Half the heat transport around the planet is controlled by the oceans making them a huge part of the Earth’s climate control system.

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There are a number of ocean currents found around the Earth. A current is like a vast river within the ocean, flowing from one place to another. These currents are caused by differences in temperature, differences in salinity, and by wind. Currents are responsible for a vast amount of movement of the water found in the Earth’s oceans.

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Thermohaline currents are created by differences in temperature and salinity. These two factors are two of the greatest forces behind the variation in water density. Different densities of water end up flowing in different directions, which creates a large loop of water circulation, referred to as a conveyor belt. This is caused by the water circulation.

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In wind-driven currents, the wind exerts a certain amount of force on the surface of the water, causing it to move. In some of the more well-known wind-driven currents, like the jet stream, the current can get quite strong from the same persistent wind blowing in the same direction over a long period.

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http://www.seafriends.org.nz/oceano/waves.htmhttp://www.bajalife.com/bordercrossing/surfingsafety.htmlhttp://www.mamashealth.com/surf/waves.asphttp://www.britannica.com/EBchecked/topic/424285/ocean/67103/Wind-waves-and-swellhttp://www.lobstermanspage.net/tides/tidetype.html http://www.physicalgeography.net/fundamentals/8r.html http://home.hiwaay.net/~krcool/Astro/moon/moontides/ http://www.math.ubc.ca/~cass/courses/m309-01a/lai/types.html http://www.waterlevels.gc.ca/english/Canada.shtml http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/oceanography_currents_1.html http://www.atmosphere.mpg.de/enid/1vc.html