Send the link below via email or IMCopy
Present to your audienceStart remote presentation
- Invited audience members will follow you as you navigate and present
- People invited to a presentation do not need a Prezi account
- This link expires 10 minutes after you close the presentation
- A maximum of 30 users can follow your presentation
- Learn more about this feature in our knowledge base article
Transcript of Ocean Motion
Resources of our Oceans
Oceans are a significant wealth of resources available for us to use: oil and natural gas for fuels, minerals like gold and copper are mined, and salt - all different types of salt come from ocean water. Oceans also are useful for transportation and effective shipment between countries.
Salinity is the measure of the amount of salts dissolved in seawater. There are a lot of salts dissolved in ocean water. (One kilogram of water contains 35 grams of salts = 3.5%). The ocean is not getting saltier, and tends to remain constant.
Some organisms will remove elements from ocean water: via photosynthesis or critters making their shells.
Some salts will precipitate out of ocean water and become actual sediment.
Waves and Tides
A wave is a rhythmic movement that carries energy through matter or space.
A crest is the highest point of a wave.
A trough is the lowest point.
Wavelength is how long the wave is.
Amplitude: half the distance of the wave height is the amplitude - this tells us how much energy the wave is moving. During a storm, amplitudes of waves are generally high - due to all the extra energy from a storm.
Surface currents move water horizontally, and are usually powered by the wind. These are huge circular patterns. Currents can be warm or cold. Surface currents only affect the top few hundred meters of the ocean.
Currents are forced into a circular pattern because of the Coriolis force - causing hills of water to form, which gravity pulls down. As the Earth rotates and gravity pulls, water is forced to move in a circular shape.
We track surface currents in a very old-fashioned way: we throw bottles with a contact card into the ocean and see where they end up.
Currents can be warm or cold, which doesn't do or change anything except how heat gets distributed. (Remember, weather is created by what air is blowing over.) Hurricanes form above warm ocean currents.
Upwelling: is a vertical circulation in the ocean that brings deep, cold water to the ocean surface. This water is usually filled with dead, old organisms and various other things that make this water very rich in nutrients. These nutrients help living organisms survive.
The Sun and the Moon
Tides are mostly caused by the moon. Moon's gravity exerts itself on Earth and causes a bulge to form within the oceans (on Earth closest to the moon and on the exact opposite side due to physics). The ocean bulge is the high tide and the areas not toward or away from the Moon are the low tides. As Earth rotates, different locations on its surface pass through high and low tides
A rise and fall in the sea level is referred to as a tide. A tide is actually a single, GIANT wave that is caused by the gravity influences from the moon and the Sun. Its only about 1 to 2 meters tall - but it's wavelength is thousands of kilometers long. The crest would be high tide and the trough would be low tide.
are the difference between low tide and high tide. Most places will have two low and two high tides within a day - however there are some places that only experience one low and one high tide during a day. (The Gulf of Mexico is one example.)
Tidal influences are:
The position and geography of the surrounding land.
The shape of the seafloor can affect tides.
A tidal bore is when a rising tide runs up a shallow and/or a narrow river. A wave forms and that wave is called a tidal bore. This wave literally forces the water in the river to reverse its flow.
Origin and Composition of Oceans
Early Earth had substantial volcanic activity - which packed our barely-there almost non-existent atmosphere with water vapor and other gases. As the Earth cooled, torrential rains began falling and water accumulated in low areas called basins. Now 70% of Earth is covered by oceans/water.
Ocean water contains gases (dissolved - think of a soda pop). Gases enter the ocean directly from the atmosphere and from photosynthetic critters. Ocean water also has a lot of different types of salts in it: chloride, sodium, sulfate, magnesium, calcium, and potassium are some of them. They come from rivers and groundwater systems that drain into the ocean. Volcanoes can also add salt.
As you know, you cannot drink ocean water - it's too salty. Humans, for a long time, have found different ways to remove the salt from ocean water. This is called desalination.
Some methods we use are:
Evaporation (because water will seperate from salts during evaporation.
Reverse osmosis: where we force water through a membrane that removes salts
Freezing water: when water freezes, it leaves salt behind.
Density currents are deep, circulating currents that move not because of wind pushing, but instead by changes in density of the water itself. A density current forms when a mass of seawater becomes more dense than the surrounding water, gravity will cause more dense seawater to sink below less dense seawater. Changes in temperature and salinity can affect the density of seawater. Deep waters are usually the most dense, and the coldest. There is an intermediate zone in some places that fits between surface waters and deep waters.
Keep in Mind
Unless a wave is breaking on the seashore - a wave moves through water. Waves do not push or pull water (unless at shore).
At shorelines, (which are also where the oceans are their most shallow), waves will change their shape due to the shallowness. The shallow bottom forces the wavelength to compress, which increases the wave height. When wave height gets to a certain height, then it collapses in on itself forming a breaker.
Waves form due to wind. The stronger the wind - the larger the wave.
Read Chapter 18 and complete: pages 517: 1-4; page 523: 1-3; page 530: 1-4; pages 536-537: 1-15, 18.