CHAPTER 13 OCEAN SYSTEMS

LESSON 13.1 THE OCEANS ARE A CONNECTED SYSTEM

 About 71% (nearly ¾) of the earth is covered in seawater.  The “ocean” is separated by 7 continents.  Different sections of the ocean have different names such as Atlantic, Indian, Artic, and Pacific.  Ocean water contains salts and gases. In fact, salt water contains all 92 elements found in nature.

 Ocean water is very salty. The salinity is a measure of the amount of dissolved salt in the water.  Density is the measure of the amount of matter packed into a given volume.  The higher water’s salt content, the greater its density.  The denser the water, the more easily things float in it. The Dead Sea (near Israel) has such high salinity & density, people can actually float in it. (page 429)  When water evaporates from the ocean, the salts are left behind. Remaining water becomes saltier.

 The ocean contains the same gases as the air, including oxygen, nitrogen, & carbon dioxide.  When you breathe, you use oxygen & exhale carbon dioxide. Ocean animals take in oxygen & give off carbon dioxide too.  Oxygen is added to the ocean by plants & algae that live near the surface.  Plants & algae use sunlight to convert carbon dioxide & water info food, & release oxygen into the water.

Temperatures Oceanographers –people who study the ocean, have divided the ocean water into 3 layers according to temperature. 1. The surface layer is heated by the sun, mixed with winds & waves, and is the warmest layer. This temperature varies by location & season. 2. The thermocline lies below the surface layer. The temperature of the water here drops fast with depth. 3. The deep water is cold all year. Almost anywhere in the world, the temperature of the water at the ocean’s bottom is around degrees.

Ocean Floor  Continental shelf - flat or gently sloping land that lies submerged around the edges of a continent. It extends from the shoreline out to a continental slope.  Continental slope -land that drops down steeply at the edge of a continental shelf.  Ocean trenches -narrow, steep-sided clefts in the ocean floor.  Abyssal Plain -a wide, flat area of the ocean floor that is covered with a thick layer of sediment.  Mid-ocean ridge -a chain of mountains that run through an ocean basin. Formed by molten rock that rose up for within the Earth.  Seamounts -underwater mountains.  Volcanic islands -underwater volcanoes tall enough to reach above the surface.

Ocean Exploration  Water pressure makes it difficult to explore the ocean.  Darkness, lack of air, & cold are other factors related to ocean exploration  Scuba equipment allows a diver to spend about an hour underwater with an air filled tank.  To explore deeper than 130 ft., explorers use small submarines.  Robots equipped with cameras offer views of areas too deep or difficult for humans to reach.

Review of Lesson 13.1  What substances are contained in ocean water?  Draw/Label 5 features of the ocean-floor landscape.  Describe 3 kinds of technology or equipment used to explore the ocean.  How are salinity and density related?  How is the ocean floor similar to Earth’s land surface?  Where in the ocean do you think water pressure is greatest? Explain why.

Lesson 13.2 Ocean water moves in currents.

 An ocean current is a mass of moving water.  There are many different currents that move through the oceans.  As they move water, ocean currents distribute heat & nutrients around the world.

Surface currents vs. deep currents: 1. Surface currents -strong winds blowing over the ocean are set in motion by the uneven heating of Earth’s surface. These winds cause surface currents to flow. (see page 437) for the Gulf Stream 2. Deep currents -driven by differences in water density. Seawater can become more dense because of cooling, an increase in salinity, or both. The densest water is found in the polar regions.

Downwelling/Upwelling 1. Downwelling is the movement of water from the surface to greater depths. As water sinks, it carries oxygen down from the surface which allows animals to live in the deep ocean. 2. Upwelling is the movement of water up to the surface. Because this process bring sup nutrients from the deep ocean, large numbers of ocean animals live in areas where upwelling occurs.

Climate & Weather  Weather is daily conditions and climate is patterns of weather in an area over a long period of time.  Ocean and atmosphere interact in unpredictable ways  Change in one current can result in huge changes  El Nino is when global weather changes for months (more/less snow, warmer/cooler)

Review of Lesson 13.2  What are 2 causes of currents in the ocean?  How do currents distribute heat around the globe?  How are climate and weather related to currents? Give 2 examples.  Describe at least 2 ways in which upwelled water might differ from the water around it.  How does the Gulf Stream affect Great Britain?

Lesson 13.3 Waves move through oceans.

 Wave -an up-and-down motion along the surface of a body of water. They come in various sizes and are caused by winds. Moving air drags across the water’s surface and passes energy to the water, causing waves.  Earthquakes, landslides, & underwater volcanic eruptions can also cause waves. Basic shape of a wave:  The crest -the high point of a wave.  The trough is the low point of the wave.  The wave height is the vertical distance between the top of the crest and the bottom of the trough.  Wavelength -the distance between one wave crest and the next.

Currents move water from place to another. In contrast, wave do not transport water; they move energy. Waves lose energy as they break onto shore. Pay attention to the drawings on page 443. Waves may pass through the ocean for 100’s or 1,000’s of km before moving into shallow water. Waves lose speed and eventually topple over, losing their energy as they break ashore. Undertow - the pull of water as it runs back to sea.

Longshore currents -move water parallel to the shore Rip currents -narrow streams of water that break through sandbars and drain rapidly back to sea. Occur when high winds or waves cause a larger-than-usual amount of water to wash back from the shore.

Review of Lesson 13.3  How does moving air form waves in water?  Describe the movement of a water particle as a wave passes through.  What happens to waves near shore?  Name & describe 2 kinds of currents that wave action can cause near shore.  Describe the similarities & differences between surface currents and waves.  Imagine you find a piece of wood on the beach. The next day, the wood is 100 meters farther north. How might it have moved? Your answer should refer to currents.

Lesson 13.4 Waters rise and fall in tides.  Tide is the periodic rising and falling of the water level of the ocean  High tide is when the water level along a beach is high- exposing little beach/sand.  Low tide is when the water level along a beach is low- exposing more beach/sand.  There are 2 high and 2 low tides per day (totaling 4)

Gravity causes Tides  Gravity of sun and moon pull on Earth causing oceans to bulge on the side facing the moon and the opposite side-high tide  Between the two bulges are dips- low tide (pic p. 449)  As Earth rotates, different parts of Earth pass through the bulges and dips  Tidal range is difference in height of high and low tide and it depends on the shape of land above and below ocean

Monthly Tides  Spring tide – an extra high tide and an extra low tide – occurs when both gravity of sun and moon pull at the same time  Neap tide - a smaller high tide and a smaller low tide (less extreme between) – occurs when sun and moon are not lined up with Earth so gravity pulls in different directions (pic p. 451)

Generate Electricity  Energy of tides generates electricity  Dam built near path of water, water flows and is trapped in dam during high tide, when tide is low dam gates open and water rushes out. Water spins turbines that power electric generators.  Benefit of hydroelectricity – less pollution and water is a renewable resource

 Review of Lesson 13.4  Describe the appearance of tidal changes at the beach.  Explain the difference between sun and moon and creating tides.  How are tides used to generate electricity?  Compare & contrast neap and spring tides.  How would tides differ if the moon revolved around the Earth twice a month?  What are the benefits of hydroelectricity?

Prepare to Test  Review the powerpoint and any notes you may have.  Complete page 455 #’s 1-14  When answering 4-10, answer with capital letters.  Write in complete sentences for