Chapter 14 ­ The Movement of Ocean Water Chapter 14, Section 1 ­ Currents Ocean Current ­ a movement of ocean water that follows a regular pattern. Surface Currents vs. Deep Currents Surface Current ­ a horizontal movement of ocean water that is caused by wind and that occurs at or near the ocean's surface. Coriolis Effect ­ the apparent curving of the path of a moving object from an otherwise straight path due to the Earth's rotation. Continental Deflections ­ when an ocean current meets a continent, it is deflected, or caused to change direction. Deep Current ­ a streamlike movement of ocean water far below the surface. The Sun, Convection, and Currents The sun heats the earth near the equator more directly and rapidly than near the poles. This, in turn, causes the oceans, land, and air at and near the equator (tropics) to be warmer than any other place on earth. Therefore, the ocean currents, in general, move from the equator to the poles (north and south poles). This makes what are called convection currents in the ocean. The warm water moves along the top of the oceans while the cool water moves along the bottom of the ocean. This is called a convection current (convection cycle) (convection cell). DEMONSTRATION ­ CONVECTION FOOD COLORING 1 Chapter 14, Section 2 ­ Currents and Climate Although surface currents are generally warmer than deep currents, the temperature of surface currents can vary. Surface currents are classified two ways: 1) Warm­Water Currents 2) Cold­Water Currents Warm­water currents make the coastal lands around them much warmer than they might normally be. For example, weather patterns follow the warm­water currents of the ocean and affect the land around them. Cold­water currents make the coastal lands around them much cooler than they might normally be. For example, weather patterns follow the cold­water currents of the ocean and affect the land around them. Currents and Climate El Nino ­ a change in the water temperature in the Pacific Ocean that produces a warm current. La Nina ­ a change in the eastern Pacific Ocean in which the surface water temperature becomes unusually cool . El Nino is a warming of the Pacific Ocean that can last 1 or more years. When the Pacific Ocean warms, this causes a change in the interaction between the ocean and the atmosphere. That, in turn, causes weather patterns to change. Severe weather like floods, droughts, and mudslides can result. HOMEWORK: Connection to Current Events * Find a current science article that discusses either El Nino or La Nina. (Internet, Newspaper, Magazine) * The article has to be within the last year. * Read the article. * Complete a "Science in the News" handout for your article. * Bring the article with you to class. DUE: 2 Chapter 14, Section 3 ­ Waves What is a Wave? Wave ­ a disturbance that moves through matter that transfers energy. DO NOT CONFUSE WAVES AND TIDES! THEY ARE VERY DIFFERENT! Type of Ocean Waves Ocean waves can form from a variety of things. They are: wind, earthquakes, landslides, weather, climate, sun, boats, etc. Deep­Water Waves vs. Shallow­Water Waves (NOT to be confused with Surface Currents and Deep Currents) Deep­water waves are those that move in the open ocean while shallow­water waves are those that move closer to the shoreline. Undertow ­ water that is flowing back out to sea underneath new incoming waves. (Fig. 5, Pg. 429) Longshore Current ­ when waves hit the shoreline at an angle, they cause water to then move parallel to the shoreline, known as longshore current. (Fig. 6, Pg. 429) Whitecap ­ white waves with very steep crests that break in the open ocean. (Fig. 7, Pg. 430) Swell ­ gentle, rolling waves that move across the ocean. (Fig. 7, Pg. 430) Tsunami ­ a giant ocean wave that forms after a volcanic eruption, underwater earthquake, or landslide. (Fig. 8, Pg. 430) Storm Surge ­ a local rise in sea level near the shore that is caused by strong winds, usually from a severe weather event such as a hurricane. 3 Chapter 14, Section 4 ­ Tides What are Tides? Tide ­ the rise and fall of the oceans. DO NOT CONFUSE WAVES AND TIDES! THEY ARE VERY DIFFERENT! Causes of High Tide and Low Tide The sun and moons gravity affect the ocean waters. When the sun and moon "pull" on the ocean water, it forces it to move. This, in turn, causes high tide on the side of the Earth facing the moon, as well as the side of the earth opposite the moon. However, during high tide for those two areas of earth, it is low tide for the areas at a 90 degree angle to the moon. Figure 2 on page 433 shows this very well. PICTURE Tidal Range Tidal Range ­ the difference in levels of ocean water at high tide and low tide. (Fig. 5, Pg. 435) 4.