Transcript Slide 1
Cowabunga! Ocean Movements • A wave is a rhythmic movement that carries energy through space or matter Surface Waves cont • Surface waves have a rolling pattern of particle motion. Ocean Movements • A trough is the lowest point of a wave. • A crest is the highest point of a wave. The crest-to-crest distance is the wavelength. Ocean Movements Wave Characteristics Wave Height – Ocean Movements Wave heights depend upon three factors: 1. wind speed 2. wind duration – how long it has blown 3. Fetch – how far that the wind blows across the ocean. Breaking Waves Ocean Movements – Ocean waves begin to lose energy and slow down near the shore because of friction with the ocean bottom. – Breakers are waves where the crests collapse forward when the wave becomes higher, steeper, and unstable as it nears shore. Ocean Movements Breaking Waves Tides Ocean Movements • Tides are the periodic rise and fall of sea level. • highest level water rises = high tide • lowest level water goes down to = low tide. • daily cycle of high and low tides takes 24 hours and 50 minutes. Bay of Fundy High Tide vs. Ocean Movements Low Tide Ocean Movements Tides Differences in topography and latitude cause three different daily tide cycles. • The basic causes of tides are 1. the gravitational attraction among Earth, the Moon and the Sun Ocean Movements Causes of Tides Ocean Movements Ocean Currents • Surface currents - winddriven currents in upper ocean and can move as fast as 100 km per day. • Density (deep water) current - moves slowly in the deep ocean caused by differences in the temperature and salinity - continents deflect ocean currents to the north and south causing closed circular current systems Gyres – 5 major gyres: North Pacific, North Atlantic, South Pacific, South Atlantic, Indian Ocean. • Upwelling - the upward motion of ocean water rich in nutrients which support marine life Ocean Movements Upwelling Ocean Movements Section Assessment 1. Match the following terms with their A. the upward motion of ocean definitions. ___ D crest ___ B trough C tide ___ A upwelling ___ E breakers ___ water, caused by an offshore wind B. the lowest point of a wave C. the periodic rise and fall of sea level. D. the highest point of a wave E. waves that become higher, steeper, and unstable which causes their crest to collapse Ocean Movements Section Assessment 3. Identify whether the following statements are true or false. false ______Gyres rotate in a counterclockwise direction in the northern hemisphere. false ______ true The water in a wave moves steadily forward. false ______Wave speed increases with wavelength. ______Spring and neap tides alternate every four weeks. Chapter Assessment Multiple Choice 1. Approximately how much of Earth’s surface is covered by oceans? a. 51 percent c. 71 percent b. 61 percent d. 81 percent Because most landmasses are located in the northern hemisphere, oceans cover only 61 percent of the surface there. However, 81 percent of the southern hemisphere is covered by water. Chapter Assessment Multiple Choice 2. Of the areas listed below, which generally has the lowest ocean salinity? a. subtropical regions c. temperate regions b. tropical regions d. polar regions In the polar regions, seawater is diluted by melting sea ice. On a localized level, the lowest salinities often occur where large rivers empty into the oceans. Chapter Assessment Multiple Choice 3. Which term below best describes the tide when the Sun, the Moon, and Earth form a right angle? a. spring tide c. high tide b. neap tide d. low tide During a neap tide, high tides are lower than normal and low tides are higher than normal. During a spring tide the solar and lunar tides are aligned, causing high tides to be higher than normal and low tides to be lower than normal. Spring and neap tides alternate every two weeks. Chapter Assessment Multiple Choice 4. What is the average ocean surface temperature? a. 8ºC c. 15ºC b. 12ºC d. 18ºC Surface temperature of Earth’s oceans varies between –2ºC in the polar regions to 30ºC in equatorial regions. Chapter Assessment Multiple Choice 5. Which of the following is the most prevalent ion in seawater? a. chloride c. sodium b. sulfate d. magnesium Chloride has a concentration of 19.35 ppt in seawater. It is followed by sodium (10.76 ppt), sulfate (2.71 ppt), and magnesium (1.29 ppt).