Unit 2 Lesson 2 Ocean Waves Copyright Houghton

Unit 2 Lesson 2 Ocean Waves Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves Catch the Wave What are some properties of a wave? • A wave is any disturbance that transfers energy through matter or empty space. • An ocean wave is a disturbance that transfers energy through ocean water. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What are some properties of a wave? • A wave is made up of two main parts: a crest, which is the highest point of the wave, and a trough, the lowest point of the wave. • The distance between two adjacent wave crests or troughs is a wavelength. • Wave amplitude is half the distance between the crest and the trough. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What are some properties of a wave? • Frequency is the number of waves produced in a given amount of time. • Wave period is a measurement of how much time it takes for a wave to pass a fixed point. It is the inverse of frequency. • Wave speed is how fast a wave travels. To calculate a wave’s speed, multiply its wavelength by its frequency. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What are some properties of a wave? • How could you find the wave speed of this wave? Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves Surf’s Up! What causes ocean waves? • Ocean waves are a type of wave known as a mechanical wave. Mechanical waves carry energy through matter, such as water. • Most ocean waves form when energy in the atmosphere is transferred to the ocean’s surface. • Wind blows across the water’s surface and transfers energy to the water, and this energy is carried by the wave. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What causes ocean waves? • Ocean waves can also be produced by underwater earthquakes, underwater landslides, and underwater volcanoes. • If a meteorite or an asteroid landed in the ocean, it could displace enough water to cause large waves. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What causes ocean waves? • Explain what is happening in each image below. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What causes ocean waves? • Explain what is happening in each image below Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves Doing the Wave What happens when a wave moves through the water? • Ocean waves are formed when wind transfers energy to the water. As the energy moves through the water, so do the waves. • The water itself does not travel with the energy. But water at the surface undergoes circular movement. • Wave energy affects surface water to a depth of about half a wavelength. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves Watts from Waves • Some of our electrical energy needs could be met by capturing the wave energy along our coastlines. • A wave power generator converts the up-anddown motion of waves into electrical energy. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves Watts from Waves • This electrical energy can be carried by a power cable back to shore. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves Totally Turbulent What happens when a wave reaches the shore? • When waves reach water shallower than one-half their wavelength, they begin to interact with the ocean floor. • As waves touch the ocean floor, they transfer energy to the ocean floor. • As a result, the water at the bottom of the wave slows down. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What happens when a wave reaches the shore? • As water depth decreases, wave height increases, because more water is forced between wave crests. • The top of the wave travels faster than the bottom of the wave, which drags on the ocean floor. • Eventually, gravity pulls the wave crests down, and they crash onto the shore. These waves that crash onto shore are called breakers. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What happens when a wave reaches the shore? • Most ocean waves reach the shore and transfer their energy to the beach environment. • The energy of the wave and the angle at which the wave hits the shore determine how much energy is transferred. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What happens when a wave reaches the shore? • High-energy waves can quickly erode beaches. Strong waves can even throw boulders and other debris up on the beach. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What is a tsunami? • A tsunami is a series of waves that form when a large volume of ocean water is suddenly moved up or down. • This movement can be caused by earthquakes, volcanic eruptions, landslides, or the impact of a meteorite or asteroid. • When a tsunami approaches land, the waves slow down and get taller as they interact with the ocean floor. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What is a tsunami? • Tsunamis can reach more than 30 meters in height as they slam into the coast, destroying almost everything in their path. • The huge volume of water that crashes onto shore then rushes back into the ocean. • This powerful flow of water, called an undertow, can be as destructive as the tsunami itself. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 2 Ocean Waves What is a tsunami? • Describe the sequence of events shown here. Copyright © Houghton Mifflin Harcourt Publishing Company