Waves

Wave: A periodic disturbance in a solid, liquid, or gas as energy is transmitted through a medium (such as air, water, or rock).

Wave Structure The crest is the highest point above the equilibrium position, and the trough is the lowest point below the equilibrium position. The wavelength ( ) is the distance between two adjacent similar points of a wave.

Wave Formation in the Ocean What do you think causes most waves in the ocean to form? Answer: Wind! The longer wind blows, the more energy is transferred to the ocean’s surface causing a wave to form.

Types of Waves Wind Waves- usually less than 3 meters high. Capillary wave- ripples that turn into wind waves. Seiche- water confined to a small space like a bay will slosh back and forth at resonant frequency. Tsunami- Seismic wave created by an earthquake on the ocean floor. Tides- caused by gravitational pull on the earth by the moon and sun.

Wave Movement Energy in a wave only moves up and down in a circular- type motion. Energy does not travel laterally (side to side). This is why you move up and down as a wave moves past you.

Wave

Wave Heights

Factors Affecting Wave Development 1.) Mean Speed or Wind Strength- Wind must be moving faster than the wave crests for energy to transfer from air to sea. 2.) Wind Duration- High winds that blow only a short time will not generate large waves. Low winds that blow for a long time can generate very large waves. 3.) Fetch- uninterrupted distance over which the wind blows without significant change in direction. Strong wind must blow in one direction for 3 days for large waves to be fully developed (called a fully developed Sea)/

Wave Interference

Rogue Waves Caused by positive (in phase) interference) of waves in open ocean. Until recently, thought to be impossible.

Breaking Waves What causes a wave to crest or “break?” Answer: As wave approaches the coastline, the slope is shallower. The bottom of the wave drags along the floor slowing it down. The top of the wave continues at it’s previous speed causing it to go faster than the bottom. This makes the wave break.

Wave Refraction Slowing and bending of waves in shallow water. Caused due to waves hitting shoreline at an angle. This is why waves break at different points as they approach the shoreline

Wave Diffraction Wave changing direction due to an obstacle like a breakwater or jetty.

Wave Reflection Waves will reflect if they hit an object straight on. Will cause minor constructive interference.

Undertow and Rip Currents Undertow: Formed when water breaking onto a beach is pulled back into deeper water by gravity. Rip Currents: Form when there is a break in a sand bar. Water is quickly funneled out to sea. Rip Currents can flow from 1-8 feet per second. That’s faster than an Olympic swimmer! How do you escape a rip current? Swim parallel to the shoreline!

Longshore Currents/Drift Longshore Current: Form when waves approach the beach at an angle. Sand is moved by these currents forming sandbars and spits. Often called longshore drift.

Longshore Drift