Waves, Tides and Currents Ocean’s Motion Waves, Tides and Currents

Ocean Waves

What is a Wave? . A wave is described as the periodic up-and-down movement of water. They are caused by the wind blowing over the surface of the water. Tsunami’s are large waves caused by earthquakes underwater.

Wave Features Wave period = the time it takes 2 consecutive wave crests to pass a given point. A wave’s speed is calculated by dividing wavelength over wave period.

Water Movement in a Wave Like the bottle in the diagram, water molecules do not travel horizontally through the water with the wave. Have the class do the wave. Notice how the energy flows across the crowd but each person is standing in the same location. Let’s try it!

What impacts Wave Size? 3 factors determine the size of the wave Speed of the wind Length of time wind blows Fetch – distance wind can blow across open water Large waves produced by strong, steady winds blowing across a long fetch. When wind blows crest of wave off, whitecaps are formed Whitecaps

How do waves impact the shoreline? Long shore drift is the movement of sand along the beach due to wave actions.

What are Ocean Currents? Ocean currents are moving streams of water within the ocean. There are two types of currents: surface currents and deep currents.

What causes surface currents? Currents that move on or near the surface of the ocean 3 factors that control surface currents – air currents, Earth’s rotation, and location of continents All surface currents are affected by winds

What do you notice about the direction of the currents?

Why do currents spin? The Earth spins counter-clockwise. This spinning body deflects winds and currents depending on what side the equator they are on. This is called the corialis effect

The Great Conveyor Belt moves heat around the globe with the help of warm surface currents and colder deep currents.

How do deep current form? Deep currents are caused by changes in temperature and salinity.

What causes deep currents to move if the wind doesn’t have an effect on it? Water density moves the water. Cold water is more dense and it sinks and moves. Warm water is less dense and it rises. Note: surface currents travel much faster than deep ocean currents.

How are deep water currents helpful? Deep currents help move nutrients around the ocean. Upwelling's are cold deep currents that move to the surface bring with them nutrients from the ocean floor.

What are tides? Periodic rise and fall of water level in the oceans High tide – water level is at its highest Low tide – water level is at its lowest Tides at the Bay of Fundy

What is the Cause of Tides? The gravitational pull of the moon on Earth and Earth’s waters is the major cause Sun also causes tides but they are smaller because the sun is so much farther from Earth than the moon

Formation of Tides

There are two types of tides Spring Tides Neap Tides Occur when the Earth, Sun and Moon are in a line. Causes extra high and low tides. Occur when the Sun and the Moon are at right angles to one another. Causes the smallest tidal movements. There is little difference between low and high tides.

Types of Tides Tidal range = difference in levels of ocean water at high tide & low tide Spring tides = Occurs during the new moon & full moon; results in higher high tides and lower low tides. Neap tides = occurs during 1st & 3rd quarter moons; daily tidal range is small.