WIND:
 Winds are caused by differences in air pressure.
 They move from areas of high pressure to low pressure.
 Differences in air pressure are caused by unequal heating of the atmosphere.
 Cool air has higher air pressure so it flows underneath the warm, less dense air.
 Winds that blow over short distances and are caused by unequal heating of Earth’s surface within a small area.

Waves
 Waves start in the open ocean
 The size of a wave depends on the strength of the wind, the length of time that it blows, and the distance over which it blows
 Waves move energy, not water. The water in a wave does not actually move forward, just the energy generated by the wind.
 The wind affects the water at the surface more than it does the deep water.
 As waves approach the shore, the water becomes shallower.
 The bottom of the waves begin to touch the sloping ocean floor.
 Friction between the ocean floor and the water causes the waves to
 slow down.
 As the speed of the wave slows down the shape of the wave begins to change
 Near the shore wave length decreases and wave height increases.
 When the wave reaches a certain height, the crest of the wave topples.

CURRENT:
A current is a large stream of water that flows through the ocean
Two types of currents
Surface Currents
 Driven mainly by the wind
 They follow Earth’s major wind patterns which move in a circular pattern
 Due to the Coriolis effect, currents in the Northern Hemisphere curve to the right and to the left in the Southern Hemisphere
 A surface current warms or cools the air above it, influencing the climate of the land near the coast
 At certain places on Earth, sometimes the wind patterns reverse, causing the surface currents to reverse directions Deep Currents  Deep currents are caused by differences in the density of ocean water.
 Ocean water density depends on its temperature and its salinity.
 Cold water is more dense than warm water.
 Saltier water is more dense than less saltier water. (Demos)
 As warm surface currents near the poles the water cools and its salinity increases due to ocean water freezing and leaving the water near the poles more salty. (Page 384)
 The cold, saltier water sinks and starts moving back towards the equator along the bottom of the ocean.
 When the water reaches the equator, it warms and rises again.
 Deep currents flow slowly. They may take as long as 1,000 years to flow from pole to equator and back again.
TIDES:
 Tides are the daily rise and fall of Earth's waters on its coastlines
 When water on the coast reaches its highest point it is high tide.
 When water on the coast reaches its lowest point it is low tide.
 Unlike surface waves, tides are regular and do not depend on wind. If not wind, then what causes tides?
 Tides are caused by the interaction between the Earth, the moon, and the sun.
 The gravity exerted on Earth's oceans by the moon and the sun cause the water to move from one side of the planet to the other side.
 The moon is much closer to the Earth than the sun, so it exerts a greater gravitational effect on the tides.
 There are two high tides and two low tides about every 25 hours.
 That means every six or so hours you have a high tide and then a bit
 more than six hours later you have a low tide.
 Changes in the positions of Earth, the moon, and the sun affect the
 heights of tides during a month.