Tides Oceans 11

What causes tides? Winds and currents move the surface water causing waves. Winds and currents move the surface water causing waves. Ocean levels fluctuate daily as the sun, moon and earth interact. Ocean levels fluctuate daily as the sun, moon and earth interact. As the moon travels around the earth and as they, together, travel around the sun, the combined gravitational forces cause the world's oceans to rise and fall. As the moon travels around the earth and as they, together, travel around the sun, the combined gravitational forces cause the world's oceans to rise and fall.

the moon’s role in tides The moon has a gravitational on the water as it orbits the earth. The moon has a gravitational on the water as it orbits the earth. This pull causes the water to bulge toward the moon. This pull causes the water to bulge toward the moon. Because the earth is spinning there will be a bulge on the opposite side of the earth as well. Because the earth is spinning there will be a bulge on the opposite side of the earth as well.

Spring Tides Spring tides - When the sun and moon are aligned, there are exceptionally strong gravitational forces, causing very high and very low tides Spring tides - When the sun and moon are aligned, there are exceptionally strong gravitational forces, causing very high and very low tides Occur 2 a month Occur 2 a month

Neap Tides When the sun and moon are not aligned, the gravitational forces cancel each other out, and the tides are not as dramatically high and low. When the sun and moon are not aligned, the gravitational forces cancel each other out, and the tides are not as dramatically high and low. Occur twice a month Occur twice a month

Some more info about tides…. Tides vary from day to day and place to place Tides vary from day to day and place to place As the earth, moon, and sun orbit, their positions constantly shift, causing slightly different gravitational effects. This causes the tides to occur at slightly different times. As the earth, moon, and sun orbit, their positions constantly shift, causing slightly different gravitational effects. This causes the tides to occur at slightly different times. Geographical position determines the level of tide. Geographical position determines the level of tide.

Tidal Range Is the vertical distance between high and low tide (various but averages a few meters) Is the vertical distance between high and low tide (various but averages a few meters) Bay of Fundy – has a tide range of 16m during spring tide (the largest anywhere in the world!!) Bay of Fundy – has a tide range of 16m during spring tide (the largest anywhere in the world!!)

Types of tides 1. Diurnal – 1 high and 1 low tide daily (ie Florida) 2. Semidiurnal – 2 high and 2 low tides daily (ie Boston) 3. Mixed tides – vary irregularly twice a day (ie California)

Tidal Bore An event that occurs in some rivers An event that occurs in some rivers A “wall” of water that surges up the river during advancing tides A “wall” of water that surges up the river during advancing tides

Factors that cause Tidal Bores 1. A large tidal range 2. A basin that narrows 3. A river that decreases in depth the further up you go