1. Tides Cause Tides- daily variations in sea level
Caused by gravitational pull of moon and sun
Moon’s influence on tides is about twice that of sun because it is much closer to the Earth
This creates two bulges on either side of Earth
Newton’s Equilibrium theory- simple explanation of tides that assumes the Earth is perfectly uniform, ocean is very deep, and that there are no landmasses

2. Causes
Laplace’s Dynamic Theory- there are several tidal bulges because the imperfect sphere of Earth, seasons, time of month, continents, and Coriolis effect
Amphidromic point- points where water does not rise and fall with the tides
Tides move in a pinwheel-shaped standing wave around the amphidromic point

3. Tidal Patterns: Semidiurnal- 2 equal high and low tides daily
Diurnal – 1 high and low tide daily
Mixed- 2 unequal high and low tides each day

4. Types of Tides Spring tide- extreme tides during each month
Caused by Earth, sun and moon being aligned
Occur during the full or new moon

5. Neap tide- weak tides during the month
Caused by sun, Earth, and moon forming a right angle
Occurs during the 1st and 3rd quarter of moon phase