Motion of the Ocean
Tides are created by the moon’s gravitational pull For any location on Earth, there are 2 high tides and 2 low tides per day The ocean bulge that is directly facing the moon is called “direct high tide” The ocean bulge opposite the moon is the “indirect high tide” Low tides are caused by water rushing away to fill in the high tides
Tides arrive 50 minutes later each day Remember that the moon revolves as Earth rotates The extra fifty minutes comes from Earth needing to “catch up” to the moon so the location is directly facing the moon (for a high tide) If high tide comes at 12:00 PM on Monday, it will come around 12:50 PM on Tues.
Tidal Range is the difference between average high tide levels and average low tide levels Tidal Range = High WLA – Low WLA (WLA = water level average) Tidal ranges for a location change throughout the month
Spring Tide- occur during New and Full Moons (when E,M,S are aligned) Sun and Moon’s gravity “team up” to increase tidal range High tides are higher than usual, low tides are lower
Neap Tide- occur during 1st and 3rd Quarter moons (when E,M,S are at a right angle) Sun and Moon’s gravity work against each other to decrease tidal range High tides are lower than usual, low tides are higher