GLE Produce a model to demonstrate how the moon produces tides. SPI Predict the types of tides that occur when the earth and moon occupy various positions Illustrate the positions of the earth, moon, and sun during specific tidal conditions.

Tides, the Sun and the Moon 10.3

The Lure of the Moon  Tides are the periodic daily rise and fall of Earth’s water level in the ocean and other bodies of water.  As the tide comes in, the level of water on the beach rises, and as the tide goes out, the level of water on the beach goes down.

What Causes Tides?  Tides are caused by the interaction of the Earth, moon, and the Sun.  Gravity is the reason for tides.  Gravity is the force exerted by an object that pulls other objects toward it.  The moon’s gravity affects the water on the Earth’s surface.  Since the moon is close to the Earth, it has a strong gravitational pull on it (closer objects have stronger gravitational pull).

Moon’s Gravity and Tides

High Tide and Low Tide - Daily Tide Cycle  Most seashores have four tides every day – two high tides and two low tides.  A change from low to high tide or vice versa takes about 6 hours and 12 minutes.

High Tides  High tides are when the water reaches its highest point.

Low Tides  Low tides are when the water reaches its lowest point. They are caused when the high tides draw water away from the area between the high tides.

Battle of the Bulge - Moon’s Gravity  The moon pulls the water on the side nearest to it more strongly than it pulls on the center of the Earth.  This pull creates a bulge of water, called a tidal bulge, on the side of Earth facing the Moon.

Tidal Bulge

Timing Tides Tides timing depends on:  Earth’s rotation  Moon’s revolution around Earth  Tides occur because the moon revolves around Earth too slowly to always have the same position in relation to Earth.

Tidal Variations -Sun’s Gravity and Tides  The Sun is so large that its gravity also affects tides. It is much farther away from the Earth, so its effect is much less.  At times, the Sun and Moon pull together on Earth’s waters in the same direction.  At other times they pull in different directions.  The combined forces of the sun and the moon on Earth result in tidal ranges which is the difference between the level of ocean water at high tide and the level at low tide.

Spring Tides  Spring tides occur 2 times a month, during a full and New Moon.  Earth, Sun, and Moon are lined up.  Spring tides are “highest” high tide and lowest low tides (compared to normal tides).  Very strong tides  Remember: “SPRING STRAIGHT” (positioned in straight line)

Neap Tides  Neap tides occur in between spring tides, at the first and third quarter Moons.  Both Sun and Moon pull at right angles to each other.  High tides are lower & low tides higher than normal  very weak tides  Remember: “Ninety Neap” (positioned at 90 * angle)

Earth-Moon-Sun Positions Spring Tide  Sun-Moon-Earth  in straight line  Full & New Moons Neap Tide  Sun-Earth-Moon  form right angle  First and Third Quarter Moons

Monthly Tide Cycle  Changes in the positions of Earth, the Moon, and Sun affect the height of tides during a month.

Putting it together  Illustrate the positions of the Earth, Moon, and Sun during Spring and Neap tides. Include tidal bulge in drawing. Color and label.  WITH YOUR PARTNER….. Use your Sun-Moon-Earth paper models, to predict the types of tides that occur during new, full, first/third quarter moons. Challenge each other!