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Earths Tides Objectives: Define tides What causes tides How often tides occur Types of tides Slide 2 Earth Moon Tides Tides are the vertical movement of water, specifically the alternate rise (flood) and fall (ebb) of water in the ocean. This is mostly noticeable along continental shorelines. The influence of the Moons gravitational force acting on the Earths oceans and the Earth (the rocky part). Caused by: Slide 3 Earth Moon Sun High Tide High Tide Low Tide Low Tide Tides are more influenced by the gravitational effect of the Moon than they are by that of the Sun (the Moon's closeness to us outweighs by far the Sun's greater size). So, as the Earth spins around its axis, how many high and low tides do we have a day? 2 Slide 4 Earth Moon Moon Spring Tides The gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth. New Moon Phase of the moon? Full Moon Phase of the moon? Moon New Moon Phase of the moon? Higher high tides and lower low tides Sun Slide 5 Earth Moon Moon First Quarter Phase of the moon? Third Quarter Phase of the moon? Neap Tides The gravitational affects of the moon and sun fight each other with their influence on the flow of the oceans on Earth. Moon Third Quarter Phase of the moon? Lowest high tides and highest low tides Sun Slide 6 Tidal Range: The difference between high and low tide. Slide 7 Slide 8 Slide 9 Slide 10 Review Q: What are tides? Tide = the periodic rise and fall of the water level in the oceans and other large bodies of water. Q: What are the dominant forces causing tides in ocean waters? The gravitational forces from both the sun and the moon. Slide 11 Review (contd) Q: Which one (the sun or the moon) has a bigger effect on tides? The moon Slide 12 Review (contd) Q: What is the difference in levels of ocean water at high tide and low tide called? Tidal Range Q: Tidal ranges vary greatly due to the combined forces of the _________ and the ________ on the Earth Sun, moon Slide 13 Review (contd) Q: How are the sun, Earth, and moon situated so we experience a spring tide? Sun, Earth, and the moon are aligned Which eclipse?? Slide 14 Review (contd) Q: How are the sun, Earth, and moon situated so we experience a neap tide? The sun, Earth, and moon form a 90 degree angle Slide 15 Earths Tides Slide 16 Tides & Consequences This little tidal behavior goes both ways! The Earth rises tides on the Moon. The Earth "brakes" the Moon's rotation AND the braking is complete! Synchronous Rotation of the Moon and its orbital period! (27.3 days!) Moon also brakes the Earth's Rotation Moon's orbit is growing because of all of this interaction. We see a permanent "near" and "far side" of the Moon. The length of the "day" is increasing! From fossil reef corals of about 4 10 8 years old - daily growth/annual growth 400 days/year ~ 22 hours a day! Day is increasing about 0.001 seconds/century. Therefore, the day is getting longer, Moon looks smaller, and tides are weakening.