Presentation on theme: "Earth’s Tides Objectives: Define tides What causes tides"— Presentation transcript:
1Earth’s Tides Objectives: Define tides What causes tides How often tides occurTypes of tides
2Tides 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.MoonEarthCaused by:The influence of the Moon’s gravitational force acting on the Earth’s oceans and the Earth (the rocky part).
3Tides 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).Low TideMoonEarthHigh TideHigh TideSo, as the Earth spins around its axis, how many high and low tides do we have a day?Low TideSun2
4Higher high tides and lower low tides Spring TidesThe gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth.MoonMoonMoonEarthPhase of the moon?Phase of the moon?Phase of the moon?New MoonSunNew MoonFull MoonHigher high tides and lower low tides
5Lowest high tides and highest low tides Neap TidesThe gravitational affects of the moon and sun fight each other with their influence on the flow of the oceans on Earth.Phase of the moon?MoonMoonPhase of the moon?Third QuarterThird QuarterEarthPhase of the moon?MoonSunFirst QuarterLowest high tides and highest low tides
6Tidal Range:The difference between high and low tide.
10Review 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.
11Review (cont’d)Q: Which one (the sun or the moon) has a bigger effect on tides?The moon
12Review (cont’d)Q: What is the difference in levels of ocean water at high tide and low tide called?Tidal RangeQ: Tidal ranges vary greatly due to the combined forces of the _________ and the ________ on the EarthSun, moon
13Review (cont’d)Which eclipse??Q: How are the sun, Earth, and moon situated so we experience a spring tide?Sun, Earth, and the moon are alignedWhich eclipse??
14Review (cont’d)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
16Tides & ConsequencesThis 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!)We see a permanent "near" and "far side" of the Moon.Moon also brakes the Earth's RotationThe length of the "day" is increasing!From fossil reef corals of about 4´108 years old - daily growth/annual growth 400 days/year ~ 22 hours a day!Day is increasing about seconds/century.Moon's orbit is growing because of all of this interaction.Therefore, the day is getting longer, Moon looks smaller, and tides are weakening.