Earth’s Tides Objectives: Define tides What causes tides How often tides occur Types of 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. Moon Earth Caused by: The influence of the Moon’s gravitational force acting on the Earth’s oceans and the Earth (the rocky part).

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). Low Tide Moon Earth High Tide High Tide So, as the Earth spins around its axis, how many high and low tides do we have a day? Low Tide Sun 2

Higher high tides and lower low tides Spring Tides The gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth. Moon Moon Moon Earth Phase of the moon? Phase of the moon? Phase of the moon? New Moon Sun New Moon Full Moon Higher high tides and lower low tides

Lowest high tides and highest low tides Neap Tides The 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? Moon Moon Phase of the moon? Third Quarter Third Quarter Earth Phase of the moon? Moon Sun First Quarter Lowest high tides and highest low tides

Tidal Range: The difference between high and low tide.

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.

Review (cont’d) Q: Which one (the sun or the moon) has a bigger effect on tides? The moon

Review (cont’d) 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

Review (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 aligned Which eclipse??

Review (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

Earth’s Tides

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!) We see a permanent "near" and "far side" of the Moon. Moon also brakes the Earth's Rotation The 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 0.001 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.