tides. section 13 - 2 tides eq: what causes tides?

TidesTides

Section 13 - 2Section 13 - 2

TidesTidesEQ: What causes tides?EQ: What causes tides?

TidesTides

What causes tides?What causes tides?

How can tides be How can tides be used to generate used to generate electricity?electricity?

Describe the Describe the positions of the positions of the sun and the moon, sun and the moon, in relation to Earth in relation to Earth when spring tides when spring tides occur.occur.

TidesTides

• A A tidetide is the rise and fall of the is the rise and fall of the ocean’s surface ocean’s surface caused mostlycaused mostly by by the the gravitationalgravitational pull of pull of the moonthe moon..

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• At high tide, the ocean At high tide, the ocean water has risen as high water has risen as high as it will go on a shore.as it will go on a shore.

• At low tide, the ocean At low tide, the ocean water has fallen as low water has fallen as low as it can go on a shore.as it can go on a shore.

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•Earth’s rotation on its axis Earth’s rotation on its axis affects which tides will occur affects which tides will occur at a certain place on Earth.at a certain place on Earth.

What causes tides?What causes tides?•Tides are caused by Tides are caused by

the interaction of the interaction of Earth, the moon, Earth, the moon, and the sun.and the sun.

•The moon pulls on The moon pulls on the water on the the water on the side closest to it side closest to it more strongly than more strongly than it pulls on the it pulls on the center of the Earth.center of the Earth.

What causes tides?What causes tides?• The moon’s pull The moon’s pull

creates a bulge of creates a bulge of water, called a tidal water, called a tidal bulge, on the side of bulge, on the side of Earth facing the moon.Earth facing the moon.

• The water opposite the The water opposite the moon is pulled toward moon is pulled toward the moon less strongly the moon less strongly than the water facing than the water facing the moon.the moon.

• This water is “left This water is “left behind,” forming a behind,” forming a second bulge.second bulge.

The Daily Tide CycleThe Daily Tide Cycle•As Earth turns completely As Earth turns completely

around once each day, people around once each day, people on or near the shore observe on or near the shore observe the rise and fall of the tides the rise and fall of the tides as they reach the area of as they reach the area of each tidal bulge.each tidal bulge.

The Daily Tide CycleThe Daily Tide Cycle• High tides occur about every 12 hrs. and High tides occur about every 12 hrs. and

25 mins. 25 mins.

• Low tides occur about every 12 hrs and 25 Low tides occur about every 12 hrs and 25 mins.mins.

• The time between low tide and high tide is The time between low tide and high tide is about 6 hours. about 6 hours.

Drawing of low tide/high tide for a 24 hour period. If it is 3pm for the first low tide, six hours later it will

be (the next box). Label and put time and picture. Also show the number of hours between each picture of

the tides.

Tides occur at different locations on Tides occur at different locations on Earth because the Earth rotates more Earth because the Earth rotates more quickly than the moon revolves quickly than the moon revolves around the Earth.around the Earth.

Effects of Daily TidesEffects of Daily Tides

Photos Showing Progress Photos Showing Progress of high tide coming in of high tide coming in

http://www.watchknowlearn.http://www.watchknowlearn.org/Video.aspx?org/Video.aspx?

VideoID=23446&CategoryIDVideoID=23446&CategoryID=6422=6422

The Monthly Tide CycleThe Monthly Tide Cycle• Changes in the positions of Earth, the Changes in the positions of Earth, the

moon, and the sun affect the height of the moon, and the sun affect the height of the tides during a month.tides during a month.

Spring TideSpring Tide• Twice a month, at Twice a month, at

the new moon and the new moon and the full moon, the the full moon, the sun and moon are sun and moon are in a straight line.in a straight line.

• Their combined Their combined gravitational pull gravitational pull produces the produces the greatest range greatest range between high and between high and low tide, called a low tide, called a spring tidespring tide..

Neap TideNeap Tide

•In between spring In between spring tides, at the first and tides, at the first and third quarters of the third quarters of the month, the sun and month, the sun and moon pull at right moon pull at right angles to each other, angles to each other, producing a producing a neap tideneap tide..•A neap tide is a tide A neap tide is a tide with the least with the least difference between low difference between low and high tide.and high tide.

The Monthly Tide CycleThe Monthly Tide Cycle

The Monthly Tide CycleThe Monthly Tide Cycle

The Monthly Tide CycleThe Monthly Tide Cycle

•The movement of large amounts The movement of large amounts of water between high and low of water between high and low tide are a source of potential tide are a source of potential energy—energy that is stored energy—energy that is stored and waiting to be used.and waiting to be used.

•Spring tideSpring tide– Full moon-highest tideFull moon-highest tide– New moonNew moon

•Neap Tide- half moonNeap Tide- half moon

Spring Tides and Neap TidesSpring Tides and Neap Tides

Spring Tides and Neap TidesSpring Tides and Neap Tides

Spring Tides and Neap TidesSpring Tides and Neap Tides

Answers to TidesAnswers to Tides

1.1. A and DA and D

2.2. C or EC or E

3.3. Spring Spring

4.4. LowerLower

5.5. SpringSpring

6.6. GreaterGreater

7. Neap tide – tide with the 7. Neap tide – tide with the least difference between least difference between high and low tide ©high and low tide ©

8. High tide – tide in which 8. High tide – tide in which water reaches its highest water reaches its highest point on the beach each point on the beach each day (d)day (d)

9. Spring tide – tide with the 9. Spring tide – tide with the greatest difference greatest difference between high and low tide between high and low tide (a)(a)

10. Low tide – tide in which 10. Low tide – tide in which water reaches its lowest water reaches its lowest point on the beach each point on the beach each day (b)day (b)

Quick CheckQuick Check

1. What causes tides but NOT waves 1. What causes tides but NOT waves and currents?and currents?

A. winds and the moon’s gravityA. winds and the moon’s gravity

B. mostly the moon’s gravityB. mostly the moon’s gravity

C. mostly the sun’s gravityC. mostly the sun’s gravity

D. only windsD. only winds

Quick CheckQuick Check

2. At the full moon, the combined 2. At the full moon, the combined gravitational pulls of the sun and the gravitational pulls of the sun and the moon produce amoon produce a

A. surface current.A. surface current.

B. neap tide.B. neap tide.

C. spring tide.C. spring tide.

D. rip current.D. rip current.

Quick CheckQuick Check

3. A tide which water reaches its lowest 3. A tide which water reaches its lowest point on the beach each day is calledpoint on the beach each day is called

A. neap tide.A. neap tide.

B. high tide.B. high tide.

C. spring tide.C. spring tide.

D. low tide.D. low tide.

Quick CheckQuick Check

4. Tide with the least difference 4. Tide with the least difference between high and low tide is calledbetween high and low tide is called

A. neap tide.A. neap tide.

B. high tide.B. high tide.

C. spring tide.C. spring tide.

D. low tide.D. low tide.

Quick CheckQuick Check

5. A tide in which water reaches its 5. A tide in which water reaches its highest point on the beach each day is highest point on the beach each day is called a called a

A. neap tide.A. neap tide.

B. high tide.B. high tide.

C. spring tide.C. spring tide.

D. low tide.D. low tide.

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6. If the first high tide of the day 6. If the first high tide of the day occurs at 1:00 am, the next high tide occurs at 1:00 am, the next high tide will come closest towill come closest to

A. 7:00 amA. 7:00 am

B. 1:00 am the next dayB. 1:00 am the next day

C. 7:00 pmC. 7:00 pm

D. 1:00 pmD. 1:00 pm

Quick CheckQuick Check

7. Tide with the greatest difference 7. Tide with the greatest difference between high and low tide is called a between high and low tide is called a

A. neap tide.A. neap tide.

B. high tide.B. high tide.

C. spring tide.C. spring tide.

D. low tide.D. low tide.

Quick CheckQuick Check

8. High tides occur 8. High tides occur

A. once every two days.A. once every two days.

B. once a day.B. once a day.

C. twice a day.C. twice a day.

D. four times a day.D. four times a day.