NOTES

What are the tides?

TURN TO PAGEpage 434-438 IN YOUR

SCIENCE BOOK

By: Mr. D'Angelone 2

Learning Objective

• Students will describe what causes and affects the tides.

By: Mr. D'Angelone 3

Key Terms

•tide•Spring Tides•Neap Tides

By: Mr. D'Angelone 4

Ocean Water Levels

• The water level of the ocean rises and falls throughout the day.

• Early in the day, ocean water rises and covers part of the beach.

• Later in the day, the ocean level falls. • The beach is exposed. • These regular changes in ocean water levels are

called tides. • A low water level is called low tide. • A high water level is called high tide.

By: Mr. D'Angelone 5

• Once a month we have a lower than normal Low tide (above) and a higher than normal high tide (below) in the same location.

By: Mr. D'Angelone 6

Causes of Tides

• The Earth's gravitational pull on the Moon keeps the Moon in orbit around us.

• The Moon also pulls back on Earth and causes the tides.

By: Mr. D'Angelone 7

Causes of Tides

• The Sun's gravitational pull also affects Earth's tides, but because it is so far away from us, not as strongly.

By: Mr. D'Angelone 8

Causes of Tides (2)

• Earth's continents are slightly stretched by the pull of the Moon.

• Earth's oceans, which move more freely, are stretched even more.

• This stretching effect creates two bulges of water on Earth, one facing the Moon, the other directly opposite it.

• These bulges are the high tides. • The bulging water also causes two areas with

low tides between the high tides. • As the Earth turns on its axis, the tide levels rise

and fall.

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• The Moon, along with the Sun, causes the tides. • Whether it is high tide or low tide depends

mostly on where you are on Earth relative to the Moon.

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Changing Tides

• Some newspapers print tide tables.

• A tide table tells the times at which high tide and low tide will occur.

• If you look at a tide table, you will notice that it often shows two high tides and two low tides each day.

• The tides change about every 6 hours and 15 minutes.

By: Mr. D'Angelone 11

Tide Table

A newspaper gives the times for high and low tide.

By: Mr. D'Angelone 12

Spring Tide

• A new moon phase and a full moon phase causes a major change in tides.

• This causes the Earth, moon, and sun to align which causes a very high tide called a Spring Tide. (2 spring tides per month)

By: Mr. D'Angelone 13

Neap Tide• A 1st quarter and a third quarter

moon phase causes a major change in tides.

• This causes the Earth and moon to be at a right angle to each other which causes a extremely low tide called a Neap Tide. (2 spring tides per month)

By: Mr. D'Angelone 14

Checking Concepts

• What is the the two highest tides per month called?

• How often each day do tides occur?

• What is the the lowest tide called?

• How many really low tides do we have per month?

• What has to be aligned to have a very, very high tide?

By: Mr. D'Angelone 15

Answers

• An spring tide

• Twice

• A neap tide

• two

• the Earth, moon, sun

The End