Tides
Tides are the daily changes in the elevation of the ocean
surface. Tides are the daily rise and fall of the Earth’s
waters on its coastlines.
Tides are caused by the interaction of the Earth, the
moon and the sun.
A. Tides form from the gravitational attraction
exerted upon the Earth by the moon.
B. Tidal Cycle-Is influenced by the sun and moon.
When they are aligned together their forces are added.
Gravity is the force exerted by an object that pulls another
object toward it. As the distance between two objects
is greater the force becomes weaker.
Daily Tides
Tides happen regularly no matter what the wind is doing
Tides occur in all bodies of water but are most noticeable
in oceans.
High Tide- as the tide comes in toward the beach and
reaches its highest point
Low Tide-as the tide flows back toward the sea and
reaches its lowest point
Daily Tides
The moon gravity pulls on the water on the Earth’s
Surface. The moon pulls on the water on the side
closest to it more than it pulls on the center of the earth.
This pull creates a Tidal bulge, a bulge of water on the
side of the earth that is facing the moon . On the other
side of the earth is a bulge of water that is pulled less
strongly than the center of the earth. Where the tidal
bulges are is where high tides occur. As the earth
rotates different part of the earth's surface pass by these
areas and experience the water level changes.
Tide Causing Force
The Moon is the primary tide causing force. The
gravitational pull of the moon causes bulges of
water towards and away from the moon.
The Daily Tidal Cycle
1. All areas of the world oceans pass under the
2.
3.
moon every 24 hours and 50 minutes. The
cycle takes more than one day, each day the
tides occur at different times
Every coastal area has at least one high tide
and one low tide every day
Factors which influence the daily Tidal patterns
are:
1. The earth’s surface
2. Shape of the ocean floor/coastline
3. Coriolis effect
Tidal Patterns
determined by how many high and low tides in
a 24 hour period.
1. Diurnal Tides-Include a single high tide
and a single low tide each day.
Example-Southeastern US along Gulf of
Mexico
2. Semidiurnal Tides-Include two high
tides and two low tides each day.
Example-Atlantic Coast of US
3. Mixed Tides-Inequality of tide levels
that has multiple high and low tides.
Example- Pacific Coast of US
Tide patterns around the world
Monthly Tide Cycle
1. The sun’s gravity also effects the Earth,
even though it is far away it is very
large. The sun’s gravity pulls the earth’s
water toward it. Sometimes the moon
and sun pull the earth’s water in the
same direction other times they pull in
different directions.
Spring tides
1. Twice a month at the new moon and the
full moon, the sun and moon are lined
up.
2. These combined gravitational pulls cause
the greatest tidal ranges.
3. Spring comes from the word to jump and
does not refer to the season!!!
Neap Tides
1. At the first quarter (waxing) and third
quarter (waning) moons, the sun and
moon pull at right angles to each other.
2. Least tidal range due to the sun’s gravity
pulling some of the water away from the
tidal bulge facing the moon thus evening
out the difference between low and high
tide.
Spring and Neap Tide Cycle
Tidal Range
Tidal Range is the difference in height between high
and low tides.
1. Spring Tides-Are the highest tidal range
2. Neap Tides-Lowest tidal range
http://home.h
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cool/Astro/mo
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Monthly Tide Tables
Scientists can fairly accurately predict tides
at various locations. These are published
as tide tables. Who is it important to, in
order to know the times and heights of
the tides?